Sample records for gan films grown

  1. Low temperature thin film transistors with hollow cathode plasma-assisted atomic layer deposition based GaN channels

    SciTech Connect (OSTI)

    Bolat, S., E-mail: bolat@ee.bilkent.edu.tr, E-mail: aokyay@ee.bilkent.edu.tr; Tekcan, B. [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey); UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Ozgit-Akgun, C.; Biyikli, N. [UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Okyay, A. K., E-mail: bolat@ee.bilkent.edu.tr, E-mail: aokyay@ee.bilkent.edu.tr [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey); UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey)

    2014-06-16T23:59:59.000Z

    We report GaN thin film transistors (TFT) with a thermal budget below 250?°C. GaN thin films are grown at 200?°C by hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD). HCPA-ALD-based GaN thin films are found to have a polycrystalline wurtzite structure with an average crystallite size of 9.3?nm. TFTs with bottom gate configuration are fabricated with HCPA-ALD grown GaN channel layers. Fabricated TFTs exhibit n-type field effect characteristics. N-channel GaN TFTs demonstrated on-to-off ratios (I{sub ON}/I{sub OFF}) of 10{sup 3} and sub-threshold swing of 3.3?V/decade. The entire TFT device fabrication process temperature is below 250?°C, which is the lowest process temperature reported for GaN based transistors, so far.

  2. Evaluation of GaN substrates grown in supercritical basic ammonia

    SciTech Connect (OSTI)

    Saito, Makoto; Yamada, Hisashi; Iso, Kenji; Sato, Hitoshi; Hirasawa, Hirohiko; Kamber, Derrick S.; Hashimoto, Tadao; Baars, Steven P. den; Speck, James S.; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2009-02-02T23:59:59.000Z

    GaN crystals grown by the basic ammonothermal method were investigated for their use as substrates for device regrowth. X-ray diffraction analysis indicated that the substrates contained multiple grains while secondary ion mass spectroscopy (SIMS) revealed a high concentration of hydrogen, oxygen, and sodium. Despite these drawbacks, the emission from the light emitting diode structures grown by metal organic chemical vapor deposition on both the c-plane and m-plane epitaxial wafers was demonstrated. The SIMS depth profiles showed that the diffusion of the alkali metal from the substrate into the epitaxial film was small, especially in the m-direction.

  3. Observation of photoluminescence from Al1 xInxN heteroepitaxial films grown by metalorganic vapor phase epitaxy

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Observation of photoluminescence from Al1 xInxN heteroepitaxial films grown by metalorganic vapor have observed photoluminescence of Al1 xInxN films. The films were grown on GaN by atmospheric pressure-temperature deposited AlN buffer layer. Photoluminescence, absorption, and x-ray diffraction measurements have shown

  4. Substrate-dependent wetting layer formation during GaN growth: Impact on the morphology of the films

    SciTech Connect (OSTI)

    Sidorenko, A.; Peisert, H.; Neumann, H.; Chasse, T. [Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, D-72076 Tuebingen (Germany); Leibniz-Institut fuer Oberflaechenmodifizierung e.V. Permoserstrasse 15, D-04318 Leipzig (Germany); Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, D-72076 Tuebingen (Germany)

    2007-08-15T23:59:59.000Z

    We have compared epitaxial growth of GaN films on 6H-SiC(0001)-({radical}(3)x{radical}(3))R30 deg. -Ga and on (0001)-sapphire. Predeposited Ga layers were nitrided by ion beam assisted molecular beam epitaxy. Whereas on SiC the initially deposited Ga covers the substrate surface completely, on sapphire only Ga droplets are present. The different distribution of the predeposited Ga affects the morphology of GaN significantly. Scanning electron microscopy and atomic force microscopy analysis of the grown films show that the complete wetting of the SiC substrate with Ga enhances finally the size and the flatness of GaN terraces and thus the quality of the film. X-ray photoelectron spectroscopy measurements reveal that metallic Ga resides also on top of the GaN films during the growth.

  5. Growth and characterizations of GaN micro-rods on graphene films for flexible light emitting diodes

    SciTech Connect (OSTI)

    Chung, Kunook; Beak, Hyeonjun; Tchoe, Youngbin; Oh, Hongseok; Yi, Gyu-Chul, E-mail: gcyi@snu.ac.kr [Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 151-747 (Korea, Republic of); Yoo, Hyobin; Kim, Miyoung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2014-09-01T23:59:59.000Z

    We report the growth of GaN micro-rods and coaxial quantum-well heterostructures on graphene films, together with structural and optical characterization, for applications in flexible optical devices. Graphene films were grown on Cu foil by means of chemical vapor deposition, and used as the substrates for the growth of the GaN micro-rods, which were subsequently transferred onto SiO{sub 2}/Si substrates. Highly Si-doped, n-type GaN micro-rods were grown on the graphene films using metal–organic chemical vapor deposition. The growth and vertical alignment of the GaN micro-rods, which is a critical factor for the fabrication of high-performance light-emitting diodes (LEDs), were characterized using electron microscopy and X-ray diffraction. The GaN micro-rods exhibited promising photoluminescence characteristics for optoelectronic device applications, including room-temperature stimulated emission. To fabricate flexible LEDs, In{sub x}Ga{sub 1–x}N/GaN multiple quantum wells and a p-type GaN layer were deposited coaxially on the GaN micro-rods, and transferred onto Ag-coated polymer substrates using lift-off. Ti/Au and Ni/Au metal layers were formed to provide electrical contacts to the n-type and p-type GaN regions, respectively. The micro-rod LEDs exhibited intense emission of visible light, even after transfer onto the flexible polymer substrate, and reliable operation was achieved following numerous cycles of mechanical deformation.

  6. Journal of Crystal Growth 293 (2006) 273277 A study of semi-insulating GaN grown on AlN buffer/sapphire

    E-Print Network [OSTI]

    Ozbay, Ekmel

    -temperature GaN interlayer. In comparison with the normal GaN grown on sapphire, the crystal quality measurement results of GaN grown directly on an AlN buffer indicated that the as-grown-undoped Ga, or high density of edge-type dislocations [6­10]. However, Fe and other heavy metals tend to have reactor

  7. Conductivity of Oriented Samaria-Doped Ceria Thin Films Grown...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Conductivity of Oriented Samaria-Doped Ceria Thin Films Grown by Oxygen-plasma-assisted Molecular Beam Epitaxy. Conductivity of Oriented Samaria-Doped Ceria Thin Films Grown by...

  8. A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Evans and Associates, Sunnyvale, CA 94086 ABSTRACT Step-doped structures of both magnesium and beryllium activation energy of approximately 100 meV. INTRODUCTION While magnesium is currently the most

  9. Hydrothermally grown nanostructured WO films and their electrochromic characteristics

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Hydrothermally grown nanostructured WO 3 films and their electrochromic characteristics.1088/0022-3727/43/28/285501 Hydrothermally grown nanostructured WO3 films and their electrochromic characteristics Zhihui Jiao1 , Xiao Wei and their electrochromic characteristics. Plate-like monoclinic WO3 nanostructures were grown directly on fluorine

  10. Thermal annealing characteristics of Si and Mg-implanted GaN thin films

    SciTech Connect (OSTI)

    Chan, J.S.; Cheung, N.W. [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States)] [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States); Schloss, L.; Jones, E.; Wong, W.S.; Newman, N.; Liu, X.; Weber, E.R. [Department of Material Science and Mineral Engineering, University of California, Berkeley, California 64720 (United States)] [Department of Material Science and Mineral Engineering, University of California, Berkeley, California 64720 (United States); Gassman, A.; Rubin, M.D. [Lawrence Berkeley Laboratory, 1 Cyclotron Road, University of California, Berkeley, California 64720 (United States)] [Lawrence Berkeley Laboratory, 1 Cyclotron Road, University of California, Berkeley, California 64720 (United States)

    1996-05-01T23:59:59.000Z

    In this letter, we report the results of ion implantation of GaN using {sup 28}Si and {sup 24}Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 40 keV 10{sup 14} cm{sup {minus}2} Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690{degree}C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties. {copyright} {ital 1996 American Institute of Physics.}

  11. ag films grown: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    conduction-band states of NiO 100 thin films grown onto Ag 100 have charac- terized NiO monocrystalline thin films has shown up both onto insulating i.e., MgO, Ref. 21 Marcon,...

  12. aln films grown: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    conduction-band states of NiO 100 thin films grown onto Ag 100 have charac- terized NiO monocrystalline thin films has shown up both onto insulating i.e., MgO, Ref. 21 Marcon,...

  13. Group III-nitride thin films grown using MBE and bismuth

    DOE Patents [OSTI]

    Kisielowski, Christian K. (Peidmont, CA); Rubin, Michael (Berkeley, CA)

    2000-01-01T23:59:59.000Z

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  14. Group III-nitride thin films grown using MBE and bismuth

    DOE Patents [OSTI]

    Kisielowski, Christian K. (Piedmont, CA); Rubin, Michael (Berkeley, CA)

    2002-01-01T23:59:59.000Z

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  15. Hexagonal Growth Spirals on GaN Grown by Molecular Beam Epitaxy: Kinetics vs Thermodynamics

    E-Print Network [OSTI]

    Cohen, Philip I.

    prepared, Ga-polar GaN(0001) templates. The surface morphology was studied using reflection high-energy-edge energy of 0.26 eV/Ã?. They suggest that local conditions at step edges dominate the growth. 1 conducted ex situ using AFM. Desorption mass spectrometry (DMS) was used to measure the GaN growth rate. Our

  16. Thermoelectric properties of ZnSb films grown by MOCVD

    SciTech Connect (OSTI)

    Venkatasubramanian, R.; Watko, E.; Colpitts, T.

    1997-07-01T23:59:59.000Z

    The thermoelectric properties of ZnSb films grown by metallorganic chemical vapor deposition (MOCVD) are reported. The growth conditions necessary to obtain stoichiometric ZnSb films and the effects of various growth parameters on the electrical conductivity and Seebeck coefficients of the films are described. The as-grown ZnSb films are p-type. It was observed that the thicker ZnSb films offer improved carrier mobilities and lower free-carrier concentration levels. The Seebeck coefficient of ZnSb films was found to rise rapidly at approximately 160 C. The thicker films, due to the lower doping levels, indicate higher Seebeck coefficients between 25 to 200 C. A short annealing of the ZnSb film at temperatures of {approximately}200 C results in reduced free-carrier level. Thermal conductivity measurements of ZnSb films using the 3-{omega} method are also presented.

  17. Partially filled intermediate band of Cr-doped GaN films

    SciTech Connect (OSTI)

    Sonoda, S. [Department of Electronics, Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2012-05-14T23:59:59.000Z

    We investigated the band structure of sputtered Cr-doped GaN (GaCrN) films using optical absorption, photoelectron yield spectroscopy, and charge transport measurements. It was found that an additional energy band is formed in the intrinsic band gap of GaN upon Cr doping, and that charge carriers in the material move in the inserted band. Prototype solar cells showed enhanced short circuit current and open circuit voltage in the n-GaN/GaCrN/p-GaN structure compared to the GaCrN/p-GaN structure, which validates the proposed concept of an intermediate-band solar cell.

  18. GaN nanorod light emitting diodes with suspended graphene transparent electrodes grown by rapid chemical vapor deposition

    SciTech Connect (OSTI)

    Xu, Kun; Xu, Chen, E-mail: xuchen58@bjut.edu.cn; Deng, Jun; Zhu, Yanxu; Guo, Weiling; Mao, Mingming; Xun, Meng; Chen, Maoxing; Zheng, Lei [Key Laboratory of Optoelectronics Technology, Beijing University of Technology, Ministry of Education, Beijing 100124 (China)] [Key Laboratory of Optoelectronics Technology, Beijing University of Technology, Ministry of Education, Beijing 100124 (China); Xie, Yiyang [State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductor, Chinese Academy of Sciences, Beijing 100083 (China)] [State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductor, Chinese Academy of Sciences, Beijing 100083 (China); Sun, Jie, E-mail: jie.sun@chalmers.se [Key Laboratory of Optoelectronics Technology, Beijing University of Technology, Ministry of Education, Beijing 100124 (China) [Key Laboratory of Optoelectronics Technology, Beijing University of Technology, Ministry of Education, Beijing 100124 (China); Mikroteknologi och Nanovetenskap, Chalmers Tekniska Högskola AB, Göteborg 41296 (Sweden)

    2013-11-25T23:59:59.000Z

    Ordered and dense GaN light emitting nanorods are studied with polycrystalline graphene grown by rapid chemical vapor deposition as suspended transparent electrodes. As the substitute of indium tin oxide, the graphene avoids complex processing to fill up the gaps between nanorods and subsequent surface flattening and offers high conductivity to improve the carrier injection. The as-fabricated devices have 32% improvement in light output power compared to conventional planar GaN-graphene diodes. The suspended graphene remains electrically stable up to 300?°C in air. The graphene can be obtained at low cost and high efficiency, indicating its high potential in future applications.

  19. Heteroepitaxial growth and surface structure of L1{sub 0}-MnGa(111) ultra-thin films on GaN(0001)

    SciTech Connect (OSTI)

    Mandru, Andrada-Oana; Wang, Kangkang; Cooper, Kevin; Ingram, David C.; Smith, Arthur R. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States)] [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Garcia Diaz, Reyes; Takeuchi, Noboru [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States) [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autónoma de México, Apartado Postal 14, Ensenada Baja California, Codigo Postal 22800 (Mexico); Haider, Muhammad [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States) [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran, 31261 (Saudi Arabia)

    2013-10-14T23:59:59.000Z

    L1{sub 0}-structured MnGa(111) ultra-thin films were heteroepitaxially grown on GaN(0001) under lightly Mn-rich conditions using molecular beam epitaxy. Room-temperature scanning tunneling microscopy (STM) investigations reveal smooth terraces and angular step edges, with the surface structure consisting primarily of a 2 × 2 reconstruction along with small patches of 1 × 2. Theoretical calculations were carried out using density functional theory, and the simulated STM images were calculated using the Tersoff-Hamman approximation, revealing that a stoichiometric 1 × 2 and a Mn-rich 2 × 2 surface structure give the best agreement with the observed experimental images.

  20. Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions

    SciTech Connect (OSTI)

    Zhang Meng; Bhattacharya, Pallab; Guo Wei; Banerjee, Animesh [Department of Electrical Engineering and Computer Science, Solid-State Electronics Laboratory, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

    2010-03-29T23:59:59.000Z

    Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 deg. C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1x10{sup 18} cm{sup -3}. The corresponding doping efficiency and hole mobility are approx4.9% and 3.7 cm{sup 2}/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (lambda{sub peak}=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 OMEGA.

  1. X-ray determination of threading dislocation densities in GaN/Al{sub 2}O{sub 3}(0001) films grown by metalorganic vapor phase epitaxy

    SciTech Connect (OSTI)

    Kopp, Viktor S., E-mail: victor.kopp@pdi-berlin.de; Kaganer, Vladimir M. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany); Baidakova, Marina V.; Lundin, Wsevolod V.; Nikolaev, Andrey E.; Verkhovtceva, Elena V.; Yagovkina, Maria A. [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, 194021 St.-Petersburg (Russian Federation); Cherkashin, Nikolay [CEMES-CNRS and Université de Toulouse, 29 rue J. Marvig, 31055 Toulouse (France)

    2014-02-21T23:59:59.000Z

    Densities of a- and a+c-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films.

  2. Nanoair-bridged lateral overgrowth of GaN on ordered nanoporous GaN template

    SciTech Connect (OSTI)

    Wang, Y.D.; Zang, K.Y.; Chua, S.J.; Tripathy, S.; Chen, P.; Fonstad, C.G. [Singapore-MIT Alliance, E4-04-10, 4 Engineering Drive 3, Singapore 117576 (Singapore) and Centre for Optoelectronics, Department of Electrical and Computer Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore); Department of Electrical and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2005-12-19T23:59:59.000Z

    We report the growth of high-quality GaN epilayers on an ordered nanoporous GaN template by metalorganic chemical vapor deposition. The nanopores in GaN template were created by inductively coupled plasma etching using anodic aluminum oxide film as an etch mask. The average pore diameter and interpore distance is about 65 and 110 nm, respectively. Subsequent overgrowth of GaN first begins at the GaN crystallite surface between the pores, and then air-bridge-mediated lateral overgrowth leads to the formation of the continuous layer. Microphotoluminescence and micro-Raman measurements show improved optical properties and significant strain relaxation in the overgrown layer when compared to GaN layer of same thickness simultaneously grown on sapphire without any template. Similar to conventional epitaxial lateral overgrown GaN, such overgrown GaN on a nanopatterned surface would also serve as a template for the growth of ultraviolet-visible light-emitting III-nitride devices.

  3. Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers C. Wetzel, Nagoya, Japan Received 11 December 1995; accepted for publication 21 February 1996 Infrared reflection, their alloys and potential substrates need to be investigated as well. Here we present a study of the infrared

  4. Preparation of Ag Schottky contacts on n-type GaN bulk crystals grown in nitrogen rich atmosphere by the hydride vapor phase epitaxy technique

    SciTech Connect (OSTI)

    Stübner, R., E-mail: ronald.stuebner@physik.tu-dresden.de; Kolkovsky, Vl.; Weber, J. [Technische Universität Dresden, 01062 Dresden (Germany); Leibiger, Gunnar; Habel, Frank [Freiberger Compound Materials GmbH, 09599 Freiberg (Germany)

    2014-10-14T23:59:59.000Z

    Electrical properties of Schottky contacts on n-type GaN grown in nitrogen rich atmosphere with different N/Ga ratios by hydride vapor phase epitaxy were investigated. We show that tunneling of electrons from the conduction band of GaN to the metal is dominant in our samples. The quality of Schottky contacts does not only depend on surface preparation but also on the growth conditions of the crystals. Schottky contacts on these crystals show an increasing deterioration when higher N/Ga growth ratios are used. We correlate our results with the presence of negatively charged gallium vacancies in the samples. These charges compensate the positively charged donors and lead to a significant increase in series resistance.

  5. Bi-Sr-Ca-Cu-O thin films grown by flash evaporation and pulsed laser deposition

    E-Print Network [OSTI]

    Ganapathy Subramanian, Santhana

    2004-09-30T23:59:59.000Z

    -phase 2212 films were grown on a MgO substrate using the pulsed laser deposition technique from commercially available 2212 powder. The effect of annealing on the thin films was also studied....

  6. Development of a Bulk GaN Growth Technique for Low Defect Density...

    Broader source: Energy.gov (indexed) [DOE]

    current due to bulk defects GaN is Grown Heteroepitaxially on Sapphire (and Silicon Carbide) Substrates * As grown GaN nucleation layers contain disordered GaN with many...

  7. Thin crystalline silicon solar cells based on epitaxial films grown at 165C by RF PECVD

    E-Print Network [OSTI]

    1 Thin crystalline silicon solar cells based on epitaxial films grown at 165°C by RF PECVD Romain temperatures. Keywords : Low temperature, epitaxy, PECVD, Si thin film, Solar cell hal-00749873,version1-25Nov shortage until 2010. Research on epitaxial growth for thin film crystalline silicon solar cells has gained

  8. Dual-polarity GaN micropillars grown by metalorganic vapour phase epitaxy: Cross-correlation between structural and optical properties

    SciTech Connect (OSTI)

    Coulon, P. M. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France); Université de Nice Sophia-Antipolis (UNS), 28 Ave. Valrose, 06103 Nice (France); Mexis, M.; Teisseire, M.; Vennéguès, P.; Leroux, M.; Zuniga-Perez, J., E-mail: jzp@crhea.cnrs.fr [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France); Jublot, M. [Faculté des Sciences de Saint Jérôme—CP2M, Ave. Escadrille Normandie Niemen, 13397 Marseille (France)

    2014-04-21T23:59:59.000Z

    Self-assembled catalyst-free GaN micropillars grown on (0001) sapphire substrates by metal organic vapor phase epitaxy are investigated. Transmission electron microscopy, as well as KOH etching, shows the systematic presence of two domains of opposite polarity within each single micropillar. The analysis of the initial growth stages indicates that such double polarity originates at the micropillar/substrate interface, i.e., during the micropillar nucleation, and it propagates along the micropillar. Furthermore, dislocations are also generated at the wire/substrate interface, but bend after several hundreds of nanometers. This leads to micropillars several tens of micrometers in length that are dislocation-free. Spatially resolved cathodoluminescence and microphotoluminescence show large differences in the optical properties of each polarity domain, suggesting unequal impurity/dopant/vacancy incorporation depending on the polarity.

  9. Dependence of the Mg-related acceptor ionization energy with the acceptor concentration in p-type GaN layers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Brochen, Stephane; Brault, Julien; Chenot, Sebastien; Dussaigne, Amelie; Leroux, Mathieu; Damilano, Benjamin [CNRS-CRHEA, Rue Bernard Gregory, F-06560 Valbonne (France)

    2013-07-15T23:59:59.000Z

    Hall effect and capacitance-voltage C(V) measurements were performed on p-type GaN:Mg layers grown on GaN templates by molecular beam epitaxy with a high range of Mg-doping concentrations. The free hole density and the effective dopant concentration N{sub A}-N{sub D} as a function of magnesium incorporation measured by secondary ion mass spectroscopy clearly reveal both a magnesium doping efficiency up to 90% and a strong dependence of the acceptor ionization energy Ea with the acceptor concentration N{sub A}. These experimental observations highlight an isolated acceptor binding energy of 245{+-}25 meV compatible, at high acceptor concentration, with the achievement of p-type GaN:Mg layers with a hole concentration at room temperature close to 10{sup 19} cm{sup -3}.

  10. Polarity characterization by anomalous x-ray dispersion of ZnO films and GaN lateral polar structures

    SciTech Connect (OSTI)

    Shelton, Christopher T.; Sachet, Edward; Paisley, Elizabeth A.; Hoffmann, Marc P.; Rajan, Joseph; Collazo, Ramón; Sitar, Zlatko; Maria, Jon-Paul [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-01-28T23:59:59.000Z

    We demonstrate the use of anomalous x-ray scattering of constituent cations at their absorption edge, in a conventional Bragg-Brentano diffractometer, to measure absolutely and quantitatively the polar orientation and polarity fraction of unipolar and mixed polar wurtzitic crystals. In one set of experiments, the gradual transition between c+ and c? polarity of epitaxial ZnO films on sapphire as a function of MgO buffer layer thickness is monitored quantitatively, while in a second experiment, we map the polarity of a lateral polar homojunction in GaN. The dispersion measurements are compared with piezoforce microscopy images, and we demonstrate how x-ray dispersion and scanning probe methods can provide complementary information that can discriminate between polarity fractions at a material surface and polarity fractions averaged over the film bulk.

  11. Optimization of High Tunability Barium Strontium Titanate Thin Films Grown by RF Magnetron

    E-Print Network [OSTI]

    York, Robert A.

    Optimization of High Tunability Barium Strontium Titanate Thin Films Grown by RF Magnetron Abstract-- Barium strontium titanate is a solid solution perovskite with a field-dependent permittivity.7 MV/cm. I. INTRODUCTION In recent years there has been much interest in thin-film barium strontium

  12. Thin crystalline silicon solar cells based on epitaxial films grown at 165C by RF PECVD

    E-Print Network [OSTI]

    1 Thin crystalline silicon solar cells based on epitaxial films grown at 165°C by RF PECVD Romain temperatures. Keywords : Low temperature, epitaxy, PECVD, Si thin film, Solar cell #12;2 1. Introduction: martin.labrune@polytechnique.edu ABSTRACT We report on heterojunction solar cells whose thin intrinsic

  13. Magnesium outdiffusion through magnetite films grown on magnesium oxide (001) (abstract)

    E-Print Network [OSTI]

    Diebold, Ulrike

    Magnesium outdiffusion through magnetite films grown on magnesium oxide (001) (abstract) K. A. Shaw of magnesium in the uppermost layers of the film, and indicate a concentration gradient, with the highest concentrations of magnesium in the surface layer. X-ray fluorescence in scanning electron microscopy

  14. Pulsed laser annealing of Be-implanted GaN

    SciTech Connect (OSTI)

    Wang, H.T.; Tan, L.S.; Chor, E.F. [Centre for Optoelectronics, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2005-11-01T23:59:59.000Z

    Postimplantation thermal processing of Be in molecular-beam-epitaxy-grown GaN by rapid thermal annealing (RTA) and pulsed laser annealing (PLA) was investigated. It has been found that the activation of Be dopants and the repair of implantation-induced defects in GaN films cannot be achieved efficiently by conventional RTA alone. On the other hand, good dopant activation and surface morphology and quality were obtained when the Be-implanted GaN film was annealed by PLA with a 248 nm KrF excimer laser. However, observations of off-resonant micro-Raman and high-resolution x-ray-diffraction spectra indicated that crystal defects and strain resulting from Be implantation were still existent after PLA, which probably degraded the carrier mobility and limited the activation efficiency to some extent. This can be attributed to the shallow penetration depth of the 248 nm laser in GaN, which only repaired the crystal defects in a thin near-surface layer, while the deeper defects were not annealed out well. This situation was significantly improved when the Be-implanted GaN was subjected to a combined process of PLA followed by RTA, which produced good activation of the dopants, good surface morphology, and repaired bulk and surface defects well.

  15. Piezo-Phototronic Effect on Electroluminescence Properties of p-Type GaN Thin Films

    E-Print Network [OSTI]

    Wang, Zhong L.

    significance on the practical applications of GaN in optoelectronic devices under a working environment where,9 Recent studies have shown its applications in improving the performance of optoelectronic devices based result in great influence for this most popular III-V semiconductor used in optoelectronic devices

  16. Photoresponse in thin films of WO{sub 3} grown by pulsed laser deposition

    SciTech Connect (OSTI)

    Roy Moulik, Samik [Unit for Nanoscience, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata (India); ICON Analytical Equipment Pvt. Ltd., Kolkata (India); Samanta, Sudeshna; Ghosh, Barnali, E-mail: barnali@bose.res.in [Unit for Nanoscience, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata (India)

    2014-06-09T23:59:59.000Z

    We report, the photoresponse behaviour of Tungsten trioxide (WO{sub 3}) films of different surface morphology, grown by using pulsed laser deposition (PLD). The Growth parameters for PLD were changed for two substrates SiO{sub 2}/Si (SO) and SrTiO{sub 3} (STO), such a way which, result nanocrystalline film on SO and needle like structured film on STO. The photoresponse is greatly modified in these two films because of two different surface morphologies. The nanocrystalline film (film on SO) shows distinct photocurrent (PC) ON/OFF states when light was turned on/off, the enhancement of PC is ?27%. Whereas, the film with needle like structure (film on STO) exhibits significantly enhanced persistent photocurrent even in light off condition, in this case, the enhancement of PC???50% at room temperature at lowest wavelength (??=?360?nm) at a nominal bias voltage of 0.1 V.

  17. Characterization of Nanoporous WO3 Films Grown via Ballistic...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    on the preparation and characterization of high surface area, supported nanoporous tungsten oxide films prepared under different conditions on polished polycrystalline Ta and...

  18. Influence of growth temperature and temperature ramps on deep level defect incorporation in m-plane GaN

    SciTech Connect (OSTI)

    Armstrong, A. M., E-mail: aarmstr@sandia.gov [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Kelchner, K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)] [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Nakamura, S.; DenBaars, S. P. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States) [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2013-12-02T23:59:59.000Z

    The dependence of deep level defect incorporation in m-plane GaN films grown by metal-organic chemical vapor deposition on bulk m-plane GaN substrates as a function of growth temperature (T{sub g}) and T{sub g} ramping method was investigated using deep level optical spectroscopy. Understanding the influence of T{sub g} on GaN deep level incorporation is important for InGaN/GaN multi-quantum well (MQW) light emitting diodes (LEDs) and laser diodes (LDs) because GaN quantum barrier (QB) layers are grown much colder than thin film GaN to accommodate InGaN QW growth. Deep level spectra of low T{sub g} (800?°C) GaN films grown under QB conditions were compared to deep level spectra of high T{sub g} (1150?°C) GaN. Reducing T{sub g}, increased the defect density significantly (>50×) through introduction of emergent deep level defects at 2.09?eV and 2.9?eV below the conduction band minimum. However, optimizing growth conditions during the temperature ramp when transitioning from high to low T{sub g} substantially reduced the density of these emergent deep levels by approximately 40%. The results suggest that it is important to consider the potential for non-radiative recombination in QBs of LED or LD active regions, and tailoring the transition from high T{sub g} GaN growth to active layer growth can mitigate such non-radiative channels.

  19. Multicycle rapid thermal annealing optimization of Mg-implanted GaN: Evolution of surface, optical, and structural properties

    SciTech Connect (OSTI)

    Greenlee, Jordan D., E-mail: jordan.greenlee.ctr@nrl.navy.mil [National Research Council, 500 Fifth St. NW, Washington, DC 20001 (United States); Feigelson, Boris N.; Anderson, Travis J.; Hite, Jennifer K.; Mastro, Michael A.; Eddy, Charles R.; Hobart, Karl D.; Kub, Francis J. [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Tadjer, Marko J. [American Society for Engineering Education, 1818 N St. NW, Washington, DC 20036 (United States)

    2014-08-14T23:59:59.000Z

    The first step of a multi-cycle rapid thermal annealing process was systematically studied. The surface, structure, and optical properties of Mg implanted GaN thin films annealed at temperatures ranging from 900 to 1200?°C were investigated by Raman spectroscopy, photoluminescence, UV-visible spectroscopy, atomic force microscopy, and Nomarski microscopy. The GaN thin films are capped with two layers of in-situ metal organic chemical vapor deposition -grown AlN and annealed in 24 bar of N{sub 2} overpressure to avoid GaN decomposition. The crystal quality of the GaN improves with increasing annealing temperature as confirmed by UV-visible spectroscopy and the full widths at half maximums of the E{sub 2} and A{sub 1} (LO) Raman modes. The crystal quality of films annealed above 1100?°C exceeds the quality of the as-grown films. At 1200?°C, Mg is optically activated, which is determined by photoluminescence measurements. However, at 1200?°C, the GaN begins to decompose as evidenced by pit formation on the surface of the samples. Therefore, it was determined that the optimal temperature for the first step in a multi-cycle rapid thermal anneal process should be conducted at 1150?°C due to crystal quality and surface morphology considerations.

  20. THE RATCHETING OF COMPRESSED THERMALLY GROWN THIN FILMS ON DUCTILE SUBSTRATES

    E-Print Network [OSTI]

    Hutchinson, John W.

    THE RATCHETING OF COMPRESSED THERMALLY GROWN THIN FILMS ON DUCTILE SUBSTRATES M. Y. HE1 , A. G by oxidation of the substrate. It is shown that, in some circumstances, ratcheting occurs, wherein which ratcheting does not occur. This critical size is related to the expansion mis®t, the substrate

  1. Raman and Photoluminescence Spectroscopy of Nanocrystalline Diamond Films grown by Hot Filament CVD

    E-Print Network [OSTI]

    Bristol, University of

    H4 flow-rate ratio of standard polycrystalline diamond deposition parameters on formationRaman and Photoluminescence Spectroscopy of Nanocrystalline Diamond Films grown by Hot Filament CVD of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia b,c Diamond Research Laboratory, School

  2. Do CVD grown graphene films have antibacterial activity on metallic substrates?

    E-Print Network [OSTI]

    Dellieu, Louis; Reckinger, Nicolas; Didembourg, Christian; Letesson, Jean-Jacques; Sarrazin, Michael; Deparis, Olivier; Matroule, Jean-Yves; Colomer, Jean-François

    2014-01-01T23:59:59.000Z

    Accurate assessment of the antibacterial activity of graphene requires consideration of both the graphene fabrication method and, for supported films, the properties of the substrate. Large-area graphene films produced by chemical vapor deposition were grown directly on copper substrates or transferred on a gold substrate and their effect on the viability and proliferation of the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli were assessed. The viability and the proliferation of both bacterial species were not affected when they were grown on a graphene film entirely covering the gold substrate, indicating that conductivity plays no role on bacterial viability and graphene has no antibacterial activity against S. aureus and E. coli. On the other hand, antibacterial activity was observed when graphene coated the copper substrates, resulting from the release of bactericidal cupric ions in inverse proportion to the graphene surface coverage.

  3. Properties of CoSb{sub 3} films grown by pulsed laser deposition

    SciTech Connect (OSTI)

    Christen, H.M.; Mandrus, D.G.; Norton, D.P.; Boatner, L.A.; Sales, B.C.

    1997-07-01T23:59:59.000Z

    Polycrystalline CoSb{sub 3} films were grown on a variety of electrically insulating substrates by pulsed laser ablation from a stoichiometric hot-pressed target. These films are fully crystallized in the skutterudite structure, and the grains exhibit a strongly preferred alignment of the cubic [310]-axis perpendicular to the substrate surface. The film quality is studied for different single-crystal substrates and as a function of growth temperature and background gas. Hall measurements show that the films are p-type semiconducting with a room-temperature carrier density of 3 x 10{sup 20} holes/cm{sup 3}. The Hall mobility is found to be 50 to 60 cm{sup 2}/Vs, which is high for such a heavily-doped material. The Seebeck coefficient and the resistivity are measured as a function of temperature and are compared to bulk measurements.

  4. Atom probe tomography studies of Al{sub 2}O{sub 3} gate dielectrics on GaN

    SciTech Connect (OSTI)

    Mazumder, Baishakhi, E-mail: bmazumder@engineering.ucsb.edu; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Liu, Xiang; Yeluri, Ramya; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07T23:59:59.000Z

    Atom probe tomography was used to achieve three-dimensional characterization of in situ Al{sub 2}O{sub 3}/GaN structures grown by metal organic chemical vapor deposition (MOCVD). Al{sub 2}O{sub 3} dielectrics grown at three different temperatures of 700, 900, and 1000?°C were analyzed and compared. A low temperature GaN cap layer grown atop Al{sub 2}O{sub 3} enabled a high success rate in the atom probe experiments. The Al{sub 2}O{sub 3}/GaN interfaces were found to be intermixed with Ga, N, and O over the distance of a few nm. Impurity measurements data showed that the 1000?°C sample contains higher amounts of C (4?×?10{sup 19}/cm{sup 3}) and lower amounts of H (7?×?10{sup 19}/cm{sup 3}), whereas the 700?°C sample exhibits lower C impurities (<10{sup 17}/cm{sup 3}) and higher H incorporation (2.2?×?10{sup 20}/cm{sup 3}). On comparing with Al{sub 2}O{sub 3} grown by atomic layer deposition (ALD), it was found that the MOCVD Al{sub 2}O{sub 3}/GaN interface is comparatively abrupt. Scanning transmission electron microscopy data showed that the 900?°C and 1000?°C MOCVD films exhibit polycrystalline nature, while the ALD films were found to be amorphous.

  5. E-Print Network 3.0 - a-plane gan films Sample Search Results

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    films Page: << < 1 2 3 4 5 > >> 1 Demonstration of nonpolar a-plane InGaNGaN light emitting diode on r-plane sapphire substrate Summary: of the difficulty in obtaining high...

  6. Elastic properties of B-C-N films grown by N{sub 2}-reactive sputtering from boron carbide targets

    SciTech Connect (OSTI)

    Salas, E.; Jiménez Riobóo, R. J.; Jiménez-Villacorta, F.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain)] [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Sánchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain) [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid (Spain); Dept. Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Muñoz-Martín, A.; Prieto, J. E.; Joco, V. [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)] [Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2013-12-07T23:59:59.000Z

    Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B{sub 4}C target and N{sub 2} as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.

  7. Interference effects in photoreflectance and contactless electroreflectance spectra of CdTe films grown on Si substrate

    E-Print Network [OSTI]

    Ghosh, Sandip

    Interference effects in photoreflectance and contactless electroreflectance spectra of CdTe films and contactless electroreflectance CER spectra of CdTe films grown on Si substrate, at energies below the band gap of CdTe. The simultaneous observation of OF in the reflectance (R) spectrum having the same period

  8. Unexpected behaviour of one Pb monolayer deposited on aluminum oxide thin film grown on Ag(111)

    SciTech Connect (OSTI)

    Vizzini, Sébastien, E-mail: sebastien.vizzini@im2np.fr; Bertoglio, M. [IM2NP CNRS, Aix Marseille Université, F-13397 Marseille (France)] [IM2NP CNRS, Aix Marseille Université, F-13397 Marseille (France); Oughaddou, Hamid [Institut des Sciences Moléculaires d'Orsay, ISMO CNRS, Université de Paris, F-91405 Orsay, France and Deptartamento de Physique, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise (France)] [Institut des Sciences Moléculaires d'Orsay, ISMO CNRS, Université de Paris, F-91405 Orsay, France and Deptartamento de Physique, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise (France); Hoarau, J. Y.; Biberian, J. P.; Aufray, B. [CINaM CNRS, Aix Marseille Université, F-13288 Marseille (France)] [CINaM CNRS, Aix Marseille Université, F-13288 Marseille (France)

    2013-12-23T23:59:59.000Z

    Using scanning tunneling microscopy (STM), Auger electron spectroscopy, and low energy electron diffraction, we have observed a surprising complete dissolution at room temperature of one lead monolayer deposited by evaporation on an aluminum oxide thin film (?0.8?nm thick) previously grown on Ag (111). We have observed the quasi-instantaneous diffusion of the lead deposit through the oxide layer to the silver/oxide interface. After the diffusion process, lead atoms form a Moiré superstructure, which is characterized by STM through the oxide layer. This unexpected behavior puts in light the very weak interaction between the aluminum oxide and the silver substrate.

  9. Spatial modulation of in-plane magnetic anisotropy in epitaxial Co(111) films grown on macrostep-bunched Si(111)

    SciTech Connect (OSTI)

    Davydenko, A. V., E-mail: avdavydenko@gmail.com; Kozlov, A. G.; Chebotkevich, L. A. [Laboratory of Thin Film Technologies, Far Eastern Federal University, Vladivostok 690950 (Russian Federation)

    2014-10-14T23:59:59.000Z

    We compared magnetic properties of epitaxial Co(111) films grown on microstep- and macrostep-bunched vicinal Si(111) substrates. A surface of the microstep-bunched Si(111) substrate represents regular array of step-bunches with height of 1.7?nm divided from each other by flat microterraces with a width of 34?nm. A surface of the macrostep-bunched Si(111) substrate is constituted by macrostep bunches with a height of 75–85?nm divided by atomically flat macroterraces. The average sum width of a macrostep bunch and a macroterrace is 2.3??m. While in-plane magnetic anisotropy was spatially uniform in Co(111) films grown on the microstep-bunched Si(111), periodic macromodulation of the topography of the Si(111) substrate induced spatial modulation of in-plane magnetic anisotropy in Co(111) film grown on the macrostep-bunched Si(111) surface. The energy of uniaxial magnetic anisotropy in the areas of the Co(111) film deposited on the Si(111) macrosteps was higher more than by the order of magnitude than the energy of the magnetic anisotropy in the areas grown on macroterraces. Magnetization reversal in the areas with different energy of the magnetic anisotropy occurred in different magnetic fields. We showed the possibility of obtaining high density of domain walls in Co(111) film grown on the macrostep-bunched Si(111) by tuning the spatial step density of the Si(111) substrate.

  10. Laser ablation of AlN films grown on sapphire substrate

    SciTech Connect (OSTI)

    Safadi, Mona R.; Thakur, Jagdish S.; Auner, Gregory W. [Department of Biomedical Engineering, Ligon Center of Vision, Wayne State University, Detroit, Michigan 48202 (United States); Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan 48202 (United States); Department of Electrical and Computer Engineering, Department of Biomedical Engineering, Ligon Center of Vision, Wayne State University, Detroit, Michigan 48202 (United States)

    2005-04-15T23:59:59.000Z

    Ablation threshold for single-crystal AlN semiconductor films grown epitaxially on sapphire substrate using indigenously built hollow cathode plasma deposition source molecular-beam epitaxy technique is investigated for a number of pulses by varying the fluence value of each pulse. Using a KrF excimer laser ({lambda}=248 nm and {tau}=25 ns) as a radiation source, we found that ablation of AlN thin films is a discontinuous process and its onset requires a minimum threshold fluence {approx_equal}1.59 J/cm{sup 2}. The ablation depth is analyzed for different numbers of pulses and for each number as a function of increasing fluence values. The results show that the ablation depth increases linearly with increasing pulse fluence. It is found that the use of a single pulse for ablation at a given value of fluence is more efficient than a large number of pulses at the same value of fluence/pulse. In addition, we investigated the lowest pulse-fluence limit that can sustain ablation on a disordered AlN film surface. We present a theoretical discussion about the laser energy absorption mechanism and also the rate of energy transfer from the conduction-band electrons to lattice phonons which can lead to the ablation of AlN film. It is found that the rate of energy transfer increases linearly with increasing temperature of the electron gas.

  11. Composition and Bonding in Amorphous Carbon Films Grown by Ion Beam Assisted Deposition: Influence of the Assistance Voltage

    SciTech Connect (OSTI)

    Albella, J.M.; Banks, J.C.; Climent-Font, A.; Doyle, B.L.; Gago, R.; Jimenez, I.; Terminello, L.J.

    1998-11-12T23:59:59.000Z

    Amorphous carbon films have been grown by evaporation of graphite with concurrent Ar+ ions bombardment assistance. The ion energy has been varied between 0-800 V while keeping a constant ion to carbon atom arrival ratio. Film composition and density were determined by ion scattering techniques (RBS and ERDA), indicating a negligible hydrogen content and a density dependence with the assistance voltage. The bonding structure of the films has been studied by Raman and X-ray Absorption Near-Edge (XANES) spectroscopy. Different qualitative effects have been found depending on the ion energy range. For ion energies below 300 eV, there is a densification of the carbon layer due to the increase in the sp3 content. For ion energies above 300 eV sputtering phenomena dominate over densification, and thinner films are found with increasing assistance voltage until no film is grown over 600 V. The films with the highest SP3 content are grown with intermediate energies between 200-300 V.

  12. Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

    SciTech Connect (OSTI)

    Koleske, Daniel David; Lee, Stephen Roger; Lemp, Thomas Kerr; Coltrin, Michael Elliott; Cross, Karen Charlene; Thaler, Gerald

    2009-07-01T23:59:59.000Z

    With no lattice matched substrate available, sapphire continues as the substrate of choice for GaN growth, because of its reasonable cost and the extensive prior experience using it as a substrate for GaN. Surprisingly, the high dislocation density does not appear to limit UV and blue LED light intensity. However, dislocations may limit green LED light intensity and LED lifetime, especially as LEDs are pushed to higher current density for high end solid state lighting sources. To improve the performance for these higher current density LEDs, simple growth-enabled reductions in dislocation density would be highly prized. GaN nucleation layers (NLs) are not commonly thought of as an application of nano-structural engineering; yet, these layers evolve during the growth process to produce self-assembled, nanometer-scale structures. Continued growth on these nuclei ultimately leads to a fully coalesced film, and we show in this research program that their initial density is correlated to the GaN dislocation density. In this 18 month program, we developed MOCVD growth methods to reduce GaN dislocation densities on sapphire from 5 x 10{sup 8} cm{sup -2} using our standard delay recovery growth technique to 1 x 10{sup 8} cm{sup -2} using an ultra-low nucleation density technique. For this research, we firmly established a correlation between the GaN nucleation thickness, the resulting nucleation density after annealing, and dislocation density of full GaN films grown on these nucleation layers. We developed methods to reduce the nuclei density while still maintaining the ability to fully coalesce the GaN films. Ways were sought to improve the GaN nuclei orientation by improving the sapphire surface smoothness by annealing prior to the NL growth. Methods to eliminate the formation of additional nuclei once the majority of GaN nuclei were developed using a silicon nitride treatment prior to the deposition of the nucleation layer. Nucleation layer thickness was determined using optical reflectance and the nucleation density was determined using atomic force microscopy (AFM) and Nomarski microscopy. Dislocation density was measured using X-ray diffraction and AFM after coating the surface with silicon nitride to delineate all dislocation types. The program milestone of producing GaN films with dislocation densities of 1 x 10{sup 8} cm{sup -2} was met by silicon nitride treatment of annealed sapphire followed by the multiple deposition of a low density of GaN nuclei followed by high temperature GaN growth. Details of this growth process and the underlying science are presented in this final report along with problems encountered in this research and recommendations for future work.

  13. Characterization of Epitaxial Film Silicon Solar Cells Grown on Seeded Display Glass: Preprint

    SciTech Connect (OSTI)

    Young, D. L.; Grover, S.; Teplin, C.; Stradins, P.; LaSalvia, V.; Chuang, T. K.; Couillard, J. G.; Branz, H. M.

    2012-06-01T23:59:59.000Z

    We report characterizations of epitaxial film crystal silicon (c-Si) solar cells with open-circuit voltages (Voc) above 560 mV. The 2-um absorber cells are grown by low-temperature (<750 degrees C) hot-wire CVD (HWCVD) on Corning EAGLE XG display glass coated with a layer-transferred (LT) Si seed. The high Voc is a result of low-defect epitaxial Si (epi-Si) growth and effective hydrogen passivation of defects. The quality of HWCVD epitaxial growth on seeded glass substrates depends on the crystallographic quality of the seed and the morphology of the epitaxial growth surface. Heterojunction devices consist of glass/c-Si LT seed/ epi n+ Si:P/epi n- Si:P/intrinsic a-Si:H/p+ a-Si:H/ITO. Similar devices grown on electronically 'dead' n+ wafers have given Voc {approx}630 mV and {approx}8% efficiency with no light trapping features. Here we study the effects of the seed surface polish on epi-Si quality, how hydrogenation influences the device character, and the dominant junction transport physics.

  14. Epitaxial strontium titanate films grown by atomic layer deposition on SrTiO{sub 3}-buffered Si(001) substrates

    SciTech Connect (OSTI)

    McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Dhamdhere, Ajit; Smith, David J.; Demkov, Alexander A.; Ekerdt, John G. [Department of Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, Texas 78712 (United States); Department of Physics, University of Texas at Austin, 1 University Station C1600, Austin, Texas 78712 (United States); Department of Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, Texas 78712 (United States); Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Department of Physics, University of Texas at Austin, 1 University Station C1600, Austin, Texas 78712 (United States); Department of Chemical Engineering, University of Texas at Austin, 1 University Station C0400, Austin, Texas 78712 (United States)

    2013-01-15T23:59:59.000Z

    Epitaxial strontium titanate (STO) films have been grown by atomic layer deposition (ALD) on Si(001) substrates with a thin STO buffer layer grown by molecular beam epitaxy (MBE). Four unit cells of STO grown by MBE serve as the surface template for ALD growth. The STO films grown by ALD are crystalline as-deposited with minimal, if any, amorphous SiO{sub x} layer at the STO-Si interface. The growth of STO was achieved using bis(triisopropylcyclopentadienyl)-strontium, titanium tetraisopropoxide, and water as the coreactants at a substrate temperature of 250 Degree-Sign C. In situ x-ray photoelectron spectroscopy (XPS) analysis revealed that the ALD process did not induce additional Si-O bonding at the STO-Si interface. Postdeposition XPS analysis also revealed sporadic carbon incorporation in the as-deposited films. However, annealing at a temperature of 250 Degree-Sign C for 30 min in moderate to high vacuum (10{sup -6}-10{sup -9} Torr) removed the carbon species. Higher annealing temperatures (>275 Degree-Sign C) gave rise to a small increase in Si-O bonding, as indicated by XPS, but no reduced Ti species were observed. X-ray diffraction revealed that the as-deposited STO films were c-axis oriented and fully crystalline. A rocking curve around the STO(002) reflection gave a full width at half maximum of 0.30 Degree-Sign {+-} 0.06 Degree-Sign for film thicknesses ranging from 5 to 25 nm. Cross-sectional transmission electron microscopy revealed that the STO films were continuous with conformal growth to the substrate and smooth interfaces between the ALD- and MBE-grown STO. Overall, the results indicate that thick, crystalline STO can be grown on Si(001) substrates by ALD with minimal formation of an amorphous SiO{sub x} layer using a four-unit-cell STO buffer layer grown by MBE to serve as the surface template.

  15. Characterization of oxynitride dielectric films grown in NO/O{sub 2} mixtures by rapid thermal oxynitridation

    SciTech Connect (OSTI)

    EVERIST,SARAH C.; MEISENHEIMER,TIMOTHY L.; NELSON,GERALD C.; SMITH,PAUL M.

    2000-02-29T23:59:59.000Z

    Ultra-thin oxynitride films were grown on Si by direct rapid thermal processing (RTP) oxynitridation in NO/O{sub 2} ambients with NO concentrations from 5% to 50%. During oxynitridation, nitrogen accumulated at the Si/dielectric interface and the average concentration of in N through the resulting films ranged from 0.3 to 3.0 atomic percent. The average concentration of N in the films increased with increasing NO in the ambient gas, but decreased with longer RTP times. The maximum N concentration remained relatively constant for all RTP times and a given NO/O{sub 2} ambient. Re-oxidation following oxynitridation altered L the N profile and improved the electrical characteristics, with an optimal NO/O{sub 2} mixture in the range of 10% to 25% NO. Re-oxidation by RTP improves the electrical characteristics with respect to the films that were not re-oxidized and produces only slight changes in the N distribution or maximum concentration. The electrical results also indicate that oxynitride films are superior to comparably grown oxide films.

  16. Journal of Crystal Growth 310 (2008) 23202325 Self-assembled InGaN quantum dots on GaN emitting at 520 nm grown

    E-Print Network [OSTI]

    Gilchrist, James F.

    2008-01-01T23:59:59.000Z

    materials, and intrinsic quantum mechanical energy loss of the wavelength conversion process via Stokes, Muhammad Jamil, Nelson Tansu Department of Electrical and Computer Engineering, Center for Optical. These results demonstrates that high In-content InGaN QDs can be grown by MOVPE, and can potentially be utilized

  17. Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity

    SciTech Connect (OSTI)

    Chen, Xinchun, E-mail: chenxc1213@gmail.com; Kato, Takahisa [Department of Mechanical Engineering, The University of Tokyo, Tokyo 113-8656 (Japan)

    2014-01-28T23:59:59.000Z

    Growth mechanism and ion energy dependence of composition of ultrasmooth a-C:H:Si films grown from ionization of tetramethylsilane (TMS) and toluene mixture at a fixed gas ratio have been investigated by varying the applied bias voltage. The dynamic scaling theory is employed to evaluate the roughness evolution of a-C:H:Si films, and to extract roughness and growth exponents of ????0.51 and ????0, respectively. The atomically smooth surface of a-C:H:Si films with Ra???0.1?nm is thermally activated by the energetic ion-impact induced subsurface “polishing” process for ion dominated deposition. The ion energy (bias voltage) plays a paramount role in determining the hydrogen incorporation, bonding structure and final stoichiometry of a-C:H:Si films. The hydrogen content in the films measured by ERDA gradually decreases from 36.7 to 17.3 at. % with increasing the bias voltage from 0.25 to 3.5?kV, while the carbon content in the films increases correspondingly from 52.5 to 70.1 at. %. The Si content is kept almost constant at ?9–10 at. %. Depending on the ion-surface interactions, the bonding structure of a-C:H:Si films grown in different ion energy regions evolves from chain-developed polymer-like to cross-linked diamond-like to sp{sup 2}-bonded a–C as revealed by XPS, Raman, and FTIR analysis. Such a structural evolution is reflected in their measured nanomechanical properties such as hardness, modulus, and compressive stress. An enhanced viscoplastic behavior (i.e., viscoplastic exponent of ?0.06) is observed for polymeric a-C:H:Si films. A hydrogen content threshold (H?>?20 at. %) exists for the as-grown a-C:H:Si films to exhibit superlow friction in dry N{sub 2} atmosphere. An extremely low friction coefficient of ?0.001 can be obtained for polymer-like a-C:H:Si film. These near-frictionless a-C:H:Si films are strongly promising for applications in industrial lubricating systems.

