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1

Molecular Beam Epitaxy, Multi-source | EMSL  

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

beam epitaxy, is examined using a combination... Self-corrected Sensors Based On Atomic Absorption Spectroscopy For Atom Flux Measurements In Molecular Beam Epitaxy. A...

2

Molecular Beam Epitaxy | 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 JunDatastreamsmmcrcalgovInstrumentsrucLas Conchas recovery challenge fundProject8Mistakes to Avoid MistakesResponseModernMolecular

3

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

E-Print Network [OSTI]

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

Myers, Tom

4

/II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy  

E-Print Network [OSTI]

/II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy Shouleh Nikzad, Selmer S. Wong, Channing C. Ahn, Aimee L. Smith molecular beam epitaxy system, using reflection electron energy loss spectroscopy, in conjunction

Atwater, Harry

5

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature  

E-Print Network [OSTI]

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature Simone film crystal growth of silicon carbide (SiC), a semiconductor syn- thesized to replace silicon in harsh

Alfè, Dario

6

(In,Mn)As quantum dots: Molecular-beam epitaxy and optical properties  

SciTech Connect (OSTI)

Self-assembled (In,Mn)As quantum dots are synthesized by molecular-beam epitaxy on GaAs (001) substrates. The experimental results obtained by transmission electron microscopy show that doping of the central part of the quantum dots with Mn does not bring about the formation of structural defects. The optical properties of the samples, including those in external magnetic fields, are studied.

Bouravleuv, A. D., E-mail: bour@mail.ioffe.ru; Nevedomskii, V. N. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Ubyivovk, E. V. [St. Petersburg State University (Russian Federation)] [St. Petersburg State University (Russian Federation); Sapega, V. F. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Khrebtov, A. I. [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation)] [St. Petersburg Academic University, Nanotechnology Research and Education Centre (Russian Federation); Samsonenko, Yu. B.; Cirlin, G. E.; Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-08-15T23:59:59.000Z

7

Molecular Beam Epitaxial Growth of GaAs on (631) Oriented Substrates  

SciTech Connect (OSTI)

In this work, we report the study of the homoepitaxial growth of GaAs on (631) oriented substrates by molecular beam epitaxy (MBE). We observed the spontaneous formation of a high density of large scale features on the surface. The hilly like features are elongated towards the [-5, 9, 3] direction. We show the dependence of these structures with the growth conditions and we present the possibility of to create quantum wires structures on this surface.

Cruz Hernandez, Esteban; Rojas Ramirez, Juan-Salvador; Contreras Hernandez, Rocio; Lopez Lopez, Maximo [Physics Department, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, Mexico D.F., 07000 (Mexico); Pulzara Mora, Alvaro [Universidad Nacional de Colombia - Sede Manizales, A. A. 127 (Colombia); Mendez Garcia, Victor H. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Av. Karakorum 1470, Lomas 4a Seccion, C.P. 78210, San Luis Potosi (Mexico)

2007-02-09T23:59:59.000Z

8

Growth of InGaAsP by molecular beam epitaxy  

SciTech Connect (OSTI)

Molecular beam epitaxy has been used to grow good quality films of InGaAsP on InP substrates. The films have been characterized using infrared absorption, electroreflectance, x-ray diffraction, reflection electron diffraction, and Hall measurements. Lattice matching was achieved and room-temperature mobilities up to 4600 cm/sup 2/ V/sup -1/ s/sup -1/ were measured.

Holah, G.D.; Eisele, F.L.; Meeks, E.L.; Cox, N.W.

1982-12-01T23:59:59.000Z

9

Lattice constant and substitutional composition of GeSn alloys grown by molecular beam epitaxy  

SciTech Connect (OSTI)

Single crystal epitaxial Ge{sub 1?x}Sn{sub x} alloys with atomic fractions of tin up to x = 0.145 were grown by solid source molecular beam epitaxy on Ge (001) substrates. The Ge{sub 1?x}Sn{sub x} alloys formed high quality, coherent, strained layers at growth temperatures below 250 °C, as shown by high resolution X-ray diffraction. The amount of Sn that was on lattice sites, as determined by Rutherford backscattering spectrometry channeling, was found to be above 90% substitutional in all alloys. The degree of strain and the dependence of the effective unstrained bulk lattice constant of Ge{sub 1?x}Sn{sub x} alloys versus the composition of Sn have been determined.

Bhargava, Nupur; Coppinger, Matthew; Prakash Gupta, Jay; Kolodzey, James [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States)] [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States); Wielunski, Leszek [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)] [Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)

2013-07-22T23:59:59.000Z

10

Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth  

SciTech Connect (OSTI)

We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

2014-03-01T23:59:59.000Z

11

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

SciTech Connect (OSTI)

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.

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

12

Germanium diffusion during HfO{sub 2} growth on Ge by molecular beam epitaxy  

SciTech Connect (OSTI)

The authors study the Ge diffusion during HfO{sub 2} growth by molecular beam epitaxy on differently in situ prepared germanium substrates and at different growth temperatures. While HfO{sub 2} layers grown directly on Ge do not show any germanium contamination, oxygen rich interfacial layers such as GeO{sub x} or GeO{sub x}N{sub y} partly dissolve into the HfO{sub 2} layer, giving rise to high Ge contamination (from 1% to 10%). The use of nitridated interfacial layers does not prevent Ge diffusion into the HfO{sub 2} during the growth process because of the high oxygen content present in the nitridated germanium layer.

Ferrari, S.; Spiga, S.; Wiemer, C.; Fanciulli, M.; Dimoulas, A. [Laboratorio MDM-INFM-CNR, Via Olivetti, 2 Agrate Brianza, Milano 20041 (Italy); MBE Laboratory, Institute of Materials Science, DEMOKRITOS National Center for Scientific Research, 153 10 Athens (Greece)

2006-09-18T23:59:59.000Z

13

Molecular-beam epitaxial growth of boron-doped GaAs films  

SciTech Connect (OSTI)

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.

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

14

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

SciTech Connect (OSTI)

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.

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

15

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

SciTech Connect (OSTI)

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.

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

16

Antimony segregation in stressed SiGe heterostructures grown by molecular beam epitaxy  

SciTech Connect (OSTI)

The effects of the growth temperature, composition, and elastic strains in separate layers on the segregation of antimony are studied experimentally for stressed SiGe structures grown by molecular beam epitaxy. It is established that the growth conditions and parameters of the structures exert an interrelated influence on the segregation of Sb: the degree of the influence of the composition and elastic stresses in the SiGe layers on Sb segregation depends on the growth temperature. It is shown that usage of a method previously proposed by us for the selective doping of silicon structures with consideration for the obtained dependences of Sb segregation on the growth conditions and parameters of the SiGe layers makes it possible to form SiGe structures selectively doped with antimony.

Drozdov, M. N.; Novikov, A. V.; Yurasov, D. V., E-mail: Inquisitor@ipm.sci.nnov.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2013-11-15T23:59:59.000Z

17

Infrared electroluminescence from GeSn heterojunction diodes grown by molecular beam epitaxy  

SciTech Connect (OSTI)

Infrared electroluminescence was observed from GeSn/Ge p-n heterojunction diodes with 8% Sn, grown by molecular beam epitaxy. The GeSn layers were boron doped, compressively strained, and pseudomorphic on Ge substrates. Spectral measurements indicated an emission peak at 0.57 eV, about 50 meV wide, increasing in intensity with applied pulsed current, and with reducing device temperatures. The total integrated emitted power from a single edge facet was 54 {mu}W at an applied peak current of 100 mA at 100 K. These results suggest that GeSn-based materials maybe useful for practical light emitting diodes operating in the infrared wavelength range near 2 {mu}m.

Gupta, Jay Prakash; Bhargava, Nupur; Kim, Sangcheol; Kolodzey, James [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States)] [Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716 (United States); Adam, Thomas [Nanofab, University of Albany, SUNY, Albany, New York 12203 (United States)] [Nanofab, University of Albany, SUNY, Albany, New York 12203 (United States)

2013-06-24T23:59:59.000Z

18

Molecular-beam epitaxy growth of strontium thiogallate T. Yang, B. K. Wagner, M. Chaichimansour, W. Park, Z. L. Wang,a)  

E-Print Network [OSTI]

Molecular-beam epitaxy growth of strontium thiogallate T. Yang, B. K. Wagner, M. Chaichimansour, W-beam epitaxy growth and characterization of cerium doped strontium thiogallate SrGa2S4:Ce thin film phosphors growth of cerium doped strontium thiogallate on quartz substrates was first reported in 1994.3 Here we

Wang, Zhong L.

19

Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers  

SciTech Connect (OSTI)

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.

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

20

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]

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

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

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M. FEENSTRA  

E-Print Network [OSTI]

]. 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

Feenstra, Randall

22

Coherent growth of superconducting TiN thin films by plasma enhanced molecular beam epitaxy  

SciTech Connect (OSTI)

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.

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

23

Lattice-registered growth of GaSb on Si (211) with molecular beam epitaxy  

SciTech Connect (OSTI)

A GaSb film was grown on a Si(211) substrate using molecular beam epitaxy indicating full lattice relaxation as well as full lattice registration and dislocation-free growth in the plane perpendicular to the [01 - 1]-direction. Heteroepitaxy of GaSb on a Si(211) substrate is dominated by numerous first order and multiple higher order micro-twins. The atomic-resolved structural study of GaSb films by high-angle annular dark-field scanning transmission electron microscopy reveals that slight tilt, along with twinning, favors the lattice registry to Si(211) substrates. Preferential bonding of impinging Ga and Sb atoms at the interface due to two distinctive bonding sites on the Si(211) surface enables growth that is sublattice-ordered and free of anti-phase boundaries. The role of the substrate orientation on the strain distribution of GaSb epilayers is further elucidated by investigating the local change in the lattice parameter using the geometric phase analysis method and hence effectiveness of the lattice tilting in reducing the interfacial strain was confirmed further.

Hosseini Vajargah, S.; Botton, G. A. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Brockhouse Institute for Materials 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); Preston, J. S.; Kleiman, R. N. [Brockhouse Institute for Materials 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

24

Growth and phase transition characteristics of pure M-phase VO{sub 2} epitaxial film prepared by oxide molecular beam epitaxy  

SciTech Connect (OSTI)

VO{sub 2} epitaxial film with large size has been prepared by oxide-molecular beam epitaxy method on Al{sub 2}O{sub 3} (0001) substrate. The VO{sub 2} film shows a perfect crystal orientation, uniformity, and distinct metal-insulator phase transition (MIT) characteristics. It is observed that the MIT character is closely associated with the crystal defects such as oxygen vacancies. By controlling the growth condition, the MIT temperature can be tuned through modifying the content of oxygen vacancies. The role of the oxygen vacancies on the phase transition behavior of this VO{sub 2} film is discussed in the framework of the hybridization theory and the valence state of vanadium.

Fan, L. L.; Chen, S.; Wu, Y. F.; Chen, F. H.; Chu, W. S.; Chen, X.; Zou, C. W. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Wu, Z. Y. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China) [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Institute of High Energy Physics, Chinese Academy of Science, Beijing 100049 (China)

2013-09-23T23:59:59.000Z

25

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

SciTech Connect (OSTI)

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.

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

2012-12-01T23:59:59.000Z

26

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

SciTech Connect (OSTI)

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.

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

27

Chirped-pulse manipulated carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs  

SciTech Connect (OSTI)

Chirped pulse controlled carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs are investigated by degenerate pump-probe technique. Varying the chirped condition of excited pulse from negative to positive increases the carrier relaxation time so as to modify the dispersion and reshape current pulse in time domain. The spectral dependence of carrier dynamics is analytically derived and explained by Shockley-Read Hall model. This observation enables the new feasibility of controlling carrier dynamics in ultrafast optical devices via the chirped pulse excitations.

Lee, Chao-Kuei, E-mail: chuckcklee@yahoo.com [Department of Photonics, National Sun-Yat-Sen University, Kaohsiung 80400, Taiwan (China); Lin, Yuan-Yao [Department of Electrical Engineering, Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30010, Taiwan (China); Lin, Sung-Hui [Department of Photonics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lin, Gong-Ru [Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Roosevelt Road, Sec. 4, Taipei 10617, Taiwan (China); Pan, Ci-Ling [Department of Photonics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Physics, National Tsing Hwa University, Hsinchu 30010, Taiwan (China)

2014-04-28T23:59:59.000Z

28

Optical properties of strain-free AlN nanowires grown by molecular beam epitaxy on Si substrates  

SciTech Connect (OSTI)

The optical properties of catalyst-free AlN nanowires grown on Si substrates by molecular beam epitaxy were investigated. Such nanowires are nearly free of strain, with strong free exciton emission measured at room temperature. The photoluminescence intensity is significantly enhanced, compared to previously reported AlN epilayer. Moreover, the presence of phonon replicas with an energy separation of ?100?meV was identified to be associated with the surface-optical phonon rather than the commonly reported longitudinal-optical phonon, which is further supported by the micro-Raman scattering experiments.

Wang, Q.; Zhao, S.; Connie, A. T.; Shih, I.; Mi, Z., E-mail: zetian.mi@mcgill.ca [Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9 (Canada); Gonzalez, T.; Andrews, M. P. [Department of Chemistry, McGill University, 801 Sherbrooke St West, Montreal, Quebec H3A 0B8 (Canada); Du, X. Z.; Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

2014-06-02T23:59:59.000Z

29

Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy  

SciTech Connect (OSTI)

We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.

Rolland, Chloe; Coinon, Christophe; Wallart, Xavier; Leturcq, Renaud [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France)] [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France); Caroff, Philippe [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France) [Institute of Electronics Microelectronics and Nanotechnology, UMR CNRS 8520, ISEN Department, Avenue Poincare, CS60069, 59652 Villeneuve d'Ascq Cedex (France); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)

2013-06-03T23:59:59.000Z

30

Self-corrected Sensors Based On Atomic Absorption Spectroscopy For Atom Flux Measurements In Molecular Beam Epitaxy  

SciTech Connect (OSTI)

A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device (CCD) detector in a double-beam configuration, we employ a non-resonant line or a resonant line with lower absorbance from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio.

Du, Yingge; Droubay, Timothy C.; Liyu, Andrey V.; Li, Guosheng; Chambers, Scott A.

2014-04-24T23:59:59.000Z

31

Energy band alignment of atomic layer deposited HfO{sub 2} on epitaxial (110)Ge grown by molecular beam epitaxy  

SciTech Connect (OSTI)

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.

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

32

Non-adiabatic ab initio molecular dynamics of supersonic beam epitaxy of silicon carbide at room temperature  

SciTech Connect (OSTI)

In this work, we investigate the processes leading to the room-temperature growth of silicon carbide thin films by supersonic molecular beam epitaxy technique. We present experimental data showing that the collision of fullerene on a silicon surface induces strong chemical-physical perturbations and, for sufficient velocity, disruption of molecular bonds, and cage breaking with formation of nanostructures with different stoichiometric character. We show that in these out-of-equilibrium conditions, it is necessary to go beyond the standard implementations of density functional theory, as ab initio methods based on the Born-Oppenheimer approximation fail to capture the excited-state dynamics. In particular, we analyse the Si-C{sub 60} collision within the non-adiabatic nuclear dynamics framework, where stochastic hops occur between adiabatic surfaces calculated with time-dependent density functional theory. This theoretical description of the C{sub 60} impact on the Si surface is in good agreement with our experimental findings.

Taioli, Simone [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Physics, University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (Italy); Department of Chemistry, University of Bologna, Bologna (Italy); Garberoglio, Giovanni [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Simonucci, Stefano [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (Italy); Department of Physics, University of Camerino, Camerino (Italy); Beccara, Silvio a [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Physics, University of Trento, Trento (Italy); Aversa, Lucrezia [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Trento (Italy); Nardi, Marco [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Trento (Italy); Institut fuer Physik, Humboldt-Universitaet zu Berlin, Berlin (Germany); Verucchi, Roberto [Institute of Materials for Electronics and Magnetism, FBK-CNR, Trento (Italy); Iannotta, Salvatore [Institute of Materials for Electronics and Magnetism, IMEM-CNR, Parma (Italy); Dapor, Maurizio [Interdisciplinary Laboratory for Computational Science, FBK-Center for Materials and Microsystems and University of Trento, Trento (Italy); Department of Materials Engineering and Industrial Technologies, University of Trento, Trento (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Padova (Italy); and others

2013-01-28T23:59:59.000Z

33

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

E-Print Network [OSTI]

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

Pennycook, Steve

34

Intrinsic ultrathin topological insulators grown via molecular beam epitaxy characterized by in-situ angle resolved photoemission spectroscopy  

SciTech Connect (OSTI)

We demonstrate the capability of growing high quality ultrathin (10 or fewer quintuple layers) films of the topological insulators Bi{sub 2}Se{sub 3} and Bi{sub 2}Te{sub 3} using molecular beam epitaxy. Unlike previous growth techniques, which often pin the Fermi energy in the conduction band for ultrathin samples, our samples remain intrinsic bulk insulators. We characterize these films using in-situ angle resolved photoemission spectroscopy, which is a direct probe of bandstructure, and ex-situ atomic force microscopy. We find that the conduction band lies above the Fermi energy, indicating bulk insulating behavior with only the surface states crossing the Fermi energy. The use of a thermal cracker allows for more stoichiometric flux rates during growth, while still creating intrinsically doped films, paving the way for future improvements in growth of topological insulators.

Lee, J. J.; Vishik, I. M.; Ma, Y.; Shen, Z. X. [Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Schmitt, F. T.; Moore, R. G. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)

2012-07-02T23:59:59.000Z

35

Spinel-structured metal oxide on a substrate and method of making same by molecular beam epitaxy  

DOE Patents [OSTI]

A method of making a spinel-structured metal oxide on a substrate by molecular beam epitaxy, comprising the step of supplying activated oxygen, a first metal atom flux, and at least one other metal atom flux to the surface of the substrate, wherein the metal atom fluxes are individually controlled at the substrate so as to grow the spinel-structured metal oxide on the substrate and the metal oxide is substantially in a thermodynamically stable state during the growth of the metal oxide. A particular embodiment of the present invention encompasses a method of making a spinel-structured binary ferrite, including Co ferrite, without the need of a post-growth anneal to obtain the desired equilibrium state.

Chambers, Scott A.

2006-02-21T23:59:59.000Z

36

CdSe/CdTe type-II superlattices grown on GaSb (001) substrates by molecular beam epitaxy  

SciTech Connect (OSTI)

CdSe/CdTe superlattices are grown on GaSb substrates using molecular beam epitaxy. X-ray diffraction measurements and cross-sectional transmission electron microscopy images indicate high crystalline quality. Photoluminescence (PL) measurements show the effective bandgap varies with the superlattice layer thicknesses and confirm the CdSe/CdTe heterostructure has a type-II band edge alignment. The valence band offset between unstrained CdTe and CdSe is determined as 0.63 {+-} 0.06 eV by fitting the measured PL peak positions using the envelope function approximation and the Kronig-Penney model. These results suggest that CdSe/CdTe superlattices are promising candidates for multi-junction solar cells and other optoelectronic devices based on GaSb substrates.

Li Jingjing; Liu Shi; Wang Shumin; Ding Ding; Johnson, Shane R.; Zhang Yonghang [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); Liu Xinyu; Furdyna, Jacek K. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Smith, David J. [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

2012-03-19T23:59:59.000Z

37

High performance double pulse doped pseudomorphic AlGaAs/InGaAs transistors grown by molecular-beam epitaxy  

SciTech Connect (OSTI)

Double pulse doped AlGaAs/InGaAs pseudomorphic high electron mobility transistors have been grown by molecular-beam epitaxy on GaAs substrates. Hall mobilities in excess of 7100 cm{sup 2}/V s at 300 K and 25000 cm{sup 2}/V s at 77 K are obtained with a sheet density of 3 x 10{sup 12} cm{sup {minus}2}. Photoluminescence measurements indicate that two electronic subbands are occupied, and the subband energies are determined. The doping pulses are resolved in secondary ion mass spectrometry measurements. Using a double recess process, transistors have been fabricated that have produced state of the art microwave performance. At 10 GHz a 1.2 mm device has simultaneously achieved a power added efficiency of 70%, output power of 0.97 W, and gain of 10 dB. 17 refs., 5 figs., 1 tab.