  18. Electrical properties of scandium nitride epitaxial films grown on (100) magnesium oxide substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Ohgaki, Takeshi; Watanabe, Ken; Adachi, Yutaka; Sakaguchi, Isao; Hishita, Shunichi; Ohashi, Naoki; Haneda, Hajime [Environment and Energy Materials Research Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Environment and Energy Materials Research Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2013-09-07T23:59:59.000Z

    Scandium nitride (ScN) films were grown on (100) MgO single crystals by a molecular beam epitaxy method. The effects of growth conditions, including [Sc]/[N] ratio, growth temperature, and nitrogen radical state, on the electrical properties of the ScN films were studied. The ScN films comprised many small columnar grains. Hall coefficient measurements confirmed that the ScN films were highly degenerate n-type semiconductors and that the carrier concentration of the ScN films was sensitive to the growth temperature and the nitrogen radical states during the film growth. The carrier concentrations of the ScN films ranged from 10{sup 19}–10{sup 21} cm{sup ?3} while the Hall mobilities ranged from 50–130 cm{sup 2}·V{sup ?1}·s{sup ?1} for undoped films. The temperature-dependent Hall coefficient measurements showed that the carrier concentration is nearly independent of temperature, indicating that the change in resistivity with temperature is explained by a change in the Hall mobility. The temperature-dependence of the Hall mobility was strongly affected by the growth conditions.

  19. Structural, optical, and electrical characterization of hot wall epitaxy grown 1-methoxy-8-hydroxy-9,10-anthraquinone films

    SciTech Connect (OSTI)

    Mahajan, Aman; Bedi, R. K.; Kumar, Subodh

    2001-06-15T23:59:59.000Z

    1-methoxy-8-hydroxy-9,10-anthraquinone compound has been synthesized and its films are grown by the hot wall epitaxy technique onto the glass substrates kept at different temperatures in a vacuum of 10{sup {minus}5}Torr. The experimental conditions are optimized to obtain better crystallinity of the films. The films so prepared have been studied for their structural, optical, and electrical properties. Observations reveal that the crystallinity of the films increases with an increase in substrate temperature. Crystallites as large as 3.30 {mu}m are observed in the case of films deposited at 348 K. Analysis of optical absorption measurements on the films indicate that the interband transition energies lies in the range 1.87{endash}2.02 eV. The conduction in these films is found to be ohmic in nature and appears to take place by thermally activated hopping above intermolecular barriers. The electrical resistivity of films decreases with the increase in temperature, while carrier concentration increases. {copyright} 2001 American Institute of Physics.

  20. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect (OSTI)

    Liliental-Weber, Zuzanna

    2014-04-18T23:59:59.000Z

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  1. Stoichiometric, nonstoichiometric, and locally nonstoichiometric SrTiO{sub 3} films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Fisher, P.; Du, H.; Skowronski, M.; Salvador, P. A. [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Maksimov, O. [Electro-Optics Center, Pennsylvania State University, Freeport, Pennsylvania 16229 (United States); Weng, X. [Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2008-01-01T23:59:59.000Z

    SrTiO{sub 3} films were grown by reactive molecular beam epitaxy to have varying degrees of both global and local cationic nonstoichiometries (with stoichiometry defined as a 1:1 ratio of Sr:Ti). Slight global excesses of Sr and Ti resulted in two-fold reconstructions in the reflection high-energy electron diffraction patterns along the [110] and [100] azimuths, respectively. Larger global nonstoichiometries (2:1 and 1:2 ratios) were also accommodated into the film's crystalline structure and affected the long-range crystalline order as observed in the x-ray diffraction patterns, both of which were related to the parent perovskite pattern. Local nonstoichiometries were introduced by depositing multiple monolayers (MLs) (from 2 to 33) of SrO and TiO{sub 2} in an alternating fashion, while maintaining the global SrTiO{sub 3} stoichiometry. These layered structures of SrO and TiO{sub 2} blocks inter-reacted during growth to form highly crystalline epitaxial SrTiO{sub 3}. Films grown in this manner with blocks thicker than 8 MLs were fully relaxed and, when the block thicknesses ranged between 8 and 10 MLs, the full widths at half maxima of 2{theta} peaks were narrower than the standard SrTiO{sub 3} films having blocks 1 ML thick.

  2. Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH{sub 4}/Ar plasma

    SciTech Connect (OSTI)

    Sankaran, K. J.; Tai, N. H., E-mail: inanlin@mail.tku.edu.tw, E-mail: nhtai@mse.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Huang, B. R.; Saravanan, A. [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Lin, I. N., E-mail: inanlin@mail.tku.edu.tw, E-mail: nhtai@mse.nthu.edu.tw [Department of Physics, Tamkang University, Tamsui 251, Taiwan (China)

    2014-10-28T23:59:59.000Z

    Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH{sub 4} and Ar under different negative bias voltages ranging from ?50 to ?200?V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under ?200?V, the electron field emission (EFE) process can be turned on at a field as small as 4.08?V/?m, attaining a EFE current density as large as 3.19?mA/cm{sup 2} at an applied field of 8.64?V/?m. But the films grown without bias (0?V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH{sub 4}/Ar plasma due to large applied bias voltage of ?200?V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

  3. Structure disorder degree of polysilicon thin films grown by different processing: Constant C from Raman spectroscopy

    SciTech Connect (OSTI)

    Wang, Quan, E-mail: wangq@mail.ujs.edu.cn [School of mechanical engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang, Yanmin; Hu, Ran; Ren, Naifei [School of mechanical engineering, Jiangsu University, Zhenjiang 212013 (China); Ge, Daohan [School of mechanical engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2013-11-14T23:59:59.000Z

    Flat, low-stress, boron-doped polysilicon thin films were prepared on single crystalline silicon substrates by low pressure chemical vapor deposition. It was found that the polysilicon films with different deposition processing have different microstructure properties. The confinement effect, tensile stresses, defects, and the Fano effect all have a great influence on the line shape of Raman scattering peak. But the effect results are different. The microstructure and the surface layer are two important mechanisms dominating the internal stress in three types of polysilicon thin films. For low-stress polysilicon thin film, the tensile stresses are mainly due to the change of microstructure after thermal annealing. But the tensile stresses in flat polysilicon thin film are induced by the silicon carbide layer at surface. After the thin film doped with boron atoms, the phenomenon of the tensile stresses increasing can be explained by the change of microstructure and the increase in the content of silicon carbide. We also investigated the disorder degree states for three polysilicon thin films by analyzing a constant C. It was found that the disorder degree of low-stress polysilicon thin film larger than that of flat and boron-doped polysilicon thin films due to the phase transformation after annealing. After the flat polysilicon thin film doped with boron atoms, there is no obvious change in the disorder degree and the disorder degree in some regions even decreases.

  4. Critical thickness and strain relaxation in molecular beam epitaxy-grown SrTiO{sub 3} films

    SciTech Connect (OSTI)

    Wang, Tianqi; Ganguly, Koustav; Marshall, Patrick; Xu, Peng; Jalan, Bharat [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)] [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2013-11-18T23:59:59.000Z

    We report on the study of the critical thickness and the strain relaxation in epitaxial SrTiO{sub 3} film grown on (La{sub 0.3}Sr{sub 0.7})(Al{sub 0.65}Ta{sub 0.35})O{sub 3} (001) (LSAT) substrate using the hybrid molecular beam epitaxy approach. No change in the film's lattice parameter (both the in-plane and the out-of-plane) was observed up to a film thickness of 180 nm, which is in sharp contrast to the theoretical critical thickness of ?12 nm calculated using the equilibrium theory of strain relaxation. For film thicknesses greater than 180 nm, the out-of-plane lattice parameter was found to decrease hyperbolically in an excellent agreement with the relaxation via forming misfit dislocations. Possible mechanisms are discussed by which the elastic strain energy can be accommodated prior to forming misfit dislocations leading to such anomalously large critical thickness.

  5. High electron mobility thin-film transistors based on Ga{sub 2}O{sub 3} grown by atmospheric ultrasonic spray pyrolysis at low temperatures

    SciTech Connect (OSTI)

    Thomas, Stuart R., E-mail: s.thomas09@imperial.ac.uk, E-mail: thomas.anthopoulos@imperial.ac.uk; Lin, Yen-Hung; Faber, Hendrik; Anthopoulos, Thomas D., E-mail: s.thomas09@imperial.ac.uk, E-mail: thomas.anthopoulos@imperial.ac.uk [Department of Physics, Blackett Laboratory, Imperial College London, London SW7 2BW (United Kingdom); Adamopoulos, George [Department of Engineering, Engineering Building, Lancaster University, Bailrigg, Lancaster LA1 4YR (United Kingdom); Sygellou, Labrini [Institute of Chemical Engineering and High Temperature Processes (ICEHT), Foundation of Research and Technology Hellas (FORTH), Stadiou Strasse Platani, P.O. Box 1414, Patras GR-265 04 (Greece); Stratakis, Emmanuel [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71003 (Greece); Materials Science and Technology Department, University, of Crete, Heraklion 71003 (Greece); Pliatsikas, Nikos; Patsalas, Panos A. [Laboratory of Applied Physics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki GR-54124 (Greece)

    2014-09-01T23:59:59.000Z

    We report on thin-film transistors based on Ga{sub 2}O{sub 3} films grown by ultrasonic spray pyrolysis in ambient atmosphere at 400–450?°C. The elemental, electronic, optical, morphological, structural, and electrical properties of the films and devices were investigated using a range of complementary characterisation techniques, whilst the effects of post deposition annealing at higher temperature (700?°C) were also investigated. Both as-grown and post-deposition annealed Ga{sub 2}O{sub 3} films are found to be slightly oxygen deficient, exceptionally smooth and exhibit a wide energy bandgap of ?4.9?eV. Transistors based on as-deposited Ga{sub 2}O{sub 3} films show n-type conductivity with the maximum electron mobility of ?2?cm{sup 2}/V s.

  6. ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy

    SciTech Connect (OSTI)

    Valente, Anne-Marie [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Eremeev, Grigory V. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Spradlin, Joshua K. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Phillips, H. Lawrence [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Reece, Charles E. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Cao, C. [Illinois Inst. of Technology, Chicago, IL (United States); Proslier, Thomas [Argonne National Laboratory, Argonne, IL (United States); Tao, T. [Univ. of Illinois at Chicago, Chicago, IL (United States)

    2014-02-01T23:59:59.000Z

    In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favourable template for growing the final surface exposed to SRF fields. The influence of the deposition energy on film growth on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

  7. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    SciTech Connect (OSTI)

    Santra, T. S.; Liu, C. H. [Institute of Nanoengineering and Microsystems (NEMS), National Tsing Hua University, Hsinchu, Taiwan 30043 (China); Bhattacharyya, T. K. [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302, West Bengal (India); Patel, P. [Department of Electrical and Computer Engineering, University of Illinois at Urbana Champaign, Urbana, Illinois 61801 (United States); Barik, T. K. [School of Applied Sciences, Haldia Institute of Technology, Haldia 721657, Purba Medinipur, West Bengal (India)

    2010-06-15T23:59:59.000Z

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of C-C, C-H, Si-C, and Si-H bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio I{sub D}/I{sub G}. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  8. Flexible cadmium telluride thin films grown on electron-beam-irradiated graphene/thin glass substrates

    SciTech Connect (OSTI)

    Seo, Won-Oh; Kim, Jihyun, E-mail: hyunhyun7@korea.ac.kr [Department of Chemical and Biological Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-713 (Korea, Republic of); Koo, Yong Hwan; Kim, Byungnam; Lee, Byung Cheol [Radiation Integrated System Research Division, Korea Atomic Energy Research Institute (KAERI), Daejeon 305-353 (Korea, Republic of); Kim, Donghwan [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of)

    2014-08-25T23:59:59.000Z

    We demonstrate the close-spaced sublimation growth of polycrystalline cadmium telluride (CdTe) thin films on a flexible graphene electrode/thin glass substrate structure. Prior to the growth of CdTe films, chemical-vapor-deposited graphene was transferred onto a flexible glass substrate and subjected to electron-beam irradiation at an energy of 0.2?MeV in order to intentionally introduce the defects into it in a controlled manner. Micro-Raman spectroscopy and sheet resistance measurements were employed to monitor the damage and disorder in the electron-beam irradiated graphene layers. The morphology and optical properties of the CdTe thin films deposited on a graphene/flexible glass substrate were systematically characterized. The integration of the defective graphene layers with a flexible glass substrate can be a useful platform to grow various thin-film structures for flexible electronic and optoelectronic devices.

  9. Structural and interfacial characteristics of thin (<10 nm) SiO{sub 2} films grown by electron cyclotron resonance plasma oxidation on [100] Si substrates

    SciTech Connect (OSTI)

    Nguyen, T.D.; Carl, D.A.; Hess, D.W.; Lieberman, M.A.; Gronsky, R.

    1991-04-01T23:59:59.000Z

    The feasibility of fabricating ultra-thin SiO{sub 2} films on the order of a few nanometer thickness has been demonstrated. SiO{sub 2} thin films of approximately 7 nm thickness have been produced by ion flux-controlled Electron Cyclotron Resonance plasma oxidation at low temperature on [100] Si substrates, in reproducible fashion. Electrical measurements of these films indicate that they have characteristics comparable to those of thermally grown oxides. The thickness of the films was determined by ellipsometry, and further confirmed by cross-sectional High-Resolution Transmission Electron Microscopy. Comparison between the ECR and the thermal oxide films shows that the ECR films are uniform and continuous over at least a few microns in lateral direction, similar to the thermal oxide films grown at comparable thickness. In addition, HRTEM images reveal a thin (1--1.5 nm) crystalline interfacial layer between the ECR film and the [100] substrate. Thinner oxide films of approximately 5 nm thickness have also been attempted, but so far have resulted in nonuniform coverage. Reproducibility at this thickness is difficult to achieve.

  10. Structural and interfacial characteristics of thin (<10 nm) SiO sub 2 films grown by electron cyclotron resonance plasma oxidation on (100) Si substrates

    SciTech Connect (OSTI)

    Nguyen, T.D.; Carl, D.A.; Hess, D.W.; Lieberman, M.A.; Gronsky, R.

    1991-04-01T23:59:59.000Z

    The feasibility of fabricating ultra-thin SiO{sub 2} films on the order of a few nanometer thickness has been demonstrated. SiO{sub 2} thin films of approximately 7 nm thickness have been produced by ion flux-controlled Electron Cyclotron Resonance plasma oxidation at low temperature on (100) Si substrates, in reproducible fashion. Electrical measurements of these films indicate that they have characteristics comparable to those of thermally grown oxides. The thickness of the films was determined by ellipsometry, and further confirmed by cross-sectional High-Resolution Transmission Electron Microscopy. Comparison between the ECR and the thermal oxide films shows that the ECR films are uniform and continuous over at least a few microns in lateral direction, similar to the thermal oxide films grown at comparable thickness. In addition, HRTEM images reveal a thin (1--1.5 nm) crystalline interfacial layer between the ECR film and the (100) substrate. Thinner oxide films of approximately 5 nm thickness have also been attempted, but so far have resulted in nonuniform coverage. Reproducibility at this thickness is difficult to achieve.

  11. Identification of Defect Sites on SiO2 Thin Films Grown on Y. D. Kim, T. Wei, and D. W. Goodman*

    E-Print Network [OSTI]

    Goodman, Wayne

    Identification of Defect Sites on SiO2 Thin Films Grown on Mo(112) Y. D. Kim, T. Wei, and D. W properties of SiO2 thin films with a thickness of 0.7-0.8 nm are identical to those of bulk SiO2 properties of the corre- sponding bulk single crystals.1-4 In recent studies SiO2 single-crystalline thin

  12. ZnO film with ultra-low background electron concentration grown by plasma-assisted MBE using Mg film as the buffer layer

    SciTech Connect (OSTI)

    Chen, Mingming; Zhang, Quanlin; Su, Longxing; Su, Yuquan; Cao, Jiashi; Zhu, Yuan; Wu, Tianzhun; Gui, Xuchun [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China)] [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China); Yang, Chunlei [Center for Photovoltaics and Solar Energy, Shen Zhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shen Zhen (China)] [Center for Photovoltaics and Solar Energy, Shen Zhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shen Zhen (China); Xiang, Rong, E-mail: xiangr2@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China)] [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China); Tang, Zikang, E-mail: phzktang@ust.hk [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China) [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2012-09-15T23:59:59.000Z

    Highlights: ? High quality ZnO film with ultra-low background electron concentration is grown by plasma-assisted molecular beam epitaxy using Mg film as a buffer layer. ? High resolution X-ray diffraction and photoluminescence (PL) spectroscopy indicate a high degree of crystallization. ? Hall measurement shows a carrier concentration as low as ?10{sup 14} cm{sup ?3}. ? The mechanism of the improved crystallinity is discussed in detail. -- Abstract: High quality ZnO epilayer with background electron concentration as low as 2.6 × 10{sup 14} cm{sup ?3} was obtained by plasma-assisted MBE on c-sapphire using a thin Mg film as the buffer layer. High-resolution XRD measurement shows a sharp (0 0 2) peak with full width at half maximum (FWHM) of only 0.029°. Photoluminescence spectroscopy presents a weak defect-related near-edge emission. A metal–semiconductor–metal (MSM) typed photodetector based on the material demonstrates a response of ?43 A/W under the bias of 1 V and an ON/OFF ratio of 10{sup 4}. This un-doped ZnO with ultra-low background electron concentration could be a promising starting material for p-type doping.

  13. Top-gate thin-film transistors based on GaN channel layer Rongsheng Chen, Wei Zhou, and Hoi Sing Kwok

    E-Print Network [OSTI]

    liquid gallium target. The GaN TFTs exhibit good electrical performance such as field effect mobility of 1 cm2 /Vs, threshold voltage of Ã?0.4 V, on/off current ratio of 105 , and subthreshold swing of 0 electrical sta- bility of ZnO-based TFTs is still a main issue preventing from commercialization.9 Bottom

  14. Influence of growth temperature on electrical, optical, and plasmonic properties of aluminum:zinc oxide films grown by radio frequency magnetron sputtering

    SciTech Connect (OSTI)

    Dondapati, Hareesh; Santiago, Kevin; Pradhan, A. K. [Center for Materials Research, Norfolk State University, 700 Park Avenue, Norfolk, Virginia 23504 (United States)] [Center for Materials Research, Norfolk State University, 700 Park Avenue, Norfolk, Virginia 23504 (United States)

    2013-10-14T23:59:59.000Z

    We have investigated the responsible mechanism for the observation of metallic conductivity at room temperature and metal-semiconductor transition (MST) at lower temperatures for aluminum-doped zinc oxide (AZO) films. AZO films were grown on glass substrates by radio-frequency magnetron sputtering with varying substrate temperatures (T{sub s}). The films were found to be crystalline with the electrical resistivity close to 1.1 × 10{sup ?3} ? cm and transmittance more than 85% in the visible region. The saturated optical band gap of 3.76 eV was observed for the sample grown at T{sub s} of 400 °C, however, a slight decrease in the bandgap was noticed above 400 °C, which can be explained by Burstein–Moss effect. Temperature dependent resistivity measurements of these highly conducting and transparent films showed a MST at ?110 K. The observed metal-like and metal-semiconductor transitions are explained by taking into account the Mott phase transition and localization effects due to defects. All AZO films demonstrate crossover in permittivity from positive to negative and low loss in the near-infrared region, illustrating its applications for plasmonic metamaterials, including waveguides for near infrared telecommunication region. Based on the results presented in this study, the low electrical resistivity and high optical transmittance of AZO films suggested a possibility for the application in the flexible electronic devices, such as transparent conducting oxide film on LEDs, solar cells, and touch panels.

  15. Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target

    SciTech Connect (OSTI)

    Aguirre, B.; Vemuri, R. S.; Zubia, David; Engelhard, Mark H.; Shutthanandan, V.; Kamala Bharathi, K.; Ramana, Chintalapalle V.

    2011-01-01T23:59:59.000Z

    Hafnium oxide (HfO?) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO? ceramic target has been employed for sputtering while varying the Ts from room temperature to 500?C during deposition. The effect of Ts on the growth and microstructure of deposited HfO? films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO? films. Structural characterization indicates that the HfO? films grown at Ts<200 ?C are amorphous while films grown at Ts>200 ?C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ?C. Nanocrystalline HfO? films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO? films. An interface layer (IL) formation occurs due to reaction at the HfO?-Si interface for HfO? films deposited at Ts>200 ?C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO?-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.

  16. Structural properties of SrO thin films grown by molecular beam epitaxy on LaAlO{sub 3} substrates

    SciTech Connect (OSTI)

    Maksimov, O.; Heydemann, V. D.; Fisher, P.; Skowronski, M.; Salvador, P. A. [Electro-Optics Center, Pennsylvania State University, Freeport, Pennsylvania 16229 (United States); Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2006-12-25T23:59:59.000Z

    SrO films were grown on LaAlO{sub 3} substrates by molecular beam epitaxy and characterized using reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD). The evolution of the RHEED pattern is discussed as a function of film thickness. 500 A thick SrO films were relaxed and exhibited RHEED patterns indicative of an atomically smooth surface having uniform terrace heights. Films had the epitaxial relationship (001){sub SrO}(parallel sign)(001){sub LaAlO{sub 3}}; [010]{sub SrO}(parallel sign)[110]{sub LaAlO{sub 3}}. This 45 deg. in-plane rotation minimizes mismatch and leads to films of high crystalline quality, as verified by Kikuchi lines in the RHEED patterns and narrow rocking curves of the (002) XRD peak.

  17. Photoluminescence of GaAs films grown by vacuum chemical epitaxy

    SciTech Connect (OSTI)

    Bernussi, A.A.; Barreto, C.L.; Carvalho, M.M.G.; Motisuke, P.

    1988-08-01T23:59:59.000Z

    GaAs layers grown by vacuum chemical epitaxy (VCE) are investigated by low-temperature photoluminescence. A qualitative relation between the growth parameters and the shallow-impurity-incorporation mechanism is established. It was observed that the predominant shallow acceptor is carbon, and its incorporation during the growth process decreases with the As:Ga ratio, increases with growth temperature until 750 /sup 0/C, and then it diminishes. In this work we compare the characteristics observed in the VCE system with those in conventional molecular-beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Our results show that this system contains some advantages from both the MBE and MOCVD systems. The photoluminescence spectra also show that at low As:Ga ratios the generation of As vacancies or its complexes is strongly enhanced.

  18. Reactor design for uniform chemical vapor deposition-grown films without substrate rotation

    DOE Patents [OSTI]

    Wanlass, Mark (Golden, CO)

    1987-01-01T23:59:59.000Z

    A quartz reactor vessel for growth of uniform semiconductor films includes a vertical, cylindrical reaction chamber in which a substrate-supporting pedestal provides a horizontal substrate-supporting surface spaced on its perimeter from the chamber wall. A cylindrical confinement chamber of smaller diameter is disposed coaxially above the reaction chamber and receives reaction gas injected at a tangent to the inside chamber wall, forming a helical gas stream that descends into the reaction chamber. In the reaction chamber, the edge of the substrate-supporting pedestal is a separation point for the helical flow, diverting part of the flow over the horizontal surface of the substrate in an inwardly spiraling vortex.

  19. Reactor design for uniform chemical vapor deposition-grown films without substrate rotation

    DOE Patents [OSTI]

    Wanlass, M.

    1985-02-19T23:59:59.000Z

    A quartz reactor vessel for growth of uniform semiconductor films includes a vertical, cylindrical reaction chamber in which a substrate-supporting pedestal provides a horizontal substrate-supporting surface spaced on its perimeter from the chamber wall. A cylindrical confinement chamber of smaller diameter is disposed coaxially above the reaction chamber and receives reaction gas injected at a tangent to the inside chamber wall, forming a helical gas stream that descends into the reaction chamber. In the reaction chamber, the edge of the substrate-supporting pedestal is a separation point for the helical flow, diverting part of the flow over the horizontal surface of the substrate in an inwardly spiraling vortex.

  20. Reactor design for uniform chemical vapor deposition-grown films without substrate rotation

    SciTech Connect (OSTI)

    Wanlass, M.

    1987-03-17T23:59:59.000Z

    A reactor vessel is described for chemical vapor deposition of a uniform semiconductor film on a substrate, comprising: a generally cylindrical reaction chamber for receiving a substrate and a flow of reaction gas capable of depositing a film on the substrate under the conditions of the chamber, the chamber having upper and lower portion and being oriented about a vertical axis; a supporting means having a substrate support surface generally perpendicular to the vertical axis for carrying the substrate within the lower portion of the reaction chamber in a predetermined relative position with respect to the upper portion of the reaction chamber, the upper portion including a cylindrically shaped confinement chamber. The confinement chamber has a smaller diameter than the lower portion of the reaction chamber and is positioned above the substrate support surface; and a means for introducing a reaction gas into the confinement chamber in a nonaxial direction so as to direct the reaction gas into the lower portion of the reaction chamber with a non-axial flow having a rotational component with respect to the vertical axis. In this way the reaction gas defines an inward vortex flow pattern with respect to the substrate surface.

  1. Fabricating superconducting interfaces between artificially grown LaAlO{sub 3} and SrTiO{sub 3} thin films

    SciTech Connect (OSTI)

    Li, Danfeng, E-mail: Danfeng.Li@unige.ch; Gariglio, Stefano; Cancellieri, Claudia; Fête, Alexandre; Stornaiuolo, Daniela; Triscone, Jean-Marc [DPMC, University of Geneva, 24 Quai Ernest Ansermet, 1211 Geneva (Switzerland)

    2014-01-01T23:59:59.000Z

    Realization of a fully metallic two-dimensional electron gas (2DEG) at the interface between artificially grown LaAlO{sub 3} and SrTiO{sub 3} thin films has been an exciting challenge. Here we present for the first time the successful realization of a superconducting 2DEG at interfaces between artificially grown LaAlO{sub 3} and SrTiO{sub 3} thin films. Our results highlight the importance of two factors—the growth temperature and the SrTiO{sub 3} termination. We use local friction force microscopy and transport measurements to determine that in normal growth conditions the absence of a robust metallic state at low temperature in the artificially grown LaAlO{sub 3}/SrTiO{sub 3} interface is due to the nanoscale SrO segregation occurring on the SrTiO{sub 3} film surface during the growth and the associated defects in the SrTiO{sub 3} film. By adopting an extremely high SrTiO{sub 3} growth temperature, we demonstrate a way to realize metallic, down to the lowest temperature, and superconducting 2DEG at interfaces between LaAlO{sub 3} layers and artificially grown SrTiO{sub 3} thin films. This study paves the way to the realization of functional LaAlO{sub 3}/SrTiO{sub 3} superlattices and/or artificial LaAlO{sub 3}/SrTiO{sub 3} interfaces on other substrates.

  2. Co{sub 2}FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    SciTech Connect (OSTI)

    Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr; Tuzcuoglu, H.; Zighem, F.; Chérif, S. M.; Moch, P. [LSPM (CNRS-UPR 3407), 99 avenue Jean-Baptiste Clément, Université Paris 13, 93430 Villetaneuse (France); Gabor, M. S., E-mail: mihai.gabor@phys.utcluj.ro; Petrisor, T. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Tiusan, C. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Institut Jean Lamour, CNRS, Université de Nancy, BP 70239, F–54506 Vandoeuvre (France)

    2014-01-28T23:59:59.000Z

    10?nm and 50?nm Co{sub 2}FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (T{sub a}), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing T{sub a}, while the uniaxial anisotropy field is nearly unaffected by T{sub a} within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with T{sub a}. Finally, the FMR linewidth decreases when increasing T{sub a}, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10{sup ?3} and 1.3×10{sup ?3} for films of 50?nm thickness annealed at 615?°C grown on MgO and on Si, respectively)

  3. Thermal stability of Al- and Zr-doped HfO{sub 2} thin films grown by direct current magnetron sputtering

    SciTech Connect (OSTI)

    Hong, Yeong-Eui; Kim, Yong-Seok; Do, Kihoon; Lee, Dongwon; Ko, Dae-Hong; Ku, Ja-Hum; Kim, Hyoungsub [Department of Ceramic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemoon-Ku, Seoul 120-749 (Korea, Republic of); Semiconductor R and D Division, Samsung Electronics Co, Ltd., San no. 24, Nongseo-Ri, Kiheung-Eup, Yongin-City, Kyunggi-Do 449-711 (Korea, Republic of); Department of Advanced Materials Engineering, Sungkyunkwan University, 300 Chunchun-Dong, Jangan-Ku, Suwon 440-746 (Korea, Republic of)

    2005-09-15T23:59:59.000Z

    Ultrathin HfO{sub 2} dielectric films doped with Al and Zr were grown on p-type Si(100) substrates by dc magnetron sputtering, and their microstructural and electrical properties were examined. Compositions and chemical states of the dielectric films were analyzed by Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy. The HfO{sub 2} films doped with Zr were crystallized even from the as-deposited state, however, the crystallization temperature of the HfO{sub 2} film doped with 16% Al{sub 2}O{sub 3} was delayed up to 900 deg. C. As the annealing temperature increases, high-resolution transmission electron microscopy analyses of all doped HfO{sub 2} films showed an increase of the interfacial layer thickness due to the diffusion of small partial pressure of oxygen in annealing ambient. Our results also showed that the addition of Al{sub 2}O{sub 3} to 14% is not useful for blocking the oxygen diffusion through the (HfO{sub 2}){sub 0.86}(Al{sub 2}O{sub 3}){sub 0.14} film. From the capacitance-voltage measurements, the dielectric constants of the Al- and Zr-doped HfO{sub 2} thin films were measured to be 18.7 and 7.6, respectively.

  4. Domain formation due to surface steps in topological insulator Bi{sub 2}Te{sub 3} thin films grown on Si (111) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Borisova, S.; Kampmeier, J.; Mussler, G.; Grützmacher, D. [Peter Grünberg Institute-9, Forschungszentrum Jülich, Jülich 52425 (Germany) [Peter Grünberg Institute-9, Forschungszentrum Jülich, Jülich 52425 (Germany); Jülich Aachen Research Alliance, Fundamentals of Future Information Technologies, Jülich 52425 (Germany); Luysberg, M. [Peter Grünberg Institute-5 and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich 52425 (Germany)] [Peter Grünberg Institute-5 and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Jülich 52425 (Germany)

    2013-08-19T23:59:59.000Z

    The atomic structure of topological insulators Bi{sub 2}Te{sub 3} thin films on Si (111) substrates grown in van der Waals mode by molecular beam epitaxy has been investigated by in situ scanning tunneling microscopy and scanning transmission electron microscopy. Besides single and multiple quintuple layer (QL) steps, which are typical for the step-flow mode of growth, a number of 0.4 QL steps is observed. We determine that these steps originate from single steps at the substrate surface causing domain boundaries in the Bi{sub 2}Te{sub 3} film. Due to the peculiar structure of these domain boundaries the domains are stable and penetrate throughout the entire film.

  5. Thermoelectric power of Bi and Bi{sub 1{minus}x}Sb{sub x} alloy thin films and superlattices grown by MBE

    SciTech Connect (OSTI)

    Cho, S.; DiVenere, A.; Wong, G.K.; Ketterson, J.B.; Meyer, J.R.; Hoffman, C.A.

    1997-07-01T23:59:59.000Z

    The authors have measured the thermoelectric power (TEP) of MBE-grown epitaxial Bi and Bi{sub 1{minus}x} alloy thin films and superlattices as a function of temperature in the range 20--300 K. They have observed that the TEP of a Bi thin film of 1 {micro}m thickness is in good agreement with the bulk single crystal value and that the TEPs for superlattices with 400 {angstrom} and 800 {angstrom} Bi well thicknesses are enhanced over the bulk values. For x = 0.072 and 0.088 in Bi{sub 1{minus}x}Sb{sub x} thin films showing semiconducting behavior, TEP enhancement was observed by a factor of two. However as Bi or Bi{sub 1{minus}x}Sb{sub x} well thickness decreases in superlattice geometry, the TEP decreases, which may be due to unintentional p-type doping.

  6. Ultraviolet GaN photodetectors on Si via oxide buffer heterostructures with integrated short period oxide-based distributed Bragg reflectors and leakage suppressing metal-oxide-semiconductor contacts

    SciTech Connect (OSTI)

    Szyszka, A., E-mail: szyszka@ihp-microelectronics.com, E-mail: adam.szyszka@pwr.wroc.pl [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Lupina, L.; Lupina, G.; Schubert, M. A.; Zaumseil, P. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Haeberlen, M.; Storck, P.; Thapa, S. B. [Siltronic, Hanns-Seidel-Platz 4, 81737 München (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); BTU Cottbus-Senftenberg, Konrad-Zuse-Strasse 1, 03046 Cottbus (Germany)

    2014-08-28T23:59:59.000Z

    Based on a novel double step oxide buffer heterostructure approach for GaN integration on Si, we present an optimized Metal-Semiconductor-Metal (MSM)-based Ultraviolet (UV) GaN photodetector system with integrated short-period (oxide/Si) Distributed Bragg Reflector (DBR) and leakage suppressing Metal-Oxide-Semiconductor (MOS) electrode contacts. In terms of structural properties, it is demonstrated by in-situ reflection high energy electron diffraction and transmission electron microscopy-energy dispersive x-ray studies that the DBR heterostructure layers grow with high thickness homogeneity and sharp interface structures sufficient for UV applications; only minor Si diffusion into the Y{sub 2}O{sub 3} films is detected under the applied thermal growth budget. As revealed by comparative high resolution x-ray diffraction studies on GaN/oxide buffer/Si systems with and without DBR systems, the final GaN layer structure quality is not significantly influenced by the growth of the integrated DBR heterostructure. In terms of optoelectronic properties, it is demonstrated that—with respect to the basic GaN/oxide/Si system without DBR—the insertion of (a) the DBR heterostructures and (b) dark current suppressing MOS contacts enhances the photoresponsivity below the GaN band-gap related UV cut-off energy by almost up to two orders of magnitude. Given the in-situ oxide passivation capability of grown GaN surfaces and the one order of magnitude lower number of superlattice layers in case of higher refractive index contrast (oxide/Si) systems with respect to classical III-N DBR superlattices, virtual GaN substrates on Si via functional oxide buffer systems are thus a promising robust approach for future GaN-based UV detector technologies.

  7. Interaction of oxygen with samarium on Al{sub 2}O{sub 3} thin film grown on Ni{sub 3}Al(111)

    SciTech Connect (OSTI)

    Cheng, Dingling; Xu, Qian, E-mail: qianxu@ustc.edu.cn, E-mail: jfzhu@ustc.edu.cn; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa, E-mail: qianxu@ustc.edu.cn, E-mail: jfzhu@ustc.edu.cn [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029 (China)] [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei 230029 (China)

    2014-03-07T23:59:59.000Z

    The interaction between oxygen and samarium (Sm) on the well-ordered thin Al{sub 2}O{sub 3} film grown on Ni{sub 3}Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O{sub 2}{sup 2?}) states and regular samarium oxide (O{sup 2?}) states. By contrast, when exposing O{sub 2} to Sm film less than one monolayer on Al{sub 2}O{sub 3}, no O{sub 2}{sup 2?} can be observed. Upon heating to higher temperatures, these metastable O{sub 2}{sup 2?} states dissociate, supplying active O atoms which can diffuse through the Al{sub 2}O{sub 3} thin film to further oxidize the underlying Ni{sub 3}Al(111) substrate, leading to the significant increase of the Al{sub 2}O{sub 3} thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni{sub 3}Al substrate by supplying the active oxygen species at elevated temperatures.

  8. Influence of oxygen pressure and aging on LaAlO{sub 3} films grown by pulsed laser deposition on SrTiO{sub 3} substrates

    SciTech Connect (OSTI)

    Park, Jihwey; Aeppli, Gabriel [London Centre for Nanotechnology, University College London, London WC1H 0AH (United Kingdom); Soh, Yeong-Ah, E-mail: yeongahsoh@gmail.com [London Centre for Nanotechnology, University College London, London WC1H 0AH (United Kingdom); Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); David, Adrian; Lin, Weinan [Division of Physics and Applied Physics, Nanyang Technological University, Singapore 637371 (Singapore); Wu, Tom [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2014-02-24T23:59:59.000Z

    The crystal structures of LaAlO{sub 3} films grown by pulsed laser deposition on SrTiO{sub 3} substrates at oxygen pressure of 10{sup ?3} millibars or 10{sup ?5} millibars, where kinetics of ablated species hardly depend on oxygen background pressure, are compared. Our results show that the interface between LaAlO{sub 3} and SrTiO{sub 3} is sharper when the oxygen pressure is lower. Over time, the formation of various crystalline phases is observed while the crystalline thickness of the LaAlO{sub 3} layer remains unchanged. X-ray scattering as well as atomic force microscopy measurements indicate three-dimensional growth of such phases, which appear to be fed from an amorphous capping layer present in as-grown samples.

  9. Deposition of CVD diamond onto GaN P.W. May a,*, H.Y. Tsai b

    E-Print Network [OSTI]

    Bristol, University of

    of the polycrystalline diamond surface would prevent light from leaking out of the GaN layer and channel it to the endsDeposition of CVD diamond onto GaN P.W. May a,*, H.Y. Tsai b , W.N. Wang c , J.A. Smith a a School performed to deposit continuous layers of CVD diamond onto epitaxial GaN films. Such diamond coatings would

  10. Properties of zinc oxide films grown on sapphire substrates using high-temperature H{sub 2}O generated by a catalytic reaction on platinum nanoparticles

    SciTech Connect (OSTI)

    Yasui, Kanji, E-mail: kyasui@vos.nagaokaut.ac.jp; Takeuchi, Tomohiko; Nagatomi, Eichi; Satomoto, Souichi; Miura, Hitoshi; Kato, Takahiro [Department of Electrical, Electronics and Information Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188 (Japan); Konya, Takayuki [Application Laboratory, Rigaku Corporation, Akishima, Tokyo 196-8666 (Japan)

    2014-03-15T23:59:59.000Z

    The authors investigated the characteristics of ZnO films grown on a-plane (11-20) sapphire substrates at 773–873?K using a reaction between dimethylzinc and high-temperature H{sub 2}O generated by a catalytic reaction on Pt nanoparticles. The growth rate was 0.02–0.07??m min{sup ?1}. The largest electron mobility and the smallest residual carrier concentration for the ZnO films were 169 cm{sup 2} V{sup ?1} s{sup ?1} and 1.6?×?10{sup 17}?cm{sup ?3}, respectively. X-ray diffraction patterns for the ZnO films exhibited intense (0002) and (0004) peaks associated with ZnO (0001) planes. The minimum full width at half maximum of the ?-rocking curve for ZnO (0002) was less than 0.1°. In a ZnO film with a high electron mobility, no rotational domains were identified using a ZnO (10-10) ? scan. From secondary ion mass spectroscopy, a hydrogen concentration of 3?×?10{sup 18}?cm{sup ?3} and a boron concentration of 2–5?×?10{sup 17}?cm{sup ?3} were determined. These were identified as extrinsic donor impurities.

  11. Anti-phase domains in cubic GaN

    SciTech Connect (OSTI)

    Maria Kemper, Ricarda; Schupp, Thorsten; Haeberlen, Maik; Lindner, Joerg; Josef As, Donat [University of Paderborn, Department of Physics, Warburger Str. 100, D-33098 Paderborn (Germany); Niendorf, Thomas; Maier, Hans-Juergen [University of Paderborn, Lehrstuhl fuer Werkstoffkunde, Pohlweg 47-49, D-33098 Paderborn (Germany); Dempewolf, Anja; Bertram, Frank; Christen, Juergen [University of Magdeburg, Institut fuer Festkoerperphysik, P.O. Box 4120, D-39016 Magdeburg (Germany); Kirste, Ronny; Hoffmann, Axel [Technische Universitaet Berlin, Institute of Solid State Physics, Hardenbergstr. 36, D-10623 Berlin (Germany)

    2011-12-15T23:59:59.000Z

    The existence of anti-phase domains in cubic GaN grown on 3C-SiC/Si (001) substrates by plasma-assisted molecular beam epitaxy is reported. The influence of the 3C-SiC/Si (001) substrate morphology is studied with emphasis on the anti-phase domains (APDs). The GaN nucleation is governed by the APDs of the substrate, resulting in equal plane orientation and the same anti-phase boundaries. The presence of the APDs is independent of the GaN layer thickness. Atomic force microscopy surface analysis indicates lateral growth anisotropy of GaN facets in dependence of the APD orientation. This anisotropy can be linked to Ga and N face types of the {l_brace}111{r_brace} planes, similar to observations of anisotropic growth in 3C-SiC. In contrast to 3C-SiC, however, a difference in GaN phase composition for the two types of APDs can be measured by electron backscatter diffraction, {mu}-Raman and cathodoluminescence spectroscopy.

  12. Effects of substrate temperature on properties of NbNx films grown on Nb by pulsed laser deposition

    SciTech Connect (OSTI)

    Ashraf Hassan Farha, Ali Oguz Er, Yüksel Ufuktepe, Ganapati Myneni, Hani E. Elsayed-Ali

    2011-12-01T23:59:59.000Z

    NbN{sub x} films were deposited on Nb substrate using pulsed laser deposition. The effects of substrate deposition temperature, from room temperature to 950 C, on the preferred orientation, phase, and surface properties of NbN{sub x} films were studied by X-ray diffraction, atomic force microscopy, and electron probe micro analyzer. We find that the substrate temperature is a critical factor in determining the phase of the NbN{sub x} films. For a substrate temperature up to 450 C the film showed poor crystalline quality. With temperature increase the film became textured and for a substrate temperature of 650-850 C, mix of cubic {delta}-NbN and hexagonal phases ({beta}-Nb{sub 2}N + {delta}'-NbN) were formed. Films with a mainly {beta}-Nb{sub 2}N hexagonal phase were obtained at deposition temperature above 850 C. The c/a ratio of {beta}-Nb{sub 2}N hexagonal shows an increase with increased nitrogen content. The surface roughness of the NbN{sub x} films increased as the temperature was raised from 450 to 850 C.

  13. Residual and nitrogen doping of homoepitaxial nonpolar m-plane ZnO films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Taienoff, D.; Deparis, C.; Teisseire, M.; Morhain, C. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique (CRHEA-CNRS), Rue B. Gregory, F-06560 Valbonne Sophia Antipolis (France); Al-Khalfioui, M.; Vinter, B.; Chauveau, J.-M. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique (CRHEA-CNRS), Rue B. Gregory, F-06560 Valbonne Sophia Antipolis (France); Universite de Nice Sophia Antipolis, Parc Valrose F-06103 Nice (France)

    2011-03-28T23:59:59.000Z

    We report the homoepitaxial growth by molecular beam epitaxy of high quality nonpolar m-plane ZnO and ZnO:N films over a large temperature range. The nonintentionally doped ZnO layers exhibit a residual doping as low as {approx}10{sup 14} cm{sup -3}. Despite an effective incorporation of nitrogen, p-type doping was not achieved, ZnO:N films becoming insulating. The high purity of the layers and their low residual n-type doping evidence compensation mechanisms in ZnO:N films.

  14. Control of morphology for enhanced electronic transport in PECVD-grown a-Si : H Thin Films

    E-Print Network [OSTI]

    Castro Galnares, Sebastián

    2010-01-01T23:59:59.000Z

    Solar cells have become an increasingly viable alternative to traditional, pollution causing power generation methods. Although crystalline silicon (c-Si) modules make up most of the market, thin films such as hydrogenated ...

  15. Interfacial structure and defect analysis of nonpolar ZnO films grown on R-plane sapphire by molecular beam epitaxy

    SciTech Connect (OSTI)

    Vennegues, P.; Korytov, M.; Deparis, C.; Zuniga-Perez, J.; Morhain, C. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Chauveau, J. M. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Physics Department, University of Nice Sophia-Antipolis, Parc Valrose 06103 Nice (France)

    2008-04-15T23:59:59.000Z

    The interfacial relationship and the microstructure of nonpolar (11-20) ZnO films epitaxially grown on (1-102) R-plane sapphire by molecular beam epitaxy are investigated by transmission electron microscopy. The already-reported epitaxial relationships [1-100]{sub ZnO} parallel [11-20]{sub sapphire} and <0001>{sub ZnO} parallel [-1101]{sub sapphire} are confirmed, and we have determined the orientation of the Zn-O (cation-anion) bond along [0001]{sub ZnO} in the films as being uniquely defined with respect to a reference surface Al-O bond on the sapphire substrate. The microstructure of the films is dominated by the presence of I{sub 1} basal stacking faults [density=(1-2)x10{sup 5} cm{sup -1}] and related partial dislocations [density=(4-7)x10{sup 10} cm{sup -2}]. It is shown that I{sub 1} basal stacking faults correspond to dissociated perfect dislocations, either c or a+c type.

  16. Pressure effect on the magnetization of Sr{sub 2}FeMoO{sub 6} thin films grown by pulsed laser deposition

    SciTech Connect (OSTI)

    Fix, T.; Versini, G.; Loison, J.L.; Colis, S.; Schmerber, G.; Pourroy, G.; Dinia, A. [Institut de Physique et de Chimie des Materiaux de Strasbourg (IPCMS) Unite Mixte de Recherche 7504 du Centre National de la Recherche Scientifique (UMR 7504 du CNRS), Universite Louis Pasteur-Ecole Europeenne de Chimie, Polymeres et Materiaux de Strasbourg - ULP-ECPM, 23 rue du Loess BP43 F-67034 Strasbourg (France)

    2005-01-15T23:59:59.000Z

    Thin films of Sr{sub 2}FeMoO{sub 6} (SFMO) are grown on SrTiO{sub 3} (001) substrates by pulsed laser deposition. The best films provide 3.2{mu}{sub B}/f.u. at 5 K, a Curie temperature above 400 K, low roughness, high crystallinity, and low splashing. Therefore, the use of such SFMO electrodes in magnetic tunnel junctions patterned with conventional lithography is promising. Pseudomorphic epitaxial growth is obtained for thicknesses under 50 nm. Above this thickness the films do not relax homogeneously. A coherent and systematic variation of the magnetization with the deposition conditions is obtained, which highlights a high reproducibility. Under a reasonable O{sub 2} partial pressure to avoid parasite phases, the limiting factor for high magnetization is the total pressure or the deposition rate. Therefore, the deposition rate is suspected to have a strong influence on the Fe/Mo ordering. Highly magnetic samples are obtained under a low gas flow of either a 20% O{sub 2}+N{sub 2} or a 0.3% O{sub 2}+Ar.

  17. aln film deposited: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    deposited by the reactive dc magnetron sputtering technique at room, amorphous and polycrystalline GaN thin films have been deposited using the magnetron sputtering...

  18. aln thin films: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    deposited by the reactive dc magnetron sputtering technique at room, amorphous and polycrystalline GaN thin films have been deposited using the magnetron sputtering...

  19. aln films deposited: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    deposited by the reactive dc magnetron sputtering technique at room, amorphous and polycrystalline GaN thin films have been deposited using the magnetron sputtering...

  20. Residual Stress in CVD-grown 3C-SiC Films on Si Substrates Alex A. Volinsky1

    E-Print Network [OSTI]

    Volinsky, Alex A.

    on 50 mm (100) and (111) Si substrates in a hot-wall CVD reactor. The film tensile residual stress was non-uniform, having a linear profile along the growth direction. This presented a challenge of using to deposit SiC on Si wafers due to their high quality and low cost, in comparison to SiC substrates. However

  1. Roughness analysis applied to niobium thin films grown on MgO(001) surfaces for superconducting radio frequency cavity applications

    SciTech Connect (OSTI)

    D. B. Beringer, W. M. Roach, C. Clavero, C. E. Reece, R. A. Lukaszew

    2013-02-01T23:59:59.000Z

    This paper describes surface studies to address roughness issues inherent to thin film coatings deposited onto superconducting radio frequency (SRF) cavities. This is particularly relevant for multilayered thin film coatings that are being considered as a possible scheme to overcome technical issues and to surpass the fundamental limit of ?50??MV/m accelerating gradient achievable with bulk niobium. In 2006, a model by Gurevich [ Appl. Phys. Lett. 88 012511 (2006)] was proposed to overcome this limit that involves coating superconducting layers separated by insulating ones onto the inner walls of the cavities. Thus, we have undertaken a systematic effort to understand the dynamic evolution of the Nb surface under specific deposition thin film conditions onto an insulating surface in order to explore the feasibility of the proposed model. We examine and compare the morphology from two distinct Nb/MgO series, each with its own epitaxial registry, at very low growth rates and closely examine the dynamical scaling of the surface features during growth. Further, we apply analysis techniques such as power spectral density to the specific problem of thin film growth and roughness evolution to qualify the set of deposition conditions that lead to successful SRF coatings.

  2. Properties of H, O and C in GaN

    SciTech Connect (OSTI)

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W. [Univ. of Florida, Gainesville, FL (United States)] [and others

    1996-04-01T23:59:59.000Z

    The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

  3. Characterization of two different orientations of epitaxial niobium thin films grown on MgO(001) surfaces

    SciTech Connect (OSTI)

    Beringer, D. B.; Lukaszew, R. A. [Department of Physics, The College of William and Mary, Williamsburg, Virginia 23187 (United States)] [Department of Physics, The College of William and Mary, Williamsburg, Virginia 23187 (United States); Roach, W. M.; Clavero, C. [Department of Applied Science, The College of William and Mary, Williamsburg, Virginia 23187 (United States)] [Department of Applied Science, The College of William and Mary, Williamsburg, Virginia 23187 (United States); Reece, C. E. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

    2013-12-14T23:59:59.000Z

    Epitaxial Nb thin films deposited onto the same crystalline insulating surface can evolve in very different fashions depending on specific deposition conditions, thereby affecting their microstructure, surface morphology and superconducting properties. Here, we examine and compare the microstructure and ensuing surface morphology from two distinct Nb/MgO series each with its own epitaxial registry—namely Nb(001)/MgO(001) and Nb(110)/MgO(001)—leading to distinct surface anisotropy and we closely examine the dynamical scaling of the surface features during growth. We compare our findings with those in other metal/MgO epitaxial systems and for the first time, general scaling formalism is applied to analyze anisotropic surfaces exhibiting biaxial symmetry. Further, Power Spectral Density is applied to the specific problem of thin film growth and surface evolution to qualify the set of deposition conditions leading to smoother surfaces. We find good correlation between the surface morphology and microstructure of the various Nb films with superconducting properties such as their residual resistance ratio and lower critical field.

  4. Characterization of two different orientations of epitaxial niobium thin films grown on MgO(001) surfaces

    SciTech Connect (OSTI)

    Beringer, Douglas B. [William and Mary College; Roach, William M. [William and Mary College; Clavero Perez, Cesar [William and Mary College; Reece, Charles E. [JLAB; Lukaszew, Rosa [William and Mary College

    2013-12-01T23:59:59.000Z

    Epitaxial Nb thin films deposited onto the same crystalline insulating surface can evolve in very different fashions depending on specific deposition conditions, thereby affecting their microstructure, surface morphology and superconducting properties. Here, we examine and compare the microstructure and ensuing surface morphology from two distinct Nb/MgO series each with its own epitaxial registry?namely Nb(001)/MgO(001) and Nb(110)/MgO(001)?leading to distinct surface anisotropy and we closely examine the dynamical scaling of the surface features during growth. We compare our findings with those in other metal/MgO epitaxial systems and for the first time, general scaling formalism is applied to analyze anisotropic surfaces exhibiting biaxial symmetry. Further, Power Spectral Density is applied to the specific problem of thin film growth and surface evolution to qualify the set of deposition conditions leading to smoother surfaces. We find good correlation between the surface morphology and microstructure of the various Nb films with superconducting properties such as their residual resistance ratio and lower critical field.