Hoke, W.E.; Lyman, P.S.; Labossier, W.H.; Brierley, S.K.; Hendriks, H.T.; Shanfield, S.R.; Aucoin, L.M.; Kazior, T.E. [Raytheon Research Division, Lexington, MA (United States)] [Raytheon Research Division, Lexington, MA (United States)

1992-05-01T23:59:59.000Z

38

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

SciTech Connect (OSTI)

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.

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

39

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

SciTech Connect (OSTI)

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.

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

40

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

SciTech Connect (OSTI)

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.

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

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

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

SciTech Connect (OSTI)

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.

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

42

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

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

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.

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

43

Crystal orientation mechanism of ZnTe epilayers formed on different orientations of sapphire substrates by molecular beam epitaxy  

SciTech Connect (OSTI)

The electrooptic effect in ZnTe has recently attracted research attention, and various device structures using ZnTe have been explored. For application to practical terahertz wave detector devices based on ZnTe thin films, sapphire substrates are preferred because they enable the optical path alignment to be simplified. ZnTe/sapphire heterostructures were focused upon, and ZnTe epilayers were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. Epitaxial relationships between the ZnTe thin films and the sapphire substrates with their various orientations were investigated using an X-ray diffraction pole figure method. (0001) c-plane, (1-102) r-plane, (1-100) m-plane, and (11-20) a-plane oriented sapphire substrates were used in this study. The epitaxial relationship between ZnTe and c-plane sapphire was found to be (111) ZnTe//(0001) sapphire with an in-plane orientation relationship of [?211] ZnTe//[1-100] sapphire. It was found that the (211)-plane ZnTe layer was grown on the m-plane of the sapphire substrates, and the (100)-plane ZnTe layer was grown on the r-plane sapphire. When the sapphire substrates were inclined from the c-plane towards the m-axis direction, the orientation of the ZnTe thin films was then tilted from the (111)-plane to the (211)-plane. The c-plane of the sapphire substrates governs the formation of the (111) ZnTe domain and the ZnTe epilayer orientation. These crystallographic features were also related to the atom arrangements of ZnTe and sapphire.

Nakasu, T., E-mail: n-taizo.nakasu@asagi.waseda.jp; Yamashita, S.; Aiba, T.; Hattori, S.; Sun, W.; Taguri, K.; Kazami, F. [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, M. [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials and Technology, Waseda University, Tokyo 169-0051 (Japan)

2014-10-28T23:59:59.000Z

44

Direct imaging of InSb (110)-(1x1) surface grown by molecular beam epitaxy  

SciTech Connect (OSTI)

High-resolution transmission electron microscopy under a profile imaging condition (HR-profile TEM) was employed to determine the structural model for the InSb(110)-(1x1) relaxation surface grown by molecular beam epitaxy (MBE). HR-profile TEM analyses indicate that the chevron model, which is widely accepted for zinc-blende-type III-V(110)-(1x1) surfaces prepared by cleavage, is also applicable to the InSb(110)-(1x1) surface prepared under an Sb-rich MBE condition. The assignment of atomic species (In or Sb) of InSb(110)-(1x1) surfaces was confirmed based on a HR-profile TEM image that captures the connected facets of InSb(110)-(1x1) and InSb(111)B-(2x2). On the basis of the well-known atomic species of InSb(111)B-(2x2), the atomic species of the InSb(110)-(1x1) surface were deduced straightforwardly: the atoms shifted upward and downward at the topmost layer of the InSb(110)-(1x1) surface are Sb and In, respectively. The atomic arrangements of the InSb(110)-(1x1)-InSb(111)B-(2x2) facet determined by HR-profile TEM may represent the atomic arrangements of zinc-blende-type III-V(331)B surfaces.

Mishima, T. D. [Homer L. Dodge Department of Physics and Astronomy, and Center for Semiconductor Physics in Nanostructures, University of Oklahoma, Norman, Oklahoma 73019 (United States)

2011-10-01T23:59:59.000Z

45

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

SciTech Connect (OSTI)

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.

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

46

Deep levels in a-plane, high Mg-content Mg{sub x}Zn{sub 1-x}O epitaxial layers grown by molecular beam epitaxy  

SciTech Connect (OSTI)

Deep level defects in n-type unintentionally doped a-plane Mg{sub x}Zn{sub 1-x}O, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of Mg{sub x}Zn{sub 1-x}O were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of E{sub c} - 1.4 eV, 2.1 eV, 2.6 V, and E{sub v} + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at E{sub c} - 2.1 eV, E{sub v} + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at E{sub v} + 0.3 eV and E{sub c} - 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the E{sub v} + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the E{sub c} - 1.4 eV and E{sub c} - 2.6 eV levels in Mg alloyed samples.

Guer, Emre [Department of Physics, Faculty of Science, Atatuerk University, Erzurum 25240 (Turkey); 205 Dreese Laboratory, Department of Electrical and Computer Engineering, The Ohio State University, 2015 Neil Avenue, Columbus, Ohio 43210-1272 (United States); Tabares, G.; Hierro, A. [Dpto. Ingenieria Electronica and ISOM, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Arehart, A.; Ringel, S. A. [205 Dreese Laboratory, Department of Electrical and Computer Engineering, Ohio State University, 2015 Neil Avenue, Columbus, Ohio 43210-1272 (United States); Chauveau, J. M. [CRHEA-CNRS, 06560 Valbonne (France); University of Nice Sophia Antipolis, ParcValrose, 06102 Nice Cedex 2 (France)

2012-12-15T23:59:59.000Z

47

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

SciTech Connect (OSTI)

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.

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

48

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

SciTech Connect (OSTI)

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.

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

49

Molecular Beam Epitaxy | EMSL  

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

temperature monitored by a two-color pyrometer andor thermocouple In situ optical (atomic absorption) and reflection high-energy electron diffraction (RHEED) probes for...

50

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

SciTech Connect (OSTI)

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.

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

51

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

E-Print Network [OSTI]

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

Myers, Tom

52

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)

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.

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

53

Growth, steady-state, and time-resolved photoluminescence study of CdTe/MgCdTe double heterostructures on InSb substrates using molecular beam epitaxy  

SciTech Connect (OSTI)

CdTe/MgCdTe double heterostructures (DHs) are grown on InSb substrates using molecular beam epitaxy and reveal strong photoluminescence with over double the intensity of a GaAs/AlGaAs DH with an identical layer structure design grown on GaAs. Time-resolved photoluminescence of the CdTe/MgCdTe DH gives a Shockley-Read-Hall recombination lifetime of 86 ns, which is more than one order of magnitude longer than that of typical polycrystalline CdTe films. These findings indicate that monocrystalline CdTe/MgCdTe DHs effectively reduce surface recombination, have limited nonradiative interface recombination, and are promising for solar cells that could reach power conversion efficiencies similar to that of GaAs.

DiNezza, Michael J.; Liu, Shi; Kirk, Alexander P.; Zhang, Yong-Hang [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States) [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); Zhao, Xin-Hao [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States) [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287 (United States)

2013-11-04T23:59:59.000Z

54

Dislocation reduction via selective-area growth of InN accompanied by lateral growth by rf-plasma-assisted molecular-beam epitaxy  

SciTech Connect (OSTI)

We investigated the selective-area growth (SAG) of InN by rf-plasma-assisted molecular-beam epitaxy using molybdenum (Mo)-mask-patterned sapphire (0001) substrates, which resulted in the formation of regularly arranged N-polar InN microcrystals. Transmission electron microscopy observation confirmed that the laterally grown side areas were nearly dislocation-free, although many threading dislocations (10{sup 9}-10{sup 10} cm{sup -2}) were generated at the InN/sapphire interface and propagated into the center of the InN microcrystals along the crystal c-axis. The laterally grown InN microcrystals exhibited narrow near-IR emission spectra with a peak photon energy of 0.627 eV and a linewidth of 39 meV at room temperature.

Kamimura, Jumpei [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 330-0012 (Japan); Kishino, Katsumi; Kikuchi, Akihiko [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 330-0012 (Japan); Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

2010-10-04T23:59:59.000Z

55

Molecular-beam epitaxial growth and characterization of inverted, pulse-doped AlGaAs/InGaAs transistor structures  

SciTech Connect (OSTI)

Inverted, pulse-doped AlGaAs/InGaAs pseudomorphic high electron mobility transistor structures were grown by molecular-beam epitaxy. Growth conditions were optimized to improve the quality of the selectively doped AlGaAs layer and to minimize dopant diffusion into the InGaAs channel. The sheet densities and mobilities of the inverted structure were found to be essentially equivalent to those obtained with the normal structure. Shubnikov-de Haas measurements exhibited strong oscillations in the magnetoresistance and plateaus in the Hall resistance. Four optical transitions from the lowest bound electron and hole quantum well states were observed in room-temperature photoluminescence spectra. 15 refs., 4 figs.

Hoke, W.E.; Lyman, P.S.; Brierley, S.K. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

1993-05-01T23:59:59.000Z

56

In-situ spectroscopic ellipsometry for real time composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy  

SciTech Connect (OSTI)

Spectral ellipsometry (SE) was applied to in situ composition control of Hg{sub 1{minus}x}Cd{sub x}Te grown by molecular beam epitaxy (MBE), and the impact of surface topography of the Hg{sub 1{minus}x}Cd{sub x}Te layers on the accuracy of SE was investigated. Of particular importance is the presence of surface defects, such as voids in MBE-Hg{sub 1{minus}x}Cd{sub x}Te layers. While dislocations do not have any significant impact on the dielectric functions, the experimental data in this work show that MBE-Hg{sub 1{minus}x}Cd{sub x}Te samples having the same composition, but different void densities, have different effective dielectric functions.

Dat, R.; Aqariden, F.; Chandra, D.; Shih, H.D. [Raytheon TI Systems, Sensors and Infrared Lab., Dallas, TX (United States); Duncan, W.M. [Texas Instruments Inc., Dallas, TX (United States). Components and Materials Research Center

1998-12-31T23:59:59.000Z

57

A series of layered intergrowth phases grown by molecular beam epitaxy: Sr{sub m}TiO{sub 2+m}(m=1-5)  

SciTech Connect (OSTI)

Sr{sub m}TiO{sub 2+m} phases having one TiO{sub 2} layer sandwiched between m SrO layers were grown using molecular beam epitaxy. The out-of-plane (in-plane) lattice parameters determined by x-ray diffraction were c(a)=9.14 A (3.78 A), 23.55 A (3.75 A), and 14.60 A (3.75 A) for Sr{sub 3}TiO{sub 5}, Sr{sub 4}TiO{sub 6}, and Sr{sub 5}TiO{sub 7}, respectively. Both lattice parameters change abruptly on going from the m=2 Ruddlesden-Popper phase to m=3 phase, indicating a significant change in the bond lengths (or strain states) on transitioning from the known members to the higher order members of this structural family. Electron microscopy confirmed the artificially layered structures.

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

2007-12-17T23:59:59.000Z

58

Formation behavior of Be{sub x}Zn{sub 1-x}O alloys grown by plasma-assisted molecular beam epitaxy  

SciTech Connect (OSTI)

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.

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

59

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)

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}.

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

60

Design of an ultrahigh vacuum transfer mechanism to interconnect an oxide molecular beam epitaxy growth chamber and an x-ray photoemission spectroscopy analysis system  

SciTech Connect (OSTI)

We designed a mechanism and the accompanying sample holders to transfer between a VEECO 930 oxide molecular beam epitaxy (MBE) and a PHI Versa Probe X-ray photoemission spectroscopy (XPS) chamber within a multiple station growth, processing, and analysis system through ultrahigh vacuum (UHV). The mechanism consists of four parts: (1) a platen compatible with the MBE growth stage, (2) a platen compatible with the XPS analysis stage, (3) a sample coupon that is transferred between the two platens, and (4) the accompanying UHV transfer line. The mechanism offers a robust design that enables transfer back and forth between the growth chamber and the analysis chamber, and yet is flexible enough to allow transfer between standard sample holders for thin film growth and masked sample holders for making electrical contacts and Schottky junctions, all without breaking vacuum. We used this mechanism to transfer a barium strontium titanate thin film into the XPS analysis chamber and performed XPS measurements before and after exposing the sample to the air. After air exposure, a thin overlayer of carbon was found to form and a significant shift ({approx}1 eV) in the core level binding energies was observed.

Rutkowski, M. M.; Zeng Zhaoquan [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); McNicholas, K. M. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Brillson, L. J. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

2013-06-15T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Rapid silicon outdiffusion from SiC substrates during molecular-beam epitaxial growth of AlGaN/GaN/AlN transistor structures  

SciTech Connect (OSTI)

AlGaN/GaN/AlN transistor structures were grown onto SiC substrates by molecular-beam epitaxy. Under aluminum-rich growth conditions for the AlN nucleation layer, undesirable n-type conduction is observed near the GaN/AlN interface for even thick (>1000 A) AlN layers. Silicon is identified as the unwanted dopant from secondary-ion mass spectroscopy measurements. Atomic force microscopy surface maps reveal free aluminum metal on AlN surfaces grown under modest aluminum-rich conditions. It is proposed that rapid silicon migration is caused by molten aluminum reacting with the SiC substrate resulting in dissolved silicon that rapidly migrates through the growing AlN layer. This behavior is significantly reduced using a growth flux ratio of aluminum to reactive nitrogen close to unity. The resulting buffer leakage current of the GaN high electron mobility transistor structure is reduced by more than four orders of magnitude.

Hoke, W.E.; Torabi, A.; Mosca, J.J.; Hallock, R.B.; Kennedy, T.D. [Raytheon RF Components, 362 Lowell Street, Andover, Massachusetts 01810 (United States)

2005-10-15T23:59:59.000Z

62

Electrical spin injection into InGaAs/GaAs quantum wells: A comparison between MgO tunnel barriers grown by sputtering and molecular beam epitaxy methods  

SciTech Connect (OSTI)

An efficient electrical spin injection into an InGaAs/GaAs quantum well light emitting diode is demonstrated thanks to a CoFeB/MgO spin injector. The textured MgO tunnel barrier is fabricated by two different techniques: sputtering and molecular beam epitaxy. The maximal spin injection efficiency is comparable for both methods. Additionally, the effect of annealing is also investigated for the two types of samples. Both samples show the same trend: an increase of the electroluminescence circular polarization (P{sub c}) with the increase of annealing temperature, followed by a saturation of P{sub c} beyond 350?°C annealing. Since the increase of P{sub c} starts well below the crystallization temperature of the full CoFeB bulk layer, this trend could be mainly due to an improvement of chemical structure at the top CoFeB/MgO interface. This study reveals that the control of CoFeB/MgO interface is essential for an optimal spin injection into semiconductor.

Barate, P.; Zhang, T. T.; Vidal, M.; Renucci, P.; Marie, X.; Amand, T. [Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 avenue de Rangueil, 31077 Toulouse (France); Liang, S.; Devaux, X.; Hehn, M.; Mangin, S.; Lu, Y., E-mail: yuan.lu@univ-lorraine.fr [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France); Frougier, J.; Jaffrès, H.; George, J. M. [Unité Mixte de Physique CNRS/Thales and Université Paris-Sud 11, 1 avenue A. Fresnel, 91767 Palaiseau (France); Xu, B.; Wang, Z. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, Beijing 100083 (China); Zheng, Y. [Institut des NanoSciences de Paris, UPMC, CNRS UMR 7588, 4 place Jussieu, 75005 Paris (France); Tao, B. [Institut Jean Lamour, UMR 7198, CNRS-Nancy Université, BP 239, 54506 Vandoeuvre (France); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Han, X. F. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)

2014-07-07T23:59:59.000Z

63

Study of Gd-doped Bi{sub 2}Te{sub 3} thin films: Molecular beam epitaxy growth and magnetic properties  

SciTech Connect (OSTI)

Incorporation of magnetic dopants into topological insulators to break time-reversal symmetry is a prerequisite for observing the quantum anomalous Hall (QAHE) effect and other novel magnetoelectric phenomena. GdBiTe{sub 3} with a Gd:Bi ratio of 1:1 is a proposed QAHE system, however, the reported solubility limit for Gd doping into Bi{sub 2}Te{sub 3} bulk crystals is between ?0.01 and 0.05. We present a magnetic study of molecular beam epitaxy grown (Gd{sub x}Bi{sub 1–x}){sub 2}Te{sub 3} thin films with a high Gd concentration, up to x ? 0.3. Magnetometry reveals that the films are paramagnetic down to 1.5?K. X-ray magnetic circular dichroism at the Gd M{sub 4,5} edge at 1.5?K reveals a saturation field of ?6?T, and a slow decay of the magnetic moment with temperature up to 200?K. The Gd{sup 3+} ions, which are substitutional on Bi sites in the Bi{sub 2}Te{sub 3} lattice, exhibit a large atomic moment of ?7??{sub B}, as determined by bulk-sensitive superconducting quantum interference device magnetometry. Surface oxidation and the formation of Gd{sub 2}O{sub 3} lead to a reduced moment of ?4??{sub B} as determined by surface-sensitive x-ray magnetic circular dichroism. Their large atomic moment makes these films suitable for incorporation into heterostructures, where interface polarization effects can lead to the formation of magnetic order within the topological insulators.

Harrison, S. E.; Huo, Y.; Harris, J. S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Collins-McIntyre, L. J.; Hesjedal, T., E-mail: Thorsten.Hesjedal@physics.ox.ac.uk [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Li, S. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Baker, A. A. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire OX11 0DE (United Kingdom); Shelford, L. R.; Laan, G. van der [Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire OX11 0DE (United Kingdom); Pushp, A.; Parkin, S. S. P. [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2014-01-14T23:59:59.000Z

64

Molecular Beam Epitaxial Growth of Bi2Te3 and Sb2Te3 Topological Insulators on GaAs (111) Substrates: A Potential Route to Fabricate Topological Insulator p-n Junction  

E-Print Network [OSTI]

High quality Bi2Te3 and Sb2Te3 topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi2Te3 and Sb2Te3 films. Hall and magnetoresistance measurements indicate that p type Sb2Te3 and n type Bi2Te3 topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

Zhaoquan Zeng; Timothy A. Morgan; Dongsheng Fan; Chen Li; Yusuke Hirono; Xian Hu; Yanfei Zhao; Joon Sue Lee; Zhiming M. Wang; Jian Wang; Shuiqing Yu; Michael E. Hawkridge; Mourad Benamara; Gregory J. Salamo

2013-03-11T23:59:59.000Z

65

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)

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.

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

66

Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn{sub 1-x}Mg{sub x}O layers by molecular beam epitaxy  

SciTech Connect (OSTI)

Nonpolar (1120) Al{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (1120) Zn{sub 0.74}Mg{sub 0.26}O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.

Xia, Y.; Vinter, B.; Chauveau, J.-M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France); University of Nice Sophia-Antipolis, 06103 Nice (France); Brault, J.; Nemoz, M.; Teisseire, M.; Leroux, M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France)

2011-12-26T23:59:59.000Z

67

REVIEW ARTICLE Taming molecular beams  

E-Print Network [OSTI]

REVIEW ARTICLE Taming molecular beams The motion of neutral molecules in a beam can be manipulated time-varying fields can be used to decelerate or accelerate beams of molecules to any desired velocity. We review the possibilities that this molecular-beam technology offers, ranging from ultrahigh

Loss, Daniel

68

Molecular Beam Kinetics | 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 JunDatastreamsmmcrcalgovInstrumentsrucLas Conchas recovery challenge fundProject8Mistakes to AvoidKinetics Molecular Beam Kinetics

69

Chemical beam epitaxy for high efficiency photovoltaic devices  

SciTech Connect (OSTI)

InP-based multijunction tandem solar cells show great promise for the conversion efficiency (eta) and high radiation resistance. InP and its related ternary and quanternary compound semiconductors such as InGaAs and InGaAsP offer desirable combinations for energy bandgap values which are very suitable for multijunction tandem solar cell applications. The monolithically integrated InP/In(0.53)Ga(0.47)As tandem solar cells are expected to reach efficiencies above 30 percent. Wanlass, et.al., have reported AMO efficiencies as high as 20.1% for two terminal cells fabricated using atmospheric-pressure metalorganic vapor phase epitaxy (APMOVPE). The main limitations in their technique are first related to the degradation of the intercell ohmic contact (IOC), in this case the In(0.53)Ga(0.47)As tunnel junction during the growth of the top InP subcell structure, and second to the current matching, often limited by the In(0.53)Ga(0.47)As bottom subcell. Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450 C - 530 C). In a recent report it was shown that cost-wise CBE is a breakthrough technology for photovoltaic (PV) solar energy progress in the energy conversion efficiency of InP-based solar cells fabricated using chemical beam epitaxy. This communication summarizes recent results on PV devices and demonstrates the strength of this new technology.