  5. Molecular beam epitaxy-grown wurtzite MgS thin films for solar-blind ultra-violet detection

    SciTech Connect (OSTI)

    Lai, Y. H.; He, Q. L. [Nano Science and Nano Technology Program, The Hong Kong University of Science and Technology, HKSAR, People's Republic of China (China) [Nano Science and Nano Technology Program, The Hong Kong University of Science and Technology, HKSAR, People's Republic of China (China); Department of Physics and William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, HKSAR, People's Republic of China (China); Cheung, W. Y.; Lok, S. K.; Wong, K. S.; Sou, I. K. [Department of Physics and William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, HKSAR, People's Republic of China (China)] [Department of Physics and William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, HKSAR, People's Republic of China (China); Ho, S. K. [Faculty of Science and Technology, University of Macau, Macau, People's Republic of China (China)] [Faculty of Science and Technology, University of Macau, Macau, People's Republic of China (China); Tam, K. W. [Department of Electrical and Electronics Engineering, University of Macau, Macau, People's Republic of China (China)] [Department of Electrical and Electronics Engineering, University of Macau, Macau, People's Republic of China (China)

    2013-04-29T23:59:59.000Z

    Molecular beam epitaxy grown MgS on GaAs(111)B substrate was resulted in wurtzite phase, as demonstrated by detailed structural characterizations. Phenomenological arguments were used to account for why wurtzite phase is preferred over zincblende phase or its most stable rocksalt phase. Results of photoresponse and reflectance measurements performed on wurtzite MgS photodiodes suggest a direct bandgap at around 5.1 eV. Their response peaks at 245 nm with quantum efficiency of 9.9% and enjoys rejection of more than three orders at 320 nm and close to five orders at longer wavelengths, proving the photodiodes highly competitive in solar-blind ultraviolet detection.

  6. Nucleation and Growth of GaN on GaAs (001) Substrates

    SciTech Connect (OSTI)

    Drummond, Timothy J.; Hafich, Michael J.; Heller, Edwin J.; Lee, Stephen R.; Liliental-Weber, Zuzanna; Ruvimov, Sergei; Sullivan, John P.

    1999-05-03T23:59:59.000Z

    The nucleation of GaN thin films on GaAs is investigated for growth at 620 "C. An rf plasma cell is used to generate chemically active nitrogen from N2. An arsenic flux is used in the first eight monolayer of nitride growth to enhance nucleation of the cubic phase. Subsequent growth does not require an As flux to preserve the cubic phase. The nucleation of smooth interfaces and GaN films with low stacking fault densities is dependent upon relative concentrations of active nitrogen species in the plasma and on the nitrogen to gallium flux ratio.

  7. Strained single-crystal Al{sub 2}O{sub 3} grown layer by layer on Nb (110) thin films

    SciTech Connect (OSTI)

    Welander, Paul B.; Eckstein, James N. [Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2007-06-11T23:59:59.000Z

    The authors report on the growth of single-crystal Al{sub 2}O{sub 3} thin films on Nb (110) surfaces. Niobium is grown on {alpha}-Al{sub 2}O{sub 3} (1120), followed by the evaporation of Al in an O{sub 2} background. Initially, Al{sub 2}O{sub 3} grows layer by layer with hexagonal symmetry indicating either {alpha}-Al{sub 2}O{sub 3} (0001) or {gamma}-Al{sub 2}O{sub 3} (111). Diffraction measurements show that the Al{sub 2}O{sub 3} initially grows clamped to the Nb with tensile strain near 10%. This strain relaxes with further deposition and beyond about 50 A ring , the authors observe island growth. Despite the asymmetric misfit between Al{sub 2}O{sub 3} and Nb, the strain is surprisingly isotropic. Josephson junctions employing epitaxial Al{sub 2}O{sub 3} show low effective tunnel barriers and high leakage currents.

  8. Spectroscopic study of semipolar (112{sup ¯}2)-HVPE GaN exhibiting high oxygen incorporation

    SciTech Connect (OSTI)

    Schustek, Philipp, E-mail: philipp.schustek@gmail.com [Institute of Quantum Matter, Ulm University, 89081 Ulm (Germany); Research Unit, Parc Sanitari Sant Joan de Déu and Foundation Sant Joan de Déu, Esplugues de Llobregat, 08950, Barcelona (Spain); Hocker, Matthias; Thonke, Klaus [Institute of Quantum Matter, Ulm University, 89081 Ulm (Germany); Klein, Martin; Scholz, Ferdinand [Institute of Optoelectronics, Ulm University, 89081 Ulm (Germany); Simon, Ulrich [Scientific Computing Centre Ulm, Ulm University, 89081 Ulm (Germany)

    2014-10-28T23:59:59.000Z

    Spatially resolved luminescence and Raman spectroscopy investigations are applied to a series of (112{sup ¯}2)-GaN samples grown by hydride vapor phase epitaxy (HVPE) grown over an initial layer deposited by metal organic vapor phase epitaxy on patterned sapphire substrates. Whereas these two differently grown GaN layers are crystallographically homogeneous, they differ largely in their doping level due to high unintentional oxygen uptake in the HVPE layer. This high doping shows up in luminescence spectra, which can be explained by a free-electron recombination band for which an analytical model considering the Burstein-Moss shift, conduction band tailing, and the bandgap renormalization is included. Secondary ion mass spectrometry, Raman spectroscopy, and Hall measurements concordantly determine the electron density to be above 10{sup 19?}cm{sup ?3}. In addition, the strain state is assessed by Raman spectroscopy and compared to a finite element analysis.

  9. Ferromagnetism and magneto-transport properties of Mn{sub 0.92}Ca{sub 0.08}As thin film grown on Al{sub 2}O{sub 3}(0001) substrate

    SciTech Connect (OSTI)

    Dung, Dang Duc; Van Thiet, Duong [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet road, Ha Noi (Viet Nam); Anh Tuan, Duong; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Feng, Wuwei [School of Materials Science and Engineering, China University of Geosciences, Beijing 100083 (China)

    2014-05-07T23:59:59.000Z

    The epitaxial Mn{sub 0.92}Ca{sub 0.08}As thin film was grown on Al{sub 2}O{sub 3}(0001) substrate by molecular beam epitaxy. The Curie temperature (T{sub C}) around 340?K was enhanced with the addition of Ca, compared to that of bulk MnAs (T{sub C}???318?K). The maxima magnetoresistance, ?2.08% at 0.7?T, was observed near the critical magnetic transition temperature. Moreover, the giant magnetocaloric effect was found with the maximum magnetic entropy change, ?200?J/kgK, around 330?K at 5?T.

  10. Giant magnetocaloric effect of Mn{sub 0.92}Ba{sub 0.08}As thin film grown on Al{sub 2}O{sub 3}(0001) substrate

    SciTech Connect (OSTI)

    Dang Duc Dung [Department of Physics, University of Ulsan, Ulsan 690-749 (Korea, Republic of); Department of General Physics, School of Engineering, Ha Noi University of Science and Technology, 1 Dai Co Viet road, Ha Noi (Viet Nam); Duong Anh Tuan; Duong Van Thiet; Shin, Yooleemi; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 690-749 (Korea, Republic of)

    2012-04-01T23:59:59.000Z

    The epitaxial Mn{sub 0.92}Ba{sub 0.08}As thin film was grown on Al{sub 2}O{sub 3}(0001) substrate by molecular beam epitaxy. The Curie temperature (T{sub C}) around 350 K was enhanced with the addition of Ba, compared to that of bulk MnAs (T{sub C} {approx} 318 K). We have observed the linear resistivity versus the square of temperature and high negative magnetoresistance near Curie temperature. Moreover, the giant magnetocaloric effect was found with maximum magnetic entropy change, 65 J/kgK, around room temperature at 5 T.

  11. Ultra High p-doping Material Research for GaN Based Light Emitters

    SciTech Connect (OSTI)

    Vladimir Dmitriev

    2007-06-30T23:59:59.000Z

    The main goal of the Project is to investigate doping mechanisms in p-type GaN and AlGaN and controllably fabricate ultra high doped p-GaN materials and epitaxial structures. Highly doped p-type GaN-based materials with low electrical resistivity and abrupt doping profiles are of great importance for efficient light emitters for solid state lighting (SSL) applications. Cost-effective hydride vapor phase epitaxial (HVPE) technology was proposed to investigate and develop p-GaN materials for SSL. High p-type doping is required to improve (i) carrier injection efficiency in light emitting p-n junctions that will result in increasing of light emitting efficiency, (ii) current spreading in light emitting structures that will improve external quantum efficiency, and (iii) parameters of Ohmic contacts to reduce operating voltage and tolerate higher forward currents needed for the high output power operation of light emitters. Highly doped p-type GaN layers and AlGaN/GaN heterostructures with low electrical resistivity will lead to novel device and contact metallization designs for high-power high efficiency GaN-based light emitters. Overall, highly doped p-GaN is a key element to develop light emitting devices for the DOE SSL program. The project was focused on material research for highly doped p-type GaN materials and device structures for applications in high performance light emitters for general illumination P-GaN and p-AlGaN layers and multi-layer structures were grown by HVPE and investigated in terms of surface morphology and structure, doping concentrations and profiles, optical, electrical, and structural properties. Tasks of the project were successfully accomplished. Highly doped GaN materials with p-type conductivity were fabricated. As-grown GaN layers had concentration N{sub a}-N{sub d} as high as 3 x 10{sup 19} cm{sup -3}. Mechanisms of doping were investigated and results of material studies were reported at several International conferences providing better understanding of p-type GaN formation for Solid State Lighting community. Grown p-type GaN layers were used as substrates for blue and green InGaN-based LEDs made by HVPE technology at TDI. These results proved proposed technical approach and facilitate fabrication of highly conductive p-GaN materials by low-cost HVPE technology for solid state lighting applications. TDI has started the commercialization of p-GaN epitaxial materials.

  12. Laser damage properties of TiO{sub 2}/Al{sub 2}O{sub 3} thin films grown by atomic layer deposition

    SciTech Connect (OSTI)

    Wei Yaowei; Liu Hao; Sheng Ouyang; Liu Zhichao; Chen Songlin; Yang Liming

    2011-08-20T23:59:59.000Z

    Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO{sub 2}/Al{sub 2}O{sub 3} films at 110 deg. C and 280 deg. C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the films deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100 mm {Phi} samples, and the transmission is more than 99.8% at 1064 nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO{sub 2}/Al{sub 2}O{sub 3} films, the LIDTs were 6.73{+-}0.47 J/cm{sup 2} and 6.5{+-}0.46 J/cm{sup 2} at 110 deg. C on fused silica and BK7 substrates, respectively. The LIDTs at 110 deg. C are notably better than 280 deg. C.

  13. Nanostructured light-absorbing crystalline CuIn{sub (1–x)}Ga{sub x}Se{sub 2} thin films grown through high flux, low energy ion irradiation

    SciTech Connect (OSTI)

    Hall, Allen J.; Hebert, Damon; Rockett, Angus A. [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, Illinois 61801 (United States)] [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, Illinois 61801 (United States); Shah, Amish B. [Center for Microanalysis of Materials, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Ave, Urbana, Illinois 61801 (United States)] [Center for Microanalysis of Materials, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Ave, Urbana, Illinois 61801 (United States); Bettge, Martin [Chemical Sciences and Engineering, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60438 (United States)] [Chemical Sciences and Engineering, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60438 (United States)

    2013-10-21T23:59:59.000Z

    A hybrid effusion/sputtering vacuum system was modified with an inductively coupled plasma (ICP) coil enabling ion assisted physical vapor deposition of CuIn{sub 1?x}Ga{sub x}Se{sub 2} thin films on GaAs single crystals and stainless steel foils. With <80 W rf power to the ICP coil at 620–740 °C, film morphologies were unchanged compared to those grown without the ICP. At low temperature (600–670 °C) and high rf power (80–400 W), a light absorbing nanostructured highly anisotropic platelet morphology was produced with surface planes dominated by (112){sub T} facets. At 80–400 W rf power and 640–740 °C, both interconnected void and small platelet morphologies were observed while at >270 W and above >715 °C nanostructured pillars with large inter-pillar voids were produced. The latter appeared black and exhibited a strong (112){sub T} texture with interpillar twist angles of ±8°. Application of a negative dc bias of 0–50 V to the film during growth was not found to alter the film morphology or stoichiometry. The results are interpreted as resulting from the plasma causing strong etching favoring formation of (112){sub T} planes and preferential nucleation of new grains, balanced against conventional thermal diffusion and normal growth mechanisms at higher temperatures. The absence of effects due to applied substrate bias suggests that physical sputtering or ion bombardment effects were minimal. The nanostructured platelet and pillar films were found to exhibit less than one percent reflectivity at angles up to 75° from the surface normal.

  14. Epitaxial Ba{sub 2}IrO{sub 4} thin-films grown on SrTiO{sub 3} substrates by pulsed laser deposition

    SciTech Connect (OSTI)

    Nichols, J., E-mail: john.nichols@uky.edu; Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)

    2014-03-24T23:59:59.000Z

    We have synthesized epitaxial Ba{sub 2}IrO{sub 4} (BIO) thin-films on SrTiO{sub 3} (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metal-insulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr{sub 2}IrO{sub 4}. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting physical properties predicted in layered iridates.

  15. Anomalous Chemical Expansion Behavior of Pr[subscript 0.2]Ce[subscript 0.8]O[subscript 2-?] Thin Films Grown by Pulsed Laser Deposition

    E-Print Network [OSTI]

    Kuru, Y.

    The chemomechanical and electrical properties of (Pr,Ce)O[subscript 2-?] thin films were studied between 30 and 875°C in air by in situ X-ray diffraction and complex impedance spectroscopy measurements. Reduction/oxidation ...

  16. Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes

    SciTech Connect (OSTI)

    Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)] [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2013-01-28T23:59:59.000Z

    We demonstrate a GaN quantum dot ultraviolet light-emitting diode that uses tunnel injection of carriers through AlN barriers into the active region. The quantum dot heterostructure is grown by molecular beam epitaxy on AlN templates. The large lattice mismatch between GaN and AlN favors the formation of GaN quantum dots in the Stranski-Krastanov growth mode. Carrier injection by tunneling can mitigate losses incurred in hot-carrier injection in light emitting heterostructures. To achieve tunnel injection, relatively low composition AlGaN is used for n- and p-type layers to simultaneously take advantage of effective band alignment and efficient doping. The small height of the quantum dots results in short-wavelength emission and are simultaneously an effective tool to fight the reduction of oscillator strength from quantum-confined Stark effect due to polarization fields. The strong quantum confinement results in room-temperature electroluminescence peaks at 261 and 340 nm, well above the 365 nm bandgap of bulk GaN. The demonstration opens the doorway to exploit many varied features of quantum dot physics to realize high-efficiency short-wavelength light sources.

  17. On the reliability of nanoindentation hardness of Al{sub 2}O{sub 3} films grown on Si-wafer by atomic layer deposition

    SciTech Connect (OSTI)

    Liu, Xuwen, E-mail: xuwen.liu@aalto.fi; Haimi, Eero; Hannula, Simo-Pekka [Department of Materials Science and Engineering, Aalto University School of Chemical Technology, Vuorimiehentie 2A, FI-00076 Espoo (Finland); Ylivaara, Oili M. E.; Puurunen, Riikka L. [VTT Technical Research Centre of Finland, Tietotie 3, FI-02044 Espoo (Finland)

    2014-01-15T23:59:59.000Z

    The interest in applying thin films on Si-wafer substrate for microelectromechanical systems devices by using atomic layer deposition (ALD) has raised the demand on reliable mechanical property data of the films. This study aims to find a quick method for obtaining nanoindentation hardness of thin films on silicon with improved reliability. This is achieved by ensuring that the film hardness is determined under the condition that no plastic deformation occurs in the substrate. In the study, ALD Al{sub 2}O{sub 3} films having thickness varying from 10 to 600?nm were deposited on a single-side polished silicon wafer at 300?°C. A sharp cube-corner indenter was used for the nanoindentation measurements. A thorough study on the Si-wafer reference revealed that at a specific contact depth of about 8?nm the wafer deformation in loading transferred from elastic to elastic–plastic state. Furthermore, the occurrence of this transition was associated with a sharp increase of the power-law exponent, m, when the unloading data were fitted to a power-law relation. Since m is only slightly material dependent and should fall between 1.2 and 1.6 for different indenter geometry having elastic contact to common materials, it is proposed that the high m values are the results from the inelastic events during unloading. This inelasticity is linked to phase transformations during pressure releasing, a unique phenomenon widely observed in single crystal silicon. Therefore, it is concluded that m could be used to monitor the mechanical state of the Si substrate when the whole coating system is loaded. A suggested indentation depth range can then be assigned to each film thickness to provide guidelines for obtaining reliable property data. The results show good consistence for films thicker than 20?nm and the nanoindentation hardness is about 11?GPa independent of film thickness.

  18. Deposition and characterization of Cd{sub 1?x}Mg{sub x}Te thin films grown by a novel cosublimation method

    SciTech Connect (OSTI)

    Kobyakov, Pavel S., E-mail: pskobyak@rams.colostate.edu; Swanson, Drew E.; Sampath, Walajabad S. [Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, Colorado 80523 (United States); Moore, Andrew; Raguse, John M. [Department of Physics, Colorado State University, 1875 Campus Delivery, Fort Collins, Colorado 80523 (United States)

    2014-03-15T23:59:59.000Z

    Photovoltaic cells utilizing the CdS/CdTe structure have improved substantially in the past few years. Despite the recent advances, the efficiency of CdS/CdTe cells is still significantly below their Shockley–Queisser limit. CdTe based ternary alloy thin films, such as Cd{sub 1?x}Mg{sub x}Te (CMT), could be used to improve efficiency of CdS/CdTe photovoltaic cells. Higher band gap Cd{sub 1?x}Mg{sub x}Te films can be the absorber in top cells of a tandem structure or an electron reflector layer in CdS/CdTe cells. A novel cosublimation method to deposit CMT thin films has been developed. This method can deposit CMT films of band gaps ranging from 1.5 to 2.3?eV. The cosublimation method is fast, repeatable, and scalable for large areas, making it suitable for implementing into large-scale manufacturing. Characterization of as-deposited CMT films, with x varying from 0 to 0.35, reveals a linear relationship between Mg content measured by energy dispersive x-ray spectroscopy and the optical band gap. Glancing angle x-ray diffraction (GAXRD) measurements of Cd{sub 1?x}Mg{sub x}Te films show a zinc-blende structure similar to CdTe. Furthermore, increasing Mg content decreases the lattice parameter and the grain size. GAXRD shows the films are under mild tension after deposition.

  19. Structure and electronic properties of mixed (a?+?c) dislocation cores in GaN

    SciTech Connect (OSTI)

    Horton, M. K., E-mail: m.horton11@imperial.ac.uk [Department Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Rhode, S. L. [Department Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Moram, M. A. [Department Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Department Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2014-08-14T23:59:59.000Z

    Classical atomistic models and atomic-resolution scanning transmission electron microscopy studies of GaN films reveal that mixed (a?+?c)-type dislocations have multiple different core structures, including a dissociated structure consisting of a planar fault on one of the (12{sup ¯}10) planes terminated by two different partial dislocations. Density functional theory calculations show that all cores introduce localized states into the band gap, which affects device performance.

  20. Thermal conductivity of Er{sup +3}:Y{sub 2}O{sub 3} films grown by atomic layer deposition

    SciTech Connect (OSTI)

    Raeisi Fard, Hafez; Hess, Andrew; Pashayi, Kamyar; Borca-Tasciuc, Theodorian, E-mail: borcat@rpi.edu [Mechanical, Aerospace and Nuclear Engineering Department, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)] [Mechanical, Aerospace and Nuclear Engineering Department, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Becker, Nicholas; Proslier, Thomas; Pellin, Michael [Material Sciences Division, Argonne National Laboratory 9700 S. Cass Avenue, Lemont, Illinois 60439 (United States)] [Material Sciences Division, Argonne National Laboratory 9700 S. Cass Avenue, Lemont, Illinois 60439 (United States)

    2013-11-04T23:59:59.000Z

    Cross-plane thermal conductivity of 800, 458, and 110?nm erbium-doped crystalline yttria (Er{sup +3}:Y{sub 2}O{sub 3}) films deposited via atomic layer deposition was measured using the 3? method at room temperature. Thermal conductivity results show 16-fold increase in thermal conductivity from 0.49?W m{sup ?1}K{sup ?1} to 8?W m{sup ?1}K{sup ?1} upon post deposition annealing, partially due to the suppression of the number of the -OH/H{sub 2}O bonds in the films after annealing. Thermal conductivity of the annealed film was ?70% lower than undoped bulk single crystal yttria. The cumulative interface thermal resistivity of substrate-Er{sup +3}:Y{sub 2}O{sub 3}-metal heater was determined to be ?2.5?×?10{sup ?8} m{sup 2} K/W.

  1. Phase Transitions and High-Voltage Electrochemical Behavior of LiCoO2 Thin Films Grown by Pulsed Laser Deposition

    E-Print Network [OSTI]

    Ceder, Gerbrand

    Laser Deposition H. Xia,a L. Lu,b,z Y. S. Meng,c and G. Cederc, * a Advanced Materials for Micro behavior of LiCoO2 thin-film cathodes prepared by pulsed laser deposition are studied for charging voltages- discharge curves. Ex situ X-ray diffraction measurements confirm structural changes and a phase transition

  2. Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities

    SciTech Connect (OSTI)

    Bejtka, K.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); CRHEA-CNRS, Rue Bernard Gregory, Parc Sophia Antipolis, 06560 Valbonne (France); Reveret, F.; Vasson, A.; Leymarie, J. [LASMEA, UMR 6602 UBP/CNRS, 24 Avenue des Landais, F-63177 Aubiere Cedex (France); Edwards, P. R. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Sellers, I. R.; Duboz, J. Y.; Leroux, M.; Semond, F. [CRHEA-CNRS, Rue Bernard Gregory, Parc Sophia Antipolis, 06560 Valbonne (France)

    2008-06-16T23:59:59.000Z

    Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The {lambda}/2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5 K: anticrossing with a normal mode splitting of 43{+-}2 meV and 56{+-}2 meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance.

  3. Donor and acceptor levels in ZnO homoepitaxial thin films grown by molecular beam epitaxy and doped with plasma-activated nitrogen

    SciTech Connect (OSTI)

    Muret, Pierre [Departement Nanosciences, Institut Neel, CNRS, BP166, 38042 Grenoble and Universite Joseph Fourier, Grenoble (France); Tainoff, Dimitri; Morhain, Christian [Centre de Recherche sur l'HeteroEpitaxie et ses Applications, rue Bernard Gregory, CNRS, 06500 Valbonne (France); Chauveau, Jean-Michel [Centre de Recherche sur l'HeteroEpitaxie et ses Applications, rue Bernard Gregory, CNRS, 06500 Valbonne (France); Universite de Nice Sophia Antipolis, Parc Valrose F-06103 Nice (France)

    2012-09-17T23:59:59.000Z

    Deep level transient spectroscopy of both majority and minority carrier traps is performed in a n-type, nitrogen doped homoepitaxial ZnO layer grown on a m-plane by molecular beam epitaxy. Deep levels, most of them being not detected in undoped ZnO, lie close to the band edges with ionization energies in the range 0.12-0.60 eV. The two hole traps with largest capture cross sections are likely acceptors, 0.19 and 0.48 eV from the valence band edge, able to be ionized below room temperature. These results are compared with theoretical predictions and other experimental data.

  4. Film properties of low temperature HfO{sub 2} grown with H{sub 2}O, O{sub 3}, or remote O{sub 2}-plasma

    SciTech Connect (OSTI)

    Richter, Claudia, E-mail: Claudia.Richter@namlab.com; Schenk, Tony; Schroeder, Uwe [NaMLab gGmbH, Noethnitzerstr. 64, 01187 Dresden (Germany); Mikolajick, Thomas [NaMLab gGmbH, Noethnitzerstr. 64, 01187 Dresden, Germany and Institut für Halbleiter und Mikrosystemtechnik, TU Dresden, Noethnitzerstr. 64, 01187 Dresden (Germany)

    2014-01-15T23:59:59.000Z

    A reduction of the deposition temperature is necessary for atomic layer deposition (ALD) on organic devices. HfO{sub 2} films were deposited by ALD on silicon substrates in a wide temperature range from 80 to 300?°C with tetrakis[ethylmethylamino]hafnium as metal precursor and H{sub 2}O, O{sub 3}, or an remote O{sub 2}-plasma as oxygen source. Growth rate and density were correlated to electrical properties like dielectric constant and leakage current of simple capacitor structures to evaluate the impact of different process conditions. Process optimizations were performed to reduce film imperfections visible at lower deposition temperatures. Additionally, the influence of postdeposition annealing on the structural and electrical properties was studied.

  5. Structural, magnetic, and electronic properties of GdTiO{sub 3} Mott insulator thin films grown by pulsed laser deposition

    SciTech Connect (OSTI)

    Grisolia, M. N.; Bruno, F. Y.; Sando, D.; Jacquet, E.; Barthélémy, A.; Bibes, M., E-mail: manuel.bibes@thalesgroup.com [Unité Mixte de Physique, CNRS-Thales, 1 Av. Augustin Fresnel, Campus de l'Ecole Polytechnique, 91120 Palaiseau, France and Université Paris-Sud, 91405 Orsay (France); Zhao, H. J. [Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chen, X. M. [Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Bellaiche, L. [Physics Department and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2014-10-27T23:59:59.000Z

    We report on the optimization process to synthesize epitaxial thin films of GdTiO{sub 3} on SrLaGaO{sub 4} substrates by pulsed laser deposition. Optimized films are free of impurity phases and are fully strained. They possess a magnetic Curie temperature T{sub C}?=?31.8?K with a saturation magnetization of 4.2??{sub B} per formula unit at 10?K. Transport measurements reveal an insulating response, as expected. Optical spectroscopy indicates a band gap of ?0.7?eV, comparable to the bulk value. Our work adds ferrimagnetic orthotitanates to the palette of perovskite materials for the design of emergent strongly correlated states at oxide interfaces using a versatile growth technique such as pulsed laser deposition.

  6. High Efficiency m-plane LEDs on Low Defect Density Bulk GaN Substrates

    SciTech Connect (OSTI)

    David, Aurelien

    2012-10-15T23:59:59.000Z

    Solid-state lighting is a key technology for reduction of energy consumption in the US and worldwide. In principle, by replacing standard incandescent bulbs and other light sources with sources based on light-emitting diodes (LEDs), ultimate energy efficiency can be achieved. The efficiency of LEDs has improved tremendously over the past two decades, however further progress is required for solid- state lighting to reach its full potential. The ability of an LED at converting electricity to light is quantified by its internal quantum efficiency (IQE). The material of choice for visible LEDs is Gallium Nitride (GaN), which is at the basis of blue-emitting LEDs. A key factor limiting the performance of GaN LEDs is the so-called efficiency droop, whereby the IQE of the LED decreases significantly at high current density. Despite decades of research, efficiency droop remains a major issue. Since high-current operation is necessary for practical lighting applications, reducing droop is a major challenge for the scientific community and the LED industry. Our approach to solving the droop issue is the use of newly available low-defect-density bulk GaN non-polar substrates. In contrast to the standard foreign substrates (sapphire, silicon carbide, silicon) used in the industry, we have employed native bulk GaN substrates with very low defect density, thus ensuring exquisite material quality and high IQE. Whereas all commercial LEDs are grown along the c-plane crystal direction of GaN, we have used m-plane non-polar substrates; these drastically modify the physical properties of the LED and enable a reduction of droop. With this approach, we have demonstrated very high IQE performance and low droop. Our results focused on violet and blue LEDs. For these, we have demonstrated very high peak IQEs and current droops of 6% and 10% respectively (up to a high current density of 200A.cm-2). All these results were obtained under electrical operation. These high IQE and low droop values are in line with the program’s milestones. They demonstrate that bulk non-polar GaN substrates represent a disruptive technology for LED performance. Application of this technology to real-world products is feasible, provided that the cost of GaN substrates is compatible with the market’s requirement.

  7. UV photoemission efficiency of polycrystalline CVD diamond films

    E-Print Network [OSTI]

    Tremsin, A S; Siegmund, OHW

    2005-01-01T23:59:59.000Z

    efficiency of a polycrystalline diamond planar reflectivequantum efficiency of polycrystalline diamond films grown onallowed the growth of polycrystalline diamond thin films on

  8. Polarity determination for MOCVD growth of GaN on Si(111) by convergent beam electron diffraction[Metal Organic Chemical Vapor Deposition

    SciTech Connect (OSTI)

    Zhao, L.; Marchand, H.; Fini, P.; Denbaars, S.P.; Mishra, U.K.; Speck, J.S.

    2000-07-01T23:59:59.000Z

    The polarity of laterally epitaxially overgrown (LEO) GaN on Si(111) with an AlN buffer layer grown by MOCVD has been studied by convergent beam electron diffraction (CBED). The LEO GaN was studied by cross-section and plan-view transmission electron microscopy (TEM). The threading dislocation density is less than 10{sup 8} cm{sup {minus}2} and no inversion domains were observed. CBED patterns were obtained at 200 kV for the <1 {bar 1} 00> zone. Simulation was done by many-beam solution with 33 zero-order beams. The comparison of experimental CBED patterns and simulated patterns indicates that the polarity of GaN on Si(111) is Ga face.

  9. Use of reflectance spectroscopy for in-situ monitoring of InP/InGaAsP films grown by MOVPE

    SciTech Connect (OSTI)

    Lum, R.M.; McDonald, M.L.; Bean, J.C.; Vandenberg, J.; Pernell, T.L.; Chu, S.N.G. [Bell Labs., Murray Hill, NJ (United States); Robertson, A.; Karp, A. [Bell Labs., Princeton, NJ (United States). Engineering Research Center

    1996-12-31T23:59:59.000Z

    The authors report the first use of in-situ reflectance spectroscopy for real-time monitoring of the epitaxial growth of InP/InGaAsP films. Optical monitoring of this materials system has been limited by the strong absorption of InP/InGaAsP in the spectral range of commonly available Si-based array detectors ({lambda}{approximately}400--1,100 nm). In this work a Si/PbS dual detector arrangement, with a wavelength range 400--2,500 nm, and a grating spectrometer were used to acquire spectral data beyond the absorption regions of InP and InGaAsP. The quartz MOVPE reactor was modified with a simple optical viewport for acquisition of normal incidence reflectance spectra. Data were obtained on InP/InGaAs heterostructures, 1.55 {micro}m InP/InGaAsP Bragg stacks, and 1.3 {micro}m InGaAsP MQW laser structures.

  10. 4076 J. Phys. Chem. 1994,98, 4076-4082 Adsorption and Reaction of [Re2(CO)lo]on Ultrathin MgO Films Grown on a Mo(ll0) Surface

    E-Print Network [OSTI]

    Goodman, Wayne

    Grown on a Mo(ll0) Surface: Characterization by Infrared Reflection-Absorption Spectroscopy) grown on a Mo(110) substrate was investigated with infrared reflection-absorption spectroscopy on the MgO(ll1) surface. Upon heating to temperatures >400K, [Re(C0)4{OMg}]2 was decarbonylated, forming [Re

  11. Solution grown antimony doped zinc oxide films

    E-Print Network [OSTI]

    Riley, Conor T.

    2012-01-01T23:59:59.000Z

    D,; Nanowire dye-sensitized solar cells, Nat. Mater. 2005,three-dimensional dye-sensitized solar cells, Angew. Chem.photoelectrode in dye- sensitized solar cells, Cryst. Growth

  12. Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.

    SciTech Connect (OSTI)

    Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur; Siegal, Michael P.; Li, Qiming; Jones, Reese E.; Westover, Tyler; Wang, George T.; Zhou, Xiao Wang; Talin, Albert Alec; Bogart, Katherine Huderle Andersen; Harris, C. Thomas; Huang, Jian Yu

    2010-09-01T23:59:59.000Z

    We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such as ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in concert with sophisticated molecular-dynamics calculations of surface and defect-mediated NW thermal transport. This proposal seeks to elucidate long standing material science questions for GaN while addressing issues critical to realizing reliable GaN NW devices.

  13. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Limbach, F. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Gotschke, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Stoica, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Calarco, R. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Sutter, E. [Brookhaven National Lab., Upton, NY (United States); Ciston, J. [Brookhaven National Lab., Upton, NY (United States); Cusco, R. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Artus, L. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Kremling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Hofling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Worschech, L. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Grutzmacher, D. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany)

    2011-01-07T23:59:59.000Z

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.

  14. ARM - AMIE Gan Island - Data Plots

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsrucLasDelivered‰PNGExperience4AJ01) (See95TI07)Operations2AP-XPSAPS50 -IssuegovFieldOverviewGan

  15. Epitaxial TiN,,001... Grown and Analyzed In situ by XPS and UPS. II. Analysis of Ar

    E-Print Network [OSTI]

    Gall, Daniel

    Epitaxial TiN,,001... Grown and Analyzed In situ by XPS and UPS. II. Analysis of Ar¿ Sputter Etched and UPS were used to study epitaxial TiN 001 layers grown in situ which were Ar sputter etched. The films Host Material: epitaxial TiN(001) thin film sputter etched Instrument: Physical Electronics, Inc. 5400

  16. TEM studies of laterally overgrown GaN layers grown on non-polar substrates

    E-Print Network [OSTI]

    Liliental-Weber, Z.; Ni, X.; Morkoc, H.

    2006-01-01T23:59:59.000Z

    73, 1691 (1998). 11. H. Marchand, J.P. Ibbetson, P.T. Fini,1999). 17. P. Fini, H. Marchand, J.P. Ibbetson, B. Moran, L.

  17. GaN quantum dot superlattices grown by molecular beam epitaxy at high temperature

    E-Print Network [OSTI]

    P-based optoelectronic devices with Si microelectronic devices. This method uses a Au-Ge eutectic alloy as the bonding. The realization of integrafion of GaAs- and InP-based optoelectronic devices with Si microelectronic components

  18. ARM MJO Investigation Experiment on Gan Island (AMIE-Gan) Science Plan

    SciTech Connect (OSTI)

    Long, CL; Del Genio, A; Deng, M; Fu, X; Gustafson, W; Houze, R; Jakob, C; Jensen, M; Johnson, R; Liu, X; Luke, E; May, P; McFarlane, S; Minnis, P; Schumacher, C; Vogelmann, A; Wang, Y; Webster, P; Xie, S; Zhang, C

    2011-04-11T23:59:59.000Z

    The overarching campaign, which includes the ARM Mobile Facility 2 (AMF2) deployment in conjunction with the Dynamics of the Madden-Julian Oscillation (DYNAMO) and the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) campaigns, is designed to test several current hypotheses regarding the mechanisms responsible for Madden-Julian Oscillation (MJO) initiation and propagation in the Indian Ocean area. The synergy between the proposed AMF2 deployment with DYNAMO/CINDY2011, and the corresponding funded experiment on Manus, combine for an overarching ARM MJO Investigation Experiment (AMIE) with two components: AMF2 on Gan Island in the Indian Ocean (AMIE-Gan), where the MJO initiates and starts its eastward propagation; and the ARM Manus site (AMIE-Manus), which is in the general area where the MJO usually starts to weaken in climate models. AMIE-Gan will provide measurements of particular interest to Atmospheric System Research (ASR) researchers relevant to improving the representation of MJO initiation in climate models. The framework of DYNAMO/CINDY2011 includes two proposed island-based sites and two ship-based locations forming a square pattern with sonde profiles and scanning precipitation and cloud radars at both island and ship sites. These data will be used to produce a Variational Analysis data set coinciding with the one produced for AMIE-Manus. The synergy between AMIE-Manus and AMIE-Gan will allow studies of the initiation, propagation, and evolution of the convective cloud population within the framework of the MJO. As with AMIE-Manus, AMIE-Gan/DYNAMO also includes a significant modeling component geared toward improving the representation of MJO initiation and propagation in climate and forecast models. This campaign involves the deployment of the second, marine-capable, AMF; all of the included measurement systems; and especially the scanning and vertically pointing radars. The campaign will include sonde launches at a rate of eight per day for the duration of the deployment. The increased sonde launches for the entire period matches that of the AMIE-Manus campaign and makes possible a far more robust Variational Analysis forcing data set product for the entire campaign, and thus better capabilities for modeling studies and synergistic research using the data from both AMIE sites.

  19. Counting molecular-beam grown graphene layers

    SciTech Connect (OSTI)

    Plaut, Annette S. [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom)] [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Wurstbauer, Ulrich [Department of Physics, Columbia University, New York, New York 10027 (United States)] [Department of Physics, Columbia University, New York, New York 10027 (United States); Pinczuk, Aron [Department of Physics, Columbia University, New York, New York 10027 (United States) [Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Garcia, Jorge M. [MBE Lab, IMM-Instituto de Microelectronica de Madrid (CNM-CSIC), Madrid, E-28760 (Spain)] [MBE Lab, IMM-Instituto de Microelectronica de Madrid (CNM-CSIC), Madrid, E-28760 (Spain); Pfeiffer, Loren N. [Electrical Engineering Department, Princeton University, New Jersey 08544 (United States)] [Electrical Engineering Department, Princeton University, New Jersey 08544 (United States)

    2013-06-17T23:59:59.000Z

    We have used the ratio of the integrated intensity of graphene's Raman G peak to that of the silicon substrate's first-order optical phonon peak, accurately to determine the number of graphene layers across our molecular-beam (MB) grown graphene films. We find that these results agree well both, with those from our own exfoliated single and few-layer graphene flakes, and with the results of Koh et al.[ACS Nano 5, 269 (2011)]. We hence distinguish regions of single-, bi-, tri-, four-layer, etc., graphene, consecutively, as we scan coarsely across our MB-grown graphene. This is the first, but crucial, step to being able to grow, by such molecular-beam-techniques, a specified number of large-area graphene layers, to order.

  20. Electronic and vibrational properties of ultrathin SiO2 films grown on Mo(112) S. Wendt, E. Ozensoy, T. Wei, M. Frerichs, Y. Cai, M. S. Chen, and D. W. Goodman*

    E-Print Network [OSTI]

    Goodman, Wayne

    electron spectroscopy MIES , and po- larization modulation infrared reflection absorption spectroscopy PM. The physical properties of SiO2 films near one monolayer are influenced by the Mo substrate due to the Si

  1. E-Print Network 3.0 - aln gan inn Sample Search Results

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Summary: size. Introduction GaN and its alloys with InN and AlN have been used for optoelectronic devices... region. The formation of self-assembled GaN nanostructures on aluminum...

  2. The interplay between spatially separated ferromagnetic and superconducting thin films

    E-Print Network [OSTI]

    Sullivan, Isaac John

    2013-02-22T23:59:59.000Z

    Ferromagnetic thin films have been grown via physical vapor deposition utilizing the technique of flash evaporation and characterized by measuring magnetization as a function of magnetic field. An Al thin film was evaporated atop the ferromagnetic...

  3. K.K. Gan EPS 2001 1 New Results on Charm

    E-Print Network [OSTI]

    Gan, K. K.

    K.K. Gan EPS 2001 1 New Results on Charm Semileptonic Decays and Lifetime K.K. Gan The Ohio State University July 14, 2001 Representing CLEO Collaboration #12;K.K. Gan EPS 2001 2 l measurement of l first+ B(D+ K* 0 l+ l ) (D*+ ) c + #12;K.K. Gan EPS 2001 3 l P measurement of form factors helps to guide

  4. Joint ATLAS/CMS SLHC Opto WG 1 K.K. Gan Lesson Learned from

    E-Print Network [OSTI]

    Gan, K. K.

    Joint ATLAS/CMS SLHC Opto WG 1 K.K. Gan Lesson Learned from ATLAS Pixel Optical Link #12;Joint ATLAS/CMS SLHC Opto WG 2 Outline Introduction VCSEL/PIN monitoring Analysis of opto-board/VCSEL/PIN failures Summary K.K. Gan #12;K.K. Gan Joint ATLAS/CMS SLHC Opto WG 3 Introduction Architecture

  5. K.K. Gan ATLAS Tracker Upgrade Workshop 1 Progress Report on Joint ATLAS/CMS

    E-Print Network [OSTI]

    Gan, K. K.

    K.K. Gan ATLAS Tracker Upgrade Workshop 1 Progress Report on Joint ATLAS/CMS SLHC Opto ATLAS Tracker Upgrade Workshop 2 Outline Introduction Subgroups activities Summary #12;K.K. Gan ATLAS System #12;K.K. Gan ATLAS Tracker Upgrade Workshop 4 Group A: Lesson Learned and to be Learned from LHC

  6. K.K. Gan RD07 1 Radiation-Hard Optical Link for SLHC

    E-Print Network [OSTI]

    Gan, K. K.

    spliced SIMM-GRIN fiber Radiation hardness of PIN/VCSEL arrays Results on MT-style optical packages irradiation? What is optical power after irradiation? What current is needed for annealing? #12;K.K. Gan RDK.K. Gan RD07 1 Radiation-Hard Optical Link for SLHC June 28, 2007 W. Fernando, K.K. Gan, A. Law, H

  7. III-nitride quantum cascade detector grown by metal organic chemical vapor deposition

    SciTech Connect (OSTI)

    Song, Yu, E-mail: yusong@princeton.edu; Huang, Tzu-Yung; Badami, Pranav; Gmachl, Claire [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08540 (United States); Bhat, Rajaram; Zah, Chung-En [Corning Incorporated, Corning, New York 14831 (United States)

    2014-11-03T23:59:59.000Z

    Quantum cascade (QC) detectors in the GaN/Al{sub x}Ga{sub 1?x}N material system grown by metal organic chemical vapor deposition are designed, fabricated, and characterized. Only two material compositions, i.e., GaN as wells and Al{sub 0.5}Ga{sub 0.5}N as barriers are used in the active layers. The QC detectors operates around 4??m, with a peak responsivity of up to ?100??A/W and a detectivity of up to 10{sup 8} Jones at the background limited infrared performance temperature around 140?K.

  8. Determination of crystallographic orientation of lead-free piezoelectric (K,Na)NbO{sub 3} epitaxial thin films grown on SrTiO{sub 3} (100) surfaces

    SciTech Connect (OSTI)

    Yu, Qi; Zhu, Fang-Yuan; Cheng, Li-Qian; Wang, Ke; Li, Jing-Feng, E-mail: jingfeng@mail.tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China)] [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China)

    2014-03-10T23:59:59.000Z

    Crystallographic structure of sol-gel-processed lead-free (K,Na)NbO{sub 3} (KNN) epitaxial films on [100]-cut SrTiO{sub 3} single-crystalline substrates was investigated for a deeper understanding of its piezoelectric response. Lattice parameter measurement by high-resolution X-ray diffraction and transmission electron microscopy revealed that the orthorhombic KNN films on SrTiO{sub 3} (100) surfaces are [010] oriented (b-axis-oriented) rather than commonly identified c-axis orientation. Based on the crystallographic orientation and corresponding ferroelectric domain structure investigated by piezoresponse force microscopy, the superior piezoelectric property along b-axis of epitaxial KNN films than other orientations can be explained.

  9. Strain relief and AlSb buffer layer morphology in GaSb heteroepitaxial films grown on Si as revealed by high-angle annular dark-field scanning transmission electron microscopy

    SciTech Connect (OSTI)

    Vajargah, S. Hosseini; Couillard, M.; Cui, K. [Department of Material Science and Engineering, McMaster University, 1280 Main St. W., Hamilton, Ontario L8S 4M1 (Canada); Tavakoli, S. Ghanad; Robinson, B.; Kleiman, R. N.; Preston, J. S. [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Botton, G. A. [Department of Material Science and Engineering, McMaster University, 1280 Main St. W., Hamilton, Ontario L8S 4M1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

    2011-02-21T23:59:59.000Z

    The interfacial misfit (IMF) dislocation array of an epitaxial GaSb film on a Si substrate has been imaged with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The mismatch strain accommodation through dislocation formation has been investigated using geometric phase analysis (GPA) on HAADF-STEM images with atomic resolution to probe the defects' local strain distribution. These measurements indicate that the lattice parameter of the epitaxial film recovers its bulk value within three unit cells from the interface due to the relaxation through IMF dislocations. The atomic number contrast of the HAADF-STEM images and energy dispersive x-ray spectrometry illustrate the formation of islands of AlSb buffer layer along the interface. The role of the AlSb buffer layer in facilitating the GaSb film growth on Si is further elucidated by investigating the strain field of the islands with the GPA.

  10. Maskless lateral epitaxial overgrowth of GaN on sapphire

    SciTech Connect (OSTI)

    Fini, P.; Marchand, H.; Ibbetson, J.P.; Moran, B.; Zhao, L.; Denbaars, S.P.; Speck, J.S.; Mishra, U.K.

    1999-07-01T23:59:59.000Z

    The authors demonstrate a technique of lateral epitaxial overgrowth (LEO) of GaN, termed maskless LEO, in which no mask is deposited prior to LEO regrowth. Instead, a bulk (> 2 {micro}m) GaN layer on sapphire is selectively dry etched, leaving {approximately} 5 {micro}m-wide stripe mesas oriented in the <10{bar 1}0>{sub GaN} direction, with a 20 {micro}m period. These stripes serve as seeds for LEO GaN growth, which proceeds from the tops of the stripes and expands laterally, resulting in a T, or overhang, morphology. As for LEO over an SiO{sub 2} mask, significant defect reduction (from {approximately} 10{sup 9} cm{sup {minus}2} to {approximately} 10{sup 6} cm{sup {minus}2}) is observed in cross-sectional transmission electron microscopy (TEM). Atomic force microscopy of the top surface of the LEO GaN reveals that no threading dislocations with screw component terminate at the surfaces of laterally overgrown regions. X-ray diffraction measurements reveal that the wings exhibit a crystallographic tilt away from the seed regions in an azimuth perpendicular to the stripe direction; the tilt angle ({approximately} 0.4--0.5{degree}) is relatively independent of growth temperature and wing aspect ratio.

  11. Ultrahard carbon nanocomposite films

    SciTech Connect (OSTI)

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; PROVENCIO,PAULA P.; OVERMYER,DONALD L.; SIMPSON,REGINA L.; MARTINEZ-MIRANDA,L.J.

    2000-01-27T23:59:59.000Z

    Modest thermal annealing to 600 C of diamondlike amorphous-carbon (a-C) films grown at room temperature results in the formation of carbon nanocomposites with hardness similar to diamond. These nanocomposite films consist of nanometer-sized regions of high density a-C embedded in an a-C matrix with a reduced density of 5--10%. The authors report on the evolution of density and bonding topologies as a function of annealing temperature. Despite a decrease in density, film hardness actually increases {approximately} 15% due to the development of the nanocomposite structure.

  12. Scanned probe characterization of semiconductor nanostructures

    E-Print Network [OSTI]

    Law, James Jeremy MacDonald

    2009-01-01T23:59:59.000Z

    of the window and wing region of the a–plane GaN film,? m thick GaN film was then grown through the windows in thewindow regions, lateral overgrowth over the dielectric mask, and coalescence of the film

  13. Strong circular photogalvanic effect in ZnO epitaxial films

    SciTech Connect (OSTI)

    Zhang, Q.; Wang, X. Q.; Yin, C. M.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Chen, Y. H.; Chang, K. [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, CAS, Beijing 100083 (China); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2011-12-23T23:59:59.000Z

    A strong circular photogalvanic effect (CPGE) in ZnO epitaxial films was reported under interband excitation. It was observed that CPGE current is as large as 100 nA/W in ZnO, which is about one order in magnitude higher than that in InN film while the CPGE currents in GaN films are not detectable. The possible reasons for the above observations are the strong spin orbit coupling in ZnO or the inversed valence band structure of ZnO.

  14. Comparative study of GaN mesa etch characteristics in Cl{sub 2} based inductively coupled plasma with Ar and BCl{sub 3} as additive gases

    SciTech Connect (OSTI)

    Rawal, Dipendra Singh, E-mail: dsrawal15@gmail.com; Arora, Henika; Sehgal, Bhupender Kumar; Muralidharan, Rangarajan [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India)

    2014-05-15T23:59:59.000Z

    GaN thin film etching is investigated and compared for mesa formation in inductively coupled plasma (ICP) of Cl{sub 2} with Ar and BCl{sub 3} gas additives using photoresist mask. Etch characteristics are studied as a function of ICP process parameters, viz., ICP power, radio frequency (RF) power, and chamber pressure at fixed total flow rate. The etch rate at each ICP/RF power is 0.1–0.2??m/min higher for Cl{sub 2}/Ar mixture mainly due to higher Cl dissociation efficiency of Ar additive that readily provides Cl ion/radical for reaction in comparison to Cl{sub 2}/BCl{sub 3} mixture. Cl{sub 2}/Ar mixture also leads to better photoresist mask selectivity. The etch-induced roughness is investigated using atomic force microscopy. Cl{sub 2}/Ar etching has resulted in lower root-mean-square roughness of GaN etched surface in comparison to Cl{sub 2}/BCl{sub 3} etching due to increased Ar ion energy and flux with ICP/RF power that enhances the sputter removal of etch product. The GaN surface damage after etching is also evaluated using room temperature photoluminescence and found to be increasing with ICP/RF power for both the etch chemistries with higher degree of damage in Cl{sub 2}/BCl{sub 3} etching under same condition.

  15. Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?

    SciTech Connect (OSTI)

    Podhorodecki, A., E-mail: artur.p.podhorodecki@pwr.wroc.pl; Golacki, L. W.; Zatryb, G.; Misiewicz, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Wang, J.; Jadwisienczak, W. [School of EECS, Ohio University, Stocker Center 363, Athens, Ohio 45701 (United States); Fedus, K. [Institute of Physics, Nicholas Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland); Wojcik, J.; Wilson, P. R. J.; Mascher, P. [Department of Engineering Physics and Centre for Emerging Device Technologies, McMaster University, 1280 Main St. W, Hamilton, Ontario L8S4L7 (Canada)

    2014-04-14T23:59:59.000Z

    In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100?°C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

  16. Epitaxial TiN,,001... Grown and Analyzed In situ by XPS and UPS. I. Analysis of

    E-Print Network [OSTI]

    Gall, Daniel

    Epitaxial TiN,,001... Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers used to characterize as- deposited epitaxial TiN 001 layers grown in situ. The films were deposited, while the UPS data was generated by He I and He II UV radiation. The spectra show that the TiN 001

  17. Structural Properties of Eu-Doped GaN Investigated by Raman Spectroscopy

    SciTech Connect (OSTI)

    Senawiratne, J; Xia, Y; Detchprohm, T; Tringe, J W; Stevens, C G; Wetzel, C

    2006-06-20T23:59:59.000Z

    Rare-earth (RE) impurities doped GaN are highly promising candidates for light emitting device applications due to their efficient electroluminescence properties at room temperature. Among those, Eu doped GaN has been identified as an excellent material for the red spectral region due to its strong emission at 620 nm. As a transition internal to the Eu doping atom (4f-4f), light emission originates in a much smaller complex than the more flexibly controllable quantum structures of wells, wires, and dots. This is thought to make the center less susceptible to structural defects and in particular radiation damage in the lattice host. Nevertheless, the lattice host is crucial for providing the excitation in from of free electrons and holes. In this respect, the actual lattice site Eu occupies in the host lattice, i.e. in GaN, is important. A large fraction of Eu atoms are typically inactive which must be attributed to their lattice site and local environment. GaN films implanted with Eu to concentrations of {approx}10{sup 18} cm{sup -3} were subjected to a highly directed beam of 500 keV He{sup +} at a dose of 5 x 10{sup 14} cm{sup -2}. By means of a shadow mask, irradiated and unexposed regions lie very close to each other on the same sample. We used optical and structural analysis to identify the exerted radiation damage. At the full radiation dose, photoluminescence intensity has decayed to {approx}0.01 of its initial value. From the dose dependence of the radiation decay we previously concluded, that this decay is in part due to the destruction of radiative Eu sites [J.W. Tringe, unpublished (2006)]. Along the transition from virgin to irradiated material we analyze the accumulated damage in terms of surface morphology (atomic force microscopy), crystallinity (x-ray diffraction), and phonon dispersion using micro-Raman spectroscopy. In addition to the well-studied E{sub 2}(high) mode, two new vibrational modes at 659 cm{sup -1} and 201 cm{sup -1} were observed in the Eu implanted and annealed sample, prior to He{sup +} irradiation. These modes are either remnants of the implantation damage or related to the Eu impurity. As such they can be indicative of the actual lattice site the Eu atom resides on. After irradiation, broad Raman modes at 300 cm-1 are being observed. This band indicates disorder activated Raman scattering (DARS) due to the radiation damage. An additional narrow mode appears at 672 cm{sup -1}, which can possibly be due to a nitrogen vacancy related vibrational mode. The continuous transition from irradiated to un-irradiated sample allows the direct evolution of radiation damage and its coordinated effects in structural, optical and vibrational properties. By its systematic correlation we anticipate to be able to elucidate the Eu lattice interaction and the processes of radiation damage.