Bensaoula, A.; Freundlich, A.; Vilela, M. F.; Medelci, N.; Renaud, P.

1994-09-01T23:59:59.000Z

70

Molecular Beam Epitaxy, Multi-source | 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 JunDatastreamsmmcrcalgovInstrumentsrucLas Conchas recovery challenge fundProject8Mistakes to Avoid

71

Molecular beam epitaxial growth of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators on GaAs (111) substrates: a potential route to fabricate topological insulator p-n junction  

SciTech Connect (OSTI)

High quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} films. Hall and magnetoresistance measurements indicate that p type Sb{sub 2}Te{sub 3} and n type Bi{sub 2}Te{sub 3} topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

Zeng, Zhaoquan; Morgan, Timothy A.; Li, Chen; Hirono, Yusuke; Hu, Xian; Hawkridge, Michael E.; Benamara, Mourad; Salamo, Gregory J. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States)] [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Fan, Dongsheng; Yu, Shuiqing [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Zhao, Yanfei [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China)] [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); Lee, Joon Sue [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)] [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Jian [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China) [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Zhiming M. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

2013-07-15T23:59:59.000Z

72

Growth and characterization of dilute nitride GaN{sub x}P{sub 1?x} nanowires and GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowires on Si (111) by gas source molecular beam epitaxy  

SciTech Connect (OSTI)

We have demonstrated self-catalyzed GaN{sub x}P{sub 1?x} and GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowire growth by gas-source molecular beam epitaxy. The growth window for GaN{sub x}P{sub 1?x} nanowires was observed to be comparable to that of GaP nanowires (?585?°C to ?615?°C). Transmission electron microscopy showed a mixture of cubic zincblende phase and hexagonal wurtzite phase along the [111] growth direction in GaN{sub x}P{sub 1?x} nanowires. A temperature-dependent photoluminescence (PL) study performed on GaN{sub x}P{sub 1?x}/GaN{sub y}P{sub 1?y} core/shell nanowires exhibited an S-shape dependence of the PL peaks. This suggests that at low temperature, the emission stems from N-related localized states below the conduction band edge in the shell, while at high temperature, the emission stems from band-to-band transition in the shell as well as recombination in the GaN{sub x}P{sub 1?x} core.

Sukrittanon, S. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92037 (United States); Dobrovolsky, A.; Chen, W. M.; Buyanova, I. A. [Department of Physics, Chemistry and Biology, Linköping University, 581 83 Linköping (Sweden); Kang, Won-Mo; Kim, Bong-Joong [Department of Materials Science and Engineering, Gwangju institute of Science and Technology (GIST), Gwangju 500-712 (Korea, Republic of); Jang, Ja-Soon [Department of Electronic Engineering, LED-IT Fusion Technology Research Center, Yeungnam University, Daegu 712-749 (Korea, Republic of); Tu, C. W. [Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92037 (United States); Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92037 (United States)

2014-08-18T23:59:59.000Z

73

Band Offsets at the Epitaxial Anatase TiO2/n-SrTiO3(001) Interface...  

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

to measure valence band offsets at the epitaxial anatase TiO2(002)n-SrTiO3(001) heterojunction prepared by molecular beam epitaxy, Within experimental error, the valance band...

74

Low-temperature formation of epitaxial graphene on 6H-SiC induced by continuous electron beam irradiation  

SciTech Connect (OSTI)

It is observed that epitaxial graphene forms on the surface of a 6H-SiC substrate by irradiating electron beam directly on the sample surface in high vacuum at relatively low temperature ({approx}670 Degree-Sign C). The symmetric shape and full width at half maximum of 2D peak in the Raman spectra indicate that the formed epitaxial graphene is turbostratic. The gradual change of the Raman spectra with electron beam irradiation time increasing suggests that randomly distributed small grains of epitaxial graphene form first and grow laterally to cover the entire irradiated area. The sheet resistance of epitaxial graphene film is measured to be {approx}6.7 k{Omega}/sq.

Go, Heungseok; Jeon, Youngeun; Park, Kibog [School of Electrical and Computer Engineering, KIER-UNIST Advanced Center for Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Kwak, Jinsung; Yoo, Jung-Woo; Youb Kim, Sung; Kwon, Soon-Yong [School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Kim, Sung-Dae; Kim, Young-Woon [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Cheol Lee, Byung; Suk Kang, Hyun [Quantum Optics Laboratory, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Ko, Jae-Hyeon [Department of Physics, Hallym University, Chuncheon Gangwondo 200-702 (Korea, Republic of); Kim, Nam [Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Kim, Bum-Kyu [Department of Physics, Chonbuk National University, Jeonju Chonbuk 561-756 (Korea, Republic of)

2012-08-27T23:59:59.000Z

75

Physics with fast molecular-ion beams  

SciTech Connect (OSTI)

Fast (MeV) molecular-ion beams provide a unique source of energetic projectile nuclei which are correlated in space and time. The recognition of this property has prompted several recent investigations of various aspects of the interactions of these ions with matter. High-resolution measurements on the fragments resulting from these interactions have already yielded a wealth of new information on such diverse topics as plasma oscillations in solids and stereochemical structures of molecular ions as well as a variety of atomic collision phenomena. The general features of several such experiments will be discussed and recent results will be presented.

Kanter, E.P.

1980-01-01T23:59:59.000Z

76

Counting molecular-beam grown graphene layers  

SciTech Connect (OSTI)

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.

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

77

Point defect balance in epitaxial GaSb  

SciTech Connect (OSTI)

Positron annihilation spectroscopy in both conventional and coincidence Doppler broadening mode is used for studying the effect of growth conditions on the point defect balance in GaSb:Bi epitaxial layers grown by molecular beam epitaxy. Positron annihilation characteristics in GaSb are also calculated using density functional theory and compared to experimental results. We conclude that while the main positron trapping defect in bulk samples is the Ga antisite, the Ga vacancy is the most prominent trap in the samples grown by molecular beam epitaxy. The results suggest that the p–type conductivity is caused by different defects in GaSb grown with different methods.

Segercrantz, N., E-mail: natalie.segercrantz@aalto.fi; Slotte, J.; Makkonen, I.; Kujala, J.; Tuomisto, F. [Department of Applied Physics, Aalto University, P.O. Box 14100, FIN-00076 Aalto Espoo (Finland); Song, Y.; Wang, S. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg (Sweden); State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 865 Changning Road, Shanghai 200050 (China)

2014-08-25T23:59:59.000Z

78

Molecular beam studies of reaction dynamics  

SciTech Connect (OSTI)

Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

Lee, Y.T.

1987-03-01T23:59:59.000Z

79

Molecular beam studies of reaction dynamics  

SciTech Connect (OSTI)

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01T23:59:59.000Z

80

Molecular beam studies of reaction dynamics  

SciTech Connect (OSTI)

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

Lee, Yuan T.

1991-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Molecular Beam Mass Spectrometry (MBMS) (Revised) (Fact Sheet)  

SciTech Connect (OSTI)

This fact sheet provides information about Molecular Beam Mass Spectrometry (MBMS) capabilities and applications at NREL's National Bioenergy Center. NREL has six MBMS systems that researchers and industry partners can use to understand thermochemical biomass conversion and biomass composition recalcitrance.

Not Available

2011-07-01T23:59:59.000Z

82

Process for depositing an oxide epitaxially onto a silicon substrate and structures prepared with the process  

DOE Patents [OSTI]

A process and structure involving a silicon substrate utilizes an ultra high vacuum and molecular beam epitaxy (MBE) methods to grow an epitaxial oxide film upon a surface of the substrate. As the film is grown, the lattice of the compound formed at the silicon interface becomes stabilized, and a base layer comprised of an oxide having a sodium chloride-type lattice structure grows epitaxially upon the compound so as to cover the substrate surface. A perovskite may then be grown epitaxially upon the base layer to render a product which incorporates silicon, with its electronic capabilities, with a perovskite having technologically-significant properties of its own.

McKee, Rodney A. (Kingston, TN); Walker, Frederick J. (Oak Ridge, TN)

1993-01-01T23:59:59.000Z

83

Multiperiod quantum-cascade nanoheterostructures: Epitaxy and diagnostics  

SciTech Connect (OSTI)

Advances in the production technology of multiperiod nanoheterostructures of quantum-cascade lasers with 60 cascades by molecular-beam epitaxy (MBE) on an industrial multiple-substrate MBE machine are discussed. The results obtained in studying the nanoheterostructures of quantum-cascade lasers by transmission electron microscopy, high-resolution X-ray diffraction analysis, and photoluminescence mapping are presented.

Egorov, A. Yu., E-mail: Anton@beam.ioffe.ru; Brunkov, P. N.; Nikitina, E. V.; Pirogov, E. V.; Sobolev, M. S.; Lazarenko, A. A. [Russian Academy of Sciences, St. Petersburg Academic University, Nanotechnology Research and Education Center (Russian Federation); Baidakova, M. V.; Kirilenko, D. A.; Konnikov, S. G. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2014-12-15T23:59:59.000Z

84

DYNAMICS OF INFRARED MULTIPHOTON DISSOCIATION OF SF6 BY MOLECULAR BEAM METHOD  

E-Print Network [OSTI]

molecular beam apparatus has been adapted to study the dynamics of excitationdynamics of molecular decomposition and the degree of vibrational excitation,

Grant, E.R.

2010-01-01T23:59:59.000Z

85

The effect of cluster formation on mass separation in binary molecular beams  

E-Print Network [OSTI]

The effect of cluster formation on mass separation in binary molecular beams Wei Li,a) M. J composition of a skimmed supersonic binary molecular beam originally consisting of a 20% neon/80% xenon. © 2000 American Institute of Physics. S0021-9606 00 01806-7 I. INTRODUCTION Supersonic molecular beam

Sibener, Steven

86

Ion-Beam Synthesis of Epitaxial Au Nanocrystals in MgO. | 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 ProposedUsingFunInfrared LandResponses toInvestigatingAdaptedInvestor|Heavy Ions:Beam

87

Note: A helical velocity selector for continuous molecular beams  

SciTech Connect (OSTI)

We report on a modern realization of the classic helical velocity selector for gas phase particle beams. The device operates stably under high vacuum conditions at rotational frequencies limited only by commercial dc motor capabilities. Tuning the rotational frequency allows selective scanning over a broad velocity band. The width of the selected velocity distributions at full-width-half-maximum is as narrow as a few percent of the selected mean velocity and independent of the rotational speed of the selector. The selector generates low vibrational noise amplitudes comparable to mechanically damped state-of-the-art turbo-molecular pumps and is therefore compatible with vibration sensitive experiments like molecule interferometry.

Szewc, Carola; Collier, James D.; Ulbricht, Hendrik [School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ (United Kingdom)

2010-10-15T23:59:59.000Z

88

Investigation of HgTe-CdTe superlattices grown by molecular beam epitaxy.  

E-Print Network [OSTI]

??[Truncated abstract] Infrared detection finds application in a wide range of fields, including remote sensing, astronomy, medicine and defence. Many of these applications, which require… (more)

Hatch, Stuart D.

2010-01-01T23:59:59.000Z

89

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

90

Molecular beam epitaxy of InN dots on nitrided sapphire  

E-Print Network [OSTI]

potential in the optoelectronics industry. A well-knownsubstrate material in optoelectronics. In this work, we test

Romanyuk, Yaroslav E.; Dengel, Radu-Gabriel; Stebounova, Larissa V.; Leone, Stephen R.

2007-01-01T23:59:59.000Z

91

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

E-Print Network [OSTI]

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

Cohen, Philip I.

92

Growth Kinetics and Doping of Gallium Nitride Grown by rf-Plasma Assisted Molecular Beam Epitaxy  

E-Print Network [OSTI]

Thomas H. Myers, Ph.D., Chair Larry E. Halliburton, Ph.D. Nancy C. Giles, Ph.D. Charter D. Stinespring Giles, Dr. Charter Stinespring, Dr. Larry Halliburton, and Dr. Mohindar Seehra. In addition, I would

Myers, Tom

93

Modelling of InGaP nanowires morphology and composition on molecular beam epitaxy growth conditions  

SciTech Connect (OSTI)

An analytical kinetic model has been developed within this framework to describe the growth of ternary III-V semiconductor nanowires. The key to apply the model is to divide the ternary system into two separate binary systems and model each binary system separately. The model is used to describe the growth of InGaP nanowires. The growth conditions were varied among several samples, and the model was able to predict the temperature and growth rate behaviors. The model predicts the axial and radial elemental distribution along the nanowires and the dependence of the elemental distribution on the nanowire's diameter size for all growth rates. The model reveals the limitations of In incorporation into the nanowires for high temperatures or low growth rates and the effects of the group-V elements on the In incorporation.

Fakhr, A., E-mail: fakhrad@mcmaster.ca; Haddara, Y. M. [Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario L8S 4K1 (Canada)

2014-07-14T23:59:59.000Z

94

Molecular beam epitaxy of InP-based alloys for long-wavelength vertical cavity lasers  

E-Print Network [OSTI]

InGaAs and InGaAsP, are well devel- oped, having been deployed in commercial long-wavelength edge- ventional lattice-matched alloys to InP, AlInGaAs, and In- GaAsP do not have sufficient index contrast of absorption and dis- persion minima in conventional silica fiber; their circular output mode shape, low

Coldren, Larry A.

95

Synthesis of Metal Oxide Nanomaterials for Chemical Sensors by Molecular Beam Epitaxy  

SciTech Connect (OSTI)

Since the industrial revolution, detection and monitoring of toxic matter, chemical wastes, and air pollutants has become an important environmental issue. Thus, it leads to the development of chemical sensors for various environmental applications. The recent disastrous oil spills over the near-surface of ocean due to the offshore drilling emphasize the use of chemical sensors for prevention and monitoring of the processes that might lead to these mishaps.1, 2 Chemical sensors operated on a simple principle that the sensing platform undergoes a detectable change when exposed to the target substance to be sensed. Among all the types of chemical sensors, solid state gas sensors have attracted a great deal of attention due to their advantages such as high sensitivity, greater selectivity, portability, high stability and low cost.3, 4 Especially, semiconducting metal oxides such as SnO2, TiO2, and WO3 have been widely used as the active sensing platforms in solid state gas sensors.5 For the enhanced properties of solid state gas sensors, finding new sensing materials or development of existing materials will be needed. Thus, nanostructured materials such as nanotubes,6-8 nanowires,9-11 nanorods,12-15 nanobelts,16, 17 and nano-scale thin films18-23 have been synthesized and studied for chemical sensing applications.

Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Thevuthasan, Suntharampillai

2013-12-01T23:59:59.000Z

96

Wide-dynamic-range, fast-response CBr4 doping system for molecular beam epitaxy  

E-Print Network [OSTI]

to each orifice can be switched on and off independently using a pneumatic valve. The fast response time of these pneumatic valves enables us to change the doping abruptly. This system is suitable for growing sophisticated, such as beryllium and zinc, carbon has a very low diffusion coefficient1 and is less dependent on the composition,2

Coldren, Larry A.

97

Cerenkov emission induced by external beam radiation stimulates molecular fluorescence  

SciTech Connect (OSTI)

Purpose: Cerenkov emission is induced when a charged particle moves faster than the speed of light in a given medium. Both x-ray photons and electrons produce optical Cerenkov photons in everyday radiation therapy of tissue; yet, this phenomenon has never been fully documented. This study quantifies the emissions and also demonstrates that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms. Methods: In this study, Cerenkov emission induced by radiation from a clinical linear accelerator is investigated. Biological mimicking phantoms were irradiated with x-ray photons, with energies of 6 or 18 MV, or electrons at energies 6, 9, 12, 15, or 18 MeV. The Cerenkov emission and the induced molecular fluorescence were detected by a camera or a spectrometer equipped with a fiber optic cable. Results: It is shown that both x-ray photons and electrons, at MeV energies, produce optical Cerenkov photons in tissue mimicking media. Furthermore, we demonstrate that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms. Conclusions: The results here indicate that molecular fluorescence monitoring during external beam radiotherapy is possible.

Axelsson, Johan; Davis, Scott C.; Gladstone, David J.; Pogue, Brian W. [Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States); Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766 (United States); Thayer School of Engineering and Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States)

2011-07-15T23:59:59.000Z

98

E-Print Network 3.0 - assisted molecular beam Sample Search Results  

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

10.1103PhysRevLett.98.103201 PACS numbers: 39.10.+j, 03.75.Be Atomic and molecular beams have... as well as fundamental physics and precision tests 3. The highest brightness...

99

Crossed molecular beam studies of atmospheric chemical reaction dynamics  

SciTech Connect (OSTI)

The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O{sub 3} {yields} ClO + O{sub 2} reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mole. The derived product center-of-mass angular and translational energy distributions show that the reaction has a direct reaction mechanism and that there is a strong repulsion on the exit channel. The ClO product is sideways and forward scattered with respect to the Cl atom, and the translational energy release is large. The Cl atom is most likely to attack the terminal oxygen atom of the ozone molecule. The Br + O{sub 3} {yields} ClO + O{sub 2} reaction has been studied at five collision energies ranging from 5 kcal/mole to 26 kcal/mole. The derived product center-of-mass angular and translational energy distributions are quite similar to those in the Cl + O{sub 3} reaction. The Br + O{sub 3} reaction has a direct reaction mechanism similar to that of the Cl + O{sub 3} reaction. The electronic structure of the ozone molecule seems to play the central role in determining the reaction mechanism in atomic radical reactions with the ozone molecule. The Cl + NO{sub 2} {yields} ClO + NO reaction has been studied at three collision energies ranging from 10.6 kcal/mole to 22.4 kcal/mole. The center-of-mass angular distribution has some forward-backward symmetry, and the product translational energy release is quite large. The reaction proceeds through a short-lived complex whose lifetime is less than one rotational period. The experimental results seem to show that the Cl atom mainly attacks the oxygen atom instead of the nitrogen atom of the NO{sub 2} molecule.

Zhang, Jingsong

1993-04-01T23:59:59.000Z

100

Selective area growth of Bernal bilayer epitaxial graphene on 4H-SiC (0001) substrate by electron-beam irradiation  

SciTech Connect (OSTI)

We report selective area growth of large area homogeneous Bernal stacked bilayer epitaxial graphene (BLEG) on 4H-SiC (0001) substrate by electron-beam irradiation. Sublimation of Si occurs by energetic electron irradiations on SiC surface via breaking of Si–C bonds in the localized region, which allows the selective growth of graphene. Raman measurements ensure the formation of homogeneous BLEG with weak compressive strain of ?0.08%. The carrier mobility of large area BLEG is ?5100?cm{sup 2}?V{sup ?1}?s{sup ?1} with a sheet carrier density of 2.2?×?10{sup 13}?cm{sup ?2}. Current-voltage measurements reveal that BLEG on 4H-SiC forms a Schottky junction with an operation at mA level. Our study reveals that the barrier height at the Schottky junction is low (?0.58?eV) due to the Fermi-level pinning above the Dirac point.