  18. Characterization of LiNi?.?Mn?.?O? Thin Film Cathode Prepared by Pulsed Laser Deposition

    E-Print Network [OSTI]

    Xia, Hui

    LiNi?.?Mn?.?O? thin films have been grown by pulsed laser deposition (PLD) on stainless steel (SS) substrates. The crystallinity and structure of thin films were investigated by X-ray diffraction (XRD). Microstructure and ...

  19. Nitrogen doped zinc oxide thin film

    SciTech Connect (OSTI)

    Li, Sonny X.

    2003-12-15T23:59:59.000Z

    To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO{sub 2} plasma or by N{sup +} implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zn{sub i}, a native shallow donor. In NO{sub 2}-grown ZnO films, the n-type conductivity is attributed to (N{sub 2}){sub O}, a shallow double donor. In NO{sub 2}-grown ZnO films, 0.3 atomic % nitrogen was found to exist in the form of N{sub 2}O and N{sub 2}. Upon annealing, N{sub 2}O decomposes into N{sub 2} and O{sub 2}. In furnace-annealed samples N{sub 2} redistributes diffusively and forms gaseous N{sub 2} bubbles in the films. Unintentionally doped ZnO films were grown at different oxygen partial pressures. Zni was found to form even at oxygen-rich condition and led to n-type conductivity. N{sup +} implantation into unintentionally doped ZnO film deteriorates the crystallinity and optical properties and leads to higher electron concentration. The free electrons in the implanted films are attributed to the defects introduced by implantation and formation of (N{sub 2}){sub O} and Zni. Although today there is still no reliable means to produce good quality, stable p-type ZnO material, ZnO remains an attractive material with potential for high performance short wavelength optoelectronic devices. One may argue that gallium nitride was in a similar situation a decade ago. Although we did not obtain any p-type conductivity, we hope our research will provide a valuable reference to the literature.

  20. Comparative study of field-dependent carrier dynamics and emission kinetics of InGaN/GaN light-emitting diodes grown on (11 2 2) semipolar versus (0001) polar

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Articles you may be interested in Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam light-emitting diodes prepared on ( 11 2 ¯ 2 ) -plane GaN J. Appl. Phys. 100, 113109 (2006); 10.1063/1.2382667 Demonstration of a semipolar ( 10 1 ¯ 3 ¯ ) In Ga N Ga N green light emitting diode Appl. Phys. Lett. 87, 231110

  1. K.K. Gan Opto-Link PRR 1 Status of Opto-Board Development

    E-Print Network [OSTI]

    Gan, K. K.

    irradiation) LVDS fall time (after irradiation) Optical signal 4 rise and fall times after irradiation Results l Irradiation Results l Conclusions #12;K.K. Gan Opto-Link PRR 3 Opto-link #12;K.K. Gan Opto-Link PRR 4 l converts: optical signal ÷ electrical signal l provide 7 optical links: P disks and 50

  2. K.K. Gan HEP2007 1 Radiation-Hard Optical Link for SLHC

    E-Print Network [OSTI]

    Gan, K. K.

    of fusion spliced SIMM-GRIN fiber Radiation hardness of PIN/VCSEL arrays Results on MT-style optical What is rise/fall time after irradiation? What is optical power after irradiation? What currentK.K. Gan HEP2007 1 Radiation-Hard Optical Link for SLHC July 20, 2007 W. Fernando, K.K. Gan, A. Law

  3. K.K. Gan Pixel Engineering Layout 1 Optical Link Layout Options

    E-Print Network [OSTI]

    Gan, K. K.

    optical-link locations Predictions of degradation in fibers Predictions of degradation in VCSEL for r > 110 cm Loss calculated for Corning Infinicor GRIN fiber Fibers irradiated with gammas fromK.K. Gan Pixel Engineering Layout 1 Optical Link Layout Options K.K. Gan The Ohio State

  4. K.K. Gan ATLAS Tracker Upgrade Workshop 1 Summary of Optical Link R&D

    E-Print Network [OSTI]

    Gan, K. K.

    -Hardness of Optical Fiber Corning Infinicor GRIN fiber irradiated with 's from Co60 Attenuation parameterized into optical signal for transmission in fibers PINs convert optical signal into electrical signal PlanK.K. Gan ATLAS Tracker Upgrade Workshop 1 Summary of Optical Link R&D K.K. Gan The Ohio State

  5. Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy A. J. Ptak, L. J-assisted molecular-beam epitaxy to study the dependence of oxygen incorporation on polarity and oxygen partial pressure. Oxygen incorporates at a rate ten times faster on nitrogen-polar GaN than on the Ga polarity

  6. K.K. Gan Siena02 1 The Ohio State University

    E-Print Network [OSTI]

    Gan, K. K.

    .K. Gan Siena02 6 l Decode Bi-Phase Mark encoded (BPM) clock and command signals from PIN diode l Input Error Rate (BER): BPM #12;K.K. Gan Siena02 7 l Training period: ~25 ms of 20 MHz clock (BPM with no data) DORIC Logic ] Ready

  7. Dopant Ion Size and Electronic Structure Effects on Transparent Conducting Oxides. Sc-Doped CdO Thin Films

    E-Print Network [OSTI]

    Medvedeva, Julia E.

    -doped CdO (CSO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates metallic conductivities, and relatively simple crystal structures.2,4-7 Sn doping of CdO thin films grown with the highest carrier mobilities grown to date.7 In addition, Cd2SnO4, CdIn2O4, and CdO-ZnO thin films have been

  8. Bonding topologies in diamondlike amorphous-carbon films

    SciTech Connect (OSTI)

    SIEGAL,MICHAEL P.; PROVENCIO,PAULA P.; TALLANT,DAVID R.; SIMPSON,REGINA L.; KLEINSORGE,B.; MILNE,W.I.

    2000-01-27T23:59:59.000Z

    The carbon ion energy used during filtered cathodic vacuum arc deposition determines the bonding topologies of amorphous-carbon (a-C) films. Regions of relatively low density occur near the substrate/film and film/surface interfaces and their thicknesses increase with increasing deposition energy. The ion subplantation growth results in mass density gradients in the bulk portion of a-C in the growth direction; density decreases with distance from the substrate for films grown using ion energies < 60 eV and increases for films grown using ion energies > 160 eV. Films grown between these energies are the most diamondlike with relatively uniform bulk density and the highest optical transparencies. Bonding topologies evolve with increasing growth energy consistent with the propagation of subplanted carbon ions inducing a partial transformation of 4-fold to 3-fold coordinated carbon atoms.

  9. Metalorganic chemical vapor deposition of GaN on Si(111): Stress control and application to field-effect transistors

    SciTech Connect (OSTI)

    Marchand, H.; Zhao, L.; Zhang, N.; Moran, B.; Coffie, R.; Mishra, U. K.; Speck, J. S.; DenBaars, S. P.; Freitas, J. A.

    2001-06-15T23:59:59.000Z

    Two schemes of nucleation and growth of gallium nitride on Si(111) substrates are investigated and the structural and electrical properties of the resulting films are reported. Gallium nitride films grown using a 10{endash}500 nm-thick AlN buffer layer deposited at high temperature ({similar_to}1050{degree}C) are found to be under 260{endash}530 MPa of tensile stress and exhibit cracking, the origin of which is discussed. The threading dislocation density in these films increases with increasing AlN thickness, covering a range of 1.1 to {gt}5.8{times}10{sup 9}cm{sup {minus}2}. Films grown using a thick, AlN-to-GaN graded buffer layer are found to be under compressive stress and are completely crack free. Heterojunction field effect transistors fabricated on such films result in well-defined saturation and pinch-off behavior with a saturated current of {similar_to}525 mA/mm and a transconductance of {similar_to}100 mS/mm in dc operation. {copyright} 2001 American Institute of Physics.

  10. Effects of capping on GaN quantum dots deposited on Al{sub 0.5}Ga{sub 0.5}N by molecular beam epitaxy

    SciTech Connect (OSTI)

    Korytov, M. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France) and University of Nice Sophia-Antipolis, Parc Valrose, 06103 Nice (France); Benaissa, M. [CNRST, angle Allal-Fassi/FAR, Madinat al-irfane, 10000 Rabat (Morocco); Brault, J.; Vennegues, P. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Huault, T. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne, France and RIBER S.A., 31 rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France); Neisius, T. [CP2M, Faculte Saint Jerome, 13397 Marseille Cedex 20 (France)

    2009-04-06T23:59:59.000Z

    The impact of the capping process on the structural and morphological properties of GaN quantum dots (QDs) grown on fully relaxed Al{sub 0.5}Ga{sub 0.5}N templates was studied by transmission electron microscopy. A morphological transition between the surface QDs, which have a pyramidal shape, and the buried ones, which have a truncated pyramid shape, is evidenced. This shape evolution is accompanied by a volume change: buried QDs are bigger than surface ones. Furthermore a phase separation into Al{sub 0.5}Ga{sub 0.5}N barriers was observed in the close vicinity of buried QDs. As a result, the buried QDs were found to be connected with the nearest neighbors by thin Ga-rich zones, whereas Al-rich zones are situated above the QDs.

  11. Characterization of metal oxide layers grown on CVD graphene

    SciTech Connect (OSTI)

    Matsubayashi, Akitomo; Abel, Joseph; Prasad Sinha, Dhiraj; Lee, Ji Ung; LaBella, Vincent P. [College of Nanoscale Science and Engineering, University at Albany, SUNY, Albany, New York 12203 (United States)

    2013-03-15T23:59:59.000Z

    Growth of a fully oxidized aluminum oxide layer with low surface roughness on graphene grown by chemical vapor deposition is demonstrated. This is accomplished by the deposition of a 0.2 nm thick titanium seed layer on the graphene prior to the deposition of the aluminum under ultra high vacuum conditions, which was subsequently oxidized. The stoichiometry and surface roughness of the oxide layers were measured for a range of titanium and aluminum depositions utilizing ex situ x-ray photoelectron spectrometry and atomic force microscopy. These fully oxidized films are expected to produce good dielectric layers for use in graphene based electronic devices.

  12. Textures of oxide films grown on nickel electrodeposits

    SciTech Connect (OSTI)

    Czerwinski, F.; Palumbo, G.; Szpunar, J.A.

    1998-10-13T23:59:59.000Z

    High-temperature corrosion properties of heat-resistant materials depend on the formation of a protective oxide layer on their surface, which inhibits further degradation. Among many factors affecting the oxide growth rate and its resistance to spallation, the crystallographic texture of the metallic substrate plays an important role. In this study, the authors explore the possibilities of modifying the surface texture of polycrystalline Ni using electrodeposition. In addition to analyzing the texture of metallic substrates and its evolution at high temperatures, the texture of oxide formed on each substrate is also considered.

  13. Characterization of Nanoporous WO3 Films Grown via Ballistic Deposition. |

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation Proposed New Substation SitesStanding

  14. Structural Characterization of Nanoporous Pd Films Grown Via Ballistic

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administrationcontroller systemsBiSiteNeutronStrategic PlanStructural Basis

  15. In-situ ellipsometry: Identification of surface terminations during GaN growth , T. Schmidtling1

    E-Print Network [OSTI]

    Feenstra, Randall

    1 In-situ ellipsometry: Identification of surface terminations during GaN growth C. Cobet1 , T SE, one is not limited to any special bulk or surface symmetry for optical characterisation. In PAMBE

  16. Physics of electrical degradation in GaN high electron mobility transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    2009-01-01T23:59:59.000Z

    The deployment of GaN high electron mobility transistors (HEMT) in RF power applications is currently bottlenecked by their limited reliability. Obtaining the required reliability is a difficult issue due to the high voltage ...

  17. Watching GaN Nanowires Grow Eric A. Stach,*, Peter J. Pauzauskie, Tevye Kuykendall,

    E-Print Network [OSTI]

    Yang, Peidong

    Vision, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, Uni and experimentally demonstrated that congruent sublimation of GaN is possible, which yields diatomic or polymeric

  18. Light extraction in individual GaN nanowires on Si for LEDs

    E-Print Network [OSTI]

    Zhou, Xiang

    GaN-based nanowires hold great promise for solid state lighting applications because of their waveguiding properties and the ability to grow nonpolar GaN nanowire-based heterostructures, which could lead to increased light ...

  19. K.K. Gan ATLAS Pixel Week 1 New Results on Opto-Electronics

    E-Print Network [OSTI]

    Gan, K. K.

    University #12;K.K. Gan ATLAS Pixel Week 2 Outline l VDC-I5 l VDC/DORIC-I5e l QA l BeO Opto-board l Summary reset from active high to low for ease of implementation by DCS ] slightly better performance at ±3s: Engineering Run #12;K.K. Gan ATLAS Pixel Week 9 l circuit boards: designed/built/tested l LabView programs

  20. Field emission properties of the polycrystalline diamond film prepared by microwave-assisted plasma chemical vapor deposition

    E-Print Network [OSTI]

    Lee, Jong Duk

    Field emission properties of the polycrystalline diamond film prepared by microwave-assisted plasma Field emission characteristics for the diamond films grown using a gas mixture of different methane V 3.0 V/ m and 9 V 5.5 V/ m , respectively, for the diamond emitter of a little poor quality grown

  1. The Electrical and Band-Gap Properties of Amorphous Zinc-Indium-Tin Oxide Thin Films

    E-Print Network [OSTI]

    Shahriar, Selim

    MRSEC The Electrical and Band-Gap Properties of Amorphous Zinc-Indium-Tin Oxide Thin Films D Science & Engineering Center For zinc-indium-tin oxide (ZITO) films, grown by pulsed-laser deposition was replaced by substitution with zinc and tin in equal molar proportions (co-substitution). All ZITO films

  2. Mechanical Properties of 3C-SiC Films for MEMS Applications Jayadeep Deva Reddy1

    E-Print Network [OSTI]

    Volinsky, Alex A.

    . A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 µm. Under indentation loads below 500 µN both films

  3. Characterization of B-doped polycrystalline diamond films using thermally stimulated luminescence

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Characterization of B-doped polycrystalline diamond films using thermally stimulated luminescence, boron level in polycrystalline diamond films was identified by TL by an intense glow peak at 226 K polycrystalline diamond films grown by Chemical Vapor Deposition (CVD) have a wide array of potential applications

  4. Lithium manganese oxide films fabricated by electron beam directed vapor deposition

    E-Print Network [OSTI]

    Wadley, Haydn

    material for high energy den- sity battery applications.7,8 Lithium­transition metal oxide films can.2. After annealing in air at 700 °C, thin films grown with a low jet speed had a cubic spinel structure Li/Li-ion batteries. © 2008 American Vacuum Society. DOI: 10.1116/1.2823488 I. INTRODUCTION Thin film

  5. Nanostructural characterization of amorphous diamondlike carbon films

    SciTech Connect (OSTI)

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

    2000-01-27T23:59:59.000Z

    Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

  6. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect (OSTI)

    Lowndes, D.H.

    1992-10-01T23:59:59.000Z

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  7. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect (OSTI)

    Lowndes, D.H.

    1992-01-01T23:59:59.000Z

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  8. Comparative study of polar and semipolar (112{sup ¯}2) InGaN layers grown by metalorganic vapour phase epitaxy

    SciTech Connect (OSTI)

    Dinh, Duc V., E-mail: vanduc.dinh@tyndall.ie, E-mail: peter.parbrook@tyndall.ie; Zubialevich, V. Z. [Tyndall National Institute, University College Cork, Lee Matltings, Dyke Parade, Cork (Ireland); Oehler, F.; Kappers, M. J.; Humphreys, C. J. [Department of Materials Science and Metallurgy University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Alam, S. N.; Parbrook, P. J., E-mail: vanduc.dinh@tyndall.ie, E-mail: peter.parbrook@tyndall.ie [Tyndall National Institute, University College Cork, Lee Matltings, Dyke Parade, Cork (Ireland); School of Engineering, University College Cork, Cork (Ireland); Caliebe, M.; Scholtz, F. [Institute of Optoelectronics, Ulm University, Ulm 89069 (Germany)

    2014-10-21T23:59:59.000Z

    InGaN layers were grown simultaneously on (112{sup ¯}2) GaN and (0001) GaN templates by metalorganic vapour phase epitaxy. At higher growth temperature (?750?°C), the indium content (<15%) of the (112{sup ¯}2) and (0001) InGaN layers was similar. However, for temperatures less than 750?°C, the indium content of the (112{sup ¯}2) InGaN layers (15%–26%) were generally lower than those with (0001) orientation (15%–32%). The compositional deviation was attributed to the different strain relaxations between the (112{sup ¯}2) and (0001) InGaN layers. Room temperature photoluminescence measurements of the (112{sup ¯}2) InGaN layers showed an emission wavelength that shifts gradually from 380?nm to 580?nm with decreasing growth temperature (or increasing indium composition). The peak emission wavelength of the (112{sup ¯}2) InGaN layers with an indium content of more than 10% blue-shifted a constant value of ?(50–60) nm when using higher excitation power densities. This blue-shift was attributed to band filling effects in the layers.

  9. Nucleation and growth of nanostructures and films

    E-Print Network [OSTI]

    Glashausser, Charles

    - electrical conductors, electrical barriers, diffusion barriers . . . · Sensors: magnetic sensors, gas sensors (Physisorption and Chemisorption) 3. surface diffusion (Larger than bulk diffusion) 4. nucleation 5. island of higher bonding energy Highly ordered thin films can be grown at much lower temperatures than for bulk

  10. Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten masks: A method to map the free-carrier

    E-Print Network [OSTI]

    Nabben, Reinhard

    Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten properties of two epitaxial-laterally overgrown GaN structures with tungsten masks in 1100 and 1120 direction by tungsten masks3 to prevent the in-diffusion of silicon and oxygen atoms in the overgrown GaN, which

  11. Growth of CdTe Films on Amorphous Substrates Using CaF2 Nanorods as a Buffer Layer

    E-Print Network [OSTI]

    Wang, Gwo-Ching

    Growth of CdTe Films on Amorphous Substrates Using CaF2 Nanorods as a Buffer Layer NICHOLAS LICAUSI biaxially textured CdTe films were grown on biaxial CaF2 buffer layers. The CaF2 nanorods were grown by oblique angle vapor deposition and possessed a {111}h121i biaxial texture. The CdTe film was deposited

  12. Effect of Trapping on the Critical Voltage for Degradation in GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    conditions, UV illumination decreases the critical voltage for the onset of degradation in gate current in Ga traps in the fresh state. Keywords­ GaN HEMTs, critical voltage, degradation, UV illuminationEffect of Trapping on the Critical Voltage for Degradation in GaN High Electron Mobility

  13. Oxidation of In2S3 films to synthetize In2S3(1-x)O3x thin films as a buffer layer in solar cells

    E-Print Network [OSTI]

    Boyer, Edmond

    Oxidation of In2S3 films to synthetize In2S3(1-x)O3x thin films as a buffer layer in solar cells S layers for solar cells. PACS : 68.55.ag Semiconductors, 68.55.J Morphology of films , 68.55.Nq the oxidation occurs is strongly dependent on the texture of deposited films. As-grown films deposited

  14. Hall photovoltage deep-level spectroscopy of GaN films I. Shalish*

    E-Print Network [OSTI]

    Shalish, Ilan

    in semiconductor Hall voltage is proposed as a method to charac- terize deep levels. An analytical expression nucleation layer at temperatures lower than the typical growth temperature providing a bridge over

  15. Nanocomposite films

    DOE Patents [OSTI]

    Mitlin, David (Edmonton, CA); , Ophus, Colin (Edmonton, CA); Evoy, Stephane (Edmonton, CA); Radmilovic, Velimir (Piedmont, CA); Mohammadi, Reza (Edmonton, CA); Westra, Ken (Edmonton, CA); Nelson-Fitzpatrick, Nathaniel (Edmonton, CA); Lee, Zonghoon (Albany, CA)

    2010-07-20T23:59:59.000Z

    A thin-film composition of nanocrystal molybdenum in an amorphous metallic matrix may be formed by co-sputtering Mo with aluminum or nickel. NEMS cantilevers may be formed from the film. The films exhibit high nanoindentation hardness and a reduction in roughness and intrinsic stress, while maintaining resistivity in the metallic range.

  16. Synthesis, morphology and optical properties of GaN and AlGaN semiconductor nanostructures

    SciTech Connect (OSTI)

    Kuppulingam, B., E-mail: drbaskar2009@gmail.com; Singh, Shubra, E-mail: drbaskar2009@gmail.com; Baskar, K., E-mail: drbaskar2009@gmail.com [Crystal Growth Centre, Anna University, Chennai-600025 (India)

    2014-04-24T23:59:59.000Z

    Hexagonal Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) nanoparticles were synthesized by sol-gel method using Ethylene Diamine Tetra Acetic acid (EDTA) complex route. Powder X-ray diffraction (PXRD) analysis confirms the hexagonal wurtzite structure of GaN and Al{sub 0.25}Ga{sub 0.75}N nanoparticles. Surface morphology and elemental analysis were carried out by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The room temperature Photoluminescence (PL) study shows the near band edge emission for GaN at 3.35 eV and at 3.59 eV for AlGaN nanoparticles. The Aluminum (Al) composition of 20% has been obtained from PL emission around 345 nm.

  17. Refracted x-ray fluorescence (RXF) applied to the study of thermally grown oxide scales

    SciTech Connect (OSTI)

    Koshelev, I.; Paulikas, A.P.; Veal, B.W.

    1996-12-31T23:59:59.000Z

    RXF is a new technique for studying thin films. Here, it is applied to study of thermally grown oxide scales. Evolution of chromia scales on Fe-25Cr-20Ni-0.3Y alloys and the evolution of alumina scales on {beta}-NiAl are investigated. The technique provides scale composition and depth profile information, scale thicknesses and growth rates, and information about transient phase evolution.

  18. Ge doped GaN with controllable high carrier concentration for plasmonic applications

    SciTech Connect (OSTI)

    Kirste, Ronny; Hoffmann, Marc P.; Sachet, Edward; Bobea, Milena; Bryan, Zachary; Bryan, Isaac; Maria, Jon-Paul; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States)] [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Nenstiel, Christian; Hoffmann, Axel [Institut f?r Festkörperphsyik, TU-Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)] [Institut f?r Festkörperphsyik, TU-Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2013-12-09T23:59:59.000Z

    Controllable Ge doping in GaN is demonstrated for carrier concentrations of up to 2.4?×?10{sup 20} cm{sup ?3}. Low temperature luminescence spectra from the highly doped samples reveal band gap renormalization and band filling (Burstein-Moss shift) in addition to a sharp transition. Infrared ellipsometry spectra demonstrate the existence of electron plasma with an energy around 3500?cm{sup ?1} and a surface plasma with an energy around 2000?cm{sup ?1}. These findings open possibilities for the application of highly doped GaN for plasmonic devices.

  19. X-ray detectors based on GaN Schottky diodes

    SciTech Connect (OSTI)

    Duboz, Jean-Yves; Frayssinet, Eric; Chenot, Sebastien [CRHEA, CNRS, Rue Bernard Gregory, Sophia Antipolis, F-06560 Valbonne (France); Reverchon, Jean-Luc [THALES R and T, Campus Polytechnique, 1 avenue Augustin Fresnel, F-91767 Palaiseau Cedex (France); Idir, Mourad [Synchrotron SOLEIL L'Orme des Merisiers, Saint-Aubin-BP 48 91192, GIF-sur-Yvette Cedex (France)

    2010-10-18T23:59:59.000Z

    GaN Schottky diodes have been fabricated and tested as x-ray detectors in the range from 6 to 21 keV. The spectral response has been measured and is compared to its theoretical value. The study of the response and its temporal dynamics as a function of the bias allows to identify a photovoltaic behavior at low bias and a photoconductive one at larger reverse biases. The GaN diode turned out to be linear as a function of the incident power. The noise and detectivity are given and discussed.

  20. Design and Experimental Characterization of an Erbium Doped GaN Waveguide

    E-Print Network [OSTI]

    Wang, Qian

    2012-05-31T23:59:59.000Z

    temperatures as compared to other semiconductor host materials such as Si and GaAs. 1540nm optical emission in Er- doped waveguide has also been demonstrated using a 365nm light emitting diode as the optical pumping source. UV pumping above the GaN bandgap....9 eV In Table 2 - 1, GaN is the semiconductor material with the largest bandgap (SiO2 is not a semiconductor), which has proven to be an accomplished host of erbium, with reports of fabrication of light- emitting diodes operating in the visible...

  1. Structure, magnetic properties and magnetoelastic anisotropy in epitaxial Sr(Ti???Co?)O? films

    E-Print Network [OSTI]

    Bi, Lei

    We report the structure, magnetic properties and magnetoelastic anisotropy of epitaxial Sr(Ti???Co?)O? films grown on LaAlO? (001) and SrTiO? (001) substrates by pulsed laser deposition. Room temperature ferromagnetism was ...

  2. High-temperature electron emission from diamond films Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee 37235

    E-Print Network [OSTI]

    Walker, D. Greg

    This work examines electron field-emission characteristics of polycrystalline diamond films at elevated in applications where high temperatures exist. Nitrogen-doped polycrystalline diamond films were grown by plasmaHigh-temperature electron emission from diamond films S. H. Shin Department of Mechanical

  3. Optical properties of polycrystalline diamond films in the far-infrared A. J. Gatesman, R. H. Giles, J. Waldman

    E-Print Network [OSTI]

    Massachusetts at Lowell, University of

    Optical properties of polycrystalline diamond films in the far-infrared A. J. Gatesman, R. H. Giles for the complex refractive index (n - ik) of polycrystalline diamond films grown by microwave plasma enhanced a CO2 optically pumped submillimeter laser. Due to their polycrystalline nature, the diamond films

  4. Microstructure and magnetoelectric properties in Pb,,ZrxTi1-x...O3Ni composite ferroic films

    E-Print Network [OSTI]

    Laughlin, David E.

    Microstructure and magnetoelectric properties in Pb,,ZrxTi1-x...O3­Ni composite ferroic films 15213 Presented on 31 October 2005; published online 19 April 2006 Ferroic composite thin films composite films grown on SiO2/Si substrates at 650 °C, a perovskite structure was obtained when the Ni

  5. Growth of plasma-polymerized thin films by PECVD method and study on their surface and optical characteristics

    E-Print Network [OSTI]

    Boo, Jin-Hyo

    Growth of plasma-polymerized thin films by PECVD method and study on their surface and optical properties of plasma-polymerized organic thin films with various RF power. AFM data showed that the plasma-polymerized. The surface and optical properties of as-grown plasma-polymerized thin films were analyzed by contact angle

  6. 3C-SiC Films on Si for MEMS Applications: Mechanical Properties , G. Kravchenko2

    E-Print Network [OSTI]

    Volinsky, Alex A.

    diamond tip. These results indicate that polycrystalline SiC thin films are attractive for MEMS. In addition, poly-crystalline 3C- SiC was also grown on (100)Si so that a comparison with monocrystaline 3C-SiC, also grown on (100)Si, could be made. The mechanical properties of single crystal and polycrystalline 3

  7. Uranium immobilization by sulfate-reducing biofilms grown on...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    immobilization by sulfate-reducing biofilms grown on hematite, dolomite, and calcite. Uranium immobilization by sulfate-reducing biofilms grown on hematite, dolomite, and calcite....

  8. Morphology and Oxide Shell Structure of Iron Nanoparticles Grown...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Oxide Shell Structure of Iron Nanoparticles Grown by Sputter-Gas-Aggregation. Morphology and Oxide Shell Structure of Iron Nanoparticles Grown by Sputter-Gas-Aggregation. Abstract:...

  9. Ferromagnetism in Mn-Implanted Epitaxially Grown Ge on Si(100)

    SciTech Connect (OSTI)

    Guchhait, S.; Jamil, M.; Ohldag, H.; Mehta, A.; Arenholz, E.; Lian, G.; Li Fatou, A.; Ferrer, D. A.; Markert, J. T.; Colombo, L.; Banerjee, S. K.

    2011-01-05T23:59:59.000Z

    We have studied ferromagnetism of Mn-implanted epitaxial Ge films on silicon. The Ge films were grown by ultrahigh vacuum chemical vapor deposition using a mixture of germane (GeH{sub 4}) and methylgermane (CH{sub 3}GeH{sub 3}) gases with a carbon concentration of less than 1 at. %, and observed surface rms roughness of 0.5 nm, as measured by atomic force microscopy. Manganese ions were implanted in epitaxial Ge films grown on Si (100) wafers to an effective concentration of 16, 12, 6, and 2 at. %. Superconducting quantum interference device measurements showed that only the three highest Mn concentration samples are ferromagnetic, while the fourth sample, with [Mn] = 2 at. %, is paramagnetic. X-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements indicate that localized Mn moments are ferromagnetically coupled below the Curie temperature. Isothermal annealing of Mn-implanted Ge films with [Mn] = 16 at. % at 300 C for up to 1200 s decreases the magnetization but does not change the Curie temperature, suggesting that the amount of the magnetic phase slowly decreases with time at this anneal temperature. Furthermore, transmission electron microscopy and synchrotron grazing incidence x-ray diffraction experiments show that the Mn-implanted region is amorphous, and we believe that it is this phase that is responsible for the ferromagnetism. This is supported by our observation that high-temperature annealing leads to recrystallization and transformation of the material into a paramagnetic phase.

  10. Optimal Decentralized Protocol for Electric Vehicle Charging Lingwen Gan Ufuk Topcu Steven Low

    E-Print Network [OSTI]

    Low, Steven H.

    Abstract-- Motivated by the power-grid-side challenges in the integration of electric vehicles, we proposeOptimal Decentralized Protocol for Electric Vehicle Charging Lingwen Gan Ufuk Topcu Steven Low a decentralized protocol for negotiating day-ahead charging schedules for electric vehicles. The overall goal

  11. K.K. Gan ATLAS Tracker Upgrade Workshop 1 Nov 5, 2008

    E-Print Network [OSTI]

    Gan, K. K.

    Upgrade Workshop 5 Optical Fiber Irradiation Corning Infinicor GRIN fiber irradiated with 's from Co60 Upgrade Workshop 6 Optical Fiber Irradiation assume L = 3,000 fb-1 including safety factor of 1 Radiation-Hardness of Optical Components #12;K.K. Gan ATLAS Tracker Upgrade Workshop 2 Outline

  12. K.K. Gan ATLAS Tracker Upgrade Workshop 1 Irradiation Results and Transmission on

    E-Print Network [OSTI]

    Gan, K. K.

    Power vs Dosage all VCSELs still produce optical power at SLHC dosage should irradiate at lower Workshop 14 Post-Irradiation Analysis all arrays except ULM 5 G still produce optical power post-irradiationK.K. Gan ATLAS Tracker Upgrade Workshop 1 Irradiation Results and Transmission on Small Cables

  13. Fermi Level Control of Point Defects During Growth of Mg-Doped GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    , and photodetectors have been developed, but the optical transitions in GaN:Mg are still not well under- stood.2 Mg.1007/s11664-012-2342-9 Ã? 2012 TMS #12;irradiation during growth affected the material, but the nature demonstrate point defect control in Mg-doped GaN, by UV irradiation during growth. First, details

  14. K.K. Gan ATLAS Tracker Ungrade Workshop 1 Bandwidths of Micro Twisted-Pair Cables

    E-Print Network [OSTI]

    Gan, K. K.

    /fall time after irradiation? What is optical power after irradiation? What current is needed for annealing Spliced SIMM-GRIN Fibers and Radiation Hardness of PIN/VCSEL Dec 8, 2006 W. Fernando, K.K. Gan, A. Law, H Bandwidth of micro twisted-pair cables Bandwidth of fusion spliced SIMM-GRIN fibers Radiation hardness

  15. K.K. Gan IPRD06 1 Bandwidths of Micro Twisted-Pair Cables

    E-Print Network [OSTI]

    Gan, K. K.

    A or more What is rise/fall time after irradiation? What is optical power after irradiation? What currentK.K. Gan IPRD06 1 Bandwidths of Micro Twisted-Pair Cables and Fusion Spliced SIMM-GRIN Fibers Introduction Bandwidth of micro twisted-pair cables Bandwidth of fusion spliced SIMM-GRIN fibers Radiation

  16. Reverse-bias leakage current reduction in GaN Schottky diodes by electrochemical surface treatment

    E-Print Network [OSTI]

    Yu, Edward T.

    Reverse-bias leakage current reduction in GaN Schottky diodes by electrochemical surface treatment Received 15 July 2002; accepted 27 December 2002 An electrochemical surface treatment has been developed to the large power consumption and noise levels that can be present in circuits that incorporate such devices.1

  17. VISIBLE AND INFRARED RARE-EARTH ACTIVATED ELECTROLUMINESCENCE FROM ERBIUM DOPED GaN

    E-Print Network [OSTI]

    Steckl, Andrew J.

    . At the same time novel work is being conducted using rare earth elements as sources of light emission. Results. III-V semiconductors doped with rare-earth elements have also been used10VISIBLE AND INFRARED RARE-EARTH ACTIVATED ELECTROLUMINESCENCE FROM ERBIUM DOPED GaN M. Garter*, R

  18. An Effective Subdivision Algorithm for Diffuse Scattering of Ray Tracing Mingming Gan1

    E-Print Network [OSTI]

    Zemen, Thomas

    Department of Electrical and Information Technology, Lund University, Lund, Sweden Contact: gan@ftw.at Abstract Accurate modeling of electromagnetic wave propagation by means of ray tracing (RT) includes by evaluating the power delay profile (PDP), delay spread and angular spread. 1 Introduction Diffuse scattering

  19. Lattice Protein Folding With Two and Four-Body Statistical Hin Hark Gan,1

    E-Print Network [OSTI]

    Schlick, Tamar

    Lattice Protein Folding With Two and Four-Body Statistical Potentials Hin Hark Gan,1 Alexander/sequence compatibility of proteins,5,6 homology modeling,7 and protein folding simulations.8 ­10 Currently, most structures. Multibody potentials may help improve our understanding of the cooperativity of protein folding

  20. Near-field microwave microscopy of high-? oxides grown on graphene with an organic seeding layer

    SciTech Connect (OSTI)

    Tselev, Alexander, E-mail: tseleva@ornl.gov; Kalinin, Sergei V. [Oak Ridge National Laboratory, Center for Nanophase Materials Sciences, Oak Ridge, Tennessee 37831 (United States)] [Oak Ridge National Laboratory, Center for Nanophase Materials Sciences, Oak Ridge, Tennessee 37831 (United States); Sangwan, Vinod K.; Jariwala, Deep; Lauhon, Lincoln J. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)] [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Marks, Tobin J.; Hersam, Mark C. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States) [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)

    2013-12-09T23:59:59.000Z

    Near-field scanning microwave microscopy (SMM) is used for non-destructive nanoscale characterization of Al{sub 2}O{sub 3} and HfO{sub 2} films grown on epitaxial graphene on SiC by atomic layer deposition using a self-assembled perylene-3,4,9,10-tetracarboxylic dianhydride seeding layer. SMM allows imaging of buried inhomogeneities in the dielectric layer with a spatial resolution close to 100?nm. The results indicate that, while topographic features on the substrate surface cannot be eliminated as possible sites of defect nucleation, the use of a vertically heterogeneous Al{sub 2}O{sub 3}/HfO{sub 2} stack suppresses formation of large outgrowth defects in the oxide film, ultimately improving lateral uniformity of the dielectric film.

  1. Luminescence properties of ZnO layers grown on Si-on-insulator substrates

    SciTech Connect (OSTI)

    Kumar, Bhupendra; Gong, Hao; Vicknesh, S.; Chua, S. J.; Tripathy, S. [Department of Materials Science and Engineering, National University of Singapore, 119260 Singapore (Singapore); Institute of Materials Research and Engineering, 3 Research Link, 117602 Singapore (Singapore)

    2006-10-02T23:59:59.000Z

    The authors report on the photoluminescence properties of polycrystalline ZnO thin films grown on compliant silicon-on-insulator (SOI) substrates by radio frequency magnetron sputtering. The ZnO thin films on SOI were characterized by micro-Raman and photoluminescence (PL) spectroscopy. The observation of E{sub 2}{sup high} optical phonon mode near 438 cm{sup -1} in the Raman spectra of the ZnO samples represents the wurtzite crystal structure. Apart from the near-band-edge free exciton (FX) transition around 3.35 eV at 77 K, the PL spectra of such ZnO films also showed a strong defect-induced violet emission peak in the range of 3.05-3.09 eV. Realization of such ZnO layers on SOI would be useful for heterointegration with SOI-based microelectronics and microelectromechanical systems.

  2. Ab initio density functional theory study of non-polar (101{sup ¯}0),?(112{sup ¯}0) and semipolar (202{sup ¯}1) GaN surfaces

    SciTech Connect (OSTI)

    Mutombo, P.; Romanyuk, O., E-mail: romanyuk@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16200 Prague (Czech Republic)

    2014-05-28T23:59:59.000Z

    The atomic structures of non-polar GaN(101{sup ¯}0),?(112{sup ¯}0) and semipolar GaN(202{sup ¯}1),?(202{sup ¯}1{sup ¯}) surfaces were studied using ab initio calculations within density functional theory. The bulk-like truncated (1?×?1) structure with buckled Ga-N or Ga-Ga dimers was found stable on the non-polar GaN(101{sup ¯}0) surface in agreement with previous works. Ga-N heterodimers were found energetically stable on the GaN(112{sup ¯}0)-(1?×?1) surface. The formation of vacancies and substitution site defects was found unfavorable for non-polar GaN surfaces. Semipolar GaN(202{sup ¯}1)-(1?×?1) surface unit cells consist of non-polar (101{sup ¯}0) and semipolar (101{sup ¯}1) nano-facets. The (101{sup ¯}1) nano-facets consist of two-fold coordinated atoms, which form N-N dimers within a (2?×?1) surface unit cell on a GaN(202{sup ¯}1) surface. Dimers are not formed on the GaN(202{sup ¯}1{sup ¯}) surface. The stability of the surfaces with single (101{sup ¯}0) or (101{sup ¯}1) nano-facets was analyzed. A single non-polar (101{sup ¯}0)-(1?×?1) nano-facet was found stable on the GaN(202{sup ¯}1) surface, but unstable on the GaN(202{sup ¯}1{sup ¯}) surface. A single (101{sup ¯}1) nano-facet was found unstable. Semipolar GaN surfaces with (202{sup ¯}1) and (202{sup ¯}1{sup ¯}) polarity can be stabilized with a Ga overlayer at Ga-rich experimental conditions.

  3. Tunneling spectroscopy of superconducting MoN and NbTiN grown by atomic layer deposition

    SciTech Connect (OSTI)

    Groll, Nickolas R., E-mail: ngroll@anl.gov; Klug, Jeffrey A.; Claus, Helmut; Pellin, Michael J.; Proslier, Thomas, E-mail: proslier@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Cao, Chaoyue; Becker, Nicholas G.; Zasadzinski, John F. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Altin, Serdar [Fen Edebiyat Fakultesi, Fizik Bolumu, Inonu Universitesi, 44280 Malatya (Turkey)

    2014-03-03T23:59:59.000Z

    A tunneling spectroscopy study is presented of superconducting MoN and Nb{sub 0.8}Ti{sub 0.2}N thin films grown by atomic layer deposition (ALD). The films exhibited a superconducting gap of 2?meV and 2.4?meV, respectively, with a corresponding critical temperature of 11.5?K and 13.4?K, among the highest reported T{sub c} values achieved by the ALD technique. Tunnel junctions were obtained using a mechanical contact method with a Au tip. While the native oxides of these films provided poor tunnel barriers, high quality tunnel junctions with low zero bias conductance (below ?10%) were obtained using an artificial tunnel barrier of Al{sub 2}O{sub 3} on the film's surface grown ex situ by ALD. We find a large critical current density on the order of 4?×?10{sup 6}?A/cm{sup 2} at T?=?0.8T{sub c} for a 60?nm MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest that the ALD technique offers significant promise for thin film superconducting device applications.

  4. Characteristics of AlN/GaN nanowire Bragg mirror grown on (001) silicon by molecular beam epitaxy

    SciTech Connect (OSTI)

    Heo, Junseok; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)] [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States); Zhou, Zifan [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States)] [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Guo, Wei [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)] [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ooi, Boon S. [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)] [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2013-10-28T23:59:59.000Z

    GaN nanowires containing AlN/GaN distributed Bragg reflector (DBR) heterostructures have been grown on (001) silicon substrate by molecular beam epitaxy. A peak reflectance of 70% with normal incidence at 560 nm is derived from angle resolved reflectance measurements on the as-grown nanowire DBR array. The measured peak reflectance wavelength is significantly blue-shifted from the ideal calculated value. The discrepancy is explained by investigating the reflectance of the nanoscale DBRs with a finite difference time domain technique. Ensemble nanowire microcavities with In{sub 0.3}Ga{sub 0.7}N nanowires clad by AlN/GaN DBRs have also been characterized. Room temperature emission from the microcavity exhibits considerable linewidth narrowing compared to that measured for unclad In{sub 0.3}Ga{sub 0.7}N nanowires. The resonant emission is characterized by a peak wavelength and linewidth of 575 nm and 39 nm, respectively.

  5. Ultrashort pulse laser deposition of thin films

    DOE Patents [OSTI]

    Perry, Michael D. (Livermore, CA); Banks, Paul S. (Livermore, CA); Stuart, Brent C. (Fremont, CA)

    2002-01-01T23:59:59.000Z

    Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

  6. Photoluminescence study of the 1.047 eV emission in GaN K. Pressela)

    E-Print Network [OSTI]

    Nabben, Reinhard

    GaN/ AlGaN blue green light emitting diode, which has a much higher quantum efficiency than the SiC blue light emitting diode, became possible.2 Presently the wide bandgap semi- conductor GaN is intensively. Especially the 1.19 eV is very intense. Thus one can think of developing a light emitting diode in the near

  7. Analysis of the AlGaN/GaN vertical bulk current on Si, sapphire, and free-standing GaN substrates

    SciTech Connect (OSTI)

    Perez-Tomas, A.; Fontsere, A.; Llobet, J. [IMB-CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, CAT (Spain); Placidi, M. [IREC, Jardins Dones de Negre 1, 08930 Sant Adria de Besos, Barcelona (Spain); Rennesson, S.; Chenot, S.; Moreno, J. C.; Cordier, Y. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Baron, N. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); PICOGIGA International, Pl M. Rebuffat, Courtaboeuf 7, 91140 Villejust (France)

    2013-05-07T23:59:59.000Z

    The vertical bulk (drain-bulk) current (I{sub db}) properties of analogous AlGaN/GaN hetero-structures molecular beam epitaxially grown on silicon, sapphire, and free-standing GaN (FS-GaN) have been evaluated in this paper. The experimental I{sub db} (25-300 Degree-Sign C) have been well reproduced with physical models based on a combination of Poole-Frenkel (trap assisted) and hopping (resistive) conduction mechanisms. The thermal activation energies (E{sub a}), the (soft or destructive) vertical breakdown voltage (V{sub B}), and the effect of inverting the drain-bulk polarity have also been comparatively investigated. GaN-on-FS-GaN appears to adhere to the resistive mechanism (E{sub a} = 0.35 eV at T = 25-300 Degree-Sign C; V{sub B} = 840 V), GaN-on-sapphire follows the trap assisted mechanism (E{sub a} = 2.5 eV at T > 265 Degree-Sign C; V{sub B} > 1100 V), and the GaN-on-Si is well reproduced with a combination of the two mechanisms (E{sub a} = 0.35 eV at T > 150 Degree-Sign C; V{sub B} = 420 V). Finally, the relationship between the vertical bulk current and the lateral AlGaN/GaN transistor leakage current is explored.

  8. Phase Transformations in Pulsed Laser Deposited Nanocrystalline Tin Oxide Thin Films

    E-Print Network [OSTI]

    Reid, Scott A.

    Phase Transformations in Pulsed Laser Deposited Nanocrystalline Tin Oxide Thin Films Haiyan Fan associated with high pressure. Kaplan et al. found this phase in films grown by deposition of ionized tin. In another study, Shek et al. ob- served o-SnO2 when tin particles with an average size of 6 nm were oxidized

  9. THE ELECTRICAL AND OPTICAL PROPERTIES OF THIN FILM DIAMOND IMPLANTED WITH SILICON

    E-Print Network [OSTI]

    Kolodzey, James

    devices. The C:Si alloys were formed by the implantation of Si into polycrystalline diamond films grownTHE ELECTRICAL AND OPTICAL PROPERTIES OF THIN FILM DIAMOND IMPLANTED WITH SILICON K. J. Roe and J and electrical properties of diamond make it an attractive material for use in extreme conditions. Diamond

  10. FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON

    E-Print Network [OSTI]

    FIELD EMISSION FROM BORON-DOPING POLYCRYSTALLINE DIAMOND FILMS ON SILICON J. A. N. Gonçalves, G. M material fail. The field emission current from boron-doped polycrystalline diamond films grown by hot Campos, SP, Brazi Abstract This work deals with the study and development of the boron-doped diamond

  11. Phonon and thermal properties of exfoliated TaSe2 thin films T. R. Pope,2

    E-Print Network [OSTI]

    Phonon and thermal properties of exfoliated TaSe2 thin films Z. Yan,1 C. Jiang,1 T. R. Pope,2 C. F diselenide (2H-TaSe2) obtained via the "graphene-like" mechanical exfoliation of crystals grown by chemical films exfoliated from TaSe2 and other metal dichalcogenides, as well as for evaluating self

  12. Polarized photoluminescence excitation spectroscopy of a-plane InGaN/GaN multiple quantum wells grown on r-plane sapphire

    SciTech Connect (OSTI)

    Kundys, D., E-mail: dmytro.kundys@manchester.ac.uk; Sutherland, D.; Badcock, T. J.; Dawson, P. [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Schulz, S. [Photonics Theory group, Tyndall National Institute, Lee Maltings, Cork (Ireland); Oehler, F.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS (United Kingdom)

    2014-03-21T23:59:59.000Z

    We have performed a detailed study of the impact of basal plane stacking faults (BSFs) on the optical properties of both a-plane InGaN/GaN quantum wells (QWs) and GaN template samples grown on r-sapphire. In particular, we have used polarised photoluminescence excitation spectroscopy (P-PLE) to investigate the nature of the low temperature recombination as well as extracting information on the valence band (VB) polarisation anisotropy. Our low temperature P-PLE results revealed not only excitons associated with intersubband quantum well transitions and the GaN barrier material but also a transition associated with creation of excitons in BSFs. The strength of this BSF transition varied with detection energy across the quantum well emission suggesting that there is a significant contribution to the emission line width from changes in the local electronic environment of the QWs due to interactions with BSFs. Furthermore, we observed a corresponding progressive increase in the VB splitting of the QWs as the detection energy was varied across the quantum well emission spectrum.

  13. Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.

    SciTech Connect (OSTI)

    Kurtz, Steven Ross; Follstaedt, David Martin; Wright, Alan Francis; Baca, Albert G.; Briggs, Ronald D.; Provencio, Paula Polyak; Missert, Nancy A.; Allerman, Andrew Alan; Marsh, Phil F.; Koleske, Daniel David; Lee, Stephen Roger; Shul, Randy John; Seager, Carleton Hoover; Tigges, Christopher P.

    2005-12-01T23:59:59.000Z

    GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.

  14. Room temperature in-plane ?100? magnetic easy axis for Fe{sub 3}O{sub 4}/SrTiO{sub 3}(001):Nb grown by infrared pulsed laser deposition

    SciTech Connect (OSTI)

    Monti, Matteo; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta; Marco, José F.; Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano,” CSIC, Madrid E-28006 (Spain); Pedrosa, Francisco J.; Bollero, Alberto [IMDEA Nanociencia, Instituto Madrileño de Estudios Avanzados en Nanociencia, Madrid E-28049 (Spain); Camarero, Julio; Cuñado, Jose Luis F. [IMDEA Nanociencia, Instituto Madrileño de Estudios Avanzados en Nanociencia, Madrid E-28049 (Spain); Dpto. de Física de la Materia Condensada, Universidad Autónoma de Madrid, Madrid E-28049 (Spain); Nemes, Norbert M. [Dpto. de Física Aplicada III, Universidad Complutense de Madrid, Madrid E-28040 (Spain); Mompean, Federico J.; Garcia-Hernández, Mar [Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid E-28049 (Spain); Nie, Shu; McCarty, Kevin F. [Sandia National Laboratories, Livermore, California 94550 (United States); N'Diaye, Alpha T.; Chen, Gong; Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2013-12-14T23:59:59.000Z

    We examine the magnetic easy-axis directions of stoichiometric magnetite films grown on SrTiO{sub 3}:Nb by infrared pulsed-laser deposition. Spin-polarized low-energy electron microscopy reveals that the individual magnetic domains are magnetized along the in-plane ?100? film directions. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity are also along in-plane ?100? film directions. This easy-axis orientation differs from bulk magnetite and films prepared by other techniques, establishing that the magnetic anisotropy can be tuned by film growth.

  15. Symmetry Breaking in Few Layer Graphene Films

    SciTech Connect (OSTI)

    Bostwick, A.; Ohta, T.; McChesney, J.L.; Emtsev, K.; Seyller,Th.; Horn, K.; Rotenberg, E.

    2007-05-25T23:59:59.000Z

    Recently, it was demonstrated that the quasiparticledynamics, the layer-dependent charge and potential, and the c-axisscreening coefficient could be extracted from measurements of thespectral function of few layer graphene films grown epitaxially on SiCusing angle-resolved photoemission spectroscopy (ARPES). In this articlewe review these findings, and present detailed methodology for extractingsuch parameters from ARPES. We also present detailed arguments againstthe possibility of an energy gap at the Dirac crossing ED.

  16. Subpicosecond time-resolved Raman studies of nonequilibrium excitations in wurtzite GaN

    SciTech Connect (OSTI)

    Tsen, K.T.; Ferry, D.K. [Arizona State Univ., Tempe, AZ (United States). Dept. of Physics and Astronomy; Joshi, R.P. [Old Dominion Univ., Norfolk, VA (United States). Dept. of Electrical Engineering; Botchkarev, A.; Sverdlov, B.; Salvador, A.; Morkoc, H. [Univ. of Illinois, Urbana, IL (United States). Coordinated Science Lab.