Dharmaraj, P.; Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Parthiban, S.; Kwon, J. Y. [School of Integrated Technology and Yonsei Institute of Convergence Technology, Yonsei University, Yeonsu-gu, Incheon 406-840 (Korea, Republic of); Gautam, S.; Chae, K. H. [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Asokan, K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

2014-11-03T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Epitaxial growth of VO{sub 2} by periodic annealing  

SciTech Connect (OSTI)

We report the growth of ultrathin VO{sub 2} films on rutile TiO{sub 2} (001) substrates via reactive molecular-beam epitaxy. The films were formed by the cyclical deposition of amorphous vanadium and its subsequent oxidation and transformation to VO{sub 2} via solid-phase epitaxy. Significant metal-insulator transitions were observed in films as thin as 2.3?nm, where a resistance change ?R/R of 25 was measured. Low angle annular dark field scanning transmission electron microscopy was used in conjunction with electron energy loss spectroscopy to study the film/substrate interface and revealed the vanadium to be tetravalent and the titanium interdiffusion to be limited to 1.6?nm.

Tashman, J. W.; Paik, H.; Merz, T. A. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Lee, J. H. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Moyer, J. A.; Schiffer, P. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Misra, R. [Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mundy, J. A. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Spila, T. [Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Schubert, J. [Peter Grünberg Institute, PGI 9-IT, JARA-FIT, Research Centre Jülich, D-52425 Jülich (Germany); Muller, D. A. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States); Schlom, D. G., E-mail: schlom@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

2014-02-10T23:59:59.000Z

102

Quantum state specific reactant preparation in a molecular beam by rapid adiabatic passage  

SciTech Connect (OSTI)

Highly efficient preparation of molecules in a specific rovibrationally excited state for gas/surface reactivity measurements is achieved in a molecular beam using tunable infrared (IR) radiation from a single mode continuous wave optical parametric oscillator (cw-OPO). We demonstrate that with appropriate focusing of the IR radiation, molecules in the molecular beam crossing the fixed frequency IR field experience a Doppler tuning that can be adjusted to achieve complete population inversion of a two-level system by rapid adiabatic passage (RAP). A room temperature pyroelectric detector is used to monitor the excited fraction in the molecular beam and the population inversion is detected and quantified using IR bleaching by a second IR-OPO. The second OPO is also used for complete population transfer to an overtone or combination vibration via double resonance excitation using two spatially separated RAP processes.

Chadwick, Helen, E-mail: helen.chadwick@epfl.ch; Hundt, P. Morten; Reijzen, Maarten E. van; Yoder, Bruce L.; Beck, Rainer D. [Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland)] [Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland)

2014-01-21T23:59:59.000Z

103

Growth and structure of epitaxial Pb{sub 1-x}Mn{sub x}Se(Ga) films  

SciTech Connect (OSTI)

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'').

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

104

Graphene Synthesis by Thermal Cracker Enhanced Gas Source Molecular Beam Epitaxy and Its Applications in Flash Memory  

E-Print Network [OSTI]

in growing large-area graphene on Co substrates. 3.5that nanocrystal based graphene memory is promising for97, 123105 Chapter 5: Graphene nano dots memory capacitor

Zhan, Ning

2011-01-01T23:59:59.000Z

105

Graphene Synthesis by Thermal Cracker Enhanced Gas Source Molecular Beam Epitaxy and Its Applications in Flash Memory.  

E-Print Network [OSTI]

??Because of its unique properties, such as extremely high mobility, high mechanical strength, good optical transparency and high chemical stability, graphene has attracted vast interests… (more)

Zhan, Ning

2011-01-01T23:59:59.000Z

106

Graphene Synthesis by Thermal Cracker Enhanced Gas Source Molecular Beam Epitaxy and Its Applications in Flash Memory  

E-Print Network [OSTI]

windows at the source/drain areas, where the insulator filmof as-grown films. A narrow growth time window was found forthe HfO 2 thin film. However the small memory window of the

Zhan, Ning

2011-01-01T23:59:59.000Z

107

Optical properties of Zn1xMgxO nanorods using catalysis-driven molecular beam epitaxy  

E-Print Network [OSTI]

,Mg)O nanorods exhibit a strong photo- luminescence response, showing a slight shift to shorter wavelengths due­26], are of interest based on their photonic, electronic, and sensor-related properties. Of these, zinc oxide temperature. As a gas sensor material based on the near-surface modification of charge distribution

Pennycook, Steve

108

AN INVESTIGATION OF HYDROGEN-RELATED PHENOMENON AND COMPENSATION IN ZnSe GROWN BY MOLECULAR BEAM EPITAXY  

E-Print Network [OSTI]

to thank Dr. B. R. Cooper and Dr. C. D. Stinespring for serving on my committee. I want to extend my

Myers, Tom

109

High-quality InAsyP1-y step-graded buffer by molecular-beam epitaxy  

E-Print Network [OSTI]

20, 1117 ?1991?. M. W. Wanlass, J. J. Carapella, A. Duda, K.Rev. 3, 77 ?1999?. M. W. Wanlass, J. S. Ward, K. A. Emery,

2003-01-01T23:59:59.000Z

110

Molecular Beam Epitaxy of InP-Based Alloys for Long-Wavelength Vertical-Cavity Lasers  

E-Print Network [OSTI]

P-based approaches take the opposite tack: the active region materials, AlInGaAs and InGaAsP, are well developedInGaAs and InGaAsP, do not have sufficient index contrast to be effective options for DBRs with high for existing fiber-optic networks, since they take advantage of absorption and dispersion minima

Coldren, Larry A.

111

LaCrO3 heteroepitaxy on SrTiO3(001) by molecular beam epitaxy . | 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: VegetationEquipment Surfaces and Interfaces Sample6, 2011 LOS ALAMOS,Transition and TimelineLa

112

Photoluminescence of GaAs films grown by vacuum chemical epitaxy  

SciTech Connect (OSTI)

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.

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

1988-08-01T23:59:59.000Z

113

Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices  

SciTech Connect (OSTI)

The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2--2.4 {micro}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched thermophotovoltaic devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses and the incorporation of a high bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency is observed for devices with an AlGaAsSb window layer compared to those without one.

Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1997-05-01T23:59:59.000Z

114

Epitaxial Graphene - Energy Innovation Portal  

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

Epitaxial Graphene Brookhaven National Laboratory Contact BNL About This Technology

Scanning electron micrographs of epitaxial graphene grown on ruthenium films atop patterned...

115

Molecular Beam and Surface Science Studies of Heterogeneous Reaction Kinetics Including Combustion Dynamics. Final Technical Report.  

SciTech Connect (OSTI)

This research program examined the heterogeneous reaction kinetics and reaction dynamics of surface chemical processes which are of direct relevance to efficient energy production, condensed phase reactions, and mateials growth including nanoscience objectives. We have had several notable scientific and technical successes. Illustrative highlights include: (1) a thorough study of how one can efficiently produce synthesis gas (SynGas) at relatively low Rh(111) catalyst temperatures via the reaction CH{sub4}+1/2 O{sub2} {r_arrow} CO+2H{sub2}. In these studies methane activation is accomplished utilizing high-kinetic energy reagents generated via supersonic molecular beams, (2) experiments which have incisively probed the partial oxidation chemistry of adsorbed 1- and 2- butene on Rh and ice, as well as partial oxidation of propene on Au; (3) investigation of structural changes which occur to the reconstructed (23x{radical}3)-Au(111) surface upon exposure to atomic oxygen, (4) a combined experimental and theoretical examination of the fundamental atomic-level rules which govern defect minimization during the formation of self-organizing stepped nanostructures, (5) the use of these relatively defect-free nanotemplates for growing silicon nanowires having atomically-dimensioned widths, (6) a combined scanning probe and atomic beam scattering study of how the presence of self-assembling organic overlayers interact with metallic supports substrates - this work hs led to revision of the currently held view of how such adsorbates reconfigure surface structure at the atomic level, (7) an inelastic He atom scattering study in which we examined the effect of chain length on the low-energy vibrations of alkanethiol striped phase self-assembled monolayers on Au(111), yielding information on the forces that govern interfacial self-assembly, (8) a study of the vibrational properties of disordered films of SF{sub6} adsorbed on Au(111), and (9) a study of the activated chemistry and photochemistry of NO on NiO/Ni. Innovative STM and molecular beam instrumentation has been fabricated to enable this program.

Sibener, S. J.

2006-06-23T23:59:59.000Z

116

Optical absorption in epitaxial La{sub 1-x}Sr{sub x}FeO{sub 3} thin films  

SciTech Connect (OSTI)

We report the dependence of optical absorption on Sr concentration in La{sub 1-x}Sr{sub x}FeO{sub 3} (LSFO) (x{<=}0.4) perovskite thin films. Strained epitaxial films were deposited on SrTiO{sub 3} substrates using oxide molecular beam epitaxy. We find systematic changes in the optical absorption spectra with increasing x including a red-shift of transition energies and the increasing presence of a lower energy transition within the fundamental gap of pure LaFeO{sub 3}. These results serve as a demonstration of the complex manner in which absorption spectra can be altered in complex oxides via heterovalent A-site substitution.

Scafetta, M D.; Xie, Y. J.; Torres, M.; Spanier, J. E.; May, S. J. [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)] [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

2013-02-25T23:59:59.000Z

117

Rapid characterization of lignocellulosic feedstocks for fuels and chemicals: Molecular beam mass spectrometric approach  

SciTech Connect (OSTI)

Rapid characterization of biomass feedstocks has a pivotal role in the development of biomass energy because of the large number of samples that must be analyzed due to the diversity of biomass feedstocks and the significant differences in the chemical and physical properties of these feedstocks. Several biomass feedstocks (herbaceous, woody, and agricultural residues) were screened for the effects of storage, season of harvest, geographic location, clonal, and species variation on the pyrolysis products of the feed stocks. For herbaceous species such as sericea lespedeza, the season of harvest had a significant effect on the pyrolysis products. Effects of clonal variation on the composition of hybrid poplar feedstocks was easily discerned with the molecular beam mass spectrometric analysis. The effect of geographic location on the poplar clones pyrolysis products was minimal. However in the case of switchgrass, varietal influence on the pyrolysis products was minimal, but where the plant was grown had a strong influence on the pyrolysis products of the feedstock. Significant differences because of species variation could also be shown from the pyrolysis products of various biomass feedstocks. The influence of storage time on biomass samples stored outside in the open could also be discerned from the pyrolysis products of the feedstocks. The differences noted in the pyrolysis products of the feedstocks were noted for samples which were significantly degraded during storage either through the action of microflora or weathering.

Agblevor, F.A.; Davis, M.F. [National Renewable Energy Lab., Golden, CO (United States)

1996-12-31T23:59:59.000Z

118

Molecular beam mass spectrometric characterization of biomass pyrolysis products for fuels and chemicals  

SciTech Connect (OSTI)

Converting biomass feedstocks to fuels and chemicals requires rapid characterization of the wide variety of possible feedstocks. The combination of pyrolysis molecular beam mass spectrometry (Py-MBMS) and multivariate statistical analysis offers a unique capability for characterizing these feedstocks. Herbaceous and woody biomass feedstocks that were harvested at different periods were used in this study. The pyrolysis mass spectral data were acquired in real time on the MBMS, and multivariate statistical analysis (factor analysis) was used to analyze and classify Py-MBMS data into compound classes. The effect of harvest times on the thermal conversion of these feedstocks was assessed from these data. Apart from sericea lespedeza, the influence of harvest time on the pyrolysis products of the various feedstocks was insignificant. For sericea lespedeza, samples harvested before plant defoliation were significantly different from those harvested after defoliation. The defoliated plant samples had higher carbohydrate-derived pyrolysis products than the samples obtained from the foliated plant. Additionally, char yields from the defoliated plant samples were lower than those from the foliated plant samples.

Agblevor, F.A.; Davis, M.F.; Evans, R.J. [National Renewal Energy Lab., Golden, CO (United States)

1994-12-31T23:59:59.000Z

119

Free-Standing Epitaxial Graphene Shriram Shivaraman,* Robert A. Barton, Xun Yu, Jonathan Alden,  

E-Print Network [OSTI]

Free-Standing Epitaxial Graphene Shriram Shivaraman,* Robert A. Barton, Xun Yu, Jonathan Alden to produce free-standing graphene sheets from epitaxial graphene on silicon carbide (SiC) substrate. Doubly for beams under no tension. Raman spectroscopy suggests that the graphene is not chemically modified during

McEuen, Paul L.

120

Impact of Lattice Mismatch and Stoichiometry on the Structure and Bandgap of (Fe,Cr)2O3 Epitaxial Thin Films  

SciTech Connect (OSTI)

The structural properties of high-quality epitaxial (Fe1-xCrx)2O3 thin films are investigated across the composition range. Epitaxial films are deposited on a-Al2O3(0001) substrates by oxygen-plasma-assisted molecular beam epitaxy. Corundum (Fe1-xCrx)2O3 supercells relaxed by density functional theory confirm that the non-linear behavior of the bulk lattice parameters originates in the magnetic structure of the alloy films. High-resolution x-ray diffraction reveals the degree of epitaxial strain relaxation in the films, with Cr-rich films remaining partially strained to the Al2O3 substrate. For intermediate compositions, a lattice expansion and non-Poisson-like tetragonal distortion are found. Scanning transmission electron microscopy and electron energy loss spectroscopy reveal a columnar grain structure in the films, with uniform mixing of cations on the nanometer scale. Oxygen non-stoichiometry is quantified by non-Rutherford resonant elastic scattering measurements utilizing 3.04 MeV He+. Intermediate-composition films are found to be slightly over-stoichiometric, resulting in the observed lattice expansion. Cr-rich films, in contrast, appear to be slightly oxygen deficient. A model is proposed to explain these results based on the energetics of oxygen defect formation and rate of oxygen diffusion in the corundum lattice. Compressive biaxial strain is found to reduce the bandgap of epitaxial Cr2O3 relative to the bulk value. The relationships which are elucidated between epitaxial film structure and optical properties can be applied to bandgap optimization in the (Fe,Cr)2O3 system.

Kaspar, Tiffany C.; Chamberlin, Sara E.; Bowden, Mark E.; Colby, Robert J.; Shutthanandan, V.; Manandhar, Sandeep; Wang, Yong; Sushko, Petr; Chambers, Scott A.

2014-03-13T23:59:59.000Z

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121

Epitaxial growth of rare-earth silicides on (111) Si  

SciTech Connect (OSTI)

Rapid heating with an electron beam has been used to react overlayers of rare-earth (RE) metals with (111) Si, forming epitaxial layers of silicides of Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Under conventional furnace annealing, forming such silicides on Si typically leads to rough, pitted surfaces. The use of fast beam heating not only results in a much smoother surface topology but also helps promote epitaxial growth on (111) Si in both solid and liquid phase reactions. These epitaxial silicides have a hexagonal RESi/sub approximately1.7/ structure (defected AlB/sub 2/ type). Their orientation with the Si substrate is (0001)parallel(111), with predicted lattice mismatches ranging from +0.83 to -2.55%.

Knapp, J.A.; Picraux, S.T.

1986-02-17T23:59:59.000Z

122

Structure and features of the surface morphology of A{sup 4}B{sup 6} chalcogenide epitaxial films  

SciTech Connect (OSTI)

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.

Nuriyev, I. R., E-mail: afinnazarov@yahoo.com [Azerbaijan National Academy of Sciences, Institute of Physics (Azerbaijan)

2009-12-15T23:59:59.000Z

123

Epitaxial thin films  

DOE Patents [OSTI]

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.

Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

2006-04-25T23:59:59.000Z

124

Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers  

SciTech Connect (OSTI)

Impact of Bi incorporation into (Ga,Mn)As layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition.

Yastrubchak, O., E-mail: yastrub@hektor.umcs.lublin.pl [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Institute of Semiconductor Physics, National Academy of Sciences, 41 pr. Nauki, 03028 Kyiv (Ukraine); Sadowski, J. [MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Gluba, L.; ?uk, J.; Kulik, M. [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Domagala, J. Z.; Andrearczyk, T.; Wosinski, T. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Rawski, M. [Analytical Laboratory, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 3, 20-031 Lublin (Poland)

2014-08-18T23:59:59.000Z

125

Improved epitaxy of ultrathin praseodymia films on chlorine passivated Si(111) reducing silicate interface formation  

SciTech Connect (OSTI)

Ultrathin praseodymia films have been deposited on both Cl-passivated and nonpassivated Si(111) substrates by molecular beam epitaxy. Comparative studies on the crystallinity and stoichiometry are performed by x-ray photoelectron spectroscopy, x-ray standing waves, and x-ray reflectometry. On nonpassivated Si(111) an amorphous silicate film is formed. In contrast, praseodymia deposited on Cl-passivated Si(111) form a well-ordered crystalline film with cubic-Pr{sub 2}O{sub 3} (bixbyite) structure. The vertical lattice constant of the praseodymia film is increased by 1.4% compared to the bulk value. Furthermore, the formation of an extended amorphous silicate interface layers is suppressed and confined to only one monolayer.

Gevers, S.; Bruns, D.; Weisemoeller, T.; Wollschlaeger, J. [Department of Physics, University of Osnabrueck, Barbarastrasse 7, D-49069 Osnabrueck (Germany); Flege, J. I.; Kaemena, B.; Falta, J. [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen (Germany)

2010-12-13T23:59:59.000Z

126

Robust surface electronic properties of topological insulators: Bi{sub 2}Te{sub 3} films grown by molecular beam epitaxy  

SciTech Connect (OSTI)

The surface electronic properties of the important topological insulator Bi{sub 2}Te{sub 3} are shown to be robust under an extended surface preparation procedure, which includes exposure to atmosphere and subsequent cleaning and recrystallization by an optimized in situ sputter-anneal procedure under ultrahigh vacuum conditions. Clear Dirac-cone features are displayed in high-resolution angle-resolved photoemission spectra from the resulting samples, indicating remarkable insensitivity of the topological surface state to cleaning-induced surface roughness.

Plucinski, L.; Herdt, A. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, D-52425 Juelich (Germany); Mussler, G.; Krumrain, J.; Gruetzmacher, D. [Peter Gruenberg Institut (PGI-9), Forschungszentrum Juelich, D-52425 Juelich (Germany); Juelich Aachen Research Alliance-Fundamentals of Future Information Technologies (JARA-FIT), D-52425 Juelich (Germany); Suga, S. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, D-52425 Juelich (Germany); Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Schneider, C. M. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, D-52425 Juelich (Germany); Juelich Aachen Research Alliance-Fundamentals of Future Information Technologies (JARA-FIT), D-52425 Juelich (Germany)

2011-05-30T23:59:59.000Z

127

Electrical characteristics of the CdTe-n-CdHgTe structure fabricated in a single molecular-beam epitaxy process  

SciTech Connect (OSTI)

An extraordinary shape of the capacitance-voltage characteristics of CdTe-CdHgTe structures has been detected; these characteristics include a specific 'hump' in the inversion region, the height of which increased severalfold under illumination. Additional measurements using an optical probe, measurements of current-voltage characteristics, and an analysis of the energy-band diagram of the structure showed the following. CdTe, in contrast to CdHgTe, is a p-type semiconductor with an acceptor concentration of 1 x 10{sup 16} cm{sup -3}; there is a hole inversion layer in CdHgTe at the boundary with CdTe, which causes the 'hump'; and the barrier height for holes at the CdTe-Cd{sub 0.43}Hg{sub 0.57}Te interface was determined as 0.13 eV.

Mashukov, Yu. P., E-mail: dr_mashukov@mail.ru; Mikhailov, N. N.; Vasilyev, V. V. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2010-09-15T23:59:59.000Z

128

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)

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.

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

129

Gas-source molecular beam epitaxial growth and characterization of the (Al,In,Ga)NP/GaP material system and Its applications to light-emitting diodes  

E-Print Network [OSTI]

T.P. , IEE Proceedings-Optoelectronics 144, 1 (1997). Kishof Energy (BTS) and the Optoelectronics Industry Developmentin semiconductor optoelectronics in recent years. Within two

Odnoblyudov, Vladimir

2006-01-01T23:59:59.000Z

130

Molecular beam epitaxy growth and characterization of type-II InAs/GaSb strained layer superlattices for long-wave infrared detection  

E-Print Network [OSTI]

. Sharma, and S. Krishna Center for High Technology Materials, University of New Mexico, 1313 Goddard St SE, Albuquerque, New Mexico 87106 S. J. Lee and S. K. Noh Korea Research Institute Standards and Science (KRISS imaging. It includes satellite-based surveillance, atmo- spheric pollution probes, and astrophysical

New Mexico, University of

131

Importance of growth temperature on achieving lattice-matched and strained InAlN/GaN heterostructure by plasma-assisted molecular beam epitaxy  

SciTech Connect (OSTI)

We investigate the role of growth temperature on the optimization of lattice-matched In{sub 0.17}Al{sub 0.83}N/GaN heterostructure and its structural evolutions along with electrical transport studies. The indium content gradually reduces with the increase of growth temperature and approaches lattice-matched with GaN having very smooth and high structural quality at 450ºC. The InAlN layers grown at high growth temperature (480ºC) retain very low Indium content of ? 4 % in which cracks are mushroomed due to tensile strain while above lattice matched (>17%) layers maintain crack-free compressive strain nature. The near lattice-matched heterostructure demonstrate a strong carrier confinement with very high two-dimensional sheet carrier density of ?2.9 × 10{sup 13} cm{sup ?2} with the sheet resistance of ?450 ?/? at room temperature as due to the manifestation of spontaneous polarization charge differences between InAlN and GaN layers.

Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024, Tamil Nadu (India); Shimizu, M., E-mail: mitsu.shimizu@aist.go.jp [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan. (Japan)

2014-09-15T23:59:59.000Z

132

Big-Data RHEED analysis for understanding epitaxial film growth processes  

SciTech Connect (OSTI)

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.

Vasudevan, Rama K [ORNL; Tselev, Alexander [ORNL; Baddorf, Arthur P [ORNL; Kalinin, Sergei V [ORNL

2014-01-01T23:59:59.000Z

133

Defect Structure of Epitaxial CrxV1 ? x Thin Films on MgO(001)  

SciTech Connect (OSTI)

Epitaxial thin films of CrxV1-x over the entire composition range were deposited on MgO(001) by molecular beam epitaxy. The films exhibited the expected 45° in-plane rotation with no evidence of phase segregation or spinodal decomposition. Pure Cr, with the largest lattice mismatch to MgO, exhibited full relaxation and cubic lattice parameters. As the lattice mismatch decreased with alloy composition, residual epitaxial strain was observed. For 0.2 ? x ? 0.4 the films were coherently strained to the substrate with associated tetragonal distortion; near the lattice-matched composition of x = 0.33, the films exhibited strain-free pseudomorphic matching to MgO. Unusually, films on the Cr-rich side of the lattice-matched composition exhibited more in-plane compression than expected from the bulk lattice parameters; this result was confirmed with both x-ray diffraction and Rutherford backscattering spectrometry channeling measurements. Although thermal expansion mismatch in the heterostructure may play a role, the dominant mechanism for this phenomenon is still unknown. High resolution transmission electron microscopy was utilized to characterize the misfit dislocation network present at the film/MgO interface. Dislocations were found to be present with a non-uniform distribution, which is attributed to the Volmer-Weber growth mode of the films. The CrxV1-x / MgO(001) system can serve as a model system to study both the fundamentals of defect formation in bcc films and the interplay between nanoscale defects such as dislocations and radiation damage.

Kaspar, Tiffany C.; Bowden, Mark E.; Wang, Chong M.; Shutthanandan, V.; Manandhar, Sandeep; Van Ginhoven, Renee M.; Wirth, Brian D.; Kurtz, Richard J.

2014-01-01T23:59:59.000Z

134

Crossed Molecular Beam Studies of Phenyl Radical Reactions with Propene and 2-Butene Daniel R. Albert, Michael A. Todt and H. Floyd Davis*  

E-Print Network [OSTI]

Cornell University Ithaca, New York 14853 Abstract The reaction of phenyl radicals with propene has been studied at collision energies of 84 and 108 kJ/mol using the crossed molecular beams technique decreases as the collision energy increases. However, we find at both collision energies that the formation

Davis, H. Floyd

135

Effusive molecular beam-sampled Knudsen flow reactor coupled to vacuum ultraviolet single photon ionization mass spectrometry using an external free radical source  

SciTech Connect (OSTI)

A new apparatus using vacuum ultraviolet single photon ionization mass spectrometry (VUV SPIMS) of an effusive molecular beam emanating from a Knudsen flow reactor is described. It was designed to study free radical-molecule kinetics over a significant temperature range (300–630 K). Its salient features are: (1) external free radical source, (2) counterpropagating molecular beam and diffuse VUV photon beam meeting in a crossed-beam ion source of a quadrupole mass spectrometer with perpendicular ion extraction, (3) analog detection of the photocurrent of the free radical molecular cation, and (4) possibility of detecting both free radicals and closed shell species in the same apparatus and under identical reaction conditions owing to the presence of photoelectrons generated by the photoelectric effect of the used VUV-photons. The measured thermal molecular beam-to-background ratio was 6.35 ± 0.39 for Ar and 10.86 ± 1.59 for i-C{sub 4}H{sub 10} at 300 K, a factor of 2.52 and 1.50 smaller, respectively, than predicted from basic gas-dynamic considerations. Operating parameters as well as the performance of key elements of the instrument are presented and discussed. Coupled to an external free radical source a steady-state specific exit flow of 1.6 × 10{sup 11} and 5.0 × 10{sup 11} molecule s{sup ?1} cm{sup ?3} of C{sub 2}H{sub 5}{sup •} (ethyl) and t-C{sub 4}H{sub 9}{sup •} (t-butyl) free radicals have been detected using VUV SPIMS at their molecular ion m/z 29 and 57, respectively, at 300 K.

Leplat, N.; Rossi, M. J. [Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland)] [Laboratory of Atmospheric Chemistry (LAC), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland)

2013-11-15T23:59:59.000Z

136

Energy band alignment of atomic layer deposited HfO{sub 2} oxide film on epitaxial (100)Ge, (110)Ge, and (111)Ge layers  

SciTech Connect (OSTI)

Crystallographically oriented epitaxial Ge layers were grown on (100), (110), and (111)A GaAs substrates by in situ growth process using two separate molecular beam epitaxy chambers. The band alignment properties of atomic layer hafnium oxide (HfO{sub 2}) film deposited on crystallographically oriented epitaxial Ge were investigated using x-ray photoelectron spectroscopy (XPS). Valence band offset, {Delta}E{sub v} values of HfO{sub 2} relative to (100)Ge, (110)Ge, and (111)Ge orientations were 2.8 eV, 2.28 eV, and 2.5 eV, respectively. Using XPS data, variation in valence band offset, {Delta}E{sub V}(100)Ge>{Delta}E{sub V}(111)Ge>{Delta}E{sub V}(110)Ge, was obtained related to Ge orientation. Also, the conduction band offset, {Delta}E{sub c} relation, {Delta}E{sub c}(110)Ge>{Delta}E{sub c}(111)Ge>{Delta}E{sub c}(100)Ge related to Ge orientations was obtained using the measured bandgap of HfO{sub 2} on each orientation and with the Ge bandgap of 0.67 eV. These band offset parameters for carrier confinement would offer an important guidance to design Ge-based p- and n-channel metal-oxide field-effect transistor for low-power application.

Hudait, Mantu K.; Zhu Yan [Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

2013-03-21T23:59:59.000Z

137

Growth and structure of photosensitive Pb{sub 1-x}Mn{sub x}Te(Ga) epitaxial films  

SciTech Connect (OSTI)

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.

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

138

Epitaxial Thin Film XRD | EMSL  

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

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139

Growth of highly doped p-type ZnTe films by pulsed laser ablation in molecular nitrogen  

SciTech Connect (OSTI)

Highly p-doped ZnTe films have been grown on semi-insulating GaAs (001) substrates by pulsed-laser ablation (PLA) of a stoichiometric ZnTe target in a high-purity N{sub 2} ambient without the use of any assisting (DC or AC) plasma source. Free hole concentrations in the mid-10{sup 19} cm{sup {minus}3} to > 10{sup 20} cm{sup {minus}3} range were obtained for a range of nitrogen pressures The maximum hole concentration equals the highest hole doping reported to date for any wide band gap II-VI compound. The highest hole mobilities were attained for nitrogen pressures of 50--100 mTorr ({approximately}6.5-13 Pa). Unlike recent experiments in which atomic nitrogen beams, extracted from RF and DC plasma sources, were used to produce p-type doping during molecular beam epitaxy deposition, spectroscopic measurements carried out during PLA of ZnTe in N{sub 2} do not reveal the presence of atomic nitrogen. This suggests that the high hole concentrations in laser ablated ZnTe are produced by a new and different mechanism, possibly energetic beam-induced reactions with excited molecular nitrogen adsorbed on the growing film surface, or transient formation of Zn-N complexes in the energetic ablation plume. This appears to be the first time that any wide band gap (Eg > 2 eV) II-VI compound (or other) semiconductor has been impurity-doped from the gas phase by laser ablation. In combination with the recent discovery that epitaxial ZnSe{sub l-x}S{sub x} films and heterostructures with continuously variable composition can be grown by ablation from a single target of fixed composition, these results appear to open the way to explore PLA growth and doping of compound semiconductors as a possible alternative to molecular beam epitaxy.

Lowndes, D.H.; Rouleau, C.M.; Budai, J.D.; Poker, D.B.; Geohegan, D.B.; Zhu, Shen [Oak Ridge National Lab., TN (United States); McCamy, J.W. [Harvard Univ., Cambridge, MA (United States). Div. of Applied Science; Puretzky, A. [Institute of Spectroscopy, Troitsk (Russian Federation)

1995-04-01T23:59:59.000Z

140

Luminescence and superradiance in electron-beam-excited Al{sub x}Ga{sub 1?x}N  

SciTech Connect (OSTI)

Luminescence and superradiance characteristics of 0.5–1.2-?m thick Al{sub x}Ga{sub 1?x}N films grown by molecular-beam epitaxy on sapphire substrates were studied under excitation of the films with low-energy (<20?keV) and high-energy (170?keV) electron beams. In both cases, the luminescence spectra looked quite similarly; they exhibited a band-edge luminescence with x-dependent wavelength ranging from 365?nm to 310?nm and a broadband emission taking over the whole visible spectral region. Superradiance within the broad band was obtained by pumping the samples with powerful an electron beam in the form of an open-discharge-generated filament.

Bokhan, P. A.; Gugin, P. P.; Zakrevsky, Dm. E.; Malin, T. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Zhuravlev, K. S.; Osinnykh, I. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090 (Russian Federation); Solomonov, V. I.; Spirina, A. V. [Institute of Electrophysics, Ural Division of the Russian Academy of Sciences, 106, Amundsen str., Ekaterinburg 620016 (Russian Federation)

2014-09-21T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Comparative optical study of epitaxial InGaAs quantum rods grown with As{sub 2} and As{sub 4} sources  

SciTech Connect (OSTI)

Photoreflectance and photoluminescence (PL) spectroscopies are used to examine the optical properties and electronic structure of InGaAs quantum rods (QRs), embedded within InGaAs quantum well (QW). The nanostructures studied were grown by molecular beam epitaxy using As{sub 2} or As{sub 4} sources. The impact of As source on spectral features associated with interband optical transitions in the QRs and the surrounding QW are demonstrated. A red shift of the QR- and a blue shift of the QW-related optical transitions, along with a significant increase in PL intensity, have been observed if an As{sub 4} source is used. The changes in optical properties are attributed mainly to carrier confinement effects caused by variation of In content contrast between the QR material and the surrounding well.

Nedzinskas, Ram?nas; ?echavi?ius, Bronislovas; Kavaliauskas, Julius; Karpus, Vytautas; Valušis, Gintaras [Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius (Lithuania); Li, Lianhe; Khanna, Suraj P.; Linfield, Edmund H. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)

2013-12-04T23:59:59.000Z

142

Photodiode characteristics and band alignment parameters of epitaxial Al0.5Ga0.5P  

E-Print Network [OSTI]

Photodiode characteristics and band alignment parameters of epitaxial Al0.5Ga0.5P An Chen1,a-bandgap semiconductor AlxGa1-xP is a promising material candidate for low-noise photodiodes in blue/UV spectrum. Photodiodes were fabricated on Al0.5Ga0.5P epitaxial layer grown lattice matched on GaP substrate by molecular

Woodall, Jerry M.

143

Specific features of the nonradiative relaxation of Er{sup 3+} ions in epitaxial Si structures  

SciTech Connect (OSTI)

The specific features of the nonradiative relaxation of Er{sup 3+} ions in Si:Er layers grown by sublimation molecular-beam epitaxy (SMBE) are studied. In Si:Er/Si diode structures containing precipitation-type emitting centers, a resonance photoresponse at the wavelength ? ? 1.5 ?m is observed, which is indicative of the nonradiative relaxation of Er3+ ions via the energy back-transfer mechanism. Saturation of the erbium-related photocurrent is for the first time observed at high temperatures. This allows estimation of the concentration of Er centers that undergo relaxation via the above-mentioned back-transfer mechanism (N{sub 0} ? 5 × 10{sup 16} cm{sup ?3}). In terms of order of magnitude, the estimated concentration N{sub 0} corresponds to the concentration of optically active Er ions upon excitation of the Si:Er layers by means of the recombination mechanism. The features of the nonradiative relaxation of Er{sup 3+} ions in Si:Er/Si structures with different types of emitting centers are analyzed.

Kudryavtsev, K. E., E-mail: konstantin@ipmras.ru; Kryzhkov, D. I.; Antonov, A. V.; Shengurov, D. V.; Shmagin, V. B.; Krasilnik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2014-12-15T23:59:59.000Z

144

Photodiode characteristics and band alignment parameters of epitaxial Al{sub 0.5}Ga{sub 0.5}P  

SciTech Connect (OSTI)

Wide-bandgap semiconductor Al{sub x}Ga{sub 1-x}P is a promising material candidate for low-noise photodiodes in blue/UV spectrum. Photodiodes were fabricated on Al{sub 0.5}Ga{sub 0.5}P epitaxial layer grown lattice matched on GaP substrate by molecular beam epitaxy. Although quantum efficiency is low for standard p-i-n photodiode due to inadvertent photon absorption in the top p-layer, it can be significantly improved by opening a recessed window in the top p-layer or by using a Schottky junction photodiode structure. Al{sub 0.5}Ga{sub 0.5}P band alignment parameters can be extrapolated from the current-voltage characteristics of Al{sub 0.5}Ga{sub 0.5}P Schottky junctions. The bandgap of Al{sub 0.5}Ga{sub 0.5}P was measured to be 2.38 eV.

Chen An [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States); Woodall, Jerry M. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2009-01-12T23:59:59.000Z

145

Band-Gap Reduction and Dopant Interaction in Epitaxial La,Cr Co-doped SrTiO3 Thin Films  

SciTech Connect (OSTI)

We show that by co-doping SrTiO3 (STO) epitaxial thin films with equal amounts of La and Cr it is possible to produce films with an optical band gap ~0.9 eV lower than that of undoped STO. Sr1-xLaxTi1-xCrxO3 thin films were deposited by molecular beam epitaxy and characterized using x-ray photoelectron spectroscopy and x-ray absorption near-edge spectroscopy to show that the Cr dopants are almost exclusively in the Cr3+ oxidation state. Extended x-ray absorption fine structure measurements and theoretical modeling suggest that it is thermodynamically preferred for La and Cr dopants to occupy nearest neighbor A- and B-sites in the lattice. Transport measurements show that the material exhibits variable-range hopping conductivity with high resistivity. These results create new opportunities for the use of doped STO films in photovoltaic and photocatalytic applications.

Comes, Ryan B.; Sushko, Petr; Heald, Steve M.; Colby, Robert J.; Bowden, Mark E.; Chambers, Scott A.

2014-12-03T23:59:59.000Z

146

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)

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.

Devaraj, Arun; Kaspar, Tiffany C.; Ramanan, Sathvik; Walvekar, Sarita K.; Bowden, Mark E.; Shutthanandan, V.; Kurtz, Richard J.

2014-11-21T23:59:59.000Z

147

Ferroelectric and ferromagnetic properties of epitaxial BiFeO{sub 3}-BiMnO{sub 3} films on ion-beam-assisted deposited TiN buffered flexible Hastelloy  

SciTech Connect (OSTI)

Growth of multifunctional thin films on flexible substrates is of great technological significance since such a platform is needed for flexible electronics. In this study, we report the growth of biaxially aligned (BiFeO{sub 3}){sub 0.5}:(BiMnO{sub 3}){sub 0.5} [BFO-BMO] films on polycrystalline Hastelloy by using a biaxially aligned TiN as a seed layer deposited by ion-beam-assisted deposited and a La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) as a buffer layer deposited by pulsed laser deposition. The LSMO is used not only as a buffer layer but also as the bottom electrode of the BFO-BMO films. X-ray diffraction showed that the BFO-BMO films are biaxially oriented along both in-plane and out-of-plane directions. The BFO-BMO films on flexible metal substrates showed a polarization of 22.9??C/cm{sup 2}. The magnetization of the BFO-BMO/LSMO is 62?emu/cc at room temperature.

Xiong, J., E-mail: jiexiong@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Los Alamos National Laboratory, Center for Integrated Nanotechnologies, Division of Materials Physics and Applications, Los Alamos, New Mexico 87545 (United States); Matias, V.; Jia, Q. X. [Los Alamos National Laboratory, Center for Integrated Nanotechnologies, Division of Materials Physics and Applications, Los Alamos, New Mexico 87545 (United States); Tao, B. W.; Li, Y. R. [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2014-05-07T23:59:59.000Z

148

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)

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.

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

2009-01-01T23:59:59.000Z

149

Quasibound levels and shape resonances of /sup 39/K/sub 2/(B /sup 1/Pi/sub u/) crossed laser-molecular beam studies and analytical interpretation  

SciTech Connect (OSTI)

Quasibound levels and shape resonances in the (B /sup 1/Pi/sub u/ -X /sup 1/..sigma../sup +//sub g/) band system of /sup 39/K/sub 2/ have been recorded by crossed laser-molecular beam techniques. Using optical--optical double resonance, individual rovibrational levels (v'' = 15--18, J'' = 3--25) of the K/sub 2/ state are prepared by Franck--Condon pumping (FCP) in a supersonic nozzle beam. Excitation into quasibound levels below and above the (B /sup 1/Pi/sub u/) state barrier is detected as molecular and atomic (K4 /sup 2/P/sub 3//sub ///sub 2/..-->..4 /sup 2/S/sub 1//sub ///sub 2/ only) fluorescence. The resonance transition frequencies and shapes are measured and the results are used (a) to determine the scattering resonance energies, widths, and lifetimes; (b) to compare them with values obtained by a ''maximum internal amplitude'' approach (R. J. LeRoy and R. B. Bernstein, J. Chem. Phys. 54, 5114 (1971)); and (c) to check the agreement with exact calculations of the B state potential using the ''inverted perturbation approach (IPA).'' The bound and quasibound part of the B /sup 1/Pi/sub u/ state including the locus (R = 8.08 +- 0.05 A) of the barrier maximum (298 +- 8 cm/sup -1/ above the adiabatic dissociation limit) is found in excellent agreement with previous results. The shape resonances are not highly sensitive to the long-range interatomic forces, here the repulsive dipole--dipole resonance interaction.

Heinze, J.; Kowalczyk, P.; Engelke, F.

1988-09-15T23:59:59.000Z

150

Low interfacial trap density and sub-nm equivalent oxide thickness in In{sub 0.53}Ga{sub 0.47}As (001) metal-oxide-semiconductor devices using molecular beam deposited HfO{sub 2}/Al{sub 2}O{sub 3} as gate dielectrics  

SciTech Connect (OSTI)

We investigated the passivation of In{sub 0.53}Ga{sub 0.47}As (001) surface by molecular beam epitaxy techniques. After growth of strained In{sub 0.53}Ga{sub 0.47}As on InP (001) substrate, HfO{sub 2}/Al{sub 2}O{sub 3} high-{kappa} oxide stacks have been deposited in-situ after surface reconstruction engineering. Excellent capacitance-voltage characteristics have been demonstrated along with low gate leakage currents. The interfacial density of states (D{sub it}) of the Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As interface have been revealed by conductance measurement, indicating a downward D{sub it} profile from the energy close to the valence band (medium 10{sup 12} cm{sup -2}eV{sup -1}) towards that close to the conduction band (10{sup 11} cm{sup -2}eV{sup -1}). The low D{sub it}'s are in good agreement with the high Fermi-level movement efficiency of greater than 80%. Moreover, excellent scalability of the HfO{sub 2} has been demonstrated as evidenced by the good dependence of capacitance oxide thickness on the HfO{sub 2} thickness (dielectric constant of HfO{sub 2}{approx}20) and the remained low D{sub it}'s due to the thin Al{sub 2}O{sub 3} passivation layer. The sample with HfO{sub 2} (3.4 nm)/Al{sub 2}O{sub 3} (1.2 nm) as the gate dielectrics has exhibited an equivalent oxide thickness of {approx}0.93 nm.