    1997-12-31T23:59:59.000Z

    Non-equilibrium electron distributions as well as phonon dynamics in wurtzite GaN have been measured by subpicosecond time-resolved Raman spectroscopy. The experimental results have demonstrated that for electron densities n {ge} 5 {times} 10{sup 17} cm{sup {minus}3}, the non-equilibrium electron distributions in wurtzite GaN can be very well described by Fermi-Dirac distribution functions with the temperature of electrons substantially higher than that of the lattice. The population relaxation time of longitudinal optical phonons was directly measured to be {tau} {approx_equal} 5 {+-} 1 ps at T = 25 K. The experimental results on the temperature dependence of the lifetime of longitudinal optical phonons suggest that the primary decay channels for these phonons are the decay into (1) one transverse optical phonon and one high energy, longitudinal or transverse acoustical phonons; and (2) one transverse optical phonon and one E{sub 2} phonon.

  17. Charge transfer in Fe-doped GaN: The role of the donor

    SciTech Connect (OSTI)

    Sunay, Ustun; Dashdorj, J.; Zvanut, M. E.; Harrison, J. G. [Department of Physics, University of Alabama at Birmingham, 1300 University Blvd., CH 310, Birmingham, Alabama 35294-1170 (United States); Leach, J. H.; Udwary, K. [Kyma Technologies, 8829 Midway West Rd., Raleigh, North Carolina 27617 (United States)

    2014-02-21T23:59:59.000Z

    Several nitride-based device structures would benefit from the availability of high quality, large-area, freestanding semi-insulating GaN substrates. Due to the intrinsic n-type nature of GaN, however, the incorporation of compensating centers such as Fe is necessary to achieve the high resistivity required. We are using electron paramagnetic resonance (EPR) to explore charge transfer in 450 um thick GaN:Fe plates to understand the basic mechanisms related to compensation so that the material may be optimized for device applications. The results suggest that the simple model based on one shallow donor and a single Fe level is insufficient to describe compensation. Rather, the observation of the neutral donor and Fe3+ indicates that either the two species are spatially segregated or additional compensating and donor defects must be present.

  18. Transport studies on CVD-grown graphene

    E-Print Network [OSTI]

    Huntley, Miriam Hanna

    2009-01-01T23:59:59.000Z

    In this thesis, we report transport studies performed on CVD-grown graphene. We perform resistivity and hall measurements on a large-area sample at 4' K. We measure the carrier mobility of the sample and find it to be on ...

  19. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect (OSTI)

    Vargas, Mirella [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States); Murphy, N. R. [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States)] [Materials and Manufacturing Directorate (RX), 3005 Hobson Way, Wright-Patterson Air Force Base (WPAFB), Dayton, Ohio 45433 (United States); Ramana, C. V., E-mail: rvchintalapalle@utep.edu [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

    2014-03-10T23:59:59.000Z

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s}?=?25–700?°C). HfO{sub 2} films grown at T{sub s}?grown at T{sub s}???200?°C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (?) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (?)}?=?550?nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-?-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

  20. Effect of MnAs/GaAs(001) film accommodations on the phase-transition temperature

    SciTech Connect (OSTI)

    Iikawa, F.; Brasil, M.J.S.P.; Couto, O.D.D.; Adriano, C.; Giles, C.; Daeweritz, L. [Instituto de Fisica 'Gleb Wataghin', UNICAMP, Campinas-SP, C.P. 6165, 13083-970 (Brazil); Instituto de Fisica 'Gleb Wataghin', UNICAMP, Campinas-SP, C.P. 6165, 13083-970, Brazil and Laboratorio Nacional de Luz Sincrotron, CP-6192, 13084-971 Campinas-SP (Brazil); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2004-09-20T23:59:59.000Z

    The phase-transition temperature of MnAs epitaxial films grown by molecular-beam epitaxy on GaAs(001) with different crystalline accommodations was studied by specular and grazing incidence x-ray diffraction. The transition temperature of MnAs films with tilted hexagonal c-axis orientations with respect to the GaAs substrate is higher than the most investigated nontilted films and reaches a value above room temperature, which is more suitable for device applications.

  1. K.K. Gan IWORID-8 1 Bandwidths of Micro Twisted-Pair Cables

    E-Print Network [OSTI]

    Gan, K. K.

    -V Characteristics very good optical power candidate for irradiation study Optowell TP85-LCP0N 0.0 0.5 1.0 1.5 2K.K. Gan IWORID-8 1 Bandwidths of Micro Twisted-Pair Cables and Fusion Spliced SIMM-GRIN Fibers Bandwidth of micro twisted-pair cables Bandwidth of fusion spliced SIMM-GRIN fibers Measurement of VCSEL

  2. K.K. Gan DPF/JPS06 1 Bandwidths of Micro Twisted-Pair Cables

    E-Print Network [OSTI]

    Gan, K. K.

    /fall time after irradiation? What is optical power after irradiation? What current is needed for annealing during irradiation SLHC AOC 71 MRad 0.0 0.3 0.6 0.9 1.2 1.5 1.8 0 100 200 300 400 Time (Hours) DataOpticalPK.K. Gan DPF/JPS06 1 Bandwidths of Micro Twisted-Pair Cables and Fusion Spliced SIMM-GRIN Fibers

  3. K.K. Gan US Pixel Meeting 1 Tracker Optical Link Upgrade

    E-Print Network [OSTI]

    Gan, K. K.

    -V Characteristics very good optical power candidate for irradiation study AOC HFE419X-441 0.0 0.5 1.0 1.5 2.0 2 Pixel Meeting 10 I-L and I-V Characteristics very good optical power candidate for irradiation study 2500 OpticalPower(µW) #12;K.K. Gan US Pixel Meeting 11 Bandwidth of Spliced Fiber 29 m spliced fiber20

  4. K.K. Gan ATLAS Pixel Week 1 New Results on Opto-Electronics

    E-Print Network [OSTI]

    Gan, K. K.

    with lower thresholds with BPM/DRX ] opto-board design is compatible with BPM/DRX PIN Current Thresholds with BPM/DRX 0 5 10 15 20 25 30 35 link#1 link#2 link#3 link#4 link#5 link#6 link#7 Ipin(mA) Opto-Board on Test Board Opto-Board on Test Board with BPM/DRX #12;K.K. Gan ATLAS Pixel Week 8 l one irradiated VCSEL

  5. Effect of annealing on the properties of Sb doped ZnO thin films prepared by spray pyrolysis technique

    SciTech Connect (OSTI)

    Kumar, N. Sadananda; Bangera, Kasturi V.; Shivakumar, G. K. [Thin Films Laboratory, Department of Physics, National Institute of Technology Karnataka,Surathkal - 575025, Mangalore (India)

    2014-01-28T23:59:59.000Z

    Sb doped ZnO thin films have been deposited on glass substrate at 450°C using spray pyrolysis technique. The X-ray diffraction studies revealed that the as deposited films are polycrystalline in nature with (100) preferred orientation. Whereas the films annealed at 450° C for 6h show a preferential orientation along (101) direction. Crystallites size varies from 15.7 nm to 34.95 nm with annealing duration. The Scanning electron microscopic analysis shows the plane and smooth surface of the films. The optical properties of annealed films have shown a variation in the band gap between 3.37 eV and 3.19 eV. Transparency of as grown and annealed films decreases from 78 % to 65% respectively in the visible region. The electrical conductivity of the as grown film shows an increase in the electrical conductivity by one order of magnitude with increase in the annealing duration.

  6. Control of magnetization reversal in oriented strontium ferrite thin films

    SciTech Connect (OSTI)

    Roy, Debangsu, E-mail: debangsu@physics.iisc.ernet.in; Anil Kumar, P. S. [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2014-02-21T23:59:59.000Z

    Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al{sub 2}O{sub 3}(0001) substrate using Pulsed Laser Deposition technique. The angle dependent magnetic hysteresis, remanent coercivity, and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth.

  7. Vibrational spectra of CO adsorbed on oxide thin films: A tool to probe the surface defects and phase changes of oxide thin films

    SciTech Connect (OSTI)

    Savara, Aditya, E-mail: savaraa@ornl.gov [Chemical Sciences Division, Oak Ridge National Lab, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831 (United States)

    2014-03-15T23:59:59.000Z

    Thin films of iron oxide were grown on Pt(111) single crystals using cycles of physical vapor deposition of iron followed by oxidative annealing in an ultrahigh vacuum apparatus. Two procedures were utilized for film growth of ?15–30 ML thick films, where both procedures involved sequential deposition+oxidation cycles. In procedure 1, the iron oxide film was fully grown via sequential deposition+oxidation cycles, and then the fully grown film was exposed to a CO flux equivalent to 8 × 10{sup ?7} millibars, and a vibrational spectrum of adsorbed CO was obtained using infrared reflection-absorption spectroscopy. The vibrational spectra of adsorbed CO from multiple preparations using procedure 1 show changes in the film termination structure and/or chemical nature of the surface defects—some of which are correlated with another phase that forms (“phase B”), even before enough of phase B has formed to be easily detected using low energy electron diffraction (LEED). During procedure 2, CO vibrational spectra were obtained between deposition+oxidation cycles, and these spectra show that the film termination structure and/or chemical nature of the surface defects changed as a function of sequential deposition+oxidation cycles. The authors conclude that measurement of vibrational spectra of adsorbed CO on oxide thin films provides a sensitive tool to probe chemical changes of defects on the surface and can thus complement LEED techniques by probing changes not visible by LEED. Increased use of vibrational spectra of adsorbed CO on thin films would enable better comparisons between films grown with different procedures and by different groups.

  8. Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)

    SciTech Connect (OSTI)

    Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel [National Institute of Physics, University of the Philippines Diliman, Quezon City 1101 (Philippines); Que, Christopher T. [Physics Department, De La Salle University, 2401 Taft Avenue, Manila 1004 (Philippines); Yamamoto, Kohji; Tani, Masahiko [Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507 (Japan)

    2012-12-15T23:59:59.000Z

    Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

  9. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    SciTech Connect (OSTI)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28T23:59:59.000Z

    A 5?nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup ?8}]exp[?(0.31±0.02(eV)/(at) )/kT]?cm{sup 2}/s.

  10. Spectroscopic Analysis of Impurity Precipitates in CdS Films

    SciTech Connect (OSTI)

    Webb, J. D.; Keane, J.; Ribelin, R.; Gedvilas, L.; Swartzlander, A.; Ramanathan, K.; Albin, D. S.; Noufi, R.

    1999-10-31T23:59:59.000Z

    Impurities in cadmium sulfide (CdS) films are a concern in the fabrication of copper (indium, gallium) diselenide (CIGS) and cadmium telluride (CdTe) photovoltaic devices. Devices incorporating chemical-bath-deposited (CBD) CdS are comparable in quality to devices incorporating purer CdS films grown using vacuum deposition techniques, despite the higher impurity concentrations typically observed in the CBD CdS films. In this paper, we summarize and review the results of Fourier transform infrared (FTIR), Auger, electron microprobe, and X-ray photoelectron spectroscopic (XPS) analyses of the impurities in CBD CdS films. We show that these impurities differ as a function of substrate type and film deposition conditions. We also show that some of these impurities exist as 10{sup 2} micron-scale precipitates.

  11. STRUCTURAL AND CHEMICAL STUDIES ON CdTe/CdS THIN FILM SOLAR CELLS WITH ANALYTICAL TRANSMISSION ELECTRON MICROSCOPY

    E-Print Network [OSTI]

    Romeo, Alessandro

    STRUCTURAL AND CHEMICAL STUDIES ON CdTe/CdS THIN FILM SOLAR CELLS WITH ANALYTICAL TRANSMISSION, A. N. Tiwari Thin Film Physics Group, Laboratory for Solid State Physics, Technopark ETH-Building, Technoparkstr. 1, CH-8005 Zurich, Switzerland ABSTRACT: CdTe/CdS thin £lm solar cells have been grown by closed

  12. Ultra thin indium tin oxide films on various substrates by pulsed laser deposition

    SciTech Connect (OSTI)

    Sun, X.W.; Kwok, H.S. [Hong Kong Univ. of Science and Technology, Kowloon (Hong Kong). Dept. of Electrical and Electronic Engineering; Kim, D.H. [LG Electronics, Seoul (Korea, Republic of)

    1998-12-31T23:59:59.000Z

    Indium Tin Oxide (ITO) thin films with low resistivities of 0.1--0.2 m{Omega}-cm were deposited on various substrates such as YSZ, glass, and ZnO buffered glass by pulsed laser deposition (PLD). The X-ray rocking curve of crystalline (200) ITO films grown on (100) YSZ had a FWHM as narrow as 0.08{degree}. ITO films grown on ZnO (0001) buffered glass had an single (222) orientation and the X-ray rocking curve had a FWHM of 2.1{degree}. Ultrathin ITO films of 3.6nm were fabricated on YSZ and their electrical properties were measured from 10K--300K. ITO films fabricated on ZnO buffered glass and bare glass were characterized by Hall effect measurements as a function of temperature. The results indicate that the resistivity of ITO films grown by PLD does not depend on the orientation or the structure of the thin film. The resistivity is dominated by impurity scattering in the range of 10K--300K. The authors show that ZnO/glass is a good alternative to bare glass for producing commercial ITO films.

  13. Ab initio study on noncompensated CrO codoping of GaN for enhanced solar energy conversion

    SciTech Connect (OSTI)

    Pan, Hui [ORNL; Gu, Baohua [ORNL; Eres, Gyula [ORNL; Zhang, Zhenyu [ORNL

    2010-03-01T23:59:59.000Z

    We describe a novel photocatalyst obtained by codoping GaN with CrO, according to a new "noncompensated" codoping concept based on first-principles calculations. The approach enables controllable narrowing of the GaN band gap with significantly enhanced carrier mobility and photocatalytic activity in the visible light region and thus offers immense potential for application in solar energy conversion, water splitting, and a variety of solar-assisted photocatalysis. Our calculations indicate that the formation energy for the cation doping is greatly reduced by noncompensated codoping with an anion. Although Cr doping alone can split the band gap with the formation of an intermediate band, the mobility is low due to carrier trapping by the localized states. The first-principles calculations also demonstrate that CrO codoping of GaN shifts the Fermi level into the conduction band resulting in high carrier density and mobility.

  14. Impact of substrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Armstrong, A; Poblenz, C; Green, D S; Mishra, U K; Speck, J S; Ringel, S A

    2006-01-01T23:59:59.000Z

    B 22, 1145 ?2004?. A. Armstrong, A. R. Arehart, D. Green, U.San Diego, 1992?. A. Armstrong, A. R. Arehart, and S. A.molecular beam epitaxy A. Armstrong Department of Electrical

  15. Doping of MBE grown cubic GaN on 3C-SiC (001) by CBr4 ,E. Tschumak1

    E-Print Network [OSTI]

    As, Donat Josef

    source. The CBr4 beam equivalent pressure was established by a needle valve and was varied between 2x10 has a very low diffusion coefficient [3]. It is also known from p-doping in (Al)GaAs that carbon4 beam equivalent pressure (BEP) was established by a needle valve and was varied between 2x10

  16. High temperature electron spin dynamics in bulk cubic GaN: Nanosecond spin lifetimes far above room-temperature

    SciTech Connect (OSTI)

    Buß, J. H.; Schaefer, A.; Hägele, D.; Rudolph, J. [Arbeitsgruppe Spektroskopie der kondensierten Materie, Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum (Germany); Schupp, T.; As, D. J. [Department of Physics, University of Paderborn, Warburger Str. 100, D-33095 Paderborn (Germany)

    2014-11-03T23:59:59.000Z

    The electron spin dynamics in n-doped bulk cubic GaN is investigated for very high temperatures from 293?K up to 500?K by time-resolved Kerr-rotation spectroscopy. We find extraordinarily long spin lifetimes exceeding 1?ns at 500?K. The temperature dependence of the spin relaxation time is in qualitative agreement with predictions of Dyakonov-Perel theory, while the absolute experimental times are an order of magnitude shorter than predicted. Possible reasons for this discrepancy are discussed, including the role of phase mixtures of hexagonal and cubic GaN as well as the impact of localized carriers.

  17. Nanoscale size dependence parameters on lattice thermal conductivity of Wurtzite GaN nanowires

    SciTech Connect (OSTI)

    Mamand, S.M., E-mail: soran.mamand@univsul.net [Department of Physics, College of Science, University of Sulaimani, Sulaimanyah, Iraqi Kurdistan (Iraq); Omar, M.S. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)] [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Muhammad, A.J. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq)] [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq)

    2012-05-15T23:59:59.000Z

    Graphical abstract: Temperature dependence of calculated lattice thermal conductivity of Wurtzite GaN nanowires. Highlights: Black-Right-Pointing-Pointer A modified Callaway model is used to calculate lattice thermal conductivity of Wurtzite GaN nanowires. Black-Right-Pointing-Pointer A direct method is used to calculate phonon group velocity for these nanowires. Black-Right-Pointing-Pointer 3-Gruneisen parameter, surface roughness, and dislocations are successfully investigated. Black-Right-Pointing-Pointer Dislocation densities are decreases with the decrease of wires diameter. -- Abstract: A detailed calculation of lattice thermal conductivity of freestanding Wurtzite GaN nanowires with diameter ranging from 97 to 160 nm in the temperature range 2-300 K, was performed using a modified Callaway model. Both longitudinal and transverse modes are taken into account explicitly in the model. A method is used to calculate the Debye and phonon group velocities for different nanowire diameters from their related melting points. Effect of Gruneisen parameter, surface roughness, and dislocations as structure dependent parameters are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves. It was observed that Gruneisen parameter will decrease with decreasing nanowire diameters. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. At high temperatures and for dislocation densities greater than 10{sup 14} m{sup -2} the lattice thermal conductivity would be limited by dislocation density, but for dislocation densities less than 10{sup 14} m{sup -2}, lattice thermal conductivity would be independent of that.

  18. Metallicity of InN and GaN surfaces exposed to NH{sub 3}.

    SciTech Connect (OSTI)

    Walkosz, W.; Zapol, P.; Stephenson, G. B. (Materials Science Division)

    2012-01-01T23:59:59.000Z

    A systematic study of energies and structures of InN and GaN (0001) surfaces exposed to NH{sub 3} and its decomposition products was performed with first-principles methods. A phenomenological model including electron counting contributions is developed based on calculated DFT energies and is used to identify low-energy structures. These predictions are checked with additional DFT calculations. The equilibrium phase diagrams are found to contain structures that violate the electron counting rule. Densities of states for these structures indicate n-type conductivity, consistent with available experimental results.

  19. Damage Evolution in GaN Under MeV Heavy Ion Implantation. | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation Proposed Newcatalyst phases onOrganizationElectronic2005-2007 BudgetFlightEvolution in GaN

  20. Films of bacteria at interfaces: three stages of behaviour

    E-Print Network [OSTI]

    Liana Vaccari; Daniel Allan; Nima Sharifi-Mood; Aayush Singh; Robert Leheny; Kathleen Stebe

    2015-03-25T23:59:59.000Z

    Bacterial attachment to a fluid interface can lead to the formation of a film with physicochemical properties that evolve with time. We study the time evolution of interface (micro)mechanics for interfaces between oil and bacterial suspensions by following the motion of colloidal probes trapped by capillarity to determine the interface microrheology. Initially, active bacteria at and near the interface drive superdiffusive motion of the colloidal probes. Over timescales of minutes, the bacteria form a viscoelastic film which we discuss as a quasi-two-dimensional, active, glassy system. To study late stage mechanics of the film, we use pendant drop elastometry. The films, grown over tens of hours on oil drops, are expanded and compressed by changing the drop volume. For small strains, by modeling the films as 2D Hookean solids, we estimate the film elastic moduli, finding values similar to those reported in the literature for the bacteria themselves. For large strains, the films are highly hysteretic. Finally, from wrinkles formed on highly compressed drops, we estimate film bending energies. The dramatic restructuring of the interface by such robust films has broad implications, e.g. in the study of active colloids, in understanding the community dynamics of bacteria, and in applied settings including bioremediation.

  1. Investigation of the optical properties of MoS{sub 2} thin films using spectroscopic ellipsometry

    SciTech Connect (OSTI)

    Yim, Chanyoung; O'Brien, Maria; Winters, Sinéad [School of Chemistry, Trinity College Dublin, Dublin 2 (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland); McEvoy, Niall [Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland); Mirza, Inam; Lunney, James G. [Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland); School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Duesberg, Georg S., E-mail: duesberg@tcd.ie [School of Chemistry, Trinity College Dublin, Dublin 2 (Ireland); Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2 (Ireland); Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2 (Ireland)

    2014-03-10T23:59:59.000Z

    Spectroscopic ellipsometry (SE) characterization of layered transition metal dichalcogenide (TMD) thin films grown by vapor phase sulfurization is reported. By developing an optical dispersion model, the extinction coefficient and refractive index, as well as the thickness of molybdenum disulfide (MoS{sub 2}) films, were extracted. In addition, the optical band gap was obtained from SE and showed a clear dependence on the MoS{sub 2} film thickness, with thinner films having a larger band gap energy. These results are consistent with theory and observations made on MoS{sub 2} flakes prepared by exfoliation, showing the viability of vapor phase derived TMDs for optical applications.

  2. Growth, structure and electrical properties of epitaxial thulium silicide thin films on silicon

    SciTech Connect (OSTI)

    Travlos, A.; Salamouras, N.; Boukos, N. [Institute of Materials Science, National Centre for Scientific Research Demokritos, Athens, (Greece) 15310] [Institute of Materials Science, National Centre for Scientific Research Demokritos, Athens, (Greece) 15310

    1997-02-01T23:59:59.000Z

    Thulium silicide thin films were grown on (100) and (111) Si by evaporation of Tm metal and Si layers and annealing in a vacuum. Electron microscopy and x-ray diffraction results showed that the TmSi{sub 2{minus}x} layers are of high crystalline quality grown epitaxially on Si. Electrical resistivity measurements showed that TmSi{sub 2{minus}x} layers are metallic exhibiting magnetic ordering below 3 K. {copyright} {ital 1997 American Institute of Physics.}

  3. Magnetization dynamics of cobalt grown on graphene

    SciTech Connect (OSTI)

    Berger, A. J.; White, S. P.; Adur, R.; Pu, Y.; Hammel, P. C., E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Amamou, W. [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Kawakami, R. K. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States)

    2014-05-07T23:59:59.000Z

    Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which has demonstrated promising results in a variety of material systems. This technique utilizes the resonant precession of magnetization in a ferromagnet to inject spin into an adjacent non-magnetic material. Spin pumping into graphene is attractive on account of its exceptional spin transport properties. This article reports on FMR characterization of cobalt grown on chemical vapor deposition graphene and examines the validity of linewidth broadening as an indicator of spin pumping. In comparison to cobalt samples without graphene, direct contact cobalt-on-graphene exhibits increased FMR linewidth—an often used signature of spin pumping. Similar results are obtained in Co/MgO/graphene structures, where a 1?nm MgO layer acts as a tunnel barrier. However, magnetometry, magnetic force microscopy, and Kerr microscopy measurements demonstrate increased magnetic disorder in cobalt grown on graphene, perhaps due to changes in the growth process and an increase in defects. This magnetic disorder may account for the observed linewidth enhancement due to effects such as two-magnon scattering or mosaicity. As such, it is not possible to conclude successful spin injection into graphene from FMR linewidth measurements alone.

  4. Energetic condensation growth of Nb thin films

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Krishnan, M.; Valderrama, E.; James, C.; Zhao, X.; Spradlin, J.; Feliciano, A-M Valente; Phillips, L.; Reece, C. E.; Seo, K.; Sung, Z. H.

    2012-03-01T23:59:59.000Z

    This paper describes energetic condensation growth of Nb films using a cathodic arc plasma, whose 60–120 eV ions penetrate a few monolayers into the substrate and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects) is accessible to the film. Heteroepitaxial films of Nb were grown on ?-plane sapphire and MgO crystals with good superconducting properties and crystal size (10??mm × 20??mm ) limited only by substrate size. The substrates were heated to temperatures of up to 700°C and coated at 125°C, 300°C, 500°C, and 700°C . Film thickness was varied from ?0.25???m to >3???m . Residual resistivity ratio (RRR) values (up to a record (RRR)=587 on MgO and (RRR)=328 on ?-sapphire) depend strongly on substrate annealing and deposition temperatures. X-ray diffraction spectra and pole figures reveal that RRR increases as the crystal structure of the Nb film becomes more ordered, consistent with fewer defects and, hence, longer electron mean-free path. A transition from Nb(110) to Nb(100) orientation on the MgO(100) lattice occurs at higher temperatures. This transition is discussed in light of substrate heating and energetic condensation physics. Electron backscattered diffraction and scanning electron microscope images complement the XRD data.

  5. Hot filament CVD of boron nitride films

    DOE Patents [OSTI]

    Rye, Robert R. (Albuquerque, NM)

    1992-01-01T23:59:59.000Z

    Using a hot filament (.apprxeq.1400.degree. C.) to activate borazine (B.sub.3 N.sub.3 H.sub.6) molecules for subsequent reaction with a direct line-of-sight substrate, transparent boron ntiride films as thick as 25,000 angstroms are grown for a substrate temperature as low as 100.degree. C. The minimum temperature is determined by radiative heating from the adjacent hot filament. The low temperature BN films show no indication of crystallinity with X-ray diffraction (XRD). X-ray photoelectron spectra (XPS) show the films to have a B:N ratio of 0.97:1 with no other XPS detectable impurities above the 0.5% level. Both Raman and infrared (IR) spectroscopy are characteristic of h-BN with small amounts of hydrogen detected as N-H and B-H bands in the IR spectrum. An important feature of this method is the separation and localization of the thermal activation step at the hot filament from the surface reaction and film growth steps at the substrate surface. This allows both higher temperature thermal activation and lower temperature film growth.

  6. Ferroelectric ultrathin perovskite films

    DOE Patents [OSTI]

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10T23:59:59.000Z

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  7. Atomistic simulation of Er irradiation induced defects in GaN nanowires

    SciTech Connect (OSTI)

    Ullah, M. W., E-mail: mohammad.ullah@helsinki.fi; Kuronen, A.; Djurabekova, F.; Nordlund, K. [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 (Finland); Stukowski, A. [Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2014-09-28T23:59:59.000Z

    Classical molecular dynamics simulation was used to irradiate a GaN nanowire with rear-earth erbium (Er). Ten cumulative irradiations were done using an ion energy of 37.5?keV on a 10?×?10?nm{sup 2} surface area which corresponds to a fluence of 1?×?10{sup 13?}cm{sup ?2}. We studied the location and types of defects produced in the irradiation. Er implantation leads to a net positive (expansion) strain in the nanowire and especially at the top region a clear expansion has been observed in the lateral and axial directions. The lattice expansion is due to the hydrostatic strain imposed by a large number of radiation induced defects at the top of the NW. Due to the large surface-to-volume ratio, most of the defects were concentrated at the surface region, which suggests that the experimentally observed yellow luminescence (YL) in ion implanted GaN NWs arises from surface defects. We observed big clusters of point defects and vacancy clusters which are correlated with stable lattice strain and the YL band, respectively.

  8. A Transient Stability Constrained Optimal Power Flow Deqiang Gan (M) Robert J. Thomas (F) Ray D. Zimmerman (M)

    E-Print Network [OSTI]

    1 A Transient Stability Constrained Optimal Power Flow Deqiang Gan (M) Robert J. Thomas (F) Ray D. The methodology involves a stability constrained Optimal Power Flow (OPF). The theoretical development between controllable generation dispatch and indices such as an energy margin, rotor angles, etc

  9. OPTIMIZATION OF GaN WINDOW LAYER FOR InGaN SOLAR CELLS USING POLARIZATION EFFECT

    E-Print Network [OSTI]

    Honsberg, Christiana

    on the design of wide-band gap GaN window layers for InGaN solar cells. Window layers serve to passivate the top into account during design of the solar cell to improve its collection efficiency. Previously, we have. The present work is a subset of the design optimization process for such solar cells, where we focus

  10. Role of Embedded Clustering in Dilute Magnetic Semiconductors: Cr Doped GaN X. Y. Cui,1

    E-Print Network [OSTI]

    Medvedeva, Julia E.

    , typically 5 (20­30) times smaller for Cr-based (Mn-based) III-V DMS than the value expected, 3 B= Cr4 BRole of Embedded Clustering in Dilute Magnetic Semiconductors: Cr Doped GaN X. Y. Cui,1 J. E configurations coexist and the statistical distribution and associated magnetism will depend sensitively

  11. Band gap tuning in GaN through equibiaxial in-plane strains S. K. Yadav,2

    E-Print Network [OSTI]

    Alpay, S. Pamir

    in photovoltaics and light emission diodes LEDs . The InGaN system has been intensively studied during the past to the large atomic size mismatch between Ga and In.3 Thus, other methods to tune the band gap are needed for potential appli- cations of GaN and related materials systems. It is well-known that the structure

  12. Epitaxial ferromagnetic oxide thin films on silicon with atomically sharp interfaces

    SciTech Connect (OSTI)

    Coux, P. de [Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Barcelona (Spain); CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4 (France); Bachelet, R.; Fontcuberta, J.; Sánchez, F., E-mail: fsanchez@icmab.es [Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Barcelona (Spain); Warot-Fonrose, B. [CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4 (France); Skumryev, V. [Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain and Dep. de Física, Univ. Autònoma de Barcelona, 08193 Bellaterra (Spain); Lupina, L.; Niu, G.; Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany)

    2014-07-07T23:59:59.000Z

    A bottleneck in the integration of functional oxides with silicon, either directly grown or using a buffer, is the usual formation of an amorphous interfacial layer. Here, we demonstrate that ferromagnetic CoFe{sub 2}O{sub 4} films can be grown epitaxially on Si(111) using a Y{sub 2}O{sub 3} buffer layer, and remarkably the Y{sub 2}O{sub 3}/Si(111) interface is stable and remains atomically sharp. CoFe{sub 2}O{sub 4} films present high crystal quality and high saturation magnetization.

  13. Quasi-Freestanding multilayer graphene films on the carbon face of SiC

    SciTech Connect (OSTI)

    Siegel, D. A.; Hwang, C. G.; Fedorov, A. V.; Lanzara, A.

    2010-06-30T23:59:59.000Z

    The electronic band structure of as-grown and doped graphene grown on the carbon face of SiC is studied by high-resolution angle-resolved photoemission spectroscopy, where we observe both rotations between adjacent layers and AB-stacking. The band structure of quasi-freestanding AB-bilayers is directly compared with bilayer graphene grown on the Si-face of SiC to study the impact of the substrate on the electronic properties of epitaxial graphene. Our results show that the C-face films are nearly freestanding from an electronic point of view, due to the rotations between graphene layers.

  14. Growth of Epitaxial gamma-Al2O3 Films on Rigid Single-Crystal Ceramic Substrates and Flexible, Single-Crystal-Like Metallic Substrates by Pulsed Laser Deposition

    SciTech Connect (OSTI)

    Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Wee, Sung Hun [ORNL

    2009-01-01T23:59:59.000Z

    Epitaxial -Al2O3 thin films were grown on diverse substrates using pulsed laser deposition. The high quality of epitaxial growth and cubic structure of -Al2O3 films was confirmed by x-ray diffraction. SrTiO3 and MgO single crystal substrates were used to optimize the growth conditions for epitaxial -Al2O3 film. Under the optimized conditions, epitaxial -Al2O3 thin films were grown on flexible, single-crystal-like, metallic templates. These included untextured Hastelloy substrates with a biaxially textured MgO layer deposited using ion-beam-assisted-deposition and biaxially textured Ni-W metallic tapes with epitaxially grown and a biaxially textured, MgO buffer layer. These biaxially textured, -Al2O3 films on flexible, single-crystal-like substrates are promising for subsequent epitaxial growth of various complex oxide films used for electrical, magnetic and electronic device applications.

  15. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    SciTech Connect (OSTI)

    Farrell, R.; Pagan, V.R.; Kabulski, A.; Kuchibhatla, S.; Harman, J.; Kasarla, K.R.; Rodak, L.E.; Hensel, J.P.; Famouri, P.; Korakakis, D.

    2008-01-01T23:59:59.000Z

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE-grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  16. Thermal Conductivity in Nanocrystalline Ceria Thin Films

    SciTech Connect (OSTI)

    Marat Khafizov; In-Wook Park; Aleksandr Chernatynskiy; Lingfeng He; Jianliang Lin; John J. Moore; David Swank; Thomas Lillo; Simon R. Phillpot; Anter El-Azab; David H. Hurley

    2014-02-01T23:59:59.000Z

    The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO2. A variety of microstructure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.

  17. Process for forming silicon carbide films and microcomponents

    DOE Patents [OSTI]

    Hamza, Alex V. (Livermore, CA); Balooch, Mehdi (Berkeley, CA); Moalem, Mehran (Berkeley, CA)

    1999-01-01T23:59:59.000Z

    Silicon carbide films and microcomponents are grown on silicon substrates at surface temperatures between 900 K and 1700 K via C.sub.60 precursors in a hydrogen-free environment. Selective crystalline silicon carbide growth can be achieved on patterned silicon-silicon oxide samples. Patterned SiC films are produced by making use of the high reaction probability of C.sub.60 with silicon at surface temperatures greater than 900 K and the negligible reaction probability for C.sub.60 on silicon dioxide at surface temperatures less than 1250 K.

  18. Investigation of the evolution of single domain ,,111...B CdTe films by molecular beam epitaxy on miscut ,,001...Si substrate

    E-Print Network [OSTI]

    Pennycook, Steve

    Investigation of the evolution of single domain ,,111...B CdTe films by molecular beam epitaxy; accepted for publication 22 July 1998 A comprehensive view of the microstructure of 111 B CdTe films grown and scanning transmission electron microscopy. It is found that in the initial growth stage, CdTe nucleates

  19. FAR-INFRARED SPECTROSCOPIC STUDY OF DIAMOND FILMS A. J. Gatesman*, R. H. Giles*, G. C. Phillips*, J. Waldman*, L. P. Bourget** and R. Post**

    E-Print Network [OSTI]

    Massachusetts at Lowell, University of

    **Applied Science and Technology, Inc., Woburn, MA 01801 High quality polycrystalline diamond films grownFAR-INFRARED SPECTROSCOPIC STUDY OF DIAMOND FILMS A. J. Gatesman*, R. H. Giles*, G. C. Phillips*, J in this frequency regime. INTRODUCTION Recent interest in the growth, production and application of diamond thin

  20. Correlation Between Optical Properties And Chemical Composition Of Sputter-deposited Germanium Cxide (GeOx) Films

    SciTech Connect (OSTI)

    Murphy, Neil R.; Grant, J. T.; Sun, L.; Jones, J. G.; Jakubiak, R.; Shutthanandan, V.; Ramana, Chintalapalle V.

    2014-03-18T23:59:59.000Z

    Germanium oxide (GeOx) films were grown on (1 0 0) Si substrates by reactive Direct-Current (DC) magnetron sputter-deposition using an elemental Ge target. The effects of oxygen gas fraction, ? = O2/(Ar + O2), on the deposition rate, structure, chemical composition and optical properties of GeOx films have been investigated. The chemistry of the films exhibits an evolution from pure Ge to mixed Ge + GeO + GeO2 and then finally to GeO2 upon increasing ? from 0.00 to 1.00. Grazing incidence X-ray analysis indicates that the GeOx films grown were amorphous. The optical properties probed by spectroscopic ellipsometry indicate that the effect of ? is significant on the optical constants of the GeOx films. The measured index of refraction (n) at a wavelength (?) of 550 nm is 4.67 for films grown without any oxygen, indicating behavior characteristic of semiconducting Ge. The transition from germanium to mixed Ge + GeO + GeO2 composition is associated with a characteristic decrease in n (? = 550 nm) to 2.62 and occurs at ? = 0.25. Finally n drops to 1.60 for ? = 0.50–1.00, where the films become GeO2. A detailed correlation between ?, n, k and stoichiometry in DC sputtered GeOx films is presented and discussed.

  1. Density dependence of the room temperature thermal conductivity of atomic layer deposition-grown amorphous alumina (Al{sub 2}O{sub 3})

    SciTech Connect (OSTI)

    Gorham, Caroline S.; Gaskins, John T.; Hopkins, Patrick E., E-mail: phopkins@virginia.edu [Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Parsons, Gregory N.; Losego, Mark D. [Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-06-23T23:59:59.000Z

    We report on the thermal conductivity of atomic layer deposition-grown amorphous alumina thin films as a function of atomic density. Using time domain thermoreflectance, we measure the thermal conductivity of the thin alumina films at room temperature. The thermal conductivities vary ?35% for a nearly 15% change in atomic density and are substrate independent. No density dependence of the longitudinal sound speeds is observed with picosecond acoustics. The density dependence of the thermal conductivity agrees well with a minimum limit to thermal conductivity model that is modified with a differential effective-medium approximation.

  2. Photonic Crystal Cavities in Cubic Polytype Silicon Carbide Films

    E-Print Network [OSTI]

    Radulaski, Marina; Buckley, Sonia; Rundquist, Armand; Provine, J; Alassaad, Kassem; Ferro, Gabriel; Vu?kovi?, Jelena

    2013-01-01T23:59:59.000Z

    We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1250 - 1600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

  3. In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100)

    SciTech Connect (OSTI)

    Al-Mahboob A.; Vescovo, E.; Sadowski, J.T.

    2013-08-18T23:59:59.000Z

    Metal phthalocyanines are attracting significant attention, owing to their potential for applications in chemical sensors, solar cells and organic magnets. As the electronic properties of molecular films are determined by their crystallinity and molecular packing, the optimization of film quality is important for improving the performance of organic devices. Here, we present the results of in situ low-energy electron microscopy / photoemission electron microscopy (LEEM/PEEM) studies of incorporation-limited growth [1] of manganese-phthalocyanine (MnPc) on Ag(100) surfaces. MnPc thin films were grown on both, bulk Ag(100) surface and thin Ag(100)/Fe(100) films, where substrate spin-polarized electronic states can be modified through tuning the thickness of the Ag film [2]. We also discuss the electronic structure and magnetic ordering in MnPc thin films, investigated by angle- and spin-resolved photoemission spectroscopy.

  4. High sensitive formaldehyde graphene gas sensor modified by atomic layer deposition zinc oxide films

    SciTech Connect (OSTI)

    Mu, Haichuan; Zhang, Zhiqiang; Wang, Keke; Xie, Haifen, E-mail: hfxie@ecust.edu.cn [Department of Physics, School of Science, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Zhao, Xiaojing; Liu, Feng [Department of Physics, Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China)

    2014-07-21T23:59:59.000Z

    Zinc oxide (ZnO) thin films with various thicknesses were fabricated by Atomic Layer Deposition on Chemical Vapor Deposition grown graphene films and their response to formaldehyde has been investigated. It was found that 0.5?nm ZnO films modified graphene sensors showed high response to formaldehyde with the resistance change up to 52% at the concentration of 9 parts-per-million (ppm) at room temperature. Meanwhile, the detection limit could reach 180 parts-per-billion (ppb) and fast response of 36?s was also obtained. The high sensitivity could be attributed to the combining effect from the highly reactive, top mounted ZnO thin films, and high conductive graphene base network. The dependence of ZnO films surface morphology and its sensitivity on the ZnO films thickness was also investigated.

  5. Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO{sub 2{+-}x}

    SciTech Connect (OSTI)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2012-12-01T23:59:59.000Z

    We have conducted a detailed thin film growth structure of oxygen engineered monoclinic HfO{sub 2{+-}x} grown by reactive molecular beam epitaxy. The oxidation conditions induce a switching between (111) and (002) texture of hafnium oxide. The band gap of oxygen deficient hafnia decreases with increasing amount of oxygen vacancies by more than 1 eV. For high oxygen vacancy concentrations, defect bands form inside the band gap that induce optical transitions and p-type conductivity. The resistivity changes by several orders of magnitude as a function of oxidation conditions. Oxygen vacancies do not give rise to ferromagnetic behavior.

  6. GaNAsP: An intermediate band semiconductor grown by gas-source molecular beam epitaxy

    SciTech Connect (OSTI)

    Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States)] [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Yu, K. M.; Walukiewicz, W. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kudrawiec, R. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Institute of Physics, Wroclaw University of Technology, Wybrzeze, Wyspianskiego 27, 50-370 Wroclaw (Poland); Luce, A. V. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Ting, M. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)] [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States); Tu, C. W. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)] [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

    2013-03-18T23:59:59.000Z

    Dilute nitride GaNAsP thin films were grown via a GaAsP metamorphic buffer on GaP(100) substrate with gas-source molecular beam epitaxy. The compositions of this III-V-V-V compound were determined by channeling Rutherford backscattering spectroscopy and nuclear reaction analysis. Photoreflectance shows two distinctive transitions from the valence band to the split conduction bands due to N incorporation. Photoluminescence and optical absorption show the fundamental bandgap of Ga(N)AsP is largely tailored by the small amount of N. The observed multiband characteristics and the bandgap tunability of GaNAsP are two merits that fit into the intermediate-band solar cell roadmap, and GaNAsP of high crystal quality provides a strong candidate for intermediate band solar cell materials.

  7. Correlation between structure and electrical transport in ion-irradiated graphene grown on Cu foils

    SciTech Connect (OSTI)

    Buchowicz, G.; Stone, P.R.; Robinson, J.T.; Cress, C.D.; Beeman, J.W.; Dubon, O.D.

    2010-11-04T23:59:59.000Z

    Graphene grown by chemical vapor deposition and supported on SiO2 and sapphire substrates was studied following controlled introduction of defects induced by 35 keV carbon ion irradiation. Changes in Raman spectra following fluences ranging from 1012 cm-2 to 1015 cm-2 indicate that the structure of graphene evolves from a highly-ordered layer, to a patchwork of disordered domains, to an essentially amorphous film. These structural changes result in a dramatic decrease in the Hall mobility by orders of magnitude while, remarkably, the Hall concentration remains almost unchanged, suggesting that the Fermi level is pinned at a hole concentration near 1x1013 cm-2. A model for scattering by resonant scatterers is in good agreement with mobility measurements up to an ion fluence of 1x1014 cm-2.

  8. Microstructure of highly strained BiFeO{sub 3} thin films: Transmission electron microscopy and electron-energy loss spectroscopy studies

    SciTech Connect (OSTI)

    Heon Kim, Young, E-mail: young.h.kim@kriss.re.kr [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Korea Research Institute of Standards and Science (KRISS), Daejeon 305-340 (Korea, Republic of); Bhatnagar, Akash; Pippel, Eckhard; Hesse, Dietrich [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Alexe, Marin [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); University of Warwick, Coventry CV4 7AL, West Midlands (United Kingdom)

    2014-01-28T23:59:59.000Z

    Microstructure and electronic structure of highly strained bismuth ferrite (BiFeO{sub 3}) thin films grown on lanthanum aluminate substrates are studied using high-resolution transmission and scanning transmission electron microscopies and electron energy loss spectroscopy (EELS). Monoclinic and tetragonal phases were observed in films grown at different temperatures, and a mix of both phases was detected in a film grown at intermediate temperature. In this film, a smooth transition of the microstructure was found between the monoclinic and the tetragonal phases. A considerable increase in the c-axis parameters was observed in both phases compared with the rhombohedral bulk phase. The off-center displacement of iron (Fe) ions was increased in the monoclinic phase as compared with the tetragonal phase. EEL spectra show different electronic structures in the monoclinic and the tetragonal phases. These experimental observations are well consistent with the results of theoretical first-principle calculations performed.

  9. Sensing performances of ZnO nanostructures grown under different oxygen pressures to hydrogen

    SciTech Connect (OSTI)

    Chu, Jin; Peng, Xiaoyan [Department of Physics, University of Puerto Rico Rio Piedras, San Juan, 00936-8377 PR (United States)] [Department of Physics, University of Puerto Rico Rio Piedras, San Juan, 00936-8377 PR (United States); Wang, Zhenbo [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China)] [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Feng, Peter, E-mail: P.feng@upr.edu [Department of Physics, University of Puerto Rico Rio Piedras, San Juan, 00936-8377 PR (United States)] [Department of Physics, University of Puerto Rico Rio Piedras, San Juan, 00936-8377 PR (United States)

    2012-12-15T23:59:59.000Z

    Graphical abstract: Display Omitted Highlights: ? Surface morphology depends on the oxygen pressure. ? Structural degradation was observed for the ZnO samples when oxygen pressure was overhigh. ? The sensitivity of the ZnO-based sensors increase with grown oxygen pressure. -- Abstract: For extensive use in an industrialized process of individual ZnO nanostructures applied in gas sensors, a simple, inexpensive, and safe synthesis process is required. Here, nanostructured ZnO films were grown by a pulsed laser deposition technique under different oxygen pressures. Scanning electron microscopy images show nanopores, nanotips, and nanoparticles are obtained and energy dispersive X-ray spectroscopy data indicate oxygen concentration of the synthesized samples increases monotonously with oxygen pressure. The sensor based on ZnO with high oxygen concentration has high sensitivity, rapid response (9 s) and recovery (80 s) behavior to 500 ppm hydrogen below 150 °C. Experimental data indicate that high oxygen concentration effectively improves the sensing properties of nanostructured ZnO.

  10. ZnO light-emitting diode grown by plasma-assisted metal organic chemical vapor deposition

    SciTech Connect (OSTI)

    Xu, W.Z.; Ye, Z.Z.; Zeng, Y.J.; Zhu, L.P.; Zhao, B.H.; Jiang, L.; Lu, J.G.; He, H.P.; Zhang, S.B. [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    2006-04-24T23:59:59.000Z

    We report a breakthrough in fabricating ZnO homojunction light-emitting diode by metal organic chemical vapor deposition. Using NO plasma, we are able to grow p-type ZnO thin films on n-type bulk ZnO substrates. The as-grown films on glass substrates show hole concentration of 10{sup 16}-10{sup 17} cm{sup -3} and mobility of 1-10 cm{sup 2} V{sup -1} s{sup -1}. Room-temperature photoluminescence spectra reveal nitrogen-related emissions. A typical ZnO homojunction shows rectifying behavior with a turn-on voltage of about 2.3 V. Electroluminescence at room temperature has been demonstrated with band-to-band emission at I=40 mA and defect-related emissions in the blue-yellow spectrum range.

  11. Field emission properties of phosphorus doped microwave plasma chemical vapor deposition diamond films by ion implantation

    E-Print Network [OSTI]

    Lee, Jong Duk

    2002; published 5 February 2003 Phosphorus doped polycrystalline diamond films were grown using ion the electrical char- acteristics of diamond FEAs to lower the operating voltage. Polycrystalline diamond hasField emission properties of phosphorus doped microwave plasma chemical vapor deposition diamond

  12. Voltage control of magnetic anisotropy in Fe films with quantum well states

    E-Print Network [OSTI]

    Bauer, Uwe

    The influence of a gate voltage on magnetic anisotropy is investigated in a thin Fe film epitaxially grown on a Ag(1,1,10) substrate and covered by MgO. Oscillations in step-induced magnetic anisotropy due to quantum well ...

  13. Epitaxial graphene prepared by chemical vapor deposition on single crystal thin iridium films on sapphire

    E-Print Network [OSTI]

    Boyer, Edmond

    Epitaxial graphene prepared by chemical vapor deposition on single crystal thin iridium films Cedex 9, France (Dated: 15 March 2011) Uniform single layer graphene was grown on single-crystal Ir. These graphene layers have a single crystallographic orientation and a very low density of defects, as shown

  14. Composition and chemical bonding of pulsed laser deposited carbon nitride thin films

    E-Print Network [OSTI]

    Brune, Harald

    properties such as extreme hardness, infrared transparency, chemical inertness, and excellent tribological with existing lubricants.7 DLC and CNx films can be grown with different meth- ods such as sputter deposition.11 There are still several open questions regarding how the growth conditions influence the resulting

  15. Efficient Switches for Solar Power Conversion: Four Quadrant GaN Switch Enabled Three Phase Grid-Tied Microinverters

    SciTech Connect (OSTI)

    None

    2012-02-13T23:59:59.000Z

    Solar ADEPT Project: Transphorm is developing power switches for new types of inverters that improve the efficiency and reliability of converting energy from solar panels into useable electricity for the grid. Transistors act as fast switches and control the electrical energy that flows in an electrical circuit. Turning a transistor off opens the circuit and stops the flow of electrical current; turning it on closes the circuit and allows electrical current to flow. In this way a transistor can be used to convert DC from a solar panel into AC for use in a home. Transphorm’s transistors will enable a single semiconductor device to switch electrical currents at high-voltage in both directions—making the inverter more compact and reliable. Transphorm is using Gallium Nitride (GaN) as a semiconductor material in its transistors instead of silicon, which is used in most conventional transistors, because GaN transistors have lower losses at higher voltages and switching frequencies.

  16. Growth of CdTe thin films on graphene by close-spaced sublimation method

    SciTech Connect (OSTI)

    Jung, Younghun; Yang, Gwangseok; Kim, Jihyun, E-mail: hyunhyun7@korea.ac.kr [Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of)] [Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Chun, Seungju; Kim, Donghwan [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of)] [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of)

    2013-12-02T23:59:59.000Z

    CdTe thin films grown on bi-layer graphene were demonstrated by using the close-spaced sublimation method, where CdTe was selectively grown on the graphene. The density of the CdTe domains was increased with increasing the number of the defective sites in the graphene, which was controlled by the duration of UV exposure. The CdTe growth rate on the bi-layer graphene electrodes was 400?nm/min with a bandgap energy of 1.45–1.49?eV. Scanning electron microscopy, micro-Raman spectroscopy, micro-photoluminescence, and X-ray diffraction technique were used to confirm the high quality of the CdTe thin films grown on the graphene electrodes.

  17. Superconductivity in textured Bi clusters/Bi{sub 2}Te{sub 3} films

    SciTech Connect (OSTI)

    Le, Phuoc Huu [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30049, Taiwan (China); Faculty of Basic Sciences, Can Tho University of Medicine and Pharmacy, 179 Nguyen Van Cu Street, Can Tho (Viet Nam); Tzeng, Wen-Yen; Chen, Hsueh-Ju; Luo, Chih Wei, E-mail: cwluo@mail.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Lin, Jiunn-Yuan [Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Leu, Jihperng, E-mail: jimleu@mail.nctu.edu.tw [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30049, Taiwan (China)

    2014-09-01T23:59:59.000Z

    We report superconductivity at an onset critical temperature below 3.1 K in topological insulator ?200-nm-thick Bi{sub 2}Te{sub 3} thin films grown by pulsed laser deposition. Using energy-dispersive X-ray spectroscopy elemental mapping and Auger electron spectroscopy elemental depth profiling, we clearly identified bismuth (Bi) precipitation and Bi cluster signatures. Superconductivity in the Bi{sub 2}Te{sub 3} films was attributed to the proximity effect of Bi clusters precipitated on the surface of the Bi{sub 2}Te{sub 3} films.

  18. Study of gain and photoresponse characteristics for back-illuminated separate absorption and multiplication GaN avalanche photodiodes

    SciTech Connect (OSTI)

    Wang, Xiaodong; Pan, Ming; Hou, Liwei; Xie, Wei [No. 50 Research Institute of China Electronics Technology Group Corporation, 200331 Shanghai (China); Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn; Xu, Jintong; Li, Xiangyang; Chen, Xiaoshuang, E-mail: xschen@mail.sitp.ac.cn; Lu, Wei [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083 Shanghai (China)

    2014-01-07T23:59:59.000Z

    The gain and photoresponse characteristics have been numerically studied for back-illuminated separate absorption and multiplication (SAM) GaN avalanche photodiodes (APDs). The parameters of fundamental models are calibrated by simultaneously comparing the simulated dark and light current characteristics with the experimental results. Effects of environmental temperatures and device dimensions on gain characteristics have been investigated, and a method to achieve the optimum thickness of charge layer is obtained. The dependence of gain characteristics and breakdown voltage on the doping concentration of the charge layer is also studied in detail to get the optimal charge layer. The bias-dependent spectral responsivity and quantum efficiency are then presented to study the photoresponse mechanisms inside SAM GaN APDs. It is found the responsivity peak red-shifts at first due to the Franz-Keldysh effect and then blue-shifts due to the reach-through effect of the absorption layer. Finally, a new SAM GaN/AlGaN heterojunction APD structure is proposed for optimizing SAM GaN APDs.

  19. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jamer M.; Sterbinsky G.; Assaf, B.; Arena, D.; Heiman, D.

    2014-12-07T23:59:59.000Z

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. The results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value. (auth)

  20. Self-doping effects in epitaxially grown graphene

    E-Print Network [OSTI]

    Siegel, David A.

    2009-01-01T23:59:59.000Z

    The electronic properties of graphene, Rev. Mod. Phys. (inE?ects in Epitaxially-Grown Graphene D.A. Siegel, 1, 2 S.Y.2009) Abstract Self-doping in graphene has been studied by

  1. Structural characterization of nanometer Sic films grown on Si J. P. Li and A. J. Steckl

    E-Print Network [OSTI]

    Steckl, Andrew J.

    by rapid thermal chemical vapor deposition carbonization with high propane flow rates at IlOO- 1300 "C. X and growth pro- cess. The materials characterization is made particularly difficult by the very small volume

  2. Nucleation and Growth of MOCVD Grown (Cr, Zn)O Films &ndash; Uniform Doping

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administration the ContributionsArms Control R&DNuclear fuel recycling in 4vs. Secondary Phase

  3. A Study of H and D doped ZnO epitaxial films grown by pulsed laser

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May Jun Jul(Summary)morphinanInformation Desert SouthwestTechnologies |November 2011A FirstEMSL ShellA Standard

  4. Conductivity of Oriented Samaria-Doped Ceria Thin Films Grown by

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmospheric Optical Depth7-1D: Vegetation Proposed New SubstationCleanCommunity2 ComputationalConcentrating SolarScience2.1

  5. Structure of Cr Film Epitaxially Grown on MgO (001). | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr MayAtmosphericNuclear Security Administrationcontroller systemsBiSiteNeutronStrategicOur MissionStructureSynthetase |

  6. Synthesis and electrochemical capacitance of long tungsten oxide nanorod arrays grown vertically on substrate

    SciTech Connect (OSTI)

    Park, Sun Hwa [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)] [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Kim, Young Heon; Lee, Tae Geol; Shon, Hyun Kyong [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)] [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Park, Hyun Min [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of) [Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Song, Jae Yong, E-mail: jysong@kriss.re.kr [Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Department of Nano Science, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

    2012-11-15T23:59:59.000Z

    Highlights: ? Growth of long amorphous tungsten oxide nanorods on a substrate. ? Formation of single-crystalline tungsten oxide nanorods by a heat-treatment. ? High electrochemical pseudocapacitance of 2.8 mF cm{sup ?2}. ? Excellent cyclability of psuedocapacitance up to 1000 cycles. -- Abstract: Long tungsten oxide nanorods are vertically grown on Al/W/Ti coated silicon substrates using a two-step anodization process. The first anodization of the Al film forms a mesh-like mask of anodic aluminum oxide, and the second anodization of the W film results in the formation of a buffer layer, a bottom nanorod, and a top nanorod of amorphous tungsten oxide. A pore-widening process prior to the second anodization leads to the enhancement of nanorod length above approximately 500 nm. After a heat-treatment, the tungsten oxide nanorods are crystallized to form a single crystalline structure while the buffer layer forms a polycrystalline structure. The crystalline tungsten oxide nanorods show a cyclic voltammogram retaining the quasi-rectangular shape of an electrochemically reversible faradaic redox reaction, i.e., a typical pseudocapacitive behavior. The maximum electrochemical capacitance per apparent surface area reaches approximately 2.8 mF cm{sup ?2} at the voltage scan rate of 20 mV s{sup ?1}, and the excellent cyclability of charge–discharge process is maintained up to 1000 cycles.

  7. Modified magnetic ground state in NiMn2O4 thin films

    SciTech Connect (OSTI)

    Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Toney, M. F.; Arenholz, E.; Suzuki, Y.; Iwata, J.M.

    2010-08-03T23:59:59.000Z

    We demonstrate the stabilization of a magnetic ground state in epitaxial NiMn2O4 (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low temperature. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+} while the canted moment ferrimagnetic ordering is preserved below 60 K.

  8. Modified Magnetic Ground State in Nimn (2) O (4) Thin Films

    SciTech Connect (OSTI)

    Nelson-Cheeseman, B.B.; Chopdekar, R.V.; Iwata, J.M.; Toney, M.F.; Arenholz, E.; Suzuki, Y.; /SLAC

    2012-08-23T23:59:59.000Z

    The authors demonstrate the stabilization of a magnetic ground state in epitaxial NiMn{sub 2}O{sub 4} (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low T. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+}, while the canted moment ferrimagnetic ordering is preserved below 60 K.

  9. Helium release and microstructural changes in Er(D,T)2-x3Hex films).

    SciTech Connect (OSTI)

    Gelles, D. S. (Pacific Northwest National Laboratory, Richland, WA); Browning, James Frederick; Snow, Clark Sheldon; Banks, James Clifford; Mangan, Michael A.; Rodriguez, Mark Andrew; Brewer, Luke N.; Kotula, Paul Gabriel

    2007-12-01T23:59:59.000Z

    Er(D,T){sub 2-x} {sup 3}He{sub x}, erbium di-tritide, films of thicknesses 500 nm, 400 nm, 300 nm, 200 nm, and 100 nm were grown and analyzed by Transmission Electron Microscopy, X-Ray Diffraction, and Ion Beam Analysis to determine variations in film microstructure as a function of film thickness and age, due to the time-dependent build-up of {sup 3}He in the film from the radioactive decay of tritium. Several interesting features were observed: One, the amount of helium released as a function of film thickness is relatively constant. This suggests that the helium is being released only from the near surface region and that the helium is not diffusing to the surface from the bulk of the film. Two, lenticular helium bubbles are observed as a result of the radioactive decay of tritium into {sup 3}He. These bubbles grow along the [111] crystallographic direction. Three, a helium bubble free zone, or 'denuded zone' is observed near the surface. The size of this region is independent of film thickness. Four, an analysis of secondary diffraction spots in the Transmission Electron Microscopy study indicate that small erbium oxide precipitates, 5-10 nm in size, exist throughout the film. Further, all of the films had large erbium oxide inclusions, in many cases these inclusions span the depth of the film.

  10. Order on disorder: Copper phthalocyanine thin films on technical substrates

    SciTech Connect (OSTI)

    Peisert, H.; Schwieger, T.; Auerhammer, J. M.; Knupfer, M.; Golden, M. S.; Fink, J.; Bressler, P. R.; Mast, M.

    2001-07-01T23:59:59.000Z

    We have studied the molecular orientation of the commonly used organic semiconductor copper phthalocyanine (CuPC) grown as thin films on the technically relevant substrates indium tin oxide, oxidized Si, and polycrystalline gold using polarization-dependent x-ray absorption spectroscopy, and compare the results with those obtained from single crystalline substrates [Au(110) and GeS(001)]. Surprisingly, the 20{endash}50 nm thick CuPC films on the technical substrates are as highly ordered as on the single crystals. Importantly, however, the molecular orientation in the two cases is radically different: the CuPC molecules stand on the technical substrates and lie on the single crystalline substrates. The reasons for this and its consequences for our understanding of the behavior of CuPC films in devices are discussed. {copyright} 2001 American Institute of Physics.

  11. Growth strains and creep in thermally grown alumina : oxide growth mechanisms.

    SciTech Connect (OSTI)

    Veal, B. W.; Paulikas, A. P.; Materials Science Division

    2008-01-01T23:59:59.000Z

    In situ measurements of growth strains and creep relaxation in {alpha}-Al{sub 2}O{sub 3} films, isothermally grown on {beta}-NiAl alloys at 1100 C, are reported and analyzed. Samples containing the reactive element Zr, and Zr-free samples, are examined. For Zr-free samples, steady state growth strains are compressive, whereas the growth strains are tensile when the reactive element (RE) is added to the alloy. This behavior is attributed to the counterflow of oxygen and aluminum interstitials, and to simultaneous counterflow of oxygen and aluminum vacancies, all moving through the grain boundaries. Cross diffusing oxygen and aluminum interstitials may merge and combine within the film, forming new oxide along grain boundary walls, a mechanism that leads to an in-plane compressive stress. Cross diffusing oxygen and aluminum vacancies will also merge and combine within the film; in this case material is removed from grain boundary walls, a mechanism that leads to an in-plane tensile stress. When no RE is present, the interstitial mechanism dominates and the resultant stress is compressive. Consistent with the 'dynamic segregation model', the RE slows the outdiffusion of Al interstitials permitting the tensile mechanism to dominate. This interpretation invokes the unconventional view that oxygen and aluminum interstitials and vacancies, created in and driven by the strong chemical gradient, all participate meaningfully in the scale growth process. Grain boundary diffusion measurements were obtained from low stress creep data, interpreted using the Coble model of grain boundary diffusion. Reported diffusion measurements of oxygen through grain boundaries of {alpha}-Al{sub 2}O{sub 3}, which are known to be inconsistent with oxide scale growth, are critically examined. A simple picture, a 'balanced defect model', emerges that is consistent with the dynamic segregation model, observed growth stresses and their dependence on the presence of a reactive element, sequential oxidation experiments, and our best knowledge about grain boundary diffusion coefficients.

  12. Spatial distribution and magnetism in poly-Cr-doped GaN from first principles X. Y. Cui,1 J. E. Medvedeva,2 B. Delley,3 A. J. Freeman,4 and C. Stampfl1

    E-Print Network [OSTI]

    Medvedeva, Julia E.

    Spatial distribution and magnetism in poly-Cr-doped GaN from first principles X. Y. Cui,1 J. E the spatial distribution and magnetic coupling of Cr-doped GaN, in which exhaustive structural and magnetic direct evidence that the distribution of the doped magnetic ions is neither homogeneous nor random

  13. 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim p s scurrent topics in solid state physics

    E-Print Network [OSTI]

    Sirenko, Andrei

    directing elements for light emitting devices. Many recent activities in the NSAG field have focused on Ga. Comparison of the stress properties between the nanodots, nanostripes, and continu- ous GaN film grown by metal organic vapor phase epitaxy. By varying the growth reactor pressure, we have been able to grow

  14. Site-specific local structure of Mn in artificial manganese ferrite films E. Kravtsov,1,2 D. Haskel,1 A. Cady,1 A. Yang,3 C. Vittoria,3 X. Zuo,4 and V. G. Harris3

    E-Print Network [OSTI]

    Haskel, Daniel

    Site-specific local structure of Mn in artificial manganese ferrite films E. Kravtsov,1,2 D. Haskel in manganese ferrite films grown under nonequilibrium conditions. The DAFS spectra were measured at a number. INTRODUCTION There has been considerable long-term interest in spinel ferrite materials due

  15. Photoelectrochemical undercut etching for fabrication of GaN microelectromechanical systems

    E-Print Network [OSTI]

    MacDonald, Noel C.

    -scale structures for microelectromechanical systems (MEMS), and the fracture properties of mineralized tissue for microelectromechanical systems (MEMS), specifically involving the high-cycle fatigue of micron-scale thin films

  16. Temperature dependence of photoconductivity in Zn-doped GaN

    SciTech Connect (OSTI)

    Reshchikov, Michael A. [Department of Physics, Virginia Commonwealth University, Richmond, VA 23284 (United States)

    2014-02-21T23:59:59.000Z

    In agreement with predictions from a model that explained an abrupt thermal quenching of the blue luminescence (BL) band in high-resistivity Zn-doped GaN [Reshchikov et al., Phys. Rev. B 84, 075212 (2011) and Phys. Rev. B 85, 245203 (2012)], we observed the stepwise decrease of photoconductivity in this material with increasing temperature. For the sample studied in this work, the decrease in photoconductivity occurred in two steps at characteristic temperatures T{sub 1} and T{sub 2}. The characteristic temperatures increased with increasing excitation intensity, very similar to the photoluminescence (PL) behavior. The steps in photoconductivity at about 100 K and 200 K are attributed to drop in the concentration of free electrons due to the thermal emission of holes from a shallow acceptor and the Zn{sub Ga} acceptor, respectively, to the valence band and their recombination with electrons via nonradiative centers. This finding supports the model suggested previously and helps to explain other examples of tunable photoconductivity reported in literature.

  17. Thermal Conductivity Measurement of Xe-Implanted Uranium Dioxide Thick Films using Multilayer Laser Flash Analysis

    SciTech Connect (OSTI)

    Nelson, Andrew T. [Los Alamos National Laboratory

    2012-08-30T23:59:59.000Z

    The Fuel Cycle Research and Development program's Advanced Fuels campaign is currently pursuing use of ion beam assisted deposition to produce uranium dioxide thick films containing xenon in various morphologies. To date, this technique has provided materials of interest for validation of predictive fuel performance codes and to provide insight into the behavior of xenon and other fission gasses under extreme conditions. In addition to the structural data provided by such thick films, it may be possible to couple these materials with multilayer laser flash analysis in order to measure the impact of xenon on thermal transport in uranium dioxide. A number of substrate materials (single crystal silicon carbide, molybdenum, and quartz) containing uranium dioxide films ranging from one to eight microns in thickness were evaluated using multilayer laser flash analysis in order to provide recommendations on the most promising substrates and geometries for further investigation. In general, the uranium dioxide films grown to date using ion beam assisted deposition were all found too thin for accurate measurement. Of the substrates tested, molybdenum performed the best and looks to be the best candidate for further development. Results obtained within this study suggest that the technique does possess the necessary resolution for measurement of uranium dioxide thick films, provided the films are grown in excess of fifty microns. This requirement is congruent with the material needs when viewed from a fundamental standpoint, as this length scale of material is required to adequately sample grain boundaries and possible second phases present in ceramic nuclear fuel.

  18. Evaluation of growth methods for the heteroepitaxy of non-polar (11-20) GaN on sapphire by MOVPE

    E-Print Network [OSTI]

    Oehler, F.; Sutherland, D.; Zhu, T.; Emery, R.; Badcock, T. J.; Kappers, M. J.; Humphreys, C. J.; Dawson, P.; Oliver, R. A.

    2014-09-16T23:59:59.000Z

    double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier... double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier...

  19. Effect of pressure and temperature on electronic structure of GaN in the zinc-blende structure

    SciTech Connect (OSTI)

    Degheidy, A. R., E-mail: ardegheidy@mans.edu.eg; Elkenany, E. B., E-mail: kena@mans.edu.eg [Mansoura University, Department of Physics, Faculty of Science (Egypt)

    2011-10-15T23:59:59.000Z

    The effect of the hydrostatic pressure and the temperature on the electronic structure in GaN semiconductor has been calculated using the local empirical pseudopotential method. The variation of the direct and indirect energy gaps with the pressure up to 120 kbar and with the temperature up to 500 K has been done. The calculated fundamental energy gap at different pressures and different temperatures are calculated and compared with the available experimental data which show excellent agreement. The effect of pressure and temperature on the refractive index of the considered materials has also been studied.

  20. Oxygen-assisted room-temperature deposition of CoPt3 films with perpendicular magnetic anisotropy

    E-Print Network [OSTI]

    Hellman, Frances

    Oxygen-assisted room-temperature deposition of CoPt3 films with perpendicular magnetic anisotropy B Jolla, California 92093 Received 23 July 2002; accepted 30 September 2002 Trace amounts of oxygen CoPt3 grown by vapor deposition at or slightly above room temperature. Oxygen is known to act

  1. Stress evaluation on hetero-epitaxial 3C-SiC film on (100) Si substrates R. Anzalone1,*

    E-Print Network [OSTI]

    Volinsky, Alex A.

    -power, high- frequency and high-temperature electronics due its outstanding electrical and thermal properties determines the final wafer bow, which has important implications with regard to the processing, the epitaxial of the impact that the growth rate has on the residual stress, wafer bow and film crystallinity of LPCVD-grown 3

  2. Investigation of deep level defects in CdTe thin films

    SciTech Connect (OSTI)

    Shankar, H.; Castaldini, A. [Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Dieguez, E.; Rubio, S. [Crystal Growth Lab, Department of Materials Physics, Faculty of Science, University Autonoma of Madrid, Ciudad Universitaria de Cantoblanco, 28049, Madrid (Spain); Dauksta, E.; Medvid, A. [Institute of Technical Physics, Riga Technical University, 14 Azenes Str, Riga, Latvia, Department of Materials (Latvia); Cavallini, A. [Department of Physics and Astronomy,University of Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy)

    2014-02-21T23:59:59.000Z

    In the past few years, a large body of work has been dedicated to CdTe thin film semiconductors, as the electronic and optical properties of CdTe nanostructures make them desirable for photovoltaic applications. The performance of semiconductor devices is greatly influenced by the deep levels. Knowledge of parameters of deep levels present in as-grown materials and the identification of their origin is the key factor in the development of photovoltaic device performance. Photo Induced Current Transient Spectroscopy technique (PICTS) has proven to be a very powerful method for the study of deep levels enabling us to identify the type of traps, their activation energy and apparent capture cross section. In the present work, we report the effect of growth parameters and LASER irradiation intensity on the photo-electric and transport properties of CdTe thin films prepared by Close-Space Sublimation method using SiC electrical heating element. CdTe thin films were grown at three different source temperatures (630, 650 and 700 °C). The grown films were irradiated with Nd:YAG LASER and characterized by Photo-Induced Current Transient Spectroscopy, Photocurrent measurementand Current Voltage measurements. The defect levels are found to be significantly influenced by the growth temperature.

  3. (001) Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

    SciTech Connect (OSTI)

    Yeo, Hong Goo, E-mail: hxy162@psu.edu; Trolier-McKinstry, Susan [Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-07-07T23:59:59.000Z

    Flexible metal foil substrates are useful in some microelectromechanical systems applications including wearable piezoelectric sensors or energy harvesters based on Pb(Zr,Ti)O{sub 3} (PZT) thin films. Full utilization of the potential of piezoelectrics on metal foils requires control of the film crystallographic texture. In this study, (001) oriented PZT thin films were grown by chemical solution deposition (CSD) on Ni foil and Si substrates. Ni foils were passivated using HfO{sub 2} grown by atomic layer deposition in order to suppress substrate oxidation during subsequent thermal treatment. To obtain the desired orientation of PZT film, strongly (100) oriented LaNiO{sub 3} films were integrated by CSD on the HfO{sub 2} coated substrates. A high level of (001) LaNiO{sub 3} and PZT film orientation were confirmed by X-ray diffraction patterns. Before poling, the low field dielectric permittivity and loss tangents of (001) oriented PZT films on Ni are near 780 and 0.04 at 1?kHz; the permittivity drops significantly on poling due to in-plane to out-of-plane domain switching. (001) oriented PZT film on Ni displayed a well-saturated hysteresis loop with a large remanent polarization ?36??C/cm{sup 2}, while (100) oriented PZT on Si showed slanted P-E hysteresis loops with much lower remanent polarizations. The |e{sub 31,f}| piezoelectric coefficient was around 10.6?C/m{sup 2} for hot-poled (001) oriented PZT film on Ni.

  4. E. P. R. CHARACTERIZATION OF p-TYPE AS GROWN AND Cl-COMPENSATED THM GROWN CdTe

    E-Print Network [OSTI]

    Boyer, Edmond

    199 E. P. R. CHARACTERIZATION OF p-TYPE AS GROWN AND Cl-COMPENSATED THM GROWN CdTe A. GOLTZENE électronique ont été observés dans du CdTe de haute résistivité, de type p ; à 4 K, on observe toujours des intense à g = 1,830 ± 0,002. Dans CdTe, fortement dopé au Cl, une raie à g = 2,003 ± 0,001 est déjà

  5. Growth and structure of epitaxial Pb{sub 1-x}Mn{sub x}Se(Ga) films

    SciTech Connect (OSTI)

    Nuriyev, I. R., E-mail: mhagiyev@yahoo.com; Gadzhiyev, M. B.; Sadigov, R. M. [National Academy of Sciences of Azerbaijan, Institute of Physics (Azerbaijan)

    2009-03-15T23:59:59.000Z

    The growth and structure of Pb{sub 1-x}Mn{sub x}Se (Ga) (N{sub Ga} = 0.8 at %) films with thicknesses of 0.3-0.5 {mu}m, grown on single-crystal PbSe{sub 1-x}S{sub x} (100) substrates by molecular-beam epitaxy, have been studied. It is established that films grow in a face-centered cubic lattice with the (100) orientation, reproducing the substrate orientation. The optimal conditions for obtaining photosensitive epitaxial films with perfect crystal structure are determined (W{sub 1/2} = 70-80'').

  6. Nitrogen use in switchgrass grown for bioenergy across the USA

    E-Print Network [OSTI]

    Pawlowski, Wojtek

    Nitrogen use in switchgrass grown for bioenergy across the USA V.N. Owens a , D.R. Viands b , H Available online 17 August 2013 Keywords: Nitrogen removal Switchgrass Bioenergy Nitrogen use efficiency as a forage, conservation, and bioenergy crop [1e5]. It offers a number of distinct benefits including broad

  7. CVD CNT CNT (Vapor-grown carbon fiber, VGCF)

    E-Print Network [OSTI]

    Maruyama, Shigeo

    CNT CNT CVD CNT CNT (Vapor-grown carbon fiber, VGCF) 10001300 CNT CVD Smalley CO 24 CCVD 1 #12; 27 mm 3% 200 sccm 800 10 10 Torr 300 sccm Ethanol tank Hot bath boat Ar/H2 Ar or Ethanol tank Hot bath Ethanol tank Hot bath Pressure gauge Maindraintube Subdraintube

  8. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect (OSTI)

    Jamer M.; Sterbinsky G.; Assaf, B.; Arena, D.; Heiman, D.

    2014-12-07T23:59:59.000Z

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. The results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value. (auth)

  9. Structure and dielectric properties of La{sub x}Hf{sub (1?x)}O{sub y} thin films: The dependence of components

    SciTech Connect (OSTI)

    Qi, Zeming, E-mail: zmqi@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Cheng, Xuerui [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002 (China); Zhang, Guobin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China); Li, Tingting [Institute of Microelectronics of Chinese Academy of Science, Beijing 100029 (China); Wang, Yuyin; Shao, Tao; Li, Chengxiang; He, Bo [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029 (China)

    2013-07-15T23:59:59.000Z

    Graphical abstract: - Highlights: • La{sub x}Hf{sub (1?x)}O{sub y} thin films were grown by pulse laser deposition method. • The thin film with 10% La/(La + Hf) atom ratio forms a cubic HfO{sub 2} phase. • The amorphous thin films due to more La introduced have almost same local structure. • The main infrared phonon modes move to lower frequency for the amorphous thin films. • The static dielectric constants of the amorphous thin films increase with La content. - Abstract: La{sub x}Hf{sub (1?x)}O{sub y} (x = 0, 0.1, 0.3, 0.5, 0.7, y=2?(1/2)x) thin films were grown by pulsed laser deposition (PLD) method. The component dependence of the structure and vibration properties of these thin films is studied by combining X-ray diffraction, X-ray absorption fine structure (XAFS) and infrared spectroscopy. The thin film with 10% La/(La + Hf) atom ratio forms a cubic HfO{sub 2} phase and it has the largest static dielectric constant. More La atoms introduced cause amorphous phase formed and the static dielectric constants increase with the La content. Although XAFS indicates that these amorphous thin films have almost same local structures, the infrared phonon modes with most contribution to the static dielectric constant move to lower frequency, which results in the component dependence of the dielectric constant.

  10. assisted grown silicon: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    SOLAR CELLS FROM THE POROUS SILICON PROCESS APPLYING CONVECTION for the first time to monocrystalline Si thin-film solar cells from the porous silicon (PSI) layer transfer for...

  11. Stabilized chromium oxide film

    DOE Patents [OSTI]

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04T23:59:59.000Z

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  12. Stabilized chromium oxide film

    DOE Patents [OSTI]

    Garwin, Edward L. (Los Altos, CA); Nyaiesh, Ali R. (Palo Alto, CA)

    1988-01-01T23:59:59.000Z

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  13. Thick film hydrogen sensor

    DOE Patents [OSTI]

    Hoffheins, Barbara S. (Knoxville, TN); Lauf, Robert J. (Oak Ridge, TN)

    1995-01-01T23:59:59.000Z

    A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors.

  14. The reaction of carbon tetrachloride with gallium arsenide ,,001... L. Li., S, Gan, B.-K. Han, H. Qi, and R. F. Hicksa)

    E-Print Network [OSTI]

    Li, Lian

    The reaction of carbon tetrachloride with gallium arsenide ,,001... L. Li., S, Gan, B.-K. Han, H, California 90095 Received 26 June 1997; accepted for publication 30 December 1997 Carbon tetrachloride of steps during the vapor-phase epitaxial growth of III­V compound semiconductors.3,4 Carbon tetrachloride

  15. STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN K.K. GAN, W. FERNANDO, H.P. KAGAN, R.D. KASS, A. LAW,

    E-Print Network [OSTI]

    Gan, K. K.

    that the main radiation effect is bulk damage in the VCSEL and PIN with the displacement of atoms. After five and VCSEL arrays coupled to radiation-hard ASICs produced for the current pixel optical link [5], the DORIC1 STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS K.K. GAN, W. FERNANDO, H.P. KAGAN, R

  16. Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M. FEENSTRA

    E-Print Network [OSTI]

    Feenstra, Randall

    ]. Silicon carbide has a much better lattice match to GaN (3.4%), and has gained in popularity in recent years as a substrate for both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy of Ga where a transition between streaky and spotty behavior occurs in the reflection high energy electron

  17. Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

    SciTech Connect (OSTI)

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E.; Miller, D. J.; Balachandran, U.

    2002-08-12T23:59:59.000Z

    Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.

  18. Niobium thin film deposition studies on copper surfaces for superconducting radio frequency cavity applications

    SciTech Connect (OSTI)

    W. M. Roach, D. B. Beringer, J. R. Skuza, W. A. Oliver, C. Clavero, C. E. Reece, R. A. Lukaszew

    2012-06-01T23:59:59.000Z

    Thin film coatings have the potential to increase both the thermal efficiency and accelerating gradient in superconducting radio frequency accelerator cavities. However, before this potential can be realized, systematic studies on structure-property correlations in these thin films need to be carried out since the reduced geometry, combined with specific growth parameters, can modify the physical properties of the materials when compared to their bulk form. Here, we present our systematic studies of Nb thin films deposited onto Cu surfaces to clarify possible reasons for the limited success that this process exhibited in previous attempts. We compare these films with Nb grown on other surfaces. In particular, we study the crystal structure and surface morphology and their effect on superconducting properties, such as critical temperature and lower critical field. We found that higher deposition temperature leads to a sharper critical temperature transition, but also to increased roughness indicating that there are competing mechanisms that must be considered for further optimization.

  19. Pulsed laser ablation growth and doping of epitaxial compound semiconductor films

    SciTech Connect (OSTI)

    Lowndes, D.H.; Rouleau, C.M.; Geohegan, D.B.; Budai, J.D.; Poker, D.B. [Oak Ridge National Lab., TN (United States). Solid State Div.; Puretzky, A.A. [Inst. of Spectroscopy, Troitsk (Russian Federation); Strauss, M.A.; Pedraza, A.J.; Park, J.W. [Univ. of Tennessee, Knoxville, TN (United States)

    1995-12-01T23:59:59.000Z

    Pulsed laser ablation (PLA) has several characteristics that are potentially attractive for the growth and doping of chemically complex compound semiconductors including (1) stoichiometric (congruent) transfer of composition from target to film, (2) the use of reactive gases to control film composition and/or doping via energetic-beam-induced reactions, and (3) low-temperature nonequilibrium phase formation in the laser-generated plasma ``plume.`` However, the electrical properties of compound semiconductors are far more sensitive to low concentrations of defects than are the oxide metals/ceramics for which PLA has been so successful. Only recently have doped epitaxial compound semiconductor films been grown by PLA. Fundamental studies are being carried out to relate film electrical and microstructural properties to the energy distribution of ablated species, to the temporal evolution of the ablation pulse in ambient gases, and to beam assisted surface and/or gas-phase reactions. In this paper the authors describe results of ex situ Hall effect, high-resolution x-ray diffraction, transmission electron microscopy, and Rutherford backscattering measurements that are being used in combination with in situ RHEED and time-resolved ion probe measurements to evaluate PLA for growth of doped epitaxial compound semiconductor films and heterostructures. Examples are presented and results analyzed for doped II-VI, I-III-VI, and column-III nitride materials grown recently in this and other laboratories.

  20. Inclined-substrate deposition of biaxially textured magnesium oxide thin films for YBCO coated conductors.

    SciTech Connect (OSTI)

    Ma, B.; Li, M.; Jee, Y. A.; Koritala, R. E.; Fisher, B. L.; Balachandran, U.; Energy Technology

    2002-02-01T23:59:59.000Z

    Highly textured MgO films were grown by the inclined-substrate deposition (ISD) technique at a high deposition rate. A columnar grain with a roofing-tile-shaped surface was observed in these MgO films. X-ray pole figure, and {phi}- and {omega}-scan were used to characterize in-plane and out-of-plane textures. MgO films deposited when the incline angle {alpha} was 55 and 30 degrees exhibited the best in-plane and out-of-plane texture, respectively. High-quality YBCO films were epitaxially grown on ISD-MgO-buffered Hastelloy C substrates by pulsed laser deposition. {Tc}=88 K, with sharp transition, and j{sub c} values of {approx}2x10{sup 5} A/cm{sup 2} at 77 K in zero field were observed on films 5 mm wide and 1 cm long. This work has demonstrated that biaxially textured ISD MgO buffer layers deposited on metal substrates are excellent candidates for fabrication of high-quality YBCO coated conductors.

  1. Diamond and diamond-like carbon films for advanced electronic applications

    SciTech Connect (OSTI)

    Siegal, M.P.; Friedmann, T.A.; Sullivan, J.P. [and others

    1996-03-01T23:59:59.000Z

    Aim of this laboratory-directed research and development (LDRD) project was to develop diamond and/or diamond-like carbon (DLC) films for electronic applications. Quality of diamond and DLC films grown by chemical vapor deposition (CVD) is not adequate for electronic applications. Nucleation of diamond grains during growth typically results in coarse films that must be very thick in order to be physically continuous. DLC films grown by CVD are heavily hydrogenated and are stable to temperatures {le} 400{degrees}C. However, diamond and DLC`s exceptional electronic properties make them candidates for integration into a variety of microelectronic structures. This work studied new techniques for the growth of both materials. Template layers have been developed for the growth of CVD diamond films resulting in a significantly higher nucleation density on unscratched or unprepared Si surfaces. Hydrogen-free DLC with temperature stability {le} 800{degrees}C has been developed using energetic growth methods such as high-energy pulsed-laser deposition. Applications with the largest system impact include electron-emitting materials for flat-panel displays, dielectrics for interconnects, diffusion barriers, encapsulants, and nonvolatile memories, and tribological coatings that reduce wear and friction in integrated micro-electro-mechanical devices.

  2. 99.996 %{sup 12}C films isotopically enriched and deposited in situ

    SciTech Connect (OSTI)

    Dwyer, K. J. [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20740 (United States) [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20740 (United States); National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8423 (United States); Pomeroy, J. M.; Simons, D. S. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8423 (United States)] [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8423 (United States)

    2013-06-24T23:59:59.000Z

    Ionizing natural abundance carbon dioxide gas, we extract and mass select the ions, depositing thin films isotopically enriched to 99.9961(4) %{sup 12}C as measured by secondary ion mass spectrometry (SIMS). In solid state quantum information, coherence times of nitrogen-vacancy (NV) centers in {sup 12}C enriched diamond exceeding milliseconds demonstrate the viability of NV centers as qubits, motivating improved isotopic enrichment. NV centers in diamond are particularly attractive qubit candidates due to the optical accessibility of the spin states. We present SIMS analysis and cross-sectional scanning electron microscopy of {sup 12}C enriched thin film samples grown with this method.

  3. Group I-III-VI.sub.2 semiconductor films for solar cell application

    DOE Patents [OSTI]

    Basol, Bulent M. (Redondo Beach, CA); Kapur, Vijay K. (Northridge, CA)

    1991-01-01T23:59:59.000Z

    This invention relates to an improved thin film solar cell with excellent electrical and mechanical integrity. The device comprises a substrate, a Group I-III-VI.sub.2 semiconductor absorber layer and a transparent window layer. The mechanical bond between the substrate and the Group I-III-VI.sub.2 semiconductor layer is enhanced by an intermediate layer between the substrate and the Group I-III-VI.sub.2 semiconductor film being grown. The intermediate layer contains tellurium or substitutes therefor, such as Se, Sn, or Pb. The intermediate layer improves the morphology and electrical characteristics of the Group I-III-VI.sub.2 semiconductor layer.

  4. Characterization of Ultrathin Films of -Al2O3 and the Chemistry of 1,3-Butadiene on NiAl(001) and -Al2O3

    E-Print Network [OSTI]

    Characterization of Ultrathin Films of -Al2O3 and the Chemistry of 1,3-Butadiene on NiAl(001) and -Al2O3 Michelle M. Ivey, Kathryn A. Layman, Armen Avoyan, Heather C. Allen, and John C. HemmingerVine, California 92697 ReceiVed: October 3, 2002; In Final Form: March 27, 2003 Ultrathin films of -Al2O3 grown

  5. MICROSTRUCTURE STUDY ON THE La0.7Sr0.3MnO3 AND RARE-EARTH OXIDE VERTICALLY ALIGNED NANOCOMPOSITE THIN FILMS

    E-Print Network [OSTI]

    Hazariwala, Harshad

    2011-05-05T23:59:59.000Z

    Two-phase (La0.7Sr0.3MnO3)0.5:(CeO2)0.5 (LSMO:CeO2) heteroepitaxial nanocomposite films were grown on SrTiO3 (STO) (001) by pulsed laser deposition. XRD and TEM results show that LSMO:CeO2 films epitaxially grow on STO as self-assembled vertically...

  6. LiMnPO4 Nanoplate Grown via Solid-State Reaction in Molten Hydrocarbon...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    LiMnPO4 Nanoplate Grown via Solid-State Reaction in Molten Hydrocarbon for Li-ion Battery Cathode. LiMnPO4 Nanoplate Grown via Solid-State Reaction in Molten Hydrocarbon for Li-ion...

  7. Nano transfer and nanoreplication using deterministically grown sacrificial nanotemplates

    DOE Patents [OSTI]

    Melechko, Anatoli V. (Oak Ridge, TN); McKnight, Timothy E. (Greenback, TN); Guillorn, Michael A. (Ithaca, NY); Ilic, Bojan (Ithaca, NY); Merkulov, Vladimir I. (Knoxville, TX); Doktycz, Mitchel J. (Knoxville, TN); Lowndes, Douglas H. (Knoxville, TN); Simpson, Michael L. (Knoxville, TN)

    2012-03-27T23:59:59.000Z

    Methods, manufactures, machines and compositions are described for nanotransfer and nanoreplication using deterministically grown sacrificial nanotemplates. An apparatus, includes a substrate and a nanoconduit material coupled to a surface of the substrate. The substrate defines an aperture and the nanoconduit material defines a nanoconduit that is i) contiguous with the aperture and ii) aligned substantially non-parallel to a plane defined by the surface of the substrate.

  8. Thin film hydrogen sensor

    DOE Patents [OSTI]

    Cheng, Y.T.; Poli, A.A.; Meltser, M.A.

    1999-03-23T23:59:59.000Z

    A thin film hydrogen sensor includes a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end. 5 figs.

  9. Thin film hydrogen sensor

    DOE Patents [OSTI]

    Cheng, Yang-Tse (Rochester Hills, MI); Poli, Andrea A. (Livonia, MI); Meltser, Mark Alexander (Pittsford, NY)

    1999-01-01T23:59:59.000Z

    A thin film hydrogen sensor, includes: a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end.

  10. spe438-20 page 1 Garrison, N.J., Busby, C.J., Gans, P.B., Putirka, K., and Wagner, D.L., 2008, A mantle plume beneath California? The mid-Miocene Lovejoy flood basalt, northern

    E-Print Network [OSTI]

    Busby, Cathy

    -Miocene Lovejoy flood basalt, northern California Noah J. Garrison Cathy J. Busby Phillip B. Gans Department the eastern Snake River Plain toward the Yellowstone caldera (Armstrong et al., 1975; Rodgers et al., 1990

  11. Vehicle Technologies Office Merit Review 2014: Advanced Low-Cost SiC and GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives

    Broader source: Energy.gov [DOE]

    Presentation given by APEI Inc. at 2014 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about Advanced low-cost SIC and GaN wide...

  12. Photonic Crystal Cavities in Cubic (3C) Polytype Silicon Carbide Films

    E-Print Network [OSTI]

    Marina Radulaski; Thomas M. Babinec; Sonia Buckley; Armand Rundquist; J Provine; Kassem Alassaad; Gabriel Ferro; Jelena Vu?kovi?

    2013-11-30T23:59:59.000Z

    We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1,250 - 1,600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

  13. Characterization of few-layered graphene grown by carbon implantation

    SciTech Connect (OSTI)

    Lee, Kin Kiong; McCallum, Jeffrey C.; Jamieson, David N. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Parkville, Victoria 3010 (Australia)

    2014-02-21T23:59:59.000Z

    Graphene is considered to be a very promising material for applications in nanotechnology. The properties of graphene are strongly dependent on defects that occur during growth and processing. These defects can be either detrimental or beneficial to device performance depending on defect type, location and device application. Here we present experimental results on formation of few-layered graphene by carbon ion implantation into nickel films and characteristics of graphene devices formed by graphene transfer and lithographic patterning. Micro-Raman spectroscopy was used to determine the number of graphene layers formed and identify defects arising from the device processing. The graphene films were cleaned by annealing in vacuum. Transport properties of cleaned graphene films were investigated by fabrication of back-gated field-effect transistors, which exhibited high hole and electron mobility of 1935 and 1905 cm2/Vs, respectively.

  14. Thin Film Photovoltaics Research

    Broader source: Energy.gov [DOE]

    The U.S. Department of Energy (DOE) supports research and development of four thin-film technologies on the path to achieving cost-competitive solar energy, including:

  15. Inversion by metalorganic chemical vapor deposition from N- to Ga-polar gallium nitride and its application to multiple quantum well light-emitting diodes

    SciTech Connect (OSTI)

    Hosalli, A. M.; Van Den Broeck, D. M.; Bedair, S. M. [Department of Electrical and Computer Engineering, NCSU, Raleigh, North Carolina 27695 (United States)] [Department of Electrical and Computer Engineering, NCSU, Raleigh, North Carolina 27695 (United States); Bharrat, D.; El-Masry, N. A. [Department of Material Science and Engineering, NCSU, Raleigh, North Carolina 27695 (United States)] [Department of Material Science and Engineering, NCSU, Raleigh, North Carolina 27695 (United States)

    2013-12-02T23:59:59.000Z

    We demonstrate a metalorganic chemical vapor deposition growth approach for inverting N-polar to Ga-polar GaN by using a thin inversion layer grown with high Mg flux. The introduction of this inversion layer allowed us to grow p-GaN films on N-polar GaN thin film. We have studied the dependence of hole concentration, surface morphology, and degree of polarity inversion for the inverted Ga-polar surface on the thickness of the inversion layer. We then use this approach to grow a light emitting diode structure which has the MQW active region grown on the advantageous N-polar surface and the p-layer grown on the inverted Ga-polar surface.

  16. Improving thermostability of CrO{sub 2} thin films by doping with Sn

    SciTech Connect (OSTI)

    Ding, Yi; Wang, Ziyu; Liu, Shuo; Shi, Jing; Yin, Di, E-mail: dyin@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yuan, Cheng; Lu, Zhihong, E-mail: zludavid@live.com [School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Xiong, Rui, E-mail: xiongrui@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Wuhan 430062 (China)

    2014-09-01T23:59:59.000Z

    Chromium dioxide (CrO{sub 2}) is an ideal material for spin electronic devices since it has almost 100% spin polarization near Fermi level. However, it is thermally unstable and easily decomposes to Cr{sub 2}O{sub 3} even at room temperature. In this study, we try to improve the thermal stability of CrO{sub 2} thin films by doping with Sn whose oxide has the same structure as CrO{sub 2}. High quality epitaxial CrO{sub 2} and Sn-doped CrO{sub 2} films were grown on single crystalline TiO{sub 2} (100) substrates by chemical vapor deposition. Sn{sup 4+} ions were believed to be doped into CrO{sub 2} lattice and take the lattice positions of Cr{sup 4+}. The magnetic measurements show that Sn-doping leads to a decrease of magnetocrystalline anisotropy. The thermal stabilities of the films were evaluated by annealing the films at different temperatures. Sn-doped films can withstand a temperature up to 510?°C, significantly higher than what undoped films can do (lower than 435?°C), which suggests that Sn-doping indeed enhances the thermal stability of CrO{sub 2} films. Our study also indicates that Sn-doping may not change the essential half metallic properties of CrO{sub 2}. Therefore, Sn-doped CrO{sub 2} is expected to be very promising for applications in spintronic devices.

  17. Synthesis and Characterization of Pure and Doped Ceria Films by Sol-Gel and Sputtering

    SciTech Connect (OSTI)

    Koch, K.T.; Saraf, L.

    2004-01-01T23:59:59.000Z

    Pure and doped Ceria are known for their ability to gain or lose Oxygen, which is of interest to the Solid Oxide Fuel Cell (SOFC) and catalyst community. Current efforts are focused in SOFCs to reduce the operating temperature of the cell while maintaining ionic conduction. Ceria is known for its high ionic conductivity in the intermediate temperature region. (600-800° C) We have prepared pure and doped Ceria films by Sol-gel and magnetron sputtering methods. Enhanced grain-boundary contribution in the conductivity can be studied in the Sol-gel process due to excellent control over the synthesis conditions, which enabled us to control the average grain size. Sputtered films were grown and investigated as a prelude to possible multi-layered CeO2 structures in the near future. These films were characterized by X-ray diffraction (XRD), nuclear reaction analysis (NRA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Oxygen conduction measurements. We have observed greater volume diffusion in nanocrystalline Ceria compared to bulk polycrystalline films as a result of low density. Near surface diffusion properties with increasing temperature indicate a decrease in the volume diffusion as a result of grain growth. However, a linear increase in O2 content at ~600nm depth was observed and can be correlated to the redistribution of O2 in the samples. Surface roughness of <111> and <200> oriented Ceria films on Al2O3 and YSZ was observed to be 0.13nm and 0.397nm, respectively. In the case of Ceria grown on YSZ, structural properties from XRD results showed a highly oriented structure with cube on cube growth. XRD results from Ceria grown on Al2O3 showed an oriented structure whose degree of orientation appeared to be partially dependent on substrate temperature. Preliminary XPS results indicate reduction in Ceria from the Ce4+ to Ce3+ state near the surface.

  18. Proton-Conducting Films of Nanoscale Ribbons Formed by Exfoliation of the Layer Perovskite H2SrTa2O7

    E-Print Network [OSTI]

    Proton-Conducting Films of Nanoscale Ribbons Formed by Exfoliation of the Layer Perovskite H2SrTa2OTa2O7 were grown and characterized as solid-state proton conductors. The ribbons, made by exfoliation membranes made from layered materials such as exfoliated zirconium phosphate.12 Unfortunately, the proton

  19. Thickness dependence of magnetic anisotropy in thin Ni films electrodeposited onto the (011) and (001) surfaces of n-GaAs

    SciTech Connect (OSTI)

    Gubbiotti, G.; Carlotti, G.; Tacchi, S.; Liu, Y.-K.; Scheck, C.; Schad, R.; Zangari, G. [INFM CRS-SOFT, c/o Universita di Roma 'La Sapienza', I-00185, Rome (Italy); INFM UdR-Perugia, c/o Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); INFM-National Center for nanoStructures and bioSystem at Surfaces (S3) Modena, and Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); IINFM UdR-Perugia, Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); MINT Center, University of Alabama, Tuscaloosa Alabama 35401 (United States); Department of Materials Science and Engineering and Center for Electrochemical Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2005-05-15T23:59:59.000Z

    Brillouin light scattering from thermal spin waves has been exploited to investigate the thickness dependence of magnetic anisotropy of Ni films, with thickness in the range 7-35 nm, grown by electrodeposition onto either (011)- or (001)-GaAs substrates. In the former case, Ni films exhibit a well-defined in-plane uniaxial anisotropy induced by the symmetry of the substrate. In the case of the (001)-GaAs substrate, instead, the magnetic anisotropy results from a combination of both a fourfold and a twofold contribution. The physical mechanisms responsible for the observed anisotropy, as well as its dependence on film thickness, are discussed in detail.

  20. Stresses in thermally grown alumina scales near edges and corners.

    SciTech Connect (OSTI)

    Grimsditch, M.

    1998-06-03T23:59:59.000Z

    We have investigated the residual stress near edges and corners of thermally grown alumina scales. Micro-fluorescence measurements, performed on alloys with composition Fe-5Cr-28Al (at.%, bal. Fe) oxidized at 900 C, showed a large (>50%) reduction in hydrostatic stress in the vicinity of edges and corners. Surprisingly, stress relaxation persists out to distances ten times the scale thickness from the edge. Finite element analysis calculations confirm the experimental results and provide a considerably more detailed picture of the stress distribution and its components.

  1. Unusual thermopower of inhomogeneous graphene grown by chemical vapor deposition

    SciTech Connect (OSTI)

    Nam, Youngwoo, E-mail: youngwoo.nam@chalmers.se [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Sun, Jie; Lindvall, Niclas; Yurgens, August [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Jae Yang, Seung; Rae Park, Chong [Department of Materials Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of); Woo Park, Yung [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-01-13T23:59:59.000Z

    We report on thermopower (TEP) and resistance measurements of inhomogeneous graphene grown by chemical vapor deposition (CVD). Unlike the conventional resistance of pristine graphene, the gate-dependent TEP shows a large electron-hole asymmetry. This can be accounted for by inhomogeneity of the CVD-graphene where individual graphene regions contribute with different TEPs. At the high magnetic field and low temperature, the TEP has large fluctuations near the Dirac point associated with the disorder in the CVD-graphene. TEP measurements reveal additional characteristics of CVD-graphene, which are difficult to obtain from the measurement of resistance alone.

  2. Confirmation of intrinsic electron gap states at nonpolar GaN(1-100) surfaces combining photoelectron and surface optical spectroscopy

    SciTech Connect (OSTI)

    Himmerlich, M., E-mail: marcel.himmerlich@tu-ilmenau.de; Eisenhardt, A.; Shokhovets, S.; Krischok, S. [Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau (Germany); Räthel, J.; Speiser, E.; Neumann, M. D.; Navarro-Quezada, A.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Strasse 9, 12489 Berlin (Germany)

    2014-04-28T23:59:59.000Z

    The electronic structure of GaN(1–100) surfaces is investigated in-situ by photoelectron spectroscopy (PES) and reflection anisotropy spectroscopy (RAS). Occupied surface states 3.1?eV below the Fermi energy are observed by PES, accompanied by surface optical transitions found in RAS around 3.3?eV, i.e., below the bulk band gap. These results indicate that the GaN(1–100) surface band gap is smaller than the bulk one due to the existence of intra-gap states, in agreement with density functional theory calculations. Furthermore, the experiments demonstrate that RAS can be applied for optical surface studies of anisotropic crystals.

  3. Epitaxial thin films

    DOE Patents [OSTI]

    Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

    2006-04-25T23:59:59.000Z

    Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

  4. Physical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering

    SciTech Connect (OSTI)

    Mei, A. B.; Zhang, C.; Sardela, M.; Eckstein, J. N.; Rockett, A. [Departments of Materials Science, Physics, and the Materials Research Laboratory, University of Illinois, 104 South Goodwin, Urbana, Illinois 61801 (United States)] [Departments of Materials Science, Physics, and the Materials Research Laboratory, University of Illinois, 104 South Goodwin, Urbana, Illinois 61801 (United States); Howe, B. M. [Air Force Research Laboratory, Wright Patterson Air Force Base, Dayton, Ohio 45433-7817 (United States)] [Air Force Research Laboratory, Wright Patterson Air Force Base, Dayton, Ohio 45433-7817 (United States); Hultman, L. [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping (Sweden)] [Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping (Sweden); Petrov, I.; Greene, J. E. [Departments of Materials Science, Physics, and the Materials Research Laboratory, University of Illinois, 104 South Goodwin, Urbana, Illinois 61801 and Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping (Sweden)] [Departments of Materials Science, Physics, and the Materials Research Laboratory, University of Illinois, 104 South Goodwin, Urbana, Illinois 61801 and Thin Film Physics Division, Department of Physics (IFM), Linköping University, SE-58183 Linköping (Sweden)

    2013-11-15T23:59:59.000Z

    Single-crystal ZrN films, 830 nm thick, are grown on MgO(001) at 450 °C by magnetically unbalanced reactive magnetron sputtering. The combination of high-resolution x-ray diffraction reciprocal lattice maps, high-resolution cross-sectional transmission electron microscopy, and selected-area electron diffraction shows that ZrN grows epitaxially on MgO(001) with a cube-on-cube orientational relationship, (001){sub ZrN}?(001){sub MgO} and [100]{sub ZrN}?[100]{sub MgO}. The layers are essentially fully relaxed with a lattice parameter of 0.4575 nm, in good agreement with reported results for bulk ZrN crystals. X-ray reflectivity results reveal that the films are completely dense with smooth surfaces (roughness = 1.3 nm, consistent with atomic-force microscopy analyses). Based on temperature-dependent electronic transport measurements, epitaxial ZrN/MgO(001) layers have a room-temperature resistivity ?{sub 300K} of 12.0 ??-cm, a temperature coefficient of resistivity between 100 and 300 K of 5.6 × 10{sup ?8}?-cm K{sup ?1}, a residual resistivity ?{sub o} below 30 K of 0.78 ??-cm (corresponding to a residual resistivity ratio ?{sub 300?}/?{sub 15K} = 15), and the layers exhibit a superconducting transition temperature of 10.4 K. The relatively high residual resistivity ratio, combined with long in-plane and out-of-plane x-ray coherence lengths, ?{sub ?} = 18 nm and ?{sub ?} = 161 nm, indicates high crystalline quality with low mosaicity. The reflectance of ZrN(001), as determined by variable-angle spectroscopic ellipsometry, decreases slowly from 95% at 1 eV to 90% at 2 eV with a reflectance edge at 3.04 eV. Interband transitions dominate the dielectric response above 2 eV. The ZrN(001) nanoindentation hardness and modulus are 22.7 ± 1.7 and 450 ± 25 GPa.

  5. Highly conducting SrMoO{sub 3} thin films for microwave applications

    SciTech Connect (OSTI)

    Radetinac, Aldin, E-mail: aldin@oxide.tu-darmstadt.de; Mani, Arzhang; Ziegler, Jürgen; Alff, Lambert; Komissinskiy, Philipp, E-mail: komissinskiy@oxide.tu-darmstadt.de [Institute of Materials Science, TU Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Melnyk, Sergiy; Nikfalazar, Mohammad; Zheng, Yuliang; Jakoby, Rolf [Institute for Microwave Engineering and Photonics, TU Darmstadt, Merckstraße 25, 64283 Darmstadt (Germany)

    2014-09-15T23:59:59.000Z

    We have measured the microwave resistance of highly conducting perovskite oxide SrMoO{sub 3} thin film coplanar waveguides. The epitaxial SrMoO{sub 3} thin films were grown by pulsed laser deposition and showed low mosaicity and smooth surfaces with a root mean square roughness below 0.3?nm. Layer-by-layer growth could be achieved for film thicknesses up to 400?nm as monitored by reflection high-energy electron diffraction and confirmed by X-ray diffraction. We obtained a constant microwave resistivity of 29???·cm between 0.1 and 20?GHz by refining the frequency dependence of the transmission coefficients. Our result shows that SrMoO{sub 3} is a viable candidate as a highly conducting electrode material for all-oxide microwave electronic devices.