Chu, L. K. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Katholieke Universiteit Leuven, 3001 Leuven (Belgium); Merckling, C.; Dekoster, J.; Caymax, M. [Interuniversity Microelectronics Center (IMEC vzw), 3001 Leuven (Belgium); Alian, A.; Heyns, M. [Katholieke Universiteit Leuven, 3001 Leuven (Belgium); Interuniversity Microelectronics Center (IMEC vzw), 3001 Leuven (Belgium); Kwo, J. [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Hong, M. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2011-07-25T23:59:59.000Z

151

Ion beam processing of advanced electronic materials  

SciTech Connect (OSTI)

This report contains research programs discussed at the materials research society symposia on ion beam processing of advanced electronic materials. Major topics include: shallow implantation and solid-phase epitaxy; damage effects; focused ion beams; MeV implantation; high-dose implantation; implantation in III-V materials and multilayers; and implantation in electronic materials. Individual projects are processed separately for the data bases. (CBS)

Cheung, N.W.; Marwick, A.D.; Roberto, J.B. (eds.) (California Univ., Berkeley, CA (USA); International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center; Oak Ridge National Lab., TN (USA))

1989-01-01T23:59:59.000Z

152

Construção e caracterização de célula solar tipo barreira Schottky CdTe/Al.  

E-Print Network [OSTI]

??In this work the techniques of hot wall epitaxy (HWE) and molecular beam epitaxy (MBE) on thin films of CdTe (cadmium telluride) were used in… (more)

Denis Rafael de Oliveira Pereira

2011-01-01T23:59:59.000Z

153

Electric-dipole moment of CaF by molecular-beam, laser-rf, double-resonance study of Stark splittings  

SciTech Connect (OSTI)

The electronic structure of diatomic molecules is much more complex for open-shell sytems (radicals) than for the normal closed-shell systems, and the development of an adequate theoretical understanding will require a substantial upgrading of experimental knowledge in both quality and quantity. The alkaline-earth monohalide family of radicals, with only a single electron outside closed-shell cores, would appear to be a logical starting point for such studies, and there has been a great increase in work in this area in the last few years in spite of the special difficulties of working with free radicals. As the work of measuring the vibrational and rotational structure of the electronic states has become more complete, attention has turned to study of the much weaker spin-rotation and hyperfine interactions. Within the last three years, these interactions have been studied systematically at high precision in the calcium monohalide family with the molecular-beam, laser-rf double-resonance technique. The same method has now been modified and extended to make possible measurement of the electric-dipole moments of these molecules through observation of the Stark splittings of radiofrequency transitions. It is hoped that when considered together, the several types of data will make it possible to understand the ground-state electronic wave functions of these molecules at least qualitatively. 2 figures.

Childs, W.J.; Goodman, L.S.; Nielsen, U.; Pfeufer, V.

1984-01-01T23:59:59.000Z

154

Magnetic properties of epitaxial Co-doped anatase TiO2 thin films with excellent structural quality  

SciTech Connect (OSTI)

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.

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

155

Epitaxy of polar semiconductor Co{sub 3}O{sub 4} (110): Growth, structure, and characterization  

SciTech Connect (OSTI)

The (110) plane of Co{sub 3}O{sub 4} spinel exhibits significantly higher rates of carbon monoxide conversion due to the presence of active Co{sup 3+} species at the surface. However, experimental studies of Co{sub 3}O{sub 4} (110) surfaces and interfaces have been limited by the difficulties in growing high-quality films. We report thin (10–250?Å) Co{sub 3}O{sub 4} films grown by molecular beam epitaxy in the polar (110) direction on MgAl{sub 2}O{sub 4} substrates. Reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and transmission electron microscopy measurements attest to the high quality of the as-grown films. Furthermore, we investigate the electronic structure of this material by core level and valence band x-ray photoelectron spectroscopy, and first-principles density functional theory calculations. Ellipsometry reveals a direct band gap of 0.75?eV and other interband transitions at higher energies. A valence band offset of 3.2?eV is measured for the Co{sub 3}O{sub 4}/MgAl{sub 2}O{sub 4} heterostructure. Magnetic measurements show the signature of antiferromagnetic ordering at 49?K. FTIR ellipsometry finds three infrared-active phonons between 300 and 700?cm{sup ?1}.

Kormondy, Kristy J.; Posadas, Agham B.; Slepko, Alexander; Demkov, Alexander A., E-mail: demkov@physics.utexas.edu [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Dhamdhere, Ajit; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Mitchell, Khadijih N.; Willett-Gies, Travis I.; Zollner, Stefan [Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Marshall, Luke G.; Zhou, Jianshi [Materials Science and Engineering Program/Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States)

2014-06-28T23:59:59.000Z

156

GaSb molecular beam epitaxial growth on p-InP(001) and passivation with in situ deposited Al{sub 2}O{sub 3} gate oxide  

SciTech Connect (OSTI)

The integration of high carrier mobility materials into future CMOS generations is presently being studied in order to increase drive current capability and to decrease power consumption in future generation CMOS devices. If III-V materials are the candidates of choice for n-type channel devices, antimonide-based semiconductors present high hole mobility and could be used for p-type channel devices. In this work we first demonstrate the heteroepitaxy of fully relaxed GaSb epilayers on InP(001) substrates. In a second part, the properties of the Al{sub 2}O{sub 3}/GaSb interface have been studied by in situ deposition of an Al{sub 2}O{sub 3} high-{kappa} gate dielectric. The interface is abrupt without any substantial interfacial layer, and is characterized by high conduction and valence band offsets. Finally, MOS capacitors show well-behaved C-V with relatively low D{sub it} along the bandgap, these results point out an efficient electrical passivation of the Al{sub 2}O{sub 3}/GaSb interface.

Merckling, C.; Brammertz, G.; Hoffmann, T. Y.; Caymax, M.; Dekoster, J. [Interuniversity Microelectronics Center (IMEC vzw), Kapeldreef 75, 3001, Leuven (Belgium); Sun, X. [Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium); Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520-8284 (United States); Alian, A.; Heyns, M. [Interuniversity Microelectronics Center (IMEC vzw), Kapeldreef 75, 3001, Leuven (Belgium); Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium); Afanas'ev, V. V. [Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium)

2011-04-01T23:59:59.000Z

157

Quantification of Dopant Concentrations in Diluted Magnetic Semiconductors using Ion Beam Techniques  

SciTech Connect (OSTI)

It has recently been demonstrated that magnetically doped TiO2 and SnO2 show ferromagnetism at room-temperature and Curie temperatures above room temperature. However, accurate knowledge of dopant concentrations is necessary to quantify magnetic moments in these materials. Rutherford Backscattering spectrometry (RBS) is one of the powerful techniques to quantify magnetic transition metal dopant concentrations in these materials. However, in some cases, the interference of RBS signals for different dopants and substrate elements in these materials makes analysis difficult. In this work, we demonstrate that particle induced x-ray emission (PIXE) can be successfully used to quantify the magnetic transition element dopants in several room temperature ferromagnetic materials synthesized using three different synthesis methods: oxygen plasma assisted molecular beam epitaxy, ion implantation and wet chemical methods.

Shutthanandan, V.; Thevuthasan, Suntharampillai; Droubay, Timothy C.; Kaspar, Tiffany C.; Punnoose, Alex; Hays, Jason; Chambers, Scott A.

2006-08-01T23:59:59.000Z

158

Structure, Magnetism and Conductivity in Epitaxial Ti-doped ...  

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

Magnetism and Conductivity in Epitaxial Ti-doped -Fe2O3 Hematite: Experiment and density functional theory Structure, Magnetism and Conductivity in Epitaxial Ti-doped -Fe2O3...

159

Substrate-Induced Band-Gap Opening in Epitaxial Graphene  

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

Substrate-Induced Band-Gap Opening in Epitaxial Graphene Substrate-Induced Band-Gap Opening in Epitaxial Graphene Print Wednesday, 26 March 2008 00:00 Prospective challengers to...

160

Epitaxial graphene on silicon carbide: Introduction to structured graphene  

E-Print Network [OSTI]

Epitaxial graphene on silicon carbide: Introduction to structured graphene Ming Ruan 1 , Yike Hu 1, France Abstract We present an introduction to the rapidly growing field of epitaxial graphene on silicon present, highly evolved state. The potential of epitaxial graphene as a new electronic material is now

Paris-Sud XI, Université de

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While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Chemical vapor deposition of epitaxial silicon  

DOE Patents [OSTI]

A single chamber continuous chemical vapor deposition (CVD) reactor is described for depositing continuously on flat substrates, for example, epitaxial layers of semiconductor materials. The single chamber reactor is formed into three separate zones by baffles or tubes carrying chemical source material and a carrier gas in one gas stream and hydrogen gas in the other stream without interaction while the wafers are heated to deposition temperature. Diffusion of the two gas streams on heated wafers effects the epitaxial deposition in the intermediate zone and the wafers are cooled in the final zone by coolant gases. A CVD reactor for batch processing is also described embodying the deposition principles of the continuous reactor.

Berkman, Samuel (Florham Park, NJ)

1984-01-01T23:59:59.000Z

162

Temperature dependence of ion-beam mixing in crystalline and amorphous germanium isotope multilayer structures  

SciTech Connect (OSTI)

Self-atom mixing induced by 310 keV gallium (Ga) ion implantation in crystalline and preamorphized germanium (Ge) at temperatures between 164 K and 623 K and a dose of 1?×?10{sup 15}?cm{sup ?2} is investigated using isotopic multilayer structures of alternating {sup 70}Ge and {sup nat}Ge layers grown by molecular beam epitaxy. The distribution of the implanted Ga atoms and the ion-beam induced depth-dependent self-atom mixing was determined by means of secondary ion mass spectrometry. Three different temperature regimes of self-atom mixing, i.e., low-, intermediate-, and high-temperature regimes are observed. At temperatures up to 423 K, the mixing is independent of the initial structure, whereas at 523?K, the intermixing of the preamorphized Ge structure is about twice as high as that of crystalline Ge. At 623?K, the intermixing of the initially amorphous Ge structure is strongly reduced and approaches the mixing of the crystalline material. The temperature dependence of ion-beam mixing is described by competitive amorphization and recrystallization processes.

Radek, M.; Bracht, H., E-mail: bracht@uni-muenster.de [Institute of Materials Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster (Germany); Posselt, M.; Liedke, B.; Schmidt, B. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01328 Dresden (Germany); Bougeard, D. [Institut für Experimentelle und Angewandte Physik, 93040 Regensburg (Germany)

2014-01-14T23:59:59.000Z

163

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

SciTech Connect (OSTI)

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.

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

164

Wafer bonded epitaxial templates for silicon heterostructures  

DOE Patents [OSTI]

A heterostructure device layer is epitaxially grown on a virtual substrate, such as an InP/InGaAs/InP double heterostructure. A device substrate and a handle substrate form the virtual substrate. The device substrate is bonded to the handle substrate and is composed of a material suitable for fabrication of optoelectronic devices. The handle substrate is composed of a material suitable for providing mechanical support. The mechanical strength of the device and handle substrates is improved and the device substrate is thinned to leave a single-crystal film on the virtual substrate such as by exfoliation of a device film from the device substrate. An upper portion of the device film exfoliated from the device substrate is removed to provide a smoother and less defect prone surface for an optoelectronic device. A heterostructure is epitaxially grown on the smoothed surface in which an optoelectronic device may be fabricated.

Atwater, Jr., Harry A. (So. Pasadena, CA); Zahler, James M. (Pasadena, CA); Morral, Anna Fontcubera I (Paris, FR)

2008-03-11T23:59:59.000Z

165

Junction Transport in Epitaxial Film Silicon Heterojunction Solar Cells: Preprint  

SciTech Connect (OSTI)

We report our progress toward low-temperature HWCVD epitaxial film silicon solar cells on inexpensive seed layers, with a focus on the junction transport physics exhibited by our devices. Heterojunctions of i/p hydrogenated amorphous Si (a-Si) on our n-type epitaxial crystal Si on n++ Si wafers show space-charge-region recombination, tunneling or diffusive transport depending on both epitaxial Si quality and the applied forward voltage.

Young, D. L.; Li, J. V.; Teplin, C. W.; Stradins, P.; Branz, H. M.

2011-07-01T23:59:59.000Z

166

Highly tunable electron transport in epitaxial topological insulator (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} thin films  

SciTech Connect (OSTI)

Atomically smooth, single crystalline (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} films have been grown on SrTiO{sub 3}(111) substrates by molecular beam epitaxy. A full range of Sb-Bi compositions have been studied in order to obtain the lowest possible bulk conductivity. For the samples with optimized Sb compositions (x=0.5{+-}0.1), the carrier type can be tuned from n-type to p-type across the whole thickness with the help of a back-gate. Linear magnetoresistance has been observed at gate voltages close to the maximum in the longitudinal resistance of a (Bi{sub 0.5}Sb{sub 0.5}){sub 2}Te{sub 3} sample. These highly tunable (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} thin films provide an excellent platform to explore the intrinsic transport properties of the three-dimensional topological insulators.

He Xiaoyue; Guan Tong; Wang Xiuxia; Feng Baojie; Cheng Peng; Chen Lan; Li Yongqing; Wu Kehui [Institute of Physics, Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2012-09-17T23:59:59.000Z

167

Annealing temperature and thickness dependence of magnetic properties in epitaxial L1{sub 0}-Mn{sub 1.4}Ga films  

SciTech Connect (OSTI)

Mn{sub 1.4}Ga films with high perpendicular magnetic anisotropy and high crystalline quality were grown on MgO substrates with Cr buffer layer using molecular beam epitaxy. The crystalline structure and the surface morphology of the films have been systematically investigated as functions of in-situ annealing temperature (T{sub a}) and film thickness. It is found that the magnetic properties can be largely tuned by adjusting T{sub a}. As T{sub a} increases, both saturation magnetization (M{sub s}) and uniaxial perpendicular magnetic anisotropy constant (K{sub u}) increase to the maximum values of 612?emu/cc and 18?Merg/cc at 300?°C, respectively, and then decrease. The morphology also changes with T{sub a}, showing a minimum roughness of 2.2?Å at T{sub a}?=?450?°C. On the other hand, as the thickness increases, M{sub s} and K{sub u} increase while coercivity decreases, which indicates there is a magnetic dead layer with a thickness of about 1.5?nm at the interfaces. The detailed examination on the surface morphology of the films with various thicknesses shows a complicated film growth process, which can be understood from the relaxation mechanism of the interfacial strain.

Zheng, Y. H., E-mail: elezheng@nus.edu.sg; Lu, H.; Teo, K. L. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Han, G. C. [Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore)

2014-01-28T23:59:59.000Z

168

Electron holography of devices with epitaxial layers  

SciTech Connect (OSTI)

Applicability of electron holography to deep submicron Si devices with epitaxial layers is limited due to lack of the mean inner potential data and effects of the sample tilt. The mean inner potential V{sub 0}?=?12.75?V of the intrinsic epitaxial SiGe was measured by electron holography in devices with Ge content C{sub Ge}?=?18%. Nanobeam electron diffraction analysis performed on the same device structure showed that SiGe is strain-free in [220] direction. Our results showed good correlation with simulations of the mean inner potential of the strain-free SiGe using density function theory. A new method is proposed in this paper to correct electron holography data for the overlap of potentials of Si and the epitaxial layer, which is caused by the sample tilt. The method was applied to the analysis of the dopant diffusion in p-Field-effect Transistor devices with the identical gate length L?=?30?nm, which had alternative SiGe geometry in the source and drain regions and was subjected to different thermal processing. Results have helped to understand electrical data acquired from the same devices in terms of dopant diffusion.

Gribelyuk, M. A., E-mail: Michael.gribelyuk@globalfoundries.com; Ontalus, V.; Baumann, F. H.; Zhu, Z.; Holt, J. R. [IBM Systems and Technology Group, Hopewell Junction, New York 12533 (United States)

2014-11-07T23:59:59.000Z

169

ORIGINAL PAPER Epitaxial Stabilization of Face Selective Catalysts  

E-Print Network [OSTI]

with changes in catalytic performance (activity and selec- tivity), using the hydrogenation of acrolein combinations. Keywords Epitaxy Á Perovskite Á Platinum Á Heterogeneous catalysis Á Hydrogenation Á Acrolein

Marks, Laurence D.

170

Substrate-Induced Band-Gap Opening in Epitaxial Graphene  

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

Substrate-Induced Band-Gap Opening in Epitaxial Graphene Print Prospective challengers to silicon, the long-reigning king of semiconductors for computer chips and other electronic...

171

Ultra-low contact resistance at an epitaxial metal/oxide heterojunctio...  

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

Ultra-low contact resistance at an epitaxial metaloxide heterojunction through interstitial site doping. Ultra-low contact resistance at an epitaxial metaloxide heterojunction...

172

Crossed Molecular Beams Study on the Formation of Vinylacetylene in Titan's Atmosphere Fangtong Zhang, Yong Seol Kim, and Ralf I. Kaiser*  

E-Print Network [OSTI]

), was investigated at a collision energy of 20.6 ( 0.4 kJ mol-1 utilizing the crossed-beams technique. Combined such as Titan's atmosphere via the neutral-neutral reaction of ethynyl radicals with ubiquitous ethylene and their role in the build-

Kaiser, Ralf I.

173

Pulsed laser ablation growth and doping of epitaxial compound semiconductor films  

SciTech Connect (OSTI)

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.

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

174

Covalent Functionalization of Epitaxial Graphene by Azidotrimethylsilane Junghun Choi,  

E-Print Network [OSTI]

Covalent Functionalization of Epitaxial Graphene by Azidotrimethylsilane Junghun Choi, Ki-jeong Kim, 2009 Chemically modified epitaxial graphene (EG) by azidotrimethylsilane (ATS) was investigated using graphene (CSG) model, we elucidated that nitrene radicals adsorb on the graphene layer at two different

Kim, Sehun

175

Self-doping effects in epitaxially grown graphene  

E-Print Network [OSTI]

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

Siegel, David A.

2009-01-01T23:59:59.000Z

176

Growth of epitaxial thin films by pulsed laser ablation  

SciTech Connect (OSTI)

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)

Lowndes, D.H.

1992-10-01T23:59:59.000Z

177

Growth of epitaxial thin films by pulsed laser ablation  

SciTech Connect (OSTI)

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)

Lowndes, D.H.

1992-01-01T23:59:59.000Z

178

Steric effects in molecular adsorption  

SciTech Connect (OSTI)

The results of a molecular beam surface scattering experiment with preferentially orientated NO on Ag(111) are given. In adsorption molecules oriented with the O end towards the surface have a larger trapping probability.

Tenner, M.G.; Kuipers, E.W.; Kleyn, A.W.; Stolte, S.

1988-11-15T23:59:59.000Z

179

Structure-property Relationships in Pure and Doped Epitaxial Tungsten Trioxide Thin Films  

E-Print Network [OSTI]

Structure-property Relationships in Pure and Doped Epitaxial Tungsten Trioxide Thin Films Principal-property relationships of well- defined epitaxial tungsten trioxide (WO3) films with and without dopants, and thereby

180

Growth of Epitaxial Thin Pd(111) Films on Pt(111) and Oxygen...  

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

Growth of Epitaxial Thin Pd(111) Films on Pt(111) and Oxygen-Terminated FeO(111) Surfaces . Growth of Epitaxial Thin Pd(111) Films on Pt(111) and Oxygen-Terminated FeO(111)...