  6. Method for continuous control of composition and doping of pulsed laser deposited films

    DOE Patents [OSTI]

    Lowndes, Douglas H. (Knoxville, TN); McCamy, James W. (Knoxville, TN)

    1995-01-01T23:59:59.000Z

    A method for growing a deposit upon a substrate of semiconductor material involves the utilization of pulsed laser deposition techniques within a low-pressure gas environment. The substrate and a target of a first material are positioned within a deposition chamber and a low-pressure gas atmosphere is developed within the chamber. The substrate is then heated, and the target is irradiated, so that atoms of the target material are ablated from the remainder of the target, while atoms of the gas simultaneously are adsorbed on the substrate/film surface. The ablated atoms build up upon the substrate, together with the adsorbed gas atoms to form the thin-film deposit on the substrate. By controlling the pressure of the gas of the chamber atmosphere, the composition of the formed deposit can be controlled, and films of continuously variable composition or doping can be grown from a single target of fixed composition.

  7. Method for continuous control of composition and doping of pulsed laser deposited films by pressure control

    DOE Patents [OSTI]

    Lowndes, Douglas H. (Knoxville, TN); McCamy, James W. (Knoxville, TN)

    1996-01-01T23:59:59.000Z

    A method for growing a deposit upon a substrate of semiconductor material involves the utilization of pulsed laser deposition techniques within a low-pressure gas environment. The substrate and a target of a first material are positioned within a deposition chamber and a low-pressure gas atmosphere is developed within the chamber. The substrate is then heated, and the target is irradiated, so that atoms of the target material are ablated from the remainder of the target, while atoms of the gas simultaneously are adsorbed on the substrate/film surface. The ablated atoms build up upon the substrate, together with the adsorbed gas atoms to form the thin-film deposit on the substrate. By controlling the pressure of the gas of the chamber atmosphere, the composition of the formed deposit can be controlled, and films of continuously variable composition or doping can be grown from a single target of fixed composition.

  8. Pulsed laser deposition of epitaxial yttrium iron garnet films with low Gilbert damping and bulk-like magnetization

    SciTech Connect (OSTI)

    Onbasli, M. C., E-mail: onbasli@mit.edu; Kim, D. H.; Ross, C. A. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Kehlberger, A. [Institute of Physics, Johannes Gutenberg-University of Mainz, 55099 Mainz (Germany); Graduate School Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz (Germany); Jakob, G.; Kläui, M. [Institute of Physics, Johannes Gutenberg-University of Mainz, 55099 Mainz (Germany); Chumak, A. V.; Hillebrands, B. [Fachbereich Physik and Landesforschungszentrum, OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany)

    2014-10-01T23:59:59.000Z

    Yttrium iron garnet (YIG, Y {sub 3}Fe{sub 5}O{sub 12}) films have been epitaxially grown on Gadolinium Gallium Garnet (GGG, Gd{sub 3}Ga{sub 5}O{sub 12}) substrates with (100) orientation using pulsed laser deposition. The films were single-phase, epitaxial with the GGG substrate, and the root-mean-square surface roughness varied between 0.14 nm and 0.2 nm. Films with thicknesses ranging from 17 to 200 nm exhibited low coercivity (<2 Oe), near-bulk room temperature saturation moments (?135 emu cm{sup ?3}), in-plane easy axis, and damping parameters as low as 2.2 × 10{sup ?4}. These high quality YIG thin films are useful in the investigation of the origins of novel magnetic phenomena and magnetization dynamics.

  9. Uniform wafer-scale synthesis of graphene on evaporated Cu (111) film with quality comparable to exfoliated monolayer

    E-Print Network [OSTI]

    Tao, Li; Lee, Jongho; Chou, Harry; McDonnell, Stephen J; Ferrer, Domingo A; Babenco, Matias; Wallace, Robert M; Banerjee, Sanjay K; Ruoff, Rodney S; Akinwande, Deji

    2012-01-01T23:59:59.000Z

    Monolayer graphene has been grown on crystallized Cu (111) films on standard oxidized Si 100 mm wafers. The monolayer graphene demonstrates high uniformity (>97% coverage), with immeasurable defects (>95% defect-negligible) across the entire wafer. Key to these results is the phase transition of evaporated copper films from amorphous to crystalline at the growth temperature as corroborated by X-ray diffraction and electron backscatter diffraction. Noticeably, phase transition of copper film is observed on technologically ubiquitous oxidized Si wafer where the oxide is a standard amorphous thermal oxide. Ion mass spectroscopy indicates that the copper films can be purposely hydrogen-enriched during a hydrogen anneal which subsequently affords graphene growth with a sole carbonaceous precursor for low defect densities. Owing to the strong hexagonal lattice match, the graphene domains align to the Cu (111) domains, suggesting a pathway for increasing the graphene grains by maximizing the copper grain sizes. Fabr...

  10. Thin film photovoltaic device

    DOE Patents [OSTI]

    Catalano, A.W.; Bhushan, M.

    1982-08-03T23:59:59.000Z

    A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids. 5 figs.

  11. Thin film photovoltaic device

    DOE Patents [OSTI]

    Catalano, Anthony W. (Wilmington, DE); Bhushan, Manjul (Wilmington, DE)

    1982-01-01T23:59:59.000Z

    A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids.

  12. Investigation into the growth and structure of thin-film solid solutions of iron-based superconductors in the FeSe{sub 0.92}-FeSe{sub 0.5}Te{sub 0.5} system

    SciTech Connect (OSTI)

    Stepantsov, E. A., E-mail: stepantsov@ns.cryst.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Kazakov, S. M.; Belikov, V. V. [Moscow State University (Russian Federation)] [Moscow State University (Russian Federation); Makarova, I. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Arpaia, R.; Gunnarsson, R.; Lombardi, F. [Chalmers University of Technology, Department of Microtechnology and Nanoscience (Sweden)] [Chalmers University of Technology, Department of Microtechnology and Nanoscience (Sweden)

    2013-09-15T23:59:59.000Z

    Thin films of FeSe{sub 0.92} and FeSe{sub 0.5}Te{sub 0.5} iron chalcogenide superconductors and solid solutions containing these components in different ratios have been grown on the surface of LaAlO{sub 3} (10 1-bar 2) crystals by pulsed laser deposition. Films of solid solutions have been deposited by simultaneous laser ablation from two targets of the FeSe{sub 0.92} and FeSe{sub 0.5}Te{sub 0.5} stoichiometric compositions onto one substrate. An X-ray diffraction study of the film structure shows that the films grown are epitaxial and their lattice parameters regularly vary with the ratio of the deposited components, which was controllably varied by changing the ablation intensities from the targets.

  13. Formation of Nickel Silicide from Direct-liquid-injection Chemical-vapor-deposited Nickel Nitride Films

    SciTech Connect (OSTI)

    Li, Z.; Gordon, R; Li, H; Shenai, D; Lavoie, C

    2010-01-01T23:59:59.000Z

    Smooth, continuous, and highly conformal nickel nitride (NiN{sub x}) films were deposited by direct liquid injection (DLI)-chemical vapor deposition (CVD) using a solution of bis(N,N{prime}-di-tert-butylacetamidinato)nickel(II) in tetrahydronaphthalene as the nickel (Ni) source and ammonia (NH{sub 3}) as the coreactant gas. The DLI-CVD NiNx films grown on HF-last (100) silicon and on highly doped polysilicon substrates served as the intermediate for subsequent conversion into nickel silicide (NiSi), which is a key material for source, drain, and gate contacts in microelectronic devices. Rapid thermal annealing in the forming gas of DLI-CVD NiNx films formed continuous NiSi films at temperatures above 400 C. The resistivity of the NiSi films was 15{mu}{Omega} cm, close to the value for bulk crystals. The NiSi films have remarkably smooth and sharp interfaces with underlying Si substrates, thereby producing contacts for transistors with a higher drive current and a lower junction leakage. Resistivity and synchrotron X-ray diffraction in real-time during annealing of NiNx films showed the formation of a NiSi film at about 440 C, which is morphologically stable up to about 650 C. These NiSi films could find applications in future nanoscale complementary metal oxide semiconductor devices or three-dimensional metal-oxide-semiconductor devices such as Fin-type field effect transistors for the 22 nm technology node and beyond.

  14. Growth of HfO{sub 2} films using an alternate reaction of HfCl{sub 4} and O{sub 2} under atmospheric pressure

    SciTech Connect (OSTI)

    Takahashi, Naoyuki [Department of Materials Science and Technology, Faculty of Engineering Shizuoka University, 3-5-1 Johoku, Hamamatu, Shizuoka 432-8561 (Japan)]. E-mail: tntakah@ipc.shizuoka.ac.jp; Nonobe, Shinichi [Department of Materials Science and Technology, Faculty of Engineering Shizuoka University, 3-5-1 Johoku, Hamamatu, Shizuoka 432-8561 (Japan); Nakamura, Takato [Department of Materials Science and Technology, Faculty of Engineering Shizuoka University, 3-5-1 Johoku, Hamamatu, Shizuoka 432-8561 (Japan)

    2004-11-01T23:59:59.000Z

    HfO{sub 2} films were deposited onto a Si(100) substrate using an alternate reaction of HfCl{sub 4} and O{sub 2} under atmospheric pressure. Self-limiting growth of the HfO{sub 2} was achieved in the range of the growth temperature above 873K. The X-ray diffraction of the HfO{sub 2} films showed a typical diffraction pattern assigned to the monoclinic polycrystalline phase. Residual chloride concentration in HfO{sub 2} films were not higher than 0.1at%. When the growth temperature was 973K, the HfSiO{sub x} is formed in HfO{sub 2} film. This gives effective permittivity value of 9.6 for the HfO{sub 2} film grown at 573K.

  15. Magnetic properties of epitaxial Co-doped anatase TiO2 thin films with excellent structural quality

    SciTech Connect (OSTI)

    Kaspar, Tiffany C.; Droubay, Timothy C.; McCready, David E.; Nachimuthu, Ponnusamy; Heald, Steve M.; Wang, Chong M.; Lea, Alan S.; Shutthanandan, V.; Chambers, Scott A.; Toney, Michael F.

    2006-07-26T23:59:59.000Z

    The heteroepitaxy of Co-doped anatase TiO2 on LaAlO3(001) has been refined with the goal of determining the relationship between structural quality and magnetic ordering. By significantly reducing the deposition rate and substrate temperature, well-ordered Co:TiO2 films with unprecedented crystalline quality were obtained by oxygen-plasma-assisted molecular beam epitaxy, as characterized by x-ray diffraction. These films exhibit uniform Co doping, with no evidence of Co segregation or secondary phases throughout the film depth or on the surface. Despite the improvement in crystalline quality and Co distribution, the films exhibit negligible ferromagnetism, with saturation moments of only ~0.1 ?B/Co. This loss of ferromagnetism is in stark contrast to faster-grown Co:TiO2 films, where a higher growth rate and substrate temperature typically result in lower crystalline quality, a highly non-uniform Co distribution, and average saturation moments of ~1.2 ?B/Co. The presence of ferromagnetism in faster-grown Co:TiO2 does not appear to arise from intrinsic point defects present in the bulk material, such as charge-compensating oxygen vacancies, but is instead attributed to the presence of extended structural defects.

  16. Initial growth, refractive index, and crystallinity of thermal and plasma-enhanced atomic layer deposition AlN films

    SciTech Connect (OSTI)

    Van Bui, Hao, E-mail: H.VanBui@utwente.nl; Wiggers, Frank B.; Gupta, Anubha; Nguyen, Minh D.; Aarnink, Antonius A. I.; Jong, Michel P. de; Kovalgin, Alexey Y., E-mail: A.Y.Kovalgin@utwente.nl [MESA Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede (Netherlands)

    2015-01-01T23:59:59.000Z

    The authors have studied and compared the initial growth and properties of AlN films deposited on Si(111) by thermal and plasma-enhanced atomic layer deposition (ALD) using trimethylaluminum and either ammonia or a N{sub 2}-H{sub 2} mixture as precursors. In-situ spectroscopic ellipsometry was employed to monitor the growth and measure the refractive index of the films during the deposition. The authors found that an incubation stage only occurred for thermal ALD. The linear growth for plasma-enhanced ALD (PEALD) started instantly from the beginning due to the higher nuclei density provided by the presence of plasma. The authors observed the evolution of the refractive index of AlN during the growth, which showed a rapid increase up to a thickness of about 30?nm followed by a saturation. Below this thickness, higher refractive index values were obtained for AlN films grown by PEALD, whereas above that the refractive index was slightly higher for thermal ALD films. X-ray diffraction characterization showed a wurtzite crystalline structure with a (101{sup ¯}0) preferential orientation obtained for all the layers with a slightly better crystallinity for films grown by PEALD.

  17. Structure and features of the surface morphology of A{sup 4}B{sup 6} chalcogenide epitaxial films

    SciTech Connect (OSTI)

    Nuriyev, I. R., E-mail: afinnazarov@yahoo.com [Azerbaijan National Academy of Sciences, Institute of Physics (Azerbaijan)

    2009-12-15T23:59:59.000Z

    The structure and features of the surface morphology of Pb{sub 1-x}Mn{sub x}Se (x = 0.03) epitaxial films grown on freshly cleaved BaF{sub 2}(111) faces and PbSe{sub 1-x}S{sub x}(100) (x = 0.12) single-crystal wafers were investigated by molecular beam condensation and the hot-wall method. It is shown that the epitaxial films, in accordance with the data in the literature for other chalcogenides, grow in the (111) and (100) planes, repeating the substrate orientation. Black aggregates are observed on the film surface of the films grown. The results obtained are compared with the data in the literature and generalized for other chalcogenides: A{sup 4}B{sup 6}:Pb (S, Se, Te); Pb{sub 1-x}Sn{sub x} (S, Se, Te); and Pb{sub 1-x}Mn (Se, Te). It is established that the formation of black aggregates, which are second-phase inclusions on the surface of epitaxial films obtained by vacuum thermal deposition, is characteristic of narrow-gap A{sup 4}B{sup 6} chalcogenides.

  18. Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment

    SciTech Connect (OSTI)

    Trassinelli, M., E-mail: martino.trassinelli@insp.jussieu.fr; Marangolo, M.; Eddrief, M.; Etgens, V. H.; Gafton, V.; Hidki, S.; Lacaze, E.; Lamour, E.; Prigent, C.; Rozet, J.-P.; Steydli, S.; Zheng, Y.; Vernhet, D. [CNRS, UMR 7588, Institut des NanoSciences de Paris (INSP), F-75005 Paris (France); Sorbonne Universités, UPMC Univ. Paris 06, UMR 7588, INSP, F-75005 Paris (France)

    2014-02-24T23:59:59.000Z

    We present the investigation on the modifications of structural and magnetic properties of MnAs thin film epitaxially grown on GaAs induced by slow highly charged ions bombardment under well-controlled conditions. The ion-induced defects facilitate the nucleation of one phase with respect to the other in the first-order magneto-structural MnAs transition, with a consequent suppression of thermal hysteresis without any significant perturbation on the other structural and magnetic properties. In particular, the irradiated film keeps the giant magnetocaloric effect at room temperature opening new perspective on magnetic refrigeration technology for everyday use.

  19. Strain relaxation in epitaxial SrRuO{sub 3} thin films on LaAlO{sub 3} substrates

    SciTech Connect (OSTI)

    Gao, M.; Du, H.; Dai, C.; Lin, Y. [State Key Laboratory of Electronic Thin films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China)] [State Key Laboratory of Electronic Thin films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Ma, C. R.; Liu, M.; Collins, G.; Zhang, Y. M.; Chen, C. L. [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA and Department of Physics and The Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States)] [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA and Department of Physics and The Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States)

    2013-09-30T23:59:59.000Z

    Strain relaxation behavior of epitaxial SrRuO{sub 3} thin films on (001) LaAlO{sub 3} substrates was investigated using high resolution X-ray diffraction. Lattice distortion and dislocation densities were systematically studied with samples under different growth conditions. Reciprocal space maps reveal different strain relaxation behavior in SrRuO{sub 3} thin films grown at different temperatures. Two kinds of strain relaxation mechanisms were proposed to understand the growth dynamics, including the evolution of threading dislocations and the tilt of crystalline planes.

  20. Thin-film optical initiator

    DOE Patents [OSTI]

    Erickson, Kenneth L. (Albuquerque, NM)

    2001-01-01T23:59:59.000Z

    A thin-film optical initiator having an inert, transparent substrate, a reactive thin film, which can be either an explosive or a pyrotechnic, and a reflective thin film. The resultant thin-film optical initiator system also comprises a fiber-optic cable connected to a low-energy laser source, an output charge, and an initiator housing. The reactive thin film, which may contain very thin embedded layers or be a co-deposit of a light-absorbing material such as carbon, absorbs the incident laser light, is volumetrically heated, and explodes against the output charge, imparting about 5 to 20 times more energy than in the incident laser pulse.

  1. Thin Film Reliability SEMICONDUCTORS

    E-Print Network [OSTI]

    Thin Film Reliability SEMICONDUCTORS Our goal is to develop new ways to evaluate the reliability $250 billion per year. As semiconductor devices become ultra miniaturized, reliability testing becomes-world conditions as possible will enable product designers to better balance performance and reliability

  2. Thin film photovoltaic cell

    DOE Patents [OSTI]

    Meakin, John D. (Newark, DE); Bragagnolo, Julio (Newark, DE)

    1982-01-01T23:59:59.000Z

    A thin film photovoltaic cell having a transparent electrical contact and an opaque electrical contact with a pair of semiconductors therebetween includes utilizing one of the electrical contacts as a substrate and wherein the inner surface thereof is modified by microroughening while being macro-planar.

  3. Diamond films: Historical perspective

    SciTech Connect (OSTI)

    Messier, R. [Pennsylvania State Univ., University Park (United States)

    1993-01-01T23:59:59.000Z

    This section is a compilation of notes and published international articles about the development of methods of depositing diamond films. Vapor deposition articles are included from American, Russian, and Japanese publications. The international competition to develop new deposition methodologies is stressed. The current status of chemical vapor deposition of diamond is assessed.

  4. Top-gate thin-film transistors based on GaN channel layer Rongsheng Chen, Wei Zhou, and Hoi Sing Kwok

    E-Print Network [OSTI]

    exhibit good electrical performance such as field effect mobility of 1 cm2 /Vs, threshold voltage of �0 and poly-Si TFTs.6­8 However, the poor electrical sta- bility of ZnO-based TFTs is still a main issue mobility (6 � 10�2 cm2 /Vs) and low on/off current ratio (3 � 103 ), due to local- ized gap states in Ga

  5. Langmuir Films of Anthracene Derivatives on Liquid Mercury II: Asymmetric Molecules Department of Physics, Bar-Ilan UniVersity, Ramat-Gan 52900, Israel

    E-Print Network [OSTI]

    Pershan, Peter S.

    and anthraquinone. In the high-coverage phase, the molecules are either standing up (anthrone) or remain side- lying (anthralin) on the mercury surface. In contrast with the symmetric anthracene and anthraquinone, both high (LFs) of anthracene and anthraquinone molecules, the structure of which is symmetric relative to both

  6. E-Print Network 3.0 - aspergillus parasiticus grown Sample Search...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Topic List Advanced Search Sample search results for: aspergillus parasiticus grown Page: << < 1 2 3 4 5 > >> 1 Mycopathologia 153: 4148, 2001. 2002 Kluwer Academic...

  7. Native defects in MBE-grown CdTe

    SciTech Connect (OSTI)

    Olender, Karolina; Wosinski, Tadeusz; Makosa, Andrzej; Tkaczyk, Zbigniew; Kolkovsky, Valery; Karczewski, Grzegorz [Institute of Physics, Polish Academy of Sciences, Al. Lotników32/46, 02-668 Warsaw (Poland)

    2013-12-04T23:59:59.000Z

    Deep-level traps in both n- and p-type CdTe layers, grown by molecular-beam epitaxy on GaAs substrates, have been investigated by means of deep-level transient spectroscopy (DLTS). Four of the traps revealed in the DLTS spectra, which displayed exponential kinetics for capture of charge carriers into the trap states, have been assigned to native point defects: Cd interstitial, Cd vacancy, Te antisite defect and a complex formed of the Te antisite and Cd vacancy. Three further traps, displaying logarithmic capture kinetics, have been ascribed to electron states of treading dislocations generated at the mismatched interface with the substrate and propagated through the CdTe layer.

  8. Carbon nanotubes grown on bulk materials and methods for fabrication

    DOE Patents [OSTI]

    Menchhofer, Paul A. (Clinton, TN); Montgomery, Frederick C. (Oak Ridge, TN); Baker, Frederick S. (Oak Ridge, TN)

    2011-11-08T23:59:59.000Z

    Disclosed are structures formed as bulk support media having carbon nanotubes formed therewith. The bulk support media may comprise fibers or particles and the fibers or particles may be formed from such materials as quartz, carbon, or activated carbon. Metal catalyst species are formed adjacent the surfaces of the bulk support material, and carbon nanotubes are grown adjacent the surfaces of the metal catalyst species. Methods employ metal salt solutions that may comprise iron salts such as iron chloride, aluminum salts such as aluminum chloride, or nickel salts such as nickel chloride. Carbon nanotubes may be separated from the carbon-based bulk support media and the metal catalyst species by using concentrated acids to oxidize the carbon-based bulk support media and the metal catalyst species.

  9. Method for making carbon films

    SciTech Connect (OSTI)

    Tan, M.X.

    1999-07-29T23:59:59.000Z

    A method for treating an organic polymer material, preferably a vinylidene chloride/vinyl chloride copolymer (Saran) to produce a flat sheet of carbon film material having a high surface area ([approx equal]1000 m[sup 2] /g) suitable as an electrode material for super capacitor applications. The method comprises heating a vinylidene chloride/vinyl chloride copolymer film disposed between two spaced apart graphite or ceramic plates to a first temperature of about 160 C for about 14 hours to form a stabilized vinylidene chloride/vinyl chloride polymer film, thereafter heating the stabilized film to a second temperature of about 750 C in an inert atmosphere for about one hour to form a carbon film; and finally activating the carbon film to increase the surface area by heating the carbon film in an oxidizing atmosphere to a temperature of at least 750--850 C for between 1--6 hours. 2 figs.

  10. Belgirate, Italy, 28-30 September 2005 THERMAL MODELLING OF MULTI-FINGER ALGAN/GAN HEMT's

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    dissipation of 1.8W. Table 1 gives the thermal conductivity of the materials used in the simul grown on SiC or sapphire substrates. Sapphire substrates are relatively cheap, but their low thermal conductivity is a major disadvantage. To improve the thermal performance, a hybrid integration of the HEMT onto

  11. Thermoelectric properties of lattice-matched AlInN alloy grown by metal organic chemical vapor deposition

    E-Print Network [OSTI]

    Gilchrist, James F.

    Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin diskInN alloy on GaN as excellent material candidate for thermoelectric application. © 2010 American Institute-nitride alloys have shown promising results for thermoelectric applications,20­30 in particular for materi- als

  12. Evidence that an internal carbonic anhydrase is present in 5% CO/sub 2/-grown and air-grown Chlamydomonas. [Chlamydomonas reinhardtii

    SciTech Connect (OSTI)

    Moroney, J.V.; Togasaki, R.K.; Husic, H.D.; Tolbert, N.E.

    1987-07-01T23:59:59.000Z

    Inorganic carbon (C/sub i/) uptake was measured in wild-type cells of Chlamydomonas reinhardtii, and in cia-3, a mutant strain of C. reinhardtii that cannot grow with air levels of CO/sub 2/. Both air-grown cells, that have a CO/sub 2/ concentrating system, and 5% CO/sub 2/-grown cells that do not have this system, were used. When the external pH was 5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon (C/sub i/) and this accumulation was enhanced when the permeant carbonic anhydrase inhibitor, ethoxyzolamide, was added. When the external pH was 5.1, 5% CO/sub 2/-grown cells also accumulated some C/sub i/, although not as much as air-grown cells and this accumulation was stimulated by the addition of ethoxyzolamide. At the same time, ethoxyzolamide inhibited CO/sub 2/ fixation by high CO/sub 2/-grown, wild-type cells at both pH 5.1 and 7.3. These observations imply that 5% CO/sub 2/-grown, wild-type cells, have a physiologically important internal carbonic anhydrase, although the major carbonic anhydrase located in the periplasmic space is only present in air-grown cells. Inorganic carbon uptake by cia-3 cells supported this conclusion. This mutant strain, which is thought to lack an internal carbonic anhydrase, was unaffected by ethoxyzolamide at pH 5.1. Other physiological characteristics of cia-3 resemble those of wild-type cells that have been treated with ethoxyzolamide. It is concluded that an internal carbonic anhydrase is under different regulatory control than the periplasmic carbonic anhydrase.

  13. Relationship between the structure and electrical characteristics of diamond-like carbon films

    SciTech Connect (OSTI)

    Takabayashi, Susumu, E-mail: stak@riec.tohoku.ac.jp; Otsuji, Taiichi [Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yang, Meng; Ogawa, Shuichi; Hayashi, Hiroyuki; Ješko, Radek; Takakuwa, Yuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-09-07T23:59:59.000Z

    To elucidate the relationship between the structure and the electrical characteristics of diamond-like carbon (DLC) films, DLC films were synthesized in a well-controlled glow discharge with the aid of photoelectrons in an argon/methane atmosphere. The dielectric constant and breakdown strength of the films exhibited opposite behaviors, depending on the total pressure during the synthesis. The product of these two values decreased monotonically as the pressure increased. The Raman spectra were analyzed with a Voigt-type formula. Based on the results, the authors propose the “sp{sup 2} cluster model” for the DLC structure. This model consists of conductive clusters of sp{sup 2} carbons surrounded by a dielectric matrix sea of sp{sup 2} carbon, sp{sup 3} carbon, and hydrogen, and indicates that the dielectric constant of the whole DLC film is determined by the balance between the dielectric constant of the matrix and the total size of the clusters, while the breakdown strength is determined by the reciprocal of the cluster size. The model suggests that a high-? DLC film can be synthesized at a middle pressure and consists of well-grown sp{sup 2} clusters and a dense matrix. A low-? DLC film can be synthesized both at low and high pressures. The sp{sup 2} cluster model explains that a low-? DLC film synthesized at low pressure consists of a dense matrix and a low density of sp{sup 2} clusters, and exhibits a high breakdown strength. On the other hand, a low-? film synthesized at high pressure consists of a coarse matrix and a high density of clusters and exhibits a low breakdown strength.

  14. Low-temperature CVD of iron, cobalt, and nickel nitride thin films from bis[di(tert-butyl)amido]metal(II) precursors and ammonia

    SciTech Connect (OSTI)

    Cloud, Andrew N.; Abelson, John R., E-mail: abelson@illinois.edu [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 201 Materials Science and Engineering Building, 1304 W. Green St., Urbana, Illinois 61801 (United States); Davis, Luke M.; Girolami, Gregory S., E-mail: girolami@scs.illinois.edu [School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave., Urbana, Illinois 61801 (United States)

    2014-03-15T23:59:59.000Z

    Thin films of late transition metal nitrides (where the metal is iron, cobalt, or nickel) are grown by low-pressure metalorganic chemical vapor deposition from bis[di(tert-butyl)amido]metal(II) precursors and ammonia. These metal nitrides are known to have useful mechanical and magnetic properties, but there are few thin film growth techniques to produce them based on a single precursor family. The authors report the deposition of metal nitride thin films below 300?°C from three recently synthesized M[N(t-Bu){sub 2}]{sub 2} precursors, where M?=?Fe, Co, and Ni, with growth onset as low as room temperature. Metal-rich phases are obtained with constant nitrogen content from growth onset to 200?°C over a range of feedstock partial pressures. Carbon contamination in the films is minimal for iron and cobalt nitride, but similar to the nitrogen concentration for nickel nitride. X-ray photoelectron spectroscopy indicates that the incorporated nitrogen is present as metal nitride, even for films grown at the reaction onset temperature. Deposition rates of up to 18?nm/min are observed. The film morphologies, growth rates, and compositions are consistent with a gas-phase transamination reaction that produces precursor species with high sticking coefficients and low surface mobilities.

  15. Nanoscale Phase Separation In Epitaxial Cr-Mo and Cr-V Alloy Thin Films Studied Using Atom Probe Tomography: Comparison Of Experiments And Simulation

    SciTech Connect (OSTI)

    Devaraj, Arun; Kaspar, Tiffany C.; Ramanan, Sathvik; Walvekar, Sarita K.; Bowden, Mark E.; Shutthanandan, V.; Kurtz, Richard J.

    2014-11-21T23:59:59.000Z

    Tailored metal alloy thin film-oxide interfaces generated using molecular beam epitaxial (MBE) deposition of alloy thin films on a single crystalline oxide substrate can be used for detailed studies of irradiation damage response on the interface structure. However presence of nanoscale phase separation in the MBE grown alloy thin films can impact the metal-oxide interface structure. Due to nanoscale domain size of such phase separation it is very challenging to characterize by conventional techniques. Therefor laser assisted atom probe tomography (APT) was utilized to study the phase separation in epitaxial Cr0.61Mo0.39, Cr0.77Mo0.23, and Cr0.32V0.68 alloy thin films grown by MBE on MgO(001) single crystal substrates. Statistical analysis, namely frequency distribution analysis and Pearson coefficient analysis of experimental data was compared with similar analyses conducted on simulated APT datasets with known extent of phase separation. Thus the presence of phase separation in Cr-Mo films, even when phase separation was not clearly observed by x-ray diffraction, and the absence of phase separation in the Cr-V film were thus confirmed.

  16. Biomimetic thin film deposition

    SciTech Connect (OSTI)

    Rieke, P.R.; Graff, G.E.; Campbell, A.A.; Bunker, B.C.; Baskaran, S.; Song, L.; Tarasevich, B.J.; Fryxell, G.E.

    1995-09-01T23:59:59.000Z

    Biological mineral deposition for the formation of bone, mollusk shell and other hard tissues provides materials scientists with illustrative materials processing strategies. This presentation will review the key features of biomineralization and how these features can be of technical importance. We have adapted existing knowledge of biomineralization to develop a unique method of depositing inorganic thin films and coating. Our approach to thin film deposition is to modify substrate surfaces to imitate the proteins found in nature that are responsible for controlling mineral deposition. These biomimetic surfaces control the nucleation and growth of the mineral from a supersaturated aqueous solution. This has many processing advantages including simple processing equipment, environmentally benign reagents, uniform coating of highly complex shapes, and enhanced adherence of coating. Many different types of metal oxide, hydroxide, sulfide and phosphate materials with useful mechanical, optical, electronic and biomedical properties can be deposited.

  17. Identification of optimum potassium nutrition of greenhouse plants grown in recirculating subirrigation

    E-Print Network [OSTI]

    Blessington, Trisha R.

    2002-01-01T23:59:59.000Z

    of this research was to determine the optimum potassium nutrition of greenhouse plants grown in recirculating subirrigation. New Guinea impatiens 'Ovation Salmon Pink Swirl' were grown in recirculating subirrigation trays using 0 -12 mM K, with constant 1.5 mM P...

  18. Biomass, Flavonol Levels and Sensory Characteristics of Allium cultivars Grown Hydroponically at Ambient and

    E-Print Network [OSTI]

    Paré, Paul W.

    04ICES-136 Biomass, Flavonol Levels and Sensory Characteristics of Allium cultivars Grown growth chambers to evaluate the effect of elevated CO2 (1200 ppm) versus ambient CO2 (400 ppm) on biomass planting (dap). Regardless of cultivar or dap, plants grown at elevated CO2 had greater biomass

  19. Trapping cold atoms using surface-grown carbon nanotubes P. G. Petrov,1,* S. Machluf,1

    E-Print Network [OSTI]

    Joselevich, Ernesto

    Trapping cold atoms using surface-grown carbon nanotubes P. G. Petrov,1,* S. Machluf,1 S. Younis,1 atomic clouds into magnetic traps created by single-wall carbon nanotubes grown directly onto dielectric surfaces. We show that atoms may be captured for experimen- tally sustainable nanotube currents, generating

  20. Thin film composite electrolyte

    DOE Patents [OSTI]

    Schucker, Robert C. (The Woodlands, TX)

    2007-08-14T23:59:59.000Z

    The invention is a thin film composite solid (and a means for making such) suitable for use as an electrolyte, having a first layer of a dense, non-porous conductive material; a second layer of a porous ionic conductive material; and a third layer of a dense non-porous conductive material, wherein the second layer has a Coefficient of thermal expansion within 5% of the coefficient of thermal expansion of the first and third layers.

  1. Microstructural evolution of Fe grown on a (001) Cu film and its implication to the elastic anomaly in metallic superlattices

    SciTech Connect (OSTI)

    Koike, J.; Nastasi, M.

    1990-01-01T23:59:59.000Z

    A large softening of the shear modulus has been reported in metallic superlattices composed of insoluble bcc/fcc metals. In an attempt to understand this elastic anomaly, we have studied the microstructure of Fe/Cu bilayers as a function of the Fe thickness with transmission electron microscopy (TEM). Analysis of the moire fringes observed in plan-view TEM images revealed that the fcc Fe structure epitaxially grows on the (001) Cu up to a thickness of 2.0 nm. At 2.3 nm. At 2.3 nm, the bcc Fe structure nucleates, accompanying lattice rotation around the growth direction with respect to the underlying fcc structure. As the Fe thickness further increases, the submicron polycrystalline grains formed. Based on these results, the microstructure of the metallic superlattices and its relation to the softening of the shear modulus will be discussed. 22 refs., 2 figs

  2. Blueshift of optical band gap in ZnO thin films grown by metal-organic chemical-vapor deposition

    E-Print Network [OSTI]

    . INTRODUCTION Zinc oxide ZnO is a wide direct band-gap 3.37 eV semiconductor with a broad range of applications. Dimethylzinc DMZn , N2 gas, and high-purity O2 were used as the zinc source, carrier gas, and oxidizing agent including light-emitting devices,1 varistors,2 solar cells,3 and gas sensors.4 Moreover, ZnO is a promising

  3. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01T23:59:59.000Z

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V{sub Ga}. The neutral AsGa-related defects were measured by infrared absorption at 1{mu}m. Gallium vacancies, V{sub Ga}, was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10{sup 19} cm{sup {minus}3} Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As{sub Ga} in the layer. As As{sub Ga} increases, photoquenchable As{sub Ga} decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As{sub Ga} content around 500C, similar to irradiation damaged and plastically deformed Ga{sub As}, as opposed to bulk grown GaAs in which As{sub Ga}-related defects are stable up to 1100C. The lower temperature defect removal is due to V{sub Ga} enhanced diffusion of As{sub Ga} to As precipitates. The supersaturated V{sub GA} and also decreases during annealing. Annealing kinetics for As{sub Ga}-related defects gives 2.0 {plus_minus} 0.3 eV and 1.5 {plus_minus} 0.3 eV migration enthalpies for the As{sub Ga} and V{sub Ga}. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As{sub Ga}-related defects anneal with an activation energy of 1.1 {plus_minus} 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As{sub Ga}-Be{sub Ga} pairs. Si donors can only be partially activated.

  4. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01T23:59:59.000Z

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V[sub Ga]. The neutral AsGa-related defects were measured by infrared absorption at 1[mu]m. Gallium vacancies, V[sub Ga], was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10[sup 19] cm[sup [minus]3] Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As[sub Ga] in the layer. As As[sub Ga] increases, photoquenchable As[sub Ga] decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As[sub Ga] content around 500C, similar to irradiation damaged and plastically deformed Ga[sub As], as opposed to bulk grown GaAs in which As[sub Ga]-related defects are stable up to 1100C. The lower temperature defect removal is due to V[sub Ga] enhanced diffusion of As[sub Ga] to As precipitates. The supersaturated V[sub GA] and also decreases during annealing. Annealing kinetics for As[sub Ga]-related defects gives 2.0 [plus minus] 0.3 eV and 1.5 [plus minus] 0.3 eV migration enthalpies for the As[sub Ga] and V[sub Ga]. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As[sub Ga]-related defects anneal with an activation energy of 1.1 [plus minus] 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As[sub Ga]-Be[sub Ga] pairs. Si donors can only be partially activated.

  5. Interface control of surface photochemical reactivity in ultrathin epitaxial ferroelectric films

    SciTech Connect (OSTI)

    Chen, Jason [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia) [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia); Lu, Haidong; Gruverman, Alexei [Department of Physics and Astronomy, University of Nebraska Lincoln, Lincoln, Nebraska 68588 (United States)] [Department of Physics and Astronomy, University of Nebraska Lincoln, Lincoln, Nebraska 68588 (United States); Liu, Heng-Jui; Chu, Ying-Hao [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China)] [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Dunn, Steve [School of Engineering and Materials, Queen Mary University of London, Mile End Road, E1 4NS London (United Kingdom)] [School of Engineering and Materials, Queen Mary University of London, Mile End Road, E1 4NS London (United Kingdom); Ostrikov, Kostya [CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia) [CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia); School of Physics, The University of Sydney, Sydney, New South Wales 2006 (Australia); Valanoor, Nagarajan [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia)] [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia)

    2013-05-06T23:59:59.000Z

    Asymmetrical electrical boundary conditions in (001)-oriented Pb(Zr{sub 0.2}TiO{sub 0.8})O{sub 3} (PZT) epitaxial ultrathin ferroelectric films are exploited to control surface photochemical reactivity determined by the sign of the surface polarization charge. It is shown that the preferential orientation of polarization in the as-grown PZT layer can be manipulated by choosing an appropriate type of bottom electrode material. PZT films deposited on the SrRuO{sub 3} electrodes exhibit preferential upward polarization (C{sup +}) whilst the same films grown on the (La,Sr)CoO{sub 3}-electrodes are polarized downward (C{sup -}). Photochemical activity of the PZT surfaces with different surface polarization charges has been tested by studying deposition of silver nanoparticles from AgNO{sub 3} solution under UV irradiation. PZT surfaces with preferential C{sup +} orientation possess a more active surface for metal reduction than their C{sup -} counterparts, evidenced by large differences in the concentration of deposited silver nanoparticles. This effect is attributed to band bending at the bottom interface which varies depending on the difference in work functions of PZT and electrode materials.

  6. Fabrication and characterization of ferroelectric PLZT film capacitors on metallic substrates.

    SciTech Connect (OSTI)

    Ma, B.; Narayanan, M.; Tong, S.; Balachandran, U.; Energy Systems

    2010-01-01T23:59:59.000Z

    We have grown ferroelectric Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} (PLZT) films on Hastelloy C276 (HC) substrates by chemical solution deposition. Samples of 1.15-{micro}m-thick PLZT films were prepared on HC with and without lanthanum nickel oxide (LNO) films as an intermediate buffer layer. On samples with and without LNO buffers at room temperature, we measured dielectric constants of {approx}1,300 and {approx}450 and loss tangents of {approx}0.06 and {approx}0.07, respectively. For PLZT films grown on HC with LNO buffer, the dielectric constant increases, while the dielectric loss decreases, with increasing temperature. A dielectric constant of {approx}2,000 and loss of {approx}0.05 were observed at 150 C. Samples with LNO buffer also exhibited slimmer hysteresis loops and lower leakage current density when compared to samples without LNO buffer. The following results were measured on samples with and without LNO buffers: remanent polarization (P{sub r}) values of 21.3 and 36.4 {micro}C/cm{sup 2}, coercive electric field (E{sub c}) values of 41 and 173 kV/cm, and leakage current densities of {approx}1.1 x 10{sup -8} and {approx}1.6 x 10{sup -7} A/cm{sup 2}, respectively. The energy storage capability was measured at {approx}65 J/cm{sup 3} for the PLZT film-on-foil capacitor deposited on HC with LNO buffer.

  7. Study of narrowband single photon emitters in polycrystalline diamond films

    SciTech Connect (OSTI)

    Sandstrom, Russell G.; Shimoni, Olga; Martin, Aiden A.; Aharonovich, Igor, E-mail: igor.aharonovich@uts.edu.au [School of Physics and Advanced Materials, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007 (Australia)

    2014-11-03T23:59:59.000Z

    Quantum information processing and integrated nanophotonics require robust generation of single photon emitters on demand. In this work, we demonstrate that diamond films grown on a silicon substrate by microwave plasma chemical vapor deposition can host bright, narrowband single photon emitters in the visible—near infra-red spectral range. The emitters possess fast lifetime (?several ns), absolute photostability, and exhibit full polarization at excitation and emission. Pulsed and continuous laser excitations confirm their quantum behaviour at room temperature, while low temperature spectroscopy is performed to investigate inhomogeneous broadening. Our results advance the knowledge of solid state single photon sources and open pathways for their practical implementation in quantum communication and quantum information processing.

  8. Properties of ferroelectric/ferromagnetic thin film heterostructures

    SciTech Connect (OSTI)

    Chen, Daming, E-mail: chendaming1986@gmail.com [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054 Sichuan (China); Harward, Ian; Linderman, Katie; Economou, Evangelos; Celinski, Zbigniew [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); Nie, Yan [Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, 1420 Austin Bluffs Pkwy, Colorado Springs, Colorado 80918 (United States); School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074 (China)

    2014-05-07T23:59:59.000Z

    Ferroelectric/ferromagnetic thin film heterostructures, SrBi{sub 2}Ta{sub 2}O{sub 9}/BaFe{sub 12}O{sub 19} (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.

  9. Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy

    SciTech Connect (OSTI)

    Krockenberger, Yoshiharu; Karimoto, Shin-ichi; Yamamoto, Hideki; Semba, Kouich [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

    2012-10-15T23:59:59.000Z

    We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 Degree-Sign C. TiN films grown at 720 Degree-Sign C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T{sub c}) is well above 5 K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field ({mu}{sub 0}H{sub c2}) as well as the corresponding coherence length ({xi}{sub GL}) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length Script-Small-L Almost-Equal-To 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films.

  10. Big-Data RHEED analysis for understanding epitaxial film growth processes

    SciTech Connect (OSTI)

    Vasudevan, Rama K [ORNL; Tselev, Alexander [ORNL; Baddorf, Arthur P [ORNL; Kalinin, Sergei V [ORNL

    2014-01-01T23:59:59.000Z

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in-situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED image, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the dataset are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of RHEED image sequence. This approach is illustrated for growth of LaxCa1-xMnO3 films grown on etched (001) SrTiO3 substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the assymetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  11. A new LPCVD technique of producing borophosphosilicate glass films by injection of miscible liquid precursors

    SciTech Connect (OSTI)

    Levy, R.A.; Gallagher, P.K.; Schrey, F.

    1987-02-01T23:59:59.000Z

    This study introduces a new, simple, and viable LPCVD technique based on the injection of miscible liquid precursors. The preparation of BPSG films from liquid mixtures of TEOS, TMB, and TMP is used here as a prime example for implementing this concept. The relationship between starting solution composition and resulting film composition is investigated to provide guidelines for achieving desired stoichiometries. Variations in growth rate and composition are examined to assess the relative effects of deposition temperature, total pressure, solution composition, and injection rate. At the high boron and phosphorus levels (greater than or equal to4 weight percent), the reaction chemistry associated with the use of TMP is seen to produce severe depletion effects. At optimum deposition conditions, select properties of BPSG films are investigated. The results indicate high compositional uniformity within the film, a dielectric constant value in close agreement with that of thermally grown, SiO/sub 2/, conformal step coverage even in the case of severe aspect ratios, and desirable flow profiles at temperatures and phosphorus concentrations significantly lower than those being currently achieved with phosphosilicate glass films.

  12. Bulk diffusion induced structural modifications of carbon-transition metal nanocomposite films

    SciTech Connect (OSTI)

    Berndt, M.; Abrasonis, G.; Kovacs, Gy. J.; Krause, M.; Munnik, F.; Heller, R.; Kolitsch, A.; Moeller, W.

    2011-03-15T23:59:59.000Z

    The influence of transition metal (TM = V,Co,Cu) type on the bulk diffusion induced structural changes in carbon:TM nanocomposite films is investigated. The TMs have been incorporated into the carbon matrix via ion beam co-sputtering, and subsequently the films have been vacuum annealed in the temperature range of 300 - 700 deg. C. The structure of both the dispersed metal rich and the carbon matrix phases has been determined by a combination of elastic recoil detection analysis, x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-grown films consist of carbidic (V and Co) and metallic (Cu) nanoparticles dispersed in the carbon matrix. Thermal annealing induces surface segregation of Co and Cu starting at {>=} 500 deg. C, preceded by the carbide-metal transformation of Co-carbide nanoparticles at {approx} 300 deg. C. No considerable morphological changes occur in C:V films. In contrast to the surface diffusion dominated regime where all the metals enhance the six-fold ring clustering of C, in the bulk diffusion controlled regime only Co acts as a catalyst for the carbon graphitization. These results are consistent with the metal-induced crystallization mechanism in the C:Co films. The results are discussed on the basis of the metal-carbide phase stability, carbon solubility in metals or their carbides, and interface species.

  13. Characteristics of Hf-silicate thin films synthesized by plasma enhanced atomic layer deposition

    SciTech Connect (OSTI)

    Liu Jiurong; Martin, Ryan M.; Chang, Jane P. [Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California 90095 (United States)

    2008-09-15T23:59:59.000Z

    Hafnium silicate films were grown by alternating the deposition cycles of hafnium oxide and silicon oxide using a plasma enhanced atomic layer deposition process. The as-deposited and 900 deg. C annealed hafnium silicate films were determined to be amorphous using grazing incidence x-ray diffraction. This suggested that the formation of hafnium silicate suppressed the crystallization of HfO{sub 2} at high temperatures. The dielectric constants increased from {approx}5 to {approx}17 as the hafnium content increased from 9 to 17 at. % in the hafnium silicate films. The leakage currents through the Hf-rich Hf-silicate films were two to three orders of magnitude lower than that of SiO{sub 2} with the same equivalent oxide thickness in the range of 1.6-2.3 nm. The estimated band gap of Hf-silicate films from the O 1s plasma loss spectra increased with the increasing Si content due to the higher band gap of SiO{sub 2} than that of HfO{sub 2}.

  14. Templated dewetting of thin solid films

    E-Print Network [OSTI]

    Giermann, Amanda L. (Amanda Leah)

    2009-01-01T23:59:59.000Z

    The dewetting of solid metal polycrystalline films to form metal nanoparticles occurs by the nucleation and growth of holes in the film. For typical films on flat substrates, this process is not well-controlled and results ...

  15. Measuring droplet impact with piezoelectric film

    E-Print Network [OSTI]

    Basahi, Jalal M. Al-Badry M.

    2012-06-07T23:59:59.000Z

    acquisition system (a computer with two high speed boards). Eight piezoelectric films were calibrated in the laboratory. Each film was calibrated by releasing various water droplet sizes from different heights. The signal output of film was then related...

  16. Study of the growth mechanisms of GaN/(Al, Ga)N quantum dots: Correlation between structural and optical properties

    SciTech Connect (OSTI)

    Sergent, S. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Universite de Nice Sophia Antipolis, Parc Valrose, F-06102 Nice Cedex 2 (France); Damilano, B.; Huault, T.; Brault, J.; Tottereau, O.; Vennegues, P.; Leroux, M.; Semond, F.; Massies, J. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Korytov, M.

    2011-03-01T23:59:59.000Z

    The ammonia-based molecular beam epitaxy of GaN/(Al, Ga)N quantum dots is investigated using reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy and photoluminescence. The main steps of the formation kinetics are identified and the influence of diffusion and evaporation processes on both the quantum dot and the wetting layer morphology is addressed. The correlation between the optical and structural properties of such structures finally allows for the analysis of matter exchanges between the quantum dots and the wetting layer during capping.

  17. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect (OSTI)

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom); Bruckbauer, J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-11-07T23:59:59.000Z

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280?nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  18. Formation behavior of Be{sub x}Zn{sub 1-x}O alloys grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, Mingming; Zhu, Yuan; Su, Longxing; Zhang, Quanlin; Chen, Anqi; Ji, Xu; Xiang, Rong; Gui, Xuchun; Wu, Tianzhun [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)] [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Pan, Bicai [Department of Physics and Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [Department of Physics and Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Tang, Zikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China) [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2013-05-20T23:59:59.000Z

    We report the phase formation behavior of Be{sub x}Zn{sub 1-x}O alloys grown by plasma-assisted molecular beam epitaxy. We find the alloy with low- and high-Be contents could be obtained by alloying BeO into ZnO films. X-ray diffraction measurements shows the c lattice constant value shrinks, and room temperature absorption shows the energy band-gap widens after Be incorporated. However, the alloy with intermediate Be composition are unstable and segregated into low- and high-Be contents BeZnO alloys. We demonstrate the phase segregation of Be{sub x}Zn{sub 1-x}O alloys with intermediate Be composition resulted from large internal strain induced by large lattice mismatch between BeO and ZnO.

  19. Atomic-resolution study of polarity reversal in GaSb grown on Si by scanning transmission electron microscopy

    SciTech Connect (OSTI)

    Hosseini Vajargah, S.; Woo, S. Y.; Botton, G. A. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Brockhouse Institute for Material Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Ghanad-Tavakoli, S. [Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Kleiman, R. N.; Preston, J. S. [Brockhouse Institute for Material Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2012-11-01T23:59:59.000Z

    The atomic-resolved reversal of the polarity across an antiphase boundary (APB) was observed in GaSb films grown on Si by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The investigation of the interface structure at the origin of the APB reveals that coalescence of two domains with Ga-prelayer and Sb-prelayer causes the sublattice reversal. The local strain and lattice rotation distributions of the APB, attributed to the discordant bonding length at the APB with the surrounding GaSb lattice, were further studied using the geometric phase analysis technique. The crystallographic characteristics of the APBs and their interaction with other planar defects were observed with HAADF-STEM. The quantitative agreement between experimental and simulated images confirms the observed polarities in the acquired HAADF-STEM data. The self-annihilation mechanism of the APBs is addressed based on the rotation induced by anti-site bonds and APBs' faceting.

  20. Electrical initiation of an energetic nanolaminate film

    DOE Patents [OSTI]

    Tringe, Joseph W. (Walnut Creek, CA); Gash, Alexander E. (Brentwood, CA); Barbee, Jr., Troy W. (Palo Alto, CA)

    2010-03-30T23:59:59.000Z

    A heating apparatus comprising an energetic nanolaminate film that produces heat when initiated, a power source that provides an electric current, and a control that initiates the energetic nanolaminate film by directing the electric current to the energetic nanolaminate film and joule heating the energetic nanolaminate film to an initiation temperature. Also a method of heating comprising providing an energetic nanolaminate film that produces heat when initiated, and initiating the energetic nanolaminate film by directing an electric current to the energetic nanolaminate film and joule heating the energetic nanolaminate film to an initiation temperature.

  1. Diamond films treated with alkali-halides

    DOE Patents [OSTI]

    Anderson, D.F.; Kwan, S.W.

    1997-04-08T23:59:59.000Z

    A secondary electron emitter is provided and includes a substrate with a diamond film, the diamond film is treated or coated with an alkali-halide. 5 figs.

  2. Structural properties of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

    SciTech Connect (OSTI)

    Liu, X.; Leiner, J.; Dobrowolska, M.; Furdyna, J. K. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Fan, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); Zhang, Y.-H. [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Cao, H.; Chen, Y. P. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Kirby, B. J. [Center for Neutron Research, NIST, Gaithersburg, Maryland 20899 (United States)

    2011-10-24T23:59:59.000Z

    Thin films of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.

  3. Carbonaceous film coating

    DOE Patents [OSTI]

    Maya, L.

    1988-04-27T23:59:59.000Z

    A method of making a carbonaceous film comprising heating tris(1,3,2-benzodiazaborolo)borazine or dodecahydro tris(1,3,2)diazaborine(1,2-a:1'2'-c:1''2''-e)borazine in an inert atmosphere in the presence of a substrate to a temperature at which the borazine compound decomposes, and the decomposition products deposit onto the substrate to form a thin, tenacious, highly reflective conductive coating having a narrow band gap which is susceptible of modification and a relatively low coefficient of friction.

  4. Thin film hydrogen sensor

    DOE Patents [OSTI]

    Lauf, Robert J. (Oak Ridge, TN); Hoffheins, Barbara S. (Knoxville, TN); Fleming, Pamela H. (Oak Ridge, TN)

    1994-01-01T23:59:59.000Z

    A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed.

  5. Fact #844: October 27, 2014 Electricity Generated from Coal has Declined while Generation from Natural Gas has Grown – Dataset

    Broader source: Energy.gov [DOE]

    Excel file with dataset for Fact #844: Electricity Generated from Coal has Declined while Generation from Natural Gas has Grown

  6. Metal oxide films on metal

    DOE Patents [OSTI]

    Wu, Xin D. (Los Alamos, NM); Tiwari, Prabhat (Los Alamos, NM)

    1995-01-01T23:59:59.000Z

    A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

  7. Thin film ion conducting coating

    DOE Patents [OSTI]

    Goldner, Ronald B. (Lexington, MA); Haas, Terry (Sudbury, MA); Wong, Kwok-Keung (Watertown, MA); Seward, George (Arlington, MA)

    1989-01-01T23:59:59.000Z

    Durable thin film ion conducting coatings are formed on a transparent glass substrate by the controlled deposition of the mixed oxides of lithium:tantalum or lithium:niobium. The coatings provide durable ion transport sources for thin film solid state storage batteries and electrochromic energy conservation devices.

  8. System for measuring film thickness

    DOE Patents [OSTI]

    Batishko, Charles R. (West Richland, WA); Kirihara, Leslie J. (Richland, WA); Peters, Timothy J. (Richland, WA); Rasmussen, Donald E. (Richland, WA)

    1990-01-01T23:59:59.000Z

    A system for determining the thicknesses of thin films of materials exhibiting fluorescence in response to exposure to excitation energy from a suitable source of such energy. A section of film is illuminated with a fixed level of excitation energy from a source such as an argon ion laser emitting blue-green light. The amount of fluorescent light produced by the film over a limited area within the section so illuminated is then measured using a detector such as a photomultiplier tube. Since the amount of fluorescent light produced is a function of the thicknesses of thin films, the thickness of a specific film can be determined by comparing the intensity of fluorescent light produced by this film with the intensity of light produced by similar films of known thicknesses in response to the same amount of excitation energy. The preferred embodiment of the invention uses fiber optic probes in measuring the thicknesses of oil films on the operational components of machinery which are ordinarily obscured from view.

  9. Growth and structure of photosensitive Pb{sub 1-x}Mn{sub x}Te(Ga) epitaxial films

    SciTech Connect (OSTI)

    Nuriev, I. R.; Sadygov, R. M.; Nazarov, A. M., E-mail: afinnazarov@yahoo.com [Azerbaijan National Academy of Sciences, Institute of Physics (Azerbaijan)

    2008-05-15T23:59:59.000Z

    The growth and structure of (1-1.5)-{mu}m-thick Pb{sub 1-x}Mn{sub x}Te(Ga)(x = 0.06) films with 0.4-0.9 at % of gallium, grown on BaF{sub 2}(111) and Pb{sub 1-x}Sn{sub x}Te (x = 0.2) (100) substrates by molecular beam epitaxy, have been investigated. It is established that the films are crystallized into an fcc structure, and their growth planes are (111) and (100), according to the substrate orientation. The optimal conditions for obtaining high-resistivity photosensitive p-and n-type films with a perfect crystal structure (W{sub 1/2} = 80''-100'') have been determined.

  10. Ion-beam-induced magnetic and structural phase transformation of Ni-stabilized face-centered-cubic Fe films on Cu(100)

    SciTech Connect (OSTI)

    Gloss, Jonas [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria) [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria); Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); Shah Zaman, Sameena [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria) [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria); Comsats Institute of Information Technology, Park Road, 44000 Islamabad (Pakistan); Jonner, Jakub; Novotny, Zbynek; Schmid, Michael [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria)] [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria); Varga, Peter [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria) [Institute of Applied Physics, Vienna University of Technology, 1040 Vienna (Austria); CEITEC BUT, Brno University of Technology, Technická 10, 616 00 Brno (Czech Republic); Urbánek, Michal [Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic) [Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); CEITEC BUT, Brno University of Technology, Technická 10, 616 00 Brno (Czech Republic)

    2013-12-23T23:59:59.000Z

    Metastable face-centered cubic (fcc) Fe/Cu(100) thin films are good candidates for ion-beam magnetic patterning due to their magnetic transformation upon ion-beam irradiation. However, pure fcc Fe films undergo spontaneous transformation when their thickness exceeds 10 ML. This limit can be extended to approximately 22 ML by deposition of Fe at increased CO background pressures. We show that much thicker films can be grown by alloying with Ni for stabilizing the fcc ? phase. The amount of Ni necessary to stabilize nonmagnetic, transformable fcc Fe films in dependence on the residual background pressure during the deposition is determined and a phase diagram revealing the transformable region is presented.

  11. Te INCLUSIONS IN CdTe GROWN FROM A SLOWLY COOLED Te SOLUTION AND BY THE TRAVELLING SOLVENT METHOD

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    135 Te INCLUSIONS IN CdTe GROWN FROM A SLOWLY COOLED Te SOLUTION AND BY THE TRAVELLING SOLVENT. Abstract. 2014 CdTe crystals have been grown from a slowly cooled Te solution and with the travelling. Introduction. - CdTe crystals for nuclear radia- tion detectors are usually grown from a slowly cooled solution

  12. Roles of ionic strength and biofilm roughness on adhesion kinetics of Escherichia coli onto groundwater biofilm grown on

    E-Print Network [OSTI]

    Boppart, Stephen

    groundwater biofilm grown on PVC surfaces Dao Janjaroen a , Fangqiong Ling a , Guillermo Monroy b , Nicolas Pathogens a b s t r a c t Mechanisms of Escherichia coli attachment on biofilms grown on PVC coupons were. coli on clean PVC surfaces and biofilms grown on PVC surfaces for different ages. Two mechanisms of E

  13. Anode film formation and control

    DOE Patents [OSTI]

    Koski, O.; Marschman, S.C.

    1990-05-01T23:59:59.000Z

    A protective film is created about the anode within a cryolite-based electrolyte during electrolytic production of aluminum from alumina. The film functions to minimize corrosion of the anode by the cryolitic electrolyte and thereby extend the life of the anode. Various operating parameters of the electrolytic process are controlled to maintain the protective film about the anode in a protective state throughout the electrolytic reduction of alumina. Such parameters include electrolyte temperature, electrolyte ratio, current density, and Al[sub 2]O[sub 3] concentration. An apparatus is also disclosed to enable identification of the onset of anode corrosion due to disruption of the film to provide real time information regarding the state of the film. 3 figs.

  14. Anomalous scaling and super-roughness in the growth of CdTe polycrystalline films

    E-Print Network [OSTI]

    Angélica S. Mata; Silvio C. Ferreira, Jr.; Igor R. B. Ribeiro; Sukarno O. Ferreira

    2011-01-06T23:59:59.000Z

    CdTe films grown on glass substrates covered by fluorine doped tin oxide by Hot Wall Epitaxy (HWE) were studied through the interface dynamical scaling theory. Direct measures of the dynamical exponent revealed an intrinsically anomalous scaling characterized by a global roughness exponent $\\alpha$ distinct from the local one (the Hurst exponent $H$), previously reported [Ferreira \\textit{et al}., Appl. Phys. Lett. \\textbf{88}, 244103 (2006)]. A variety of scaling behaviors was obtained with varying substrate temperature. In particular, a transition from a intrinsically anomalous scaling regime with $H\

  15. Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

    SciTech Connect (OSTI)

    Alam, M. T.; Haque, M. A., E-mail: mah37@psu.edu [Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Bresnehan, M. S.; Robinson, J. A. [Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA and The Center for Two-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA and The Center for Two-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-01-06T23:59:59.000Z

    Thermal conductivity of freestanding 10?nm and 20?nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100?±?10?W m{sup ?1} K{sup ?1}, is lower than the bulk basal plane value (390?W m{sup ?1} K{sup ?1}) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

  16. Silicate-free growth of high-quality ultrathin cerium oxide films on Si(111)

    SciTech Connect (OSTI)

    Flege, Jan Ingo; Kaemena, Bjoern; Wilkens, Torsten; Schmidt, Thomas; Falta, Jens [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen (Germany); Gevers, Sebastian; Bruns, Daniel; Wollschlaeger, Joachim [Department of Physics, University of Osnabrueck, Barbarastrasse 7, D-49069 Osnabrueck (Germany); Bertram, Florian; Baetjer, Jan [Hamburger Synchrotronstrahlungslabor am Deutschen Elektronensynchrotron, Notkestrasse 85, D-22607 Hamburg (Germany)

    2011-12-15T23:59:59.000Z

    Ultrathin Ce{sub 2}O{sub 3} layers have been grown on Si(111) by reactive metal deposition in an oxygen background and characterized by x-ray standing waves, x-ray diffraction, x-ray photoelectron spectroscopy, and low-energy electron diffraction to elucidate and quantify both atomic structure and chemical composition. It is demonstrated that highly ordered, mostly B-oriented, epitaxial ceria films can be achieved by preadsorption of a monolayer of atomic chlorine, effectively passivating the substrate and thereby suppressing cerium silicate and silicon oxide formation at the interface.

  17. A comparison of thick film and thin film traffic stripes

    E-Print Network [OSTI]

    Keese, Charles J

    1952-01-01T23:59:59.000Z

    Striys. . . Pigmented Bitusmn Stripes . Asphalt %uilt-Upa Striye vith Pigmented Portland Cement Mortar Cover Course 38 . ~ 41 Thin Film Stripes Used for Comparison Results of Comparing Thick Film Stripes and Thin Film Paint Stripes . ~ ~ ~ ~ ~ 43... was aspbaltio oonorets. The pavement in Test Areas 2y 3p and 4 vas portland cesmnh ooncrete, Two test areas (3 and 4) vere located in such manner as to provide uninterrupted flow of traffic over tbs entire length of the test area. The other two test areas (1...

  18. Utility of reactively sputtered CuN{sub x} films in spintronics devices

    SciTech Connect (OSTI)

    Fang Yeyu [Physics Department, Goeteborg University, 412 96 Goeteborg (Sweden); Persson, J. [Physics Department, Goeteborg University, 412 96 Goeteborg (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Zha, C. [Materials Physics Department, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Willman, J.; Miller, Casey W. [Department of Physics, Center for Integrated Functional Materials, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620 (United States); Aakerman, Johan [Physics Department, Goeteborg University, 412 96 Goeteborg (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Materials Physics Department, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden)

    2012-04-01T23:59:59.000Z

    We have studied nitrified copper (CuN{sub x}) thin films grown by reactive sputtering in the context of spintronic devices. The Ar-to-N{sub 2} flow ratio enables tunability of the electrical resistivity and surface roughness of the CuN{sub x} films, with the former increasing to nearly 20 times that of Cu, and the latter reduced to the atomic scale. Incorporating this into a Ta/CuN{sub x}/Ta seed stack for spin valves improves the current-in-plane (CIP) magnetoresistance; maximum magnetoresistance results with CuN{sub x} seed layer and Cu interlayer. Finally, finite element modeling results are presented that suggest the use of CuN{sub x} in nanocontact spin torque oscillators can enhance current densities by limiting the current spread through the device. This may positively impact threshold currents, power requirements, and device reliability.

  19. Molecular-beam epitaxial growth of boron-doped GaAs films

    SciTech Connect (OSTI)

    Hoke, W.E.; Lemonias, P.J.; Weir, D.G. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    GaAs films doped with boron in the 10{sup 20} cm{sup {minus}3} range were grown by solid source molecular-beam epitaxy. Lattice contractions were observed in x-ray double crystal spectra. Substitutional boron concentrations up to 1.7x10{sup 20} cm{sup {minus}3} were obtained with narrow x-ray linewidths and specular surface morphology. For a given boron flux, the substitutional concentration was dependent on growth temperature. P-type conductivity due to boron incorporation was measured in the films with hole concentration reaching 1x10{sup 19} cm{sup {minus}3}. The lattice contractions exhibited good thermal stability for rapid thermal anneals. 10 refs., 3 figs., 2 tabs.

  20. Atmospheric pressure spatial atomic layer deposition web coating with in situ monitoring of film thickness

    SciTech Connect (OSTI)

    Yersak, Alexander S.; Lee, Yung C. [Department of Mechanical Engineering, University of Colorado at Boulder, 1045 Regent Drive, 422 UCB, Boulder, Colorado 80309-0422 (United States); Spencer, Joseph A.; Groner, Markus D., E-mail: mgroner@aldnanosolutions.com [ALD NanoSolutions, Inc., 580 Burbank Street, Unit 100, Broomfield, Colorado 80020 (United States)

    2014-01-15T23:59:59.000Z

    Spectral reflectometry was implemented as a method for in situ thickness monitoring in a spatial atomic layer deposition (ALD) system. Al{sub 2}O{sub 3} films were grown on a moving polymer web substrate at 100?°C using an atmospheric pressure ALD web coating system, with film growth of 0.11–0.13?nm/cycle. The modular coating head design and the in situ monitoring allowed for the characterization and optimization of the trimethylaluminum and water precursor exposures, purge flows, and web speed. A thickness uniformity of ±2% was achieved across the web. ALD cycle times as low as 76?ms were demonstrated with a web speed of 1?m/s and a vertical gap height of 0.5?mm. This atmospheric pressure ALD system with in situ process control demonstrates the feasibility of low-cost, high throughput roll-to-roll ALD.

  1. MagLab - Science in Literature: Fiction for Grown-Ups

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Fiction for Grown-Ups Skillful authors weave real science into plots featuring swashbuckling heroes, famed physicists and a Dorothy clone lost not in the Land of Oz, but of Quarks....

  2. Origami-inspired nanofabrication utilizing physical and magnetic properties of in situ grown carbon nanotubes

    E-Print Network [OSTI]

    In, Hyun Jin

    2010-01-01T23:59:59.000Z

    Carbon nanotubes (CNTs), in particular the vertically-aligned variety grown through a plasma enhanced chemical vapor deposition (PECVD)-based process, are highly versatile nanostructures that can be used in a variety of ...

  3. In less than 40 years Linkping University has grown into one of Sweden's largest academic institutions

    E-Print Network [OSTI]

    Zhao, Yuxiao

    #12;#12;3 In less than 40 years Linköping University has grown into one of Sweden's largest much emphasis on internationalisation and cooperation at Linköping University. Sweden is often cited

  4. as-grown ga1-xmnxas studied: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    processes.11 In materials such as CNTs, ion- ization is often quenched while knock-on hollow core.13 To control the quality of as-grown CNTs and to study intentionally...

  5. Development of a Scanning Probe Microscope and Studies of Graphene Grown on Copper

    E-Print Network [OSTI]

    Rasool, Haider Imad

    2012-01-01T23:59:59.000Z

    of Graphene Grown on Copper (100) Single Crystals,” JournalGraphene on Polycrystalline Copper,” Nano Letters 11, 251 (5 GRAPHENE GROWTH ON COPPER (100) SINGLE CRYSTALS 5.1

  6. E-Print Network 3.0 - affects full-grown body Sample Search Results

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of the body. It is an inch long when full grown. Cloverworms feed... a light silken web which the caterpillars spin over foliage and other parts of the plant. When...

  7. Growth and fruiting responses of diverse genotypes of American Upland cotton grown in different environments

    E-Print Network [OSTI]

    Gannaway, J. R

    1971-01-01T23:59:59.000Z

    GROWTH AND FRUITING RESPONSES OF DIVERSE GENOTYPES OF AMERICAN UPLAND COTTON GROWN IN DIFFERENT ENVIRONMENTS A Thesis JOHN ROBERT GANNAWAY Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1971 Major Subject: Plant Breeding GROWTH AND FRUITING RESPONSES OF DIVERSE GENOTYPES OF AMERICAN UPLAND COTTON GROWN IN DIFFERENT ENVIRONMENTS A Thesis by JOHN ROBERT GANNAWAY Approved as to style and content by...

  8. Optimum fertilization rate for intermediate leaf cucumber grown for once-over mechanical harvest

    E-Print Network [OSTI]

    Konderla, Timothy Michael

    1992-01-01T23:59:59.000Z

    OPTIMUM FERTILIZATION RATE FOR INTERMEDIATE LEAF CUCUMBER GROWN FOR ONCE-OVER MECHANICAL HARVEST A Thesis by TIMOTHY MICHAEL KONDERLA Submitted to the Office of Graduate Studies of Texas A& M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1992 Major Subject: Horticulture OPTIMUM FERTILIZATION RATE FOR INTERMEDIATE LEAF CUCUMBER GROWN FOR ONCE-OVER MECHANICAL HARVEST A Thesis by TIMOTHY MICHAEL KONDERLA Approved as to style...

  9. Energy band alignment of atomic layer deposited HfO{sub 2} on epitaxial (110)Ge grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    The band alignment properties of atomic layer HfO{sub 2} film deposited on epitaxial (110)Ge, grown by molecular beam epitaxy, was investigated using x-ray photoelectron spectroscopy. The cross-sectional transmission electron microscopy exhibited a sharp interface between the (110)Ge epilayer and the HfO{sub 2} film. The measured valence band offset value of HfO{sub 2} relative to (110)Ge was 2.28 {+-} 0.05 eV. The extracted conduction band offset value was 2.66 {+-} 0.1 eV using the bandgaps of HfO{sub 2} of 5.61 eV and Ge bandgap of 0.67 eV. These band offset parameters and the interface chemical properties of HfO{sub 2}/(110)Ge system are of tremendous importance for the design of future high hole mobility and low-power Ge-based metal-oxide transistor devices.

  10. Thin film hydrogen sensor

    DOE Patents [OSTI]

    Lauf, R.J.; Hoffheins, B.S.; Fleming, P.H.

    1994-11-22T23:59:59.000Z

    A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed. 6 figs.

  11. Vapor deposition of thin films

    DOE Patents [OSTI]

    Smith, David C. (Los Alamos, NM); Pattillo, Stevan G. (Los Alamos, NM); Laia, Jr., Joseph R. (Los Alamos, NM); Sattelberger, Alfred P. (Los Alamos, NM)

    1992-01-01T23:59:59.000Z

    A highly pure thin metal film having a nanocrystalline structure and a process of preparing such highly pure thin metal films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium by plasma assisted chemical vapor deposition of, e.g., rhodium(allyl).sub.3, iridium(allyl).sub.3, molybdenum(allyl).sub.4, tungsten(allyl).sub.4, rhenium(allyl).sub.4, platinum(allyl).sub.2, or palladium(allyl).sub.2 are disclosed. Additionally, a general process of reducing the carbon content of a metallic film prepared from one or more organometallic precursor compounds by plasma assisted chemical vapor deposition is disclosed.

  12. Liquid-film electron stripper

    DOE Patents [OSTI]

    Leemann, B.T.; Yourd, R.B.

    1982-03-09T23:59:59.000Z

    A thin freestanding oil film is produced in vacuum by directing an oil stream radially inward to the hollow-ground sharp outer edge of a rotating disc. The sides of the edge are roughened somewhat to aid in dispersing oil from the disc. Oil is removed from the surface of disc to prevent formation of oil droplets which might spin off the disc and disrupt the oil film. An ion beam is directed through the thin oil film so that electrons are stripped from the ions to increase their charge.

  13. Thin Solid Films 430 (2003) 3740 0040-6090/03/$ -see front matter 2003 Elsevier Science B.V. All rights reserved.

    E-Print Network [OSTI]

    Atwater, Harry

    4x. The deposition of high hydrogen content nitride films by HWCVD for photovoltaic applications has rights reserved. doi:10.1016/S0040-6090(03)00131-7 Hot-wire chemical vapor deposition of high hydrogen The stoichiometry and hydrogen content of hot-wire (HW)-grown silicon nitride was examined as a function of SiH yNH4

  14. As-Received, Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS

    SciTech Connect (OSTI)

    Engelhard, Mark H.; Herman, Jacob A.; Wallace, Robert; Baer, Donald R.

    2012-06-27T23:59:59.000Z

    In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO{sub 2}) films grown by atomic layer deposition using TEMA-Hf/H{sub 2}O at 250 C substrate temperature. HfO{sub 2} is currently being studied as a possible replacement for Silicon Oxide (SiO{sub 2}) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K{sub a} X-ray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2 kV Ar{sup +} ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar{sup +} sputtering there was still only trace amounts of carbon at {approx}1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar{sup +} used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO{sub 2} film.

  15. Wrinkling of Stiff Films on Stretched Compliant Films: Experimental and Theoretical Studies

    E-Print Network [OSTI]

    Yang, Yi

    2013-12-06T23:59:59.000Z

    substrate has not been well understood. The composite bilayer comprised with a stiff film and a stretched film has a critical application in developing advanced thin film solar cells for long duration stratosphere balloons. The presented thesis focuses...

  16. Modeling and control of thin film surface morphology: application to thin film solar cells

    E-Print Network [OSTI]

    Huang, Jianqiao

    2012-01-01T23:59:59.000Z

    of a p-i-n thin-film solar cell with front transparent con-for thin-film a-si:h solar cells. Progress in Photovoltaics,in thin-film silicon solar cells. Optics Communications,

  17. Characterization of device parameters in high-temperature metal-oxide-semiconductor field-effect transistors in. beta. -SiC thin films

    SciTech Connect (OSTI)

    Palmour, J.W.; Kong, H.S.; Davis, R.F.

    1988-08-15T23:59:59.000Z

    Both inversion- and depletion-mode n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) have been fabricated on ..beta..-SiC thin films grown by chemical-vapor deposition. The inversion-mode devices were made on in situ doped (Al) p-type ..beta..-SiC(100) thin films grown on Si(100) substrates. The depletion-mode MOSFETs were made on n-type ..beta..-SiC(111) thin films grown on the Si(0001) face of a 6H ..cap alpha..-SiC substrates. Stable saturation and low subthreshold currents were achieved at drain-source voltages exceeding 5 and 25 V for the inversion-mode and depletion-mode devices, respectively. The transconductance increased with temperature up to 673 K for the short-gate-length devices, of either mode, and then decreased with further increases in temperature. It is proposed that the transconductances and threshold voltages for the inversion-mode devices are greatly affected by minority-carrier injection from the source. Stable transistor action was observed for both types of devices at temperatures up to 823 K, with the depletion-mode devices operating very well up to 923 K.

  18. Improved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires

    E-Print Network [OSTI]

    tin oxide films in electrochromic (EC) devices. The successful integration of such graphene/NW films. KEYWORDS: Graphene, nanowires, transparent conductive films, electrochromic devices Due to low electron

  19. TIF film, substrates and nonfumigant soil disinfestation maintain fruit yields

    E-Print Network [OSTI]

    2013-01-01T23:59:59.000Z

    the perme- ability of agricultural films. 222nd Americanthe permeability of agricultural films to various fumigants.the ability of an agricultural film to block fumigant flow

  20. Review: German Film after Germany. Toward a Transnational Aesthetic

    E-Print Network [OSTI]

    Theisen, Bianca

    2011-01-01T23:59:59.000Z

    Halle. German Film After Germany. Toward a Transnationalof film production in Germany has changed rapidly. Thescale. German Film After Germany: Toward a Transnational

  1. Vertically Aligned Nanocomposite Thin Films

    E-Print Network [OSTI]

    Bi, Zhenxing

    2012-07-16T23:59:59.000Z

    and epitaxial growth ability on given substrates. In the present work, we investigated unique epitaxial two-phase VAN (BiFeO3)x:(Sm2O3)1-x and (La0.7Sr0.3MnO3)x:(Mn3O4)1-x thin film systems by pulsed laser deposition. These VAN thin films exhibit a highly...

  2. Room temperature ferromagnetic and ferroelectric properties of Bi{sub 1?x}Ca{sub x}MnO{sub 3} thin films

    SciTech Connect (OSTI)

    Pugazhvadivu, K. S.; Tamilarasan, K., E-mail: dr.k.tamilarasan@gmail.com [Thin Film Laboratory, Department of Physics, Kongu Engineering College, Perundurai - 638 052 (India); Balakrishnan, L. [Materials Physics Division, School of Advanced Sciences, VIT University, Vellore - 632 014 (India); Mohan Rao, G. [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore - 560 012 (India)

    2014-11-15T23:59:59.000Z

    Bi{sub 1?x}Ca{sub x}MnO{sub 3} (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 are successfully deposited on the n-type Si (100) substrate at two different temperatures of 400 °C and 800 °C using RF magnetron sputtering. The stoichiometry of the films and oxidation state of the elements have been described by X-ray photoelectron spectroscopy analysis. Dielectric measurement depicts the insulating property of BCMO films. Magnetic and ferroelectric studies confirm the significant enhancement in spin orientation as well as electric polarization at room temperature due to incorporation of Ca{sup 2+} ions into BiMnO{sub 3} films. The BCMO (x = 0.2) film grown at 400 °C shows better magnetization (M{sub sat}) and polarization (P{sub s})with the measured values of 869 emu / cc and 6.6 ?{sub C}/ cm{sup 2} respectively than the values of the other prepared films. Thus the realization of room temperature ferromagnetic and ferroelectric ordering in Ca{sup 2+} ions substituted BMO films makes potentially interesting for spintronic device applications.

  3. Variable temperature semiconductor film deposition

    DOE Patents [OSTI]

    Li, X.; Sheldon, P.

    1998-01-27T23:59:59.000Z

    A method of depositing a semiconductor material on a substrate is disclosed. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  4. Touch, taste & devour: phenomenology of film and the film experiencer in the cinema of sensations.

    E-Print Network [OSTI]

    Aaltonen, Minna-Ella

    2011-01-01T23:59:59.000Z

    ??This thesis explores the possibilities of reconciling corporeal and visceral film experience with theory. It provides an analyses of two contemporary films; Marina de Van's… (more)

  5. Growth and interface phase stability of barium hexaferrite films on SiC(0001)

    SciTech Connect (OSTI)

    Lazarov, V. K. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); York JEOL Nanoscience Centre, Heslington, York YO10 5DD (United Kingdom); Hasnip, P. J. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Cai, Z.; Ziemer, K. S. [Chemical Engineering Department, Northeastern University, Boston, Massachusetts 02115 (United States); Yoshida, K. [York JEOL Nanoscience Centre, Heslington, York YO10 5DD (United Kingdom)

    2011-04-01T23:59:59.000Z

    We have studied interface phase stability of the BaFe{sub 12}O{sub 19} (BaM) thin films grown by molecular beam epitaxy on SiC(0001). The films were epitaxially grown with the following crystallographic relation: BaM(0001) parallel SiC(0001) and BaM(11-20) parallel SiC(11-20). High resolution TEM reveals the existence of two interfacial bands with different structure than BaM. The first band close to SiC is SiO{sub x} while the second has spinel structure and chemically corresponds to Fe{sub 3}O{sub 4}. These findings suggest that at initial growth stages Fe{sub 3}O{sub 4} is more favorable than BaM. Density functional theory modeling of the phase stability of BaM compared to Fe{sub 3}O{sub 4} shows that BaM is only stable at high oxygen partial pressures.

  6. High quality Y-type hexaferrite thick films for microwave applications by an economical and environmentally benign crystal growth technique

    SciTech Connect (OSTI)

    Hu, Bolin; Chen, Yajie, E-mail: y.chen@neu.edu; Gillette, Scott; Su, Zhijuan; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); Wolf, Jason; McHenry, Michael E. [Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2014-02-17T23:59:59.000Z

    Thick barium hexaferrite Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} (i.e., Zn{sub 2}Y) films having thicknesses of ?100??m were epitaxially grown on MgO (111) substrates using an environmentally benign ferrite-salt mixture by vaporizing the salt. X-ray diffraction pole figure analyses showed (00l) crystallographic alignment with little in plane dispersion confirming epitaxial growth. Saturation magnetization, 4?M{sub s}, was measured for as-grown films to be 2.51?±?0.1?kG with an out of plane magnetic anisotropy field H{sub A} of 8.9?±?0.1?kOe. Ferromagnetic resonance linewidth, as the peak-to-peak power absorption derivative at 9.6?GHz, was measured to be 62?Oe. These properties demonstrate a rapid, convenient, cost-effective, and nontoxic method of growing high quality thick crystalline ferrite films which could be used widely for microwave device applications.

  7. Liquid soap film generates electricity

    E-Print Network [OSTI]

    Ahmad Amjadi; Sadegh Feiz; Reza Montazeri Namin

    2014-04-24T23:59:59.000Z

    We have observed that a rotating liquid soap film generates electricity when placed between two non-contact electrodes with a sufficiently large potential difference. In our experiments suspended liquid film (water + soap film) is formed on the surface of a circular frame, which is forced to rotate in the $x-y$ horizontal plane by a motor. This system is located at the center of two capacitor-like vertical plates to apply an external electric voltage difference in the $x-$direction. The produced electric current is collected from the liquid film using two conducting electrodes that are separated in the $y-$direction. We previously reported that a liquid film in an external electric field rotates when an electric current passes through it, naming it the liquid film motor (LFM). In this paper we report a novel technique, in which a similar device can be used as an electric generator, converting the rotating mechanical energy to electrical energy. The liquid film electric generator (LFEG) is in stark contrast to the LFM, both of which could be designed similarly in very small scales like micro scales with different applications. Although the device is comparable to commercial electric motors or electric generators, there is a significant difference in their working principles. Usually in an electric motor or generator the magnetic field causes the driving force, while in a LFM or LFEG the Coulomb force is the driving force. This fact is also interesting from the Bio-science point of view and brings a similarity to bio motors. Here we have investigated the electrical characteristics of such a generator for the first time experimentally and modelled the phenomenon with electroconvection governing equations. A numerical simulation is performed using the local approximation for the charge-potential relation and results are in qualitative agreement with experiments.

  8. “How Could She?”: The “Inappropriate” Woman in Contemporary Appropriation Films

    E-Print Network [OSTI]

    Baron, Jaimie

    2010-01-01T23:59:59.000Z

    Parrell took a number of porn films that she realized wereintended purposes. Within a porn film, people having sex into most people watching a porn film. Parrell’s film situates

  9. Thin Film Encapsulation Methods for Large Area MEMS Packaging

    E-Print Network [OSTI]

    Mahajerin, Armon

    2012-01-01T23:59:59.000Z

    penetrated c) Windows in nitride film not clearly visiblea circular window is preferred to minimize film deflection

  10. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D., E-mail: dipankarsaha@iitb.ac.in [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai 400076 (India); Adari, R.; Sankaranarayan, S.; Kumar, A. [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)] [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S. [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)] [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2013-12-09T23:59:59.000Z

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ?2.5% is obtained at 200?K.

  11. August 2013 Jianbang Gan

    E-Print Network [OSTI]

    and Marketing), Iowa State University, 1988 B.S., Forest Engineering, Fujian Agriculture and Forestry University Specialty: Forest Resource Economics, Management, and Policy Current Research Interests: Bioenergy

  12. The crystallographic texture of a great number of polyethylene films manufactured by the film

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    The crystallographic texture of a great number of polyethylene films manufactured by the film polymer films (fig. 1). It is essentially dedicated to polyethylene, espe- cially for packaging in polyethylene blown films J.-M. Haudin, J.-M. André, G. Bellet, B. Monasse, P. Navard �cole des Mines de Paris

  13. Film Studies Page 143Sonoma State University 2014-2015 Catalog FILM STUDIES

    E-Print Network [OSTI]

    Ravikumar, B.

    will study a broad range of film texts and learn to appreciate a variety of aesthetic and filmmaking in Film Studies 1-4 ENGL 430 Creative Writing: Select Genres (Screenplay) 1-4 MLL 214 French Literature and Film 4 FR 201 Third Semester French 4 GER 210 Intermediate German though Film 4 LIBS 320C Bollywood 3

  14. Semiconductor-nanocrystal/conjugated polymer thin films

    DOE Patents [OSTI]

    Alivisatos, A. Paul (Oakland, CA); Dittmer, Janke J. (Munich, DE); Huynh, Wendy U. (Munich, DE); Milliron, Delia (Berkeley, CA)

    2010-08-17T23:59:59.000Z

    The invention described herein provides for thin films and methods of making comprising inorganic semiconductor-nanocrystals dispersed in semiconducting-polymers in high loading amounts. The invention also describes photovoltaic devices incorporating the thin films.

  15. Electrostatic thin film chemical and biological sensor

    DOE Patents [OSTI]

    Prelas, Mark A. (Columbia, MO); Ghosh, Tushar K. (Columbia, MO); Tompson, Jr., Robert V. (Columbia, MO); Viswanath, Dabir (Columbia, MO); Loyalka, Sudarshan K. (Columbia, MO)

    2010-01-19T23:59:59.000Z

    A chemical and biological agent sensor includes an electrostatic thin film supported by a substrate. The film includes an electrostatic charged surface to attract predetermined biological and chemical agents of interest. A charge collector associated with said electrostatic thin film collects charge associated with surface defects in the electrostatic film induced by the predetermined biological and chemical agents of interest. A preferred sensing system includes a charge based deep level transient spectroscopy system to read out charges from the film and match responses to data sets regarding the agents of interest. A method for sensing biological and chemical agents includes providing a thin sensing film having a predetermined electrostatic charge. The film is exposed to an environment suspected of containing the biological and chemical agents. Quantum surface effects on the film are measured. Biological and/or chemical agents can be detected, identified and quantified based on the measured quantum surface effects.

  16. Low work function, stable thin films

    DOE Patents [OSTI]

    Dinh, Long N. (Concord, CA); McLean, II, William (Oakland, CA); Balooch, Mehdi (Berkeley, CA); Fehring, Jr., Edward J. (Dublin, CA); Schildbach, Marcus A. (Livermore, CA)

    2000-01-01T23:59:59.000Z

    Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

  17. LEAM Film Development Test Report Prepared by

    E-Print Network [OSTI]

    Rathbun, Julie A.

    Solar Test Test Item No. l Film Development Tests Test Item No. 2 Film Development Tests Test Item No. 3~~ ··········~~~ LEAM Film Development Test Report Prepared by: R. Sii'r'...ms ~1 rf\\:'3· ~ ij ATM Film Development Test Report -~~'·.· ··..· .··. . ~...=-~ ~ IWitJY~W ' ~· CONTENTS 1. PURPOSE 2. SCOPE

  18. Effect of growth conditions on microstructure of BiFeO{sub 3}-0.33BaTiO{sub 3} films and performance of bulk acoustic wave resonators

    SciTech Connect (OSTI)

    Vorobiev, A., E-mail: andrei.vorobiev@chalmers.se; Gevorgian, S. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Löffler, M.; Olsson, E. [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2014-02-28T23:59:59.000Z

    The effect of growth conditions on the microstructure of BiFeO{sub 3}-0.33BaTiO{sub 3} (BF-BT) films and the performance of bulk acoustic wave (BAW) resonators is analyzed using test structures with the BF-BT films grown at different positions relative to the plume axis in the pulsed laser deposition system. The BF-BT film grain size and surface roughness reveal a strong asymmetric surface distribution and decrease significantly in the film region facing the laser beam-plume interaction area. The (100) BF-BT texturing is enhanced in this film region. The variations in the BF-BT film microstructure result in corresponding variations of the BAW resonator performance. Their correlations are established using the model of the roughness induced attenuation of the reflected acoustic waves and theory of the dc field induced piezoelectric effect. The BAW resonators with the highest parameters are obtained in the BF-BT film region facing the laser beam-plume interaction area. The BAW resonators located in this film region reveal a mechanical Q-factor of 200 at 4.2?GHz, an effective electromechanical coupling coefficient of 10% and a tunability of the series resonance frequency of 4.5%.

  19. X-ray absorption spectroscopy elucidates the impact of structural disorder on electron mobility in amorphous zinc-tin-oxide thin films

    SciTech Connect (OSTI)

    Siah, Sin Cheng, E-mail: siahsincheng@gmail.com, E-mail: buonassisi@mit.edu; Lee, Yun Seog; Buonassisi, Tonio, E-mail: siahsincheng@gmail.com, E-mail: buonassisi@mit.edu [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Lee, Sang Woon; Gordon, Roy G. [Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138 (United States); Heo, Jaeyeong [Department of Materials Science and Engineering, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Shibata, Tomohiro; Segre, Carlo U. [Physics Department and CSRRI, Illinois Institute of Technology, Chicago, Illinois 606016 (United States)

    2014-06-16T23:59:59.000Z

    We investigate the correlation between the atomic structures of amorphous zinc-tin-oxide (a-ZTO) thin films grown by atomic layer deposition (ALD) and their electronic transport properties. We perform synchrotron-based X-ray absorption spectroscopy at the K-edges of Zn and Sn with varying [Zn]/[Sn] compositions in a-ZTO thin films. In extended X-ray absorption fine structure (EXAFS) measurements, signal attenuation from higher-order shells confirms the amorphous structure of a-ZTO thin films. Both quantitative EXAFS modeling and X-ray absorption near edge spectroscopy (XANES) reveal that structural disorder around Zn atoms increases with increasing [Sn]. Field- and Hall-effect mobilities are observed to decrease with increasing structural disorder around Zn atoms, suggesting that the degradation in electron mobility may be correlated with structural changes.

  20. Thin film buried anode battery

    DOE Patents [OSTI]

    Lee, Se-Hee (Lakewood, CO); Tracy, C. Edwin (Golden, CO); Liu, Ping (Denver, CO)

    2009-12-15T23:59:59.000Z

    A reverse configuration, lithium thin film battery (300) having a buried lithium anode layer (305) and process for making the same. The present invention is formed from a precursor composite structure (200) made by depositing electrolyte layer (204) onto substrate (201), followed by sequential depositions of cathode layer (203) and current collector (202) on the electrolyte layer. The precursor is subjected to an activation step, wherein a buried lithium anode layer (305) is formed via electroplating a lithium anode layer at the interface of substrate (201) and electrolyte film (204). The electroplating is accomplished by applying a current between anode current collector (201) and cathode current collector (202).

  1. Epitaxial Thin Film XRD | EMSL

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE:1 First Use of Energy for All Purposes (Fuel and Nonfuel),Feet) Year Jan Feb Mar Apr May JunDatastreamsmmcrcalgovInstrumentsruc DocumentationP-Series toESnet4:Epitaxial Thin Film XRD Epitaxial Thin Film XRD Systems

  2. Nanoscale Growth Twins in Sputtered Copper Films

    E-Print Network [OSTI]

    Anderoglu, Osman

    2011-08-08T23:59:59.000Z

    .............................................................. 7 I.1.3. Chemical vapor deposition (CVD) .................................... 8 I.2. Fabrication of copper thin films .................................................... 12... to the exposure of the film growth surface to the solution, impurities may be introduced. I.1.3. Chemical vapor deposition (CVD) CVD is a chemical process used to produce high-purity, high-performance thin films and often used in the semiconductor industry...

  3. Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

    SciTech Connect (OSTI)

    Buršík, J., E-mail: bursik@iic.cas.cz [Institute of Inorganic Chemistry of the AS CR, v.v.i., 250 68 Husinec-?ež 1001 (Czech Republic); Kužel, R. [Charles University in Prague, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Knížek, K.; Drbohlav, I. [Institute of Physics of the AS CR, v.v.i., Na Slovance 2, 182 21 Praha 8 (Czech Republic)

    2013-07-15T23:59:59.000Z

    Thin films of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO{sub 3}(1 1 1) (ST) single crystal substrates using epitaxial SrFe{sub 12}O{sub 19} (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature ramp were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and ? scans reveal perfect parallel in-plane alignment of SrTiO{sub 3} substrate and both hexaferrite phases. - Graphical abstract: XRD pole figure and AFM patterns of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} thin film epitaxially grown on SrTiO{sub 3}(1 1 1) single crystal using seeding layer templating. - Highlights: • Single phase Y-type hexagonal ferrite thin films were prepared by CSD method. • Seed M layer breaks into isolated single crystal islands and serves as a template. • Large seed grains grow by consuming the grains within the bulk of recoated film. • We explained the observed orientation relation of epitaxial domains. • Epitaxial growth on SrTiO{sub 3}(1 1 1) with relation (0 0 1){sub M,Y}//(1 1 1){sub ST}+[1 0 0]{sub M,Y}//[2 ?1 ?1]{sub ST}.

  4. Influence of a TiO{sub 2} buffer layer on the magnetic properties of anatase Co:TiO{sub 2} thin films

    SciTech Connect (OSTI)

    Gabor, M. S.; Petrisor, T. Jr.; Tiusan, C. [Technical University of Cluj-Napoca, Materials Science Laboratory, Cluj-Napoca (Romania); Institut Jean Lamour, P2M, CNRS - Nancy University, Nancy (France); Hehn, M. [Institut Jean Lamour, P2M, CNRS - Nancy University, Nancy (France); Vasile, B. S. [Faculty of Applied Chemistry and Material Science, Department of Science and Engineering of Oxide Materials and Nanomaterials, University POLITEHNICA Bucharest, Bucharest (Romania); Petrisor, T. [Technical University of Cluj-Napoca, Materials Science Laboratory, Cluj-Napoca (Romania)

    2012-04-15T23:59:59.000Z

    Our study addresses the influence of a TiO{sub 2} buffer layer on the morphological, structural, and magnetic properties of Co:TiO{sub 2} films grown on (001) SrTiO{sub 3} substrates by RF sputtering. We demonstrate that a direct correlation exist between the morphology, the Co heterogeneity, and the magnetic properties measured in the films. Correlated analysis by cross section transmission electron microscopy, energy dispersive x-ray, and x-ray photoemission spectroscopy reveals that the Co is not uniformly distributed in the film but concentrated in the surface clusters. Atomic force microscopy analysis illustrates that the unbuffered films present a large density of surface clusters. These clusters are not metallic Co but Co rich TiO{sub 2} anatase phase and they are accompanied by structural defects in the film: dislocations, small angle grain boundaries. Magnetometry analysis shows that the unbuffered films have a net ferromagnetic behavior, while in the buffered ones the ferromagnetism is quenched. Therefore, we conclude that the magnetism in unbuffered samples is related to the surface clusters and seems to have an extrinsic nature.

  5. Polymer electrolyte fuel cell electrodes grown by vapor deposition techniques Pascal Brault*

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Polymer electrolyte fuel cell electrodes grown by vapor deposition techniques Pascal Brault Abstract: Polymer fuel cell electrode growth using vapor deposition techniques is reviewed. The supports process: sputtering, CVD, PECVD, MOCVD. In each case, up-to-date fuel cell performances are highlighted

  6. Few Graphene layer/Carbon-Nanotube composite Grown at CMOS-compatible Temperature

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    the growth of the recently demonstrated composite material composed of vertically aligned carbon nanotubesFew Graphene layer/Carbon-Nanotube composite Grown at CMOS-compatible Temperature V. Jousseaume1 materials and technologies for the next-generation of Integrated Circuits (ICs). Carbon nanomaterials

  7. INVESTIGATION OF ELECTRIC CONDITIONS IN THE VICINITY OF CARBON NANOTUBES GROWN IN A DC PLASMA SHEATH

    E-Print Network [OSTI]

    Boyer, Edmond

    nanotubes (CNTs ­ long tubular carbon nanostructures) belong to the best electron field emitting materials, such as nanoelectronics devices or mechanical reinforcement in composite materials [2,3]. The field emission propertiesINVESTIGATION OF ELECTRIC CONDITIONS IN THE VICINITY OF CARBON NANOTUBES GROWN IN A DC PLASMA

  8. CHARACTERIZATION OF UNDOPED HIGH RESISTIVITY CdTe GROWN BY A THM METHOD

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    185 CHARACTERIZATION OF UNDOPED HIGH RESISTIVITY CdTe GROWN BY A THM METHOD R. STUCK, J. C. MULLER techniques of cadmium tellu- ride crystals (CdTe) allowed to obtain high resistivity crystals of detector shape of the phase diagram of CdTe, it seemed interesting to characterize these materials in order

  9. Enhanced Thermoelectric Properties of Solution Grown Bi2Te3-xSex Nanoplatelet Composites

    E-Print Network [OSTI]

    Xiong, Qihua

    is the lattice contributions) and T is average absolute temperature. An ideal thermoelectric material on the efficiency of thermoelectric materials, and hence a decoupling of these parameters is required to improveEnhanced Thermoelectric Properties of Solution Grown Bi2Te3-xSex Nanoplatelet Composites Ajay Soni

  10. Unidirectional Pt silicide nanowires grown on vicinal Si,,100... Do Kyung Lim,1

    E-Print Network [OSTI]

    Kim, Sehun

    this limitation, we focused on noble metal silicide NWs be- cause noble metals rarely form insulating metal oxideUnidirectional Pt silicide nanowires grown on vicinal Si,,100... Do Kyung Lim,1 Sung-Soo Bae,1. In particular, rare-earth silicide NWs on silicon surfaces have attracted in- terest as candidate nanostructures

  11. Sonochemically grown ZnO nanowalls on Graphene layers as Photoanode in Dye sensitized Solar cells.

    E-Print Network [OSTI]

    Pala, Nezih

    Sonochemically grown ZnO nanowalls on Graphene layers as Photoanode in Dye sensitized Solar cells whole solar spectrum Graphene can be a very promising material in Dye Sensitized Solar cells (DSSC as photoanode is presented. The effect of Graphene on dye loading and on efficiency of DSSC is quantitatively

  12. Eumelanin Dye-sensitized Solar Cell Grown with Matrix-assisted Pulsed Laser

    E-Print Network [OSTI]

    Eumelanin Dye-sensitized Solar Cell Grown with Matrix-assisted Pulsed Laser Evaporation~4 DHICA DHICA #12; III Abstract At present the majority dye-sensitized solar cell research all, and besides provides and does not have other uses for the dye-sensitized solar cell use. In order to improve

  13. POLARIZED RAMAN MEASUREMENTS IN ZEOLITE-GROWN SINGLE-WALL CARBON NANOTUBES

    E-Print Network [OSTI]

    Nabben, Reinhard

    POLARIZED RAMAN MEASUREMENTS IN ZEOLITE-GROWN SINGLE-WALL CARBON NANOTUBES J. Maultzsch*, P. M, Hardenbergstr. 36, D-10623 Berlin, E-Mail: janina@physik.tu-berlin.de The Raman spectra of carbon nanotubes able to grow carbon nanotubes inside the channels of an AlPO4 zeolite crystal [1]. The directions

  14. Microhardness of Czochralski-grown single crystals of VB{sub 2}

    SciTech Connect (OSTI)

    Bulfon, C.; Sassik, H. [Institut fuer Experimentalphysik, Wien (Austria)] [Institut fuer Experimentalphysik, Wien (Austria); Leithe-Jasper, A.; Rogl, P. [Universitaet Wien (Austria)] [Universitaet Wien (Austria)

    1997-10-01T23:59:59.000Z

    Single crystals of congruent melting hexagonal VB{sub 2} were grown used a triarc furnace applying the Czochralski technique. Orientation dependent microhardness measurements on a single crystal reveal quasi similar hardness in the crystallographic directions <00.1> and <10.0>, whereas the <10.1> shows slightly lower values.

  15. Direct Physical Exfoliation of Few-Layer Graphene from Graphite Grown on a Nickel Foil Using

    E-Print Network [OSTI]

    Maruyama, Shigeo

    Direct Physical Exfoliation of Few-Layer Graphene from Graphite Grown on a Nickel Foil Using Physical graphene exfoliation from graphite using optimized PDMS PACS codes: 68.65.Pq, 81.05.ue, 81.05.uf for the site-specific direct physical exfoliation of few-layer graphene sheets from cheap and easily

  16. Author's personal copy Antioxidant capacity reduced in scallions grown under elevated CO2

    E-Print Network [OSTI]

    Paré, Paul W.

    Author's personal copy Antioxidant capacity reduced in scallions grown under elevated CO2 was used as a model plant to study the impact of a range of CO2 concentrations and light intensities in controlled environmental chambers under a combination of 3 CO2 concentrations of 400, 1200 and 4000 lmol mol

  17. Chemical Reactivity of Pd-Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

    E-Print Network [OSTI]

    Asscher, Micha

    grown via ASW buffer layer on silica, presumably due to suppression of the trimerization pathway of both, is often rather difficult to obtain. Model catalysis has been studied in recent decades by in an industrial catalyst.16-20 Intro- duction of weakly bound buffer layers to assist the growth of clusters

  18. Ris Energy Report 3 Interest in the hydrogen economy has grown rapidly in

    E-Print Network [OSTI]

    1 Risø Energy Report 3 Interest in the hydrogen economy has grown rapidly in recent years. Those explains the current R&D situation, addresses the challenges facing the large-scale use of hydrogen countries with long traditions of activity in hydrogen research and development have now been joined

  19. Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers

    SciTech Connect (OSTI)

    Umlor, M.T.; Keeble, D.J. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Physics; Asoka-Kumar, P.; Lynn, K.G. [Brookhaven National Lab., Upton, NY (United States); Cooke, P.W. [Geo-Centers, Inc., Eatontown, NJ (United States). Fort Monmouth Operation

    1994-08-01T23:59:59.000Z

    A summary of recent positron annihilation experiments on molecular beam epitaxy (MBE) grown III-V layers is Presented. Variable energy positron beam measurements on Al{sub 0.32}Ga{sub 0.68}As undoped and Si doped have been completed. Positron trapping at a open volume defect in Al{sub 0.32}Ga{sub 0.68}:Si for temperatures from 300 to 25 K in the dark was observed. The positron trap was lost after 1.3 eV illumination at 25K. These results indicate an open volume defect is associated with the local structure of the deep donor state of the DX center. Stability of MBE GaAs to thermal annealing war, investigated over the temperature range of 230 to 700{degrees}C, Proximity wafer furnace anneals in flowing argon were used, Samples grown above 450{degrees}C were shown to be stable but for sample below this temperature an anneal induced vacancy related defect was produced for anneals between 400 and 500{degrees}C. The nature of the defect was shown to be different for material grown at 350 and 230{degrees}C. Activation energies of 2.5 eV to 2.3 eV were obtained from isochronal anneal experiments for samples grown at 350 and 230{degrees}C, respectively.

  20. Epitaxial growth of CdTe thin film on cube-textured Ni by metal-organic chemical vapor deposition

    SciTech Connect (OSTI)

    GIARE, C [Rensselaer Polytechnic Institute (RPI); RAO, S [Rensselaer Polytechnic Institute (RPI); RILEY, M [Rensselaer Polytechnic Institute (RPI); CHEN, L [Rensselaer Polytechnic Institute (RPI); Goyal, Amit [ORNL; BHAT, I [Rensselaer Polytechnic Institute (RPI); LU, T [Rensselaer Polytechnic Institute (RPI); WANG, G [Rensselaer Polytechnic Institute (RPI)

    2012-01-01T23:59:59.000Z

    CdTe thin film has been grown by metalorganic chemical vapor deposition (MOCVD) on Ni(100) substrate. Using x-ray pole figure measurements we observed the epitaxial relationship of {111}CdTe// {001}Ni with [110]CdTe//[010]Ni and [112] CdTe//[100]Ni. The 12 diffraction peaks in the (111) pole figure of CdTe film and their relative positions with respect to the four peak positions in the (111) pole figure of Ni substrate are consistent with four equivalent orientational domains of CdTe with three to four superlattice match of about 0.7% in the [110] direction of CdTe and the [010] direction of Ni. The electron backscattered diffraction (EBSD) images show that the CdTe domains are 30 degrees orientated from each other.