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Piloting epitaxy with ellipsometry as an in-situ sensor technology  

E-Print Network [OSTI]

Epitaxial processes are deposition processes that produce crystalline films with nano-scale precision. Many compound semiconductor devices rely on epitaxy to produce high-quality crystalline films with a specified compositional ...

Warnick, Sean C. (Sean Charles)

2003-01-01T23:59:59.000Z

182

Nanoscale Phase Separation In Epitaxial Cr-Mo and Cr-V Alloy...  

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

Separation In Epitaxial Cr-Mo and Cr-V Alloy Thin Films Studied Using Atom Probe Tomography: Comparison Of Nanoscale Phase Separation In Epitaxial Cr-Mo and Cr-V Alloy Thin Films...

183

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

184

Vapour-Phase Graphene Epitaxy at Low Temperatures Lianchang Zhang1,2  

E-Print Network [OSTI]

Nano Res 1 Vapour-Phase Graphene Epitaxy at Low Temperatures Lianchang Zhang1,2 , Zhiwen Shi1 2012 ABSTRACT We report an epitaxial growth of graphene, including homo- and hetero-epitaxy on graphite yield large-area high- quality graphene with the desired number of layers over the entire substrate

Zhang, Guangyu

185

Adsorption of iso-/n-butane on an Anatase Thin Film: A Molecular...  

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

iso-n-butane on an Anatase Thin Film: A Molecular Beam Scattering and TDS Study. Adsorption of iso-n-butane on an Anatase Thin Film: A Molecular Beam Scattering and TDS Study....

186

Beam History  

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 to someone6 M. Babzien, I. Ben-Zvi, P. StudyBeam History PrintBeam History

187

Growth and Characterization of Epitaxial Oxide Thin Films  

E-Print Network [OSTI]

out during past three years has been published as follows: 1. A. Garg, J. A. Leake, and Z. H. Barber, Epitaxial Growth of WO3 Films on SrTiO3 and R- Sapphire, J. Phys.: D, Appl. Phys., 33 (9), 1048 (2000) 2. A. Garg, S. Dunn, and Z. H. Barber, Growth... of these films by 3-D Stranski-Krastanov mode. However, these films did not exhibit any ferroelectric activity. Highly epitaxial (116)-oriented films were deposited on SrTiO3 (110) substrates. These films were also very smooth with root mean square (RMS...

Garg, Ashish

188

Beams 92: Proceedings. Volume 2, Ion beams, electron beams, diagnostics  

SciTech Connect (OSTI)

This report contains papers on the following topics. Ion beam papers; electron beam papers; and these papers have been indexed separately elsewhere.

Mosher, D.; Cooperstein, G. [eds.] [Naval Research Lab., Washington, DC (United States)] [eds.; Naval Research Lab., Washington, DC (United States)

1993-12-31T23:59:59.000Z

189

Cantilever Epitaxy Process Wins R&D 100 Award  

Broader source: Energy.gov [DOE]

Sandia National Laboratories received an R&D 100 Award from R&D Magazine for development of a new process for growing gallium nitride on an etched sapphire substrate. The process, called cantilever epitaxy, promises to make brighter and more efficient green, blue, and white LEDs.

190

Self-corrected Sensors Based On Atomic Absorption Spectroscopy...  

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

corrected Sensors Based On Atomic Absorption Spectroscopy For Atom Flux Measurements In Molecular Beam Epitaxy. Self-corrected Sensors Based On Atomic Absorption Spectroscopy For...

191

Accelerator beam profile analyzer  

DOE Patents [OSTI]

A beam profile analyzer employing sector or quadrant plates each servo controlled to outline the edge of a beam.

Godel, Julius B. (Bayport, NY); Guillaume, Marcel (Grivegnee, BE); Lambrecht, Richard M. (East Quogue, NY); Withnell, Ronald (East Setauket, NY)

1976-01-01T23:59:59.000Z

192

CROSSED MOLECULAR BEAM STUDIES OF CHEMILUMINESCENT REACTIONS  

E-Print Network [OSTI]

dimensions Effusive - Quasi Effusive Source Diameter of Nozzle .015 inch (.038 em) Distance to collision zone (no skimmer or spacer) .

Kahler, Carol Cuzens

2013-01-01T23:59:59.000Z

193

Yuan T. Lee and Molecular Beam Studies  

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

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194

Yuan T. Lee's Crossed Molecular Beam Experiment  

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

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195

Dudley Herschbach: Chemical Reactions and Molecular Beams  

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

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196

Methods of preparing flexible photovoltaic devices using epitaxial liftoff, and preserving the integrity of growth substrates used in epitaxial growth  

DOE Patents [OSTI]

There is disclosed methods of making photosensitive devices, such as flexible photovoltaic (PV) devices, through the use of epitaxial liftoff. Also described herein are methods of preparing flexible PV devices comprising a structure having a growth substrate, wherein the selective etching of protective layers yields a smooth growth substrate that us suitable for reuse.

Forrest, Stephen R; Zimmerman, Jeramy; Lee, Kyusang; Shiu, Kuen-Ting

2013-02-19T23:59:59.000Z

197

Vibrational spectra of nanowires measured using laser doppler vibrometry and STM studies of epitaxial graphene : an LDRD fellowship report.  

SciTech Connect (OSTI)

A few of the many applications for nanowires are high-aspect ratio conductive atomic force microscope (AFM) cantilever tips, force and mass sensors, and high-frequency resonators. Reliable estimates for the elastic modulus of nanowires and the quality factor of their oscillations are of interest to help enable these applications. Furthermore, a real-time, non-destructive technique to measure the vibrational spectra of nanowires will help enable sensor applications based on nanowires and the use of nanowires as AFM cantilevers (rather than as tips for AFM cantilevers). Laser Doppler vibrometry is used to measure the vibration spectra of individual cantilevered nanowires, specifically multiwalled carbon nanotubes (MWNTs) and silver gallium nanoneedles. Since the entire vibration spectrum is measured with high frequency resolution (100 Hz for a 10 MHz frequency scan), the resonant frequencies and quality factors of the nanowires are accurately determined. Using Euler-Bernoulli beam theory, the elastic modulus and spring constant can be calculated from the resonance frequencies of the oscillation spectrum and the dimensions of the nanowires, which are obtained from parallel SEM studies. Because the diameters of the nanowires studied are smaller than the wavelength of the vibrometer's laser, Mie scattering is used to estimate the lower diameter limit for nanowires whose vibration can be measured in this way. The techniques developed in this thesis can be used to measure the vibrational spectra of any suspended nanowire with high frequency resolution Two different nanowires were measured - MWNTs and Ag{sub 2}Ga nanoneedles. Measurements of the thermal vibration spectra of MWNTs under ambient conditions showed that the elastic modulus, E, of plasma-enhanced chemical vapor deposition (PECVD) MWNTs is 37 {+-} 26 GPa, well within the range of E previously reported for CVD-grown MWNTs. Since the Ag{sub 2}Ga nanoneedles have a greater optical scattering efficiency than MWNTs, their vibration spectra was more extensively studied. The thermal vibration spectra of Ag{sub 2}Ga nanoneedles was measured under both ambient and low-vacuum conditions. The operational deflection shapes of the vibrating Ag{sub 2}Ga nanoneedles was also measured, allowing confirmation of the eigenmodes of vibration. The modulus of the crystalline nanoneedles was 84.3 {+-} 1.0 GPa. Gas damping is the dominate mechanism of energy loss for nanowires oscillating under ambient conditions. The measured quality factors, Q, of oscillation are in line with theoretical predictions of air damping in the free molecular gas damping regime. In the free molecular regime, Q{sub gas} is linearly proportional to the density and diameter of the nanowire and inversely proportional to the air pressure. Since the density of the Ag{sub 2}Ga nanoneedles is three times that of the MWNTs, the Ag{sub 2}Ga nanoneedles have greater Q at atmospheric pressures. Our initial measurements of Q for Ag{sub 2}Ga nanoneedles in low-vacuum (10 Torr) suggest that the intrinsic Q of these nanoneedles may be on the order of 1000. The epitaxial carbon that grows after heating (000{bar 1}) silicon carbide (SiC) to high temperatures (1450-1600) in vacuum was also studied. At these high temperatures, the surface Si atoms sublime and the remaining C atoms reconstruct to form graphene. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the quality of the few-layer graphene (FLG) surface. The XPS studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples. STM studies revealed a wide variety of nanometer-scale features that include sharp carbon-rich ridges, moire superlattices, one-dimensional line defects, and grain boundaries. By imaging these features with atomic scale resolution, considerable insight into the growth mechanisms of FLG on the carbon-face of SiC is obtained.

Biedermann, Laura Butler

2009-09-01T23:59:59.000Z

198

Beam History  

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

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199

Beam History  

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

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200

Beam Transport  

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

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Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Beam Status  

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

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202

Beam geometry selection using sequential beam addition  

SciTech Connect (OSTI)

Purpose: The selection of optimal beam geometry has been of interest since the inception of conformal radiotherapy. The authors report on sequential beam addition, a simple beam geometry selection method, for intensity modulated radiation therapy. Methods: The sequential beam addition algorithm (SBA) requires definition of an objective function (score) and a set of candidate beam geometries (pool). In the first iteration, the optimal score is determined for each beam in the pool and the beam with the best score selected. In the next iteration, the optimal score is calculated for each beam remaining in the pool combined with the beam selected in the first iteration, and the best scoring beam is selected. The process is repeated until the desired number of beams is reached. The authors selected three treatment sites, breast, lung, and brain, and determined beam arrangements for up to 11 beams from a pool comprised of 25 equiangular transverse beams. For the brain, arrangements were additionally selected from a pool of 22 noncoplanar beams. Scores were determined for geometries comprised equiangular transverse beams (EQA), as well as two tangential beams for the breast case. Results: In all cases, SBA resulted in scores superior to EQA. The breast case had the strongest dependence on beam geometry, for which only the 7-beam EQA geometry had a score better than the two tangential beams, whereas all SBA geometries with more than two beams were superior. In the lung case, EQA and SBA scores monotonically improved with increasing number of beams; however, SBA required fewer beams to achieve scores equivalent to EQA. For the brain case, SBA with a coplanar pool was equivalent to EQA, while the noncoplanar pool resulted in slightly better scores; however, the dose-volume histograms demonstrated that the differences were not clinically significant. Conclusions: For situations in which beam geometry has a significant effect on the objective function, SBA can identify arrangements equivalent to equiangular geometries but using fewer beams. Furthermore, SBA provides the value of the objective function as the number of beams is increased, allowing the planner to select the minimal beam number that achieves the clinical goals. The method is simple to implement and could readily be incorporated into an existing optimization system.

Popple, Richard A., E-mail: rpopple@uabmc.edu; Brezovich, Ivan A.; Fiveash, John B. [Department of Radiation Oncology, The University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, Alabama 35294 (United States)] [Department of Radiation Oncology, The University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, Alabama 35294 (United States)

2014-05-15T23:59:59.000Z

203

Beam-Bem interactions  

SciTech Connect (OSTI)

In high energy storage-ring colliders, the nonlinear effect arising from beam-beam interactions is a major source that leads to the emittance growth, the reduction of beam life time, and limits the collider luminosity. In this paper, two models of beam-beam interactions are introduced, which are weak-strong and strong-strong beam-beam interactions. In addition, space-charge model is introduced.

Kim, Hyung Jin; /Fermilab

2011-12-01T23:59:59.000Z

204

E-Print Network 3.0 - atlas combined beam Sample Search Results  

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

Charged-particle multiplicities ... Source: Titov, Anatoly - Laboratory of Molecular Beams, Petersburg Nuclear Physics Institute Collection: Physics 2 ATLAS ATLAS ATLAS ATLAS...

205

Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom  

DOE Patents [OSTI]

A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

Goyal, Amit

2013-07-09T23:59:59.000Z

206

Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom  

DOE Patents [OSTI]

A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

Goyal, Amit (Knoxville, TN)

2012-07-24T23:59:59.000Z

207

X-ray Microdiffraction from ?-Ti0.04Fe1.96O3 (0001) Epitaxial...  

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

(0001) Epitaxial Film Grown Over ?-Cr2O3 Buffer Layer Boundary. X-ray Microdiffraction from ?-Ti0.04Fe1.96O3 (0001) Epitaxial Film Grown Over...

208

Wave mechanics of a two-wire atomic beam splitter  

SciTech Connect (OSTI)

We consider the problem of an atomic beam propagating quantum mechanically through an atom beam splitter. Casting the problem in an adiabatic representation (in the spirit of the Born-Oppenheimer approximation in molecular physics) sheds light on explicit effects due to nonadiabatic passage of the atoms through the splitter region. We are thus able to probe the fully three-dimensional structure of the beam splitter, gathering quantitative information about mode mixing, splitting ratios, and reflection and transmission probabilities.

Bortolotti, Daniele C.E.; Bohn, John L. [JILA and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2004-03-01T23:59:59.000Z

209

Small epitaxial graphene devices for magnetosensing applications V. Panchal, K. Cedergren, R. Yakimova, A. Tzalenchuk, S. Kubatkin et al.  

E-Print Network [OSTI]

Small epitaxial graphene devices for magnetosensing applications V. Panchal, K. Cedergren, R://jap.aip.org/about/rights_and_permissions #12;Small epitaxial graphene devices for magnetosensing applications V. Panchal,1,2 K. Cedergren,3 R from 0.5 to 20.0 lm have been fabricated out of a monolayer graphene epitaxially grown on Si

Sheldon, Nathan D.

210

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

E-Print Network [OSTI]

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

Gall, Daniel

211

Exploring the Potential for High-Quality Epitaxial CdTe Solar Cells , Ana Kanevce2  

E-Print Network [OSTI]

Exploring the Potential for High-Quality Epitaxial CdTe Solar Cells Tao Song1 , Ana Kanevce2 National Renewable Energy Laboratory, Golden, CO, 80401, USA Abstract -- Traditional polycrystalline CdTeV and ~ 20%. Epitaxial CdTe with high-quality, low defect-density, and high carrier density, could yield

Sites, James R.

212

Self-assembly of silicide quantum dot arrays on stepped silicon surfaces by reactive epitaxy  

E-Print Network [OSTI]

investigated on the epitaxy and self- organization of laterally nanostructured transition metal TM silicideSelf-assembly of silicide quantum dot arrays on stepped silicon surfaces by reactive epitaxy L to be a flexible and a convenient method for the preparation of dense arrays of Co silicide quantum dots

Ortega, Enrique

213

A Comparison of Auger Electron Spectra from Stoichiometric Epitaxial TiN,,001...  

E-Print Network [OSTI]

A Comparison of Auger Electron Spectra from Stoichiometric Epitaxial TiN,,001... After ,,1... UHV spectra from epitaxial B1-NaCl-structure TiN 001 layers grown on MgO 001 1 1 by ultrahigh vacuum magnetron backscattering spectroscopy RBS . AES spectra were obtained from clean TiN 100 surfaces by cleaving 5- m

Gall, Daniel

214

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

215

Spectroscopic Measurement of Interlayer Screening in Multilayer Epitaxial Graphene Charles Divin,1  

E-Print Network [OSTI]

Spectroscopic Measurement of Interlayer Screening in Multilayer Epitaxial Graphene Dong Sun,1 2010) The substrate-induced charge-density profile in carbon face epitaxial graphene is determined screening length is determined to be one graphene layer, in good agreement with theoretical predictions. DOI

Paris-Sud XI, Université de

216

Quasiparticle Chirality in Epitaxial Graphene Probed at the Nanometer Scale I. Brihuega,1  

E-Print Network [OSTI]

Quasiparticle Chirality in Epitaxial Graphene Probed at the Nanometer Scale I. Brihuega,1 P. Mallet in Physical Review Letters 101, 206802 (2008))) Graphene exhibits unconventional two-dimensional electronic and the electronic chirality in epitaxial graphene on SiC(0001) correspond to the ones predicted for ideal graphene

Boyer, Edmond

217

Coherent Control of Ballistic Photocurrents in Multilayer Epitaxial Graphene Using Quantum Interference  

E-Print Network [OSTI]

Coherent Control of Ballistic Photocurrents in Multilayer Epitaxial Graphene Using Quantum report generation of ballistic electric currents in unbiased epitaxial graphene at 300 K via quantum. The transient currents are detected via the emitted terahertz radiation. Because of graphene's special structure

Recanati, Catherine

218

Design and fabrication of photonic crystals in epitaxial free silicon for ultrathin solar cells  

E-Print Network [OSTI]

Design and fabrication of photonic crystals in epitaxial free silicon for ultrathin solar cells photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning to obtain ultrathin patterned solar cells. Keywords: Photonic crystals; Epitaxial crystalline silicon; Thin

Paris-Sud XI, Université de

219

Optimization of the tunability of barium strontium titanate films via epitaxial stresses  

E-Print Network [OSTI]

Optimization of the tunability of barium strontium titanate films via epitaxial stresses Z.-G. Ban The tunability of epitaxial barium strontium titanate films is analyzed theoretically using a phenomenological.1063/1.1524310 I. INTRODUCTION Thin films of barium strontium titanate (BaxSr1 xTiO3, BST have long been recognized

Alpay, S. Pamir

220

HNCO in molecular clouds  

SciTech Connect (OSTI)

In a survey of 18 molecular clouds, HNCO J/sub K/-1K1..-->..J'/sub K/'-1K'1 = 5/sub 05/..-->..4/sub 05/ and 4/sub 04/..-->..3/sub 03/ emission was etected in seven clouds, and possibly in one other. Emission in these transitions originates in high-density regions (n> or approx. =10/sup 6/ cm/sup -3/). The molecule's excitation requirements allow us to derive limits to excitation temperatures an optical depths. We discuss the possibility of clumping with respect to the beam and compare our results with data from other molecular species. The HNCO emission from Sgr A is an ordder of magnitude larger than the other detected sources as is the ratio ..delta..T +- /sub A/(HNCO 5/sub 05/..-->..4/sub 04/)/..delta..T +- /sub A/(C/sup 18/O 1..-->..0). HNCO is probably a constituent of most molecular clouds.

Jackson, J.M.; Armstrong, J.T.; Barrett, A.H.

1984-05-15T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Low-temperature plasma-deposited silicon epitaxial films: Growth and properties  

SciTech Connect (OSTI)

Low-temperature (?200?°C) epitaxial growth yields precise thickness, doping, and thermal-budget control, which enables advanced-design semiconductor devices. In this paper, we use plasma-enhanced chemical vapor deposition to grow homo-epitaxial layers and study the different growth modes on crystalline silicon substrates. In particular, we determine the conditions leading to epitaxial growth in light of a model that depends only on the silane concentration in the plasma and the mean free path length of surface adatoms. For such growth, we show that the presence of a persistent defective interface layer between the crystalline silicon substrate and the epitaxial layer stems not only from the growth conditions but also from unintentional contamination of the reactor. Based on our findings, we determine the plasma conditions to grow high-quality bulk epitaxial films and propose a two-step growth process to obtain device-grade material.

Demaurex, Bénédicte, E-mail: benedicte.demaurex@epfl.ch; Bartlome, Richard; Seif, Johannes P.; Geissbühler, Jonas; Ballif, Christophe; De Wolf, Stefaan [École Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin-Film Electronics Laboratory, Maladière 71B, CH-2000 Neuchâtel (Switzerland); Alexander, Duncan T. L.; Jeangros, Quentin [École Polytechnique Fédérale de Lausanne (EPFL), Interdisciplinary Centre for Electron Microscopy (CIME), Station 12, CH-1015 Lausanne (Switzerland)

2014-08-07T23:59:59.000Z

222

Neutral beam dump with cathodic arc titanium gettering  

SciTech Connect (OSTI)

An incomplete neutral beam capture can degrade the plasma performance in neutral beam driven plasma machines. The beam dumps mitigating the shine-through beam recycling must entrap and retain large particle loads while maintaining the beam-exposed surfaces clean of the residual impurities. The cathodic arc gettering, which provides high evaporation rate coupled with a fast time response, is a powerful and versatile technique for depositing clean getter films in vacuum. A compact neutral beam dump utilizing the titanium arc gettering was developed for a field-reversed configuration plasma sustained by 1 MW, 20-40 keV neutral hydrogen beams. The titanium evaporator features a new improved design. The beam dump is capable of handling large pulsed gas loads, has a high sorption capacity, and is robust and reliable. With the beam particle flux density of 5 x 10{sup 17} H/(cm{sup 2}s) sustained for 3-10 ms, the beam recycling coefficient, defined as twice the ratio of the hydrogen molecular flux leaving the beam dump to the incident flux of high-energy neutral atoms, is {approx}0.7. The use of the beam dump allows us to significantly reduce the recycling of the shine-through neutral beam as well as to improve the vacuum conditions in the machine.

Smirnov, A.; Korepanov, S. A.; Putvinski, S. [Tri Alpha Energy Inc., Rancho Santa Margarita, California 92688 (United States); Krivenko, A. S.; Murakhtin, S. V.; Savkin, V. Ya. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation)

2011-03-15T23:59:59.000Z

223

Electronic states in epitaxial graphene fabricated on silicon carbide  

SciTech Connect (OSTI)

An analytical expression for the density of states of a graphene monolayer interacting with a silicon carbide surface (epitaxial graphene) is derived. The density of states of silicon carbide is described within the Haldane-Anderson model. It is shown that the graphene-substrate interaction results in a narrow gap of {approx}0.01-0.06 eV in the density of states of graphene. The graphene atom charge is estimated; it is shown that the charge transfer from the substrate is {approx}10{sup -3}-10{sup -2}e per graphene atom.

Davydov, S. Yu., E-mail: Sergei_Davydov@mail.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-08-15T23:59:59.000Z

224

Strong circular photogalvanic effect in ZnO epitaxial films  

SciTech Connect (OSTI)

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.

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

225

247IEEE ELECTRON DEVICE LETTERS, VOL. 13,NO. 5, MAY 1992 InP/InGaAs Heterojunction Bipolar  

E-Print Network [OSTI]

been achieved by gas-source molecular beam epitaxy (GSMBE) using carbon tetrachloride (CCI a role in carbon incorporation or acceptor activity. Chin et al. [6] used carbon tetrachloride (CC1 Transistors Grown by Gas-Source Molecular Beam Epitaxy with Carbon-Doped Base Russell C. Gee, Tsung-Pei Chin

Woodall, Jerry M.

226

Apparatus for externally controlled closed-loop feedback digital epitaxy  

DOE Patents [OSTI]

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 5 figs.

Eres, D.; Sharp, J.W.

1996-07-30T23:59:59.000Z

227

Magnetismo Molecular (Molecular Magentism)  

SciTech Connect (OSTI)

The new synthesis processes in chemistry open a new world of research, new and surprising materials never before found in nature can now be synthesized and, as a wonderful result, observed a series of physical phenomena never before imagined. Among these are many new materials the molecular magnets, the subject of this book and magnetic properties that are often reflections of the quantum behavior of these materials. Aside from the wonderful experience of exploring something new, the theoretical models that describe the behavior these magnetic materials are, in most cases, soluble analytically, which allows us to know in detail the physical mechanisms governing these materials. Still, the academic interest in parallel this subject, these materials have a number of properties that are promising to be used in technological devices, such as in computers quantum magnetic recording, magnetocaloric effect, spintronics and many other devices. This volume will journey through the world of molecular magnets, from the structural description of these materials to state of the art research.

Reis, Mario S [Universidade Federal Fluminense, Brasil; Moreira Dos Santos, Antonio F [ORNL

2010-07-01T23:59:59.000Z

228

BEAMS3D Neutral Beam Injection Model  

SciTech Connect (OSTI)

With the advent of applied 3D fi elds in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous velocity reduction, and pitch angle scattering are modeled with the ADAS atomic physics database [1]. Benchmark calculations are presented to validate the collisionless particle orbits, neutral beam injection model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields.

Lazerson, Samuel

2014-04-14T23:59:59.000Z

229

A TALE OF TWO BEAMS: GAUSSIAN BEAMS AND BESSEL BEAMS ROBERT L. NOWACK  

E-Print Network [OSTI]

A TALE OF TWO BEAMS: GAUSSIAN BEAMS AND BESSEL BEAMS ROBERT L. NOWACK Abstract. An overview is given of two types of focused beams, Gaussian beams and Bessel beams. First I describe some of the basic properties of Gaussian beams in homogeneous media which stay collimated over a certain distance range after

Nowack, Robert L.

230

Beam Dynamics for ARIA  

E-Print Network [OSTI]

Beam dynamics issues are assessed for a new linear induction electron accelerator being designed for flash radiography of large explosively driven hydrodynamic experiments. Special attention is paid to equilibrium beam transport, possible emittance growth, and beam stability. It is concluded that a radiographic quality beam will be produced possible if engineering standards and construction details are equivalent to those on the present radiography accelerators at Los Alamos.

Ekdahl, Carl

2015-01-01T23:59:59.000Z

231

ATA beam director experiment  

SciTech Connect (OSTI)

This report describes beam director elements for an experiment at the Advanced Test Accelerator. The elements described include a vernier magnet for beam aiming, an achromat magnet, and an isolation system for the beam interface. These components are built at small scale for concept testing. (JDH)

Lee, E.P.; Younger, F.C.; Cruz, G.E.; Nolting, E.

1986-06-23T23:59:59.000Z

232

Applied Materials Develops an Advanced Epitaxial Growth System to Bring Down LED Costs  

Broader source: Energy.gov [DOE]

With the help of DOE funding, Applied Materials has developed an advanced epitaxial growth system for gallium nitride (GaN) LED devices that decreases operating costs, increases internal quantum efficiency, and improves binning yields.

233

Dielectric tunability of ,,110... oriented barium strontium titanate epitaxial films on ,,100... orthorhombic substrates  

E-Print Network [OSTI]

Dielectric tunability of ,,110... oriented barium strontium titanate epitaxial films on ,,100 materials such as barium strontium titanate Ba1-xSrxTiO3 BST have emerged as leading candidates

Alpay, S. Pamir

234

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

E-Print Network [OSTI]

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 ...

Bi, Lei

235

E-Print Network 3.0 - atomic layer epitaxy Sample Search Results  

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

the surface of the grown MnSi layer. On the atomic scale, scanning... Epitaxial growth of silicide layers on Si substrates has attracted much attention due to their...

236

Enhanced Magnetism in Epitaxial SrRuO3 Thin Films  

E-Print Network [OSTI]

Enhanced Magnetism in Epitaxial SrRuO 3 A. J. Grutter, 1, 2and their e?ects on magnetism. In this paper we demonstrateXMCD con?rmed that the magnetism originates from the Ru 4+

Grutter, A.J.

2010-01-01T23:59:59.000Z

237

Epitaxial Ge/Il-V Heterostructures : MOCVD growth, characterization, and applications  

E-Print Network [OSTI]

Epitaxial Ge thin films are being investigated for many important roles in next generation microelectronics. Metal-oxide-semiconductor field effect transistors (MOSFETs) utilizing Ge channels have demonstrated dramatic ...

Bai, Yu, Ph.D. Massachusetts Institute of Technology

2011-01-01T23:59:59.000Z

238

Electrocaloric properties of epitaxial strontium titanate films I. B. Misirlioglu,2  

E-Print Network [OSTI]

Electrocaloric properties of epitaxial strontium titanate films J. Zhang,1 I. B. Misirlioglu,2 S. P; published online 1 June 2012) The electrocaloric (EC) response of strontium titanate thin films is computed

Alpay, S. Pamir

239

Introduction of Artificial Pinning Center into PLD-YBCO Coated Conductor on IBAD and Self-Epitaxial CeO2 Buffered Metal Substrate  

SciTech Connect (OSTI)

In order to fabricate YBa2Cu3O7-x (YBCO) coated conductors with high critical current density Jc in magnetic fields, we fabricated YBCO coated conductors with artificial pinning centers by the pulsed laser deposition (PLD) method on a self epitaxial PLD-CeO2 layer and ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO) buffered Hastelloy tape. Artificial pinning centers were introduced by the PLD deposition using the yttria-stabilized zirconia (YSZ) oxide target (nano-dot method) and YBCO target including YSZ particles (mixed target method). In the experiments using YSZ oxide target, YSZ nano-dots were observed. They were approximately 15 nm in height and 10 nm to 70 nm in diameter. We found that the density of nano-dots was controlled by the number of laser pulses. These samples exhibited higher Jc than YBCO films in magnetic fields. Furthermore, a similar improvement of Jc was observed in the experiments using YBCO target including YSZ particles. TEM observation revealed that columnar nano-structure made of BaZrO3 was formed during YBCO deposition and it was effective for pinning. We call this new epitaxial nano-structure 'bamboo structure' from its anisotropic growth and morphology.

Kobayashi, H.; Yamada, Y.; Ishida, S.; Takahashi, K.; Konishi, M.; Ibi, A.; Miyata, S. [Superconductivity Research Laboratory, ISTEC, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, 456-8587 (Japan); Kato, T.; Hirayama, T. [Materials R and D Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587 (Japan); Shiohara, Y. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

2006-03-31T23:59:59.000Z

240

Neutral beam monitoring  

DOE Patents [OSTI]

Method and apparatus for monitoring characteristics of a high energy neutral beam. A neutral beam is generated by passing accelerated ions through a walled cell containing a low energy neutral gas, such that charge exchange neutralizes the high energy ion beam. The neutral beam is monitored by detecting the current flowing through the cell wall produced by low energy ions which drift to the wall after the charge exchange. By segmenting the wall into radial and longitudinal segments various beam conditions are further identified.

Fink, Joel H. (Livermore, CA)

1981-08-18T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Site-controlled fabrication of Ga nanodroplets by focused ion beam  

SciTech Connect (OSTI)

Ga droplets are created by focused ion beam irradiation of GaAs surface. We report that ordered Ga droplets can be formed on the GaAs surface without any implantation damage. The droplets are characterized with bigger sizes than those droplets formed on damaged area. These aligned Ga droplets are formed via the migration of Ga atoms from ion irradiation area to the edge of undamaged GaAs surface and further nucleation into droplets. The morphological evolution and size distribution of these nanodroplets are investigated systematically with different beam irradiation time and incident angles. Based on this method, well positioned Ga nanodroplets, such as chains, are achieved by using focus ion beam patterning. The controllable assembly of droplets on undamaged semiconductor surface can be used to fabricate templates, to fabricate quantum structures and quantum devices by droplet epitaxy technique.

Xu, Xingliang; Wang, Zhiming M., E-mail: zhmwang@gmail.com [State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China); Wu, Jiang; Li, Handong; Zhou, Zhihua [State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Wang, Xiaodong [Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

2014-03-31T23:59:59.000Z

242

LBNL-46223, CBP Note 350 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS IN THE LHC  

E-Print Network [OSTI]

LBNL-46223, CBP Note 350 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS IN THE LHC M. A. Furman, W. C. Turner, Center for Beam Physics, LBNL, Berkeley, CA 94720, USA Abstract We present beam-beam simulation of simulations: (a) to as- sess undesirable effects from LBNL's luminosity monitor- ing scheme for the LHC [2

Furman, Miguel

243

LBNL-45363, CBP Note 333 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS  

E-Print Network [OSTI]

LBNL-45363, CBP Note 333 BEAM-BEAM SIMULATIONS FOR SEPARATED BEAMS Miguel A. Furman, Center for Beam Physics, LBNL, Berkeley, CA 94720 Abstract We present beam-beam simulation results from a strong undesirable effects from LBNL's sweeping lumi- nosity monitoring scheme for the LHC [1], and (b) to assess

Furman, Miguel

244

Pulsed-electron-beam melting of Fe  

SciTech Connect (OSTI)

Pulsed (50 nsec) electron beams with deposited energies of 1.1 to 2.3 J/cm/sup 2/ have been used to rapidly melt a surface layer of Fe. Calculations show that this range of energies produces melt depths from 0.4 to 1.2 ..mu..m and melt times of 100 to 500 nsec. Optical microscopy and SEM of pulse treated polycrystalline foils show slip traces, as well as a general smoothing of surface features which shows that melting has occurred. TEM shows that the resolidified material is bcc, and that the material within a grain is epitaxial with the substrate. TEM also shows slip traces along (110) planes, as well as a high density of dislocations, both extended and loop. At the highest energy, subgrain boundaries are observed. Some samples were implanted with 1 x 10/sup 16/ Sn/cm/sup 2/ at 150 keV. After pulse treatment, the Sn depth profile was observed to have broadened, consistent with liquid phase diffusion. The Sn had the unexpected effect of suppressing slip at the sample surface.

Knapp, J.A.; Follstaedt, D.M.

1981-01-01T23:59:59.000Z

245

Broad beam ion implanter  

DOE Patents [OSTI]

An ion implantation device for creating a large diameter, homogeneous, ion beam is described, as well as a method for creating same, wherein the device is characterized by extraction of a diverging ion beam and its conversion by ion beam optics to an essentially parallel ion beam. The device comprises a plasma or ion source, an anode and exit aperture, an extraction electrode, a divergence-limiting electrode and an acceleration electrode, as well as the means for connecting a voltage supply to the electrodes.

Leung, Ka-Ngo (Hercules, CA)

1996-01-01T23:59:59.000Z

246

Small beam nonparaxiality arrests selffocusing of optical beams Gadi Fibich  

E-Print Network [OSTI]

Small beam nonparaxiality arrests self­focusing of optical beams Gadi Fibich Department­focusing in the presence of small beam nonparaxiality is derived. Analysis of this equation shows that nonparaxiality remains small as the beam propa­ gates. Nevertheless, nonparaxiality arrests self­focusing when the beam

Soatto, Stefano

247

Structure and epitaxy studies of cobalt silicide/silicon heterostructures  

SciTech Connect (OSTI)

When considering transition metal silicides for use in integrated circuit technology, CoSi{sub 2} stands out as a silicide possessing an excellent combination of properties. However, the detrimental effects of CoSi{sub 2} pinhole formation seriously restricts the applicability of this silicide system. This study examines the structure/processing/property relationship of thin film cobalt silicide/silicon heterostructures grown on Si(111). The two primary objectives were: (1) identify the basic mechanisms associated with pinhole formation and cobalt silicide thin film growth; and (2) characterization of cobalt silicides grown by Si{sub a}/Co/Si{sub c} multilayer deposition and reaction and the effect this deposition technique has on the microstructure of cobalt silicide thin films. Interfacial pinhole formation was identified at the CoSi/Si interface and involves several active mechanisms. Epitaxial pinhole free CoSi{sub 2} films were grown by single-step annealing Si{sub a}/Co/Si{sub c} multilayer structures. Two step annealing Si{sub a}/Co/Si{sub c} multilayer thin films results in polycrystalline CoSi{sub 2}.

Zaluzec, M.J.

1991-01-01T23:59:59.000Z

248

Maskless lateral epitaxial overgrowth of GaN on sapphire  

SciTech Connect (OSTI)

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.

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

249

Controlled epitaxial graphene growth within removable amorphous carbon corrals  

SciTech Connect (OSTI)

We address the question of control of the silicon carbide (SiC) steps and terraces under epitaxial graphene on SiC and demonstrate amorphous carbon (aC) corrals as an ideal method to pin SiC surface steps. aC is compatible with graphene growth, structurally stable at high temperatures, and can be removed after graphene growth. For this, aC is first evaporated and patterned on SiC, then annealed in the graphene growth furnace. There at temperatures above 1200?°C, mobile SiC steps accumulate at the aC corral that provide effective step flow barriers. Aligned step free regions are thereby formed for subsequent graphene growth at temperatures above 1330?°C. Atomic force microscopy imaging supports the formation of step-free terraces on SiC with the step morphology aligned to the aC corrals. Raman spectroscopy indicates the presence of good graphene sheets on the step-free terraces.

Palmer, James; Hu, Yike; Hankinson, John; Guo, Zelei; Heer, Walt A. de [School of Physics, Georgia Institute of Technology, 837 State St. NW, Atlanta, Georgia 30332 (United States); Kunc, Jan [School of Physics, Georgia Institute of Technology, 837 State St. NW, Atlanta, Georgia 30332 (United States); Faculty of Mathematics and Physics, Institute of Physics, 12116 Prague (Czech Republic); Berger, Claire [School of Physics, Georgia Institute of Technology, 837 State St. NW, Atlanta, Georgia 30332 (United States); Université Grenoble Alpes/CNRS—Institut Néel, BP166, Grenoble Cedex 9 38042 (France)

2014-07-14T23:59:59.000Z

250

Laser beam generating apparatus  

DOE Patents [OSTI]

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 11 figures.

Warner, B.E.; Duncan, D.B.

1993-12-28T23:59:59.000Z

251

Laser beam generating apparatus  

DOE Patents [OSTI]

Laser beam generating apparatus including a septum segment disposed longitudinally within the tubular structure of the apparatus is described. The septum provides for radiatively dissipating heat buildup within the tubular structure and for generating relatively uniform laser beam pulses so as to minimize or eliminate radial pulse delays (the chevron effect). 7 figures.

Warner, B.E.; Duncan, D.B.

1994-02-15T23:59:59.000Z

252

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

E-Print Network [OSTI]

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

Gall, Daniel

253

Electro-oxidized Epitaxial Graphene Channel Field-Effect Transistors with Single-Walled Carbon Nanotube Thin Film  

E-Print Network [OSTI]

Electro-oxidized Epitaxial Graphene Channel Field-Effect Transistors with Single-Walled Carbon on the electronic properties of epitaxial graphene (EG) grown on silicon carbide substrates; we demonstrate the introduction of the reaction medium into the graphene galleries during electro-oxidation. The device

254

Neutrino Factories and Beta Beams  

E-Print Network [OSTI]

a Neutrino Factory Based on Muon Beams,” Proc. 2001 ParticleMD. [19] C. Rubbia et al. , “Beam Cooling with Ionisationthe required unstable ion beams has recently been suggested

Zisman, Michael S.

2006-01-01T23:59:59.000Z

255

Method for rapid, controllable growth and thickness, of epitaxial silicon films  

DOE Patents [OSTI]

A method of producing epitaxial silicon films on a c-Si wafer substrate using hot wire chemical vapor deposition by controlling the rate of silicon deposition in a temperature range that spans the transition from a monohydride to a hydrogen free silicon surface in a vacuum, to obtain phase-pure epitaxial silicon film of increased thickness is disclosed. The method includes placing a c-Si substrate in a HWCVD reactor chamber. The method also includes supplying a gas containing silicon at a sufficient rate into the reaction chamber to interact with the substrate to deposit a layer containing silicon thereon at a predefined growth rate to obtain phase-pure epitaxial silicon film of increased thickness.

Wang, Qi (Littleton, CO); Stradins, Paul (Golden, CO); Teplin, Charles (Boulder, CO); Branz, Howard M. (Boulder, CO)

2009-10-13T23:59:59.000Z

256

Simulations of beam-beam and beam-wire interactions in RHIC  

SciTech Connect (OSTI)

The beam-beam interaction is one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and strong localized long-range beam-beam effects are experimentally investigated in the RHIC collider. Tune shift, beam transfer function, and beam loss rate are measured in dedicated experiments. In this paper, they report on simulations to study the effect of beam-wire interactions based on diffusive apertures, beam loss rates, and beam transfer function using a parallelized weak-strong beam simulation code (BBSIMC). The simulation results are compared with measurements performed in RHIC during 2007 and 2008.

Kim, Hyung J.; Sen, Tanaji; /Fermilab; Abreu, Natalia P.; Fischer, Wolfram; /Brookhaven

2009-02-01T23:59:59.000Z

257

Beta-beams  

E-Print Network [OSTI]

Beta-beams is a new concept for the production of intense and pure neutrino beams. It is at the basis of a proposed neutrino facility, whose main goal is to explore the possible existence of CP violation in the lepton sector. Here we briefly review the original scenario and the low energy beta-beam. This option would offer a unique opportunity to perform neutrino interaction studies of interest for particle physics, astrophysics and nuclear physics. Other proposed scenarios for the search of CP violation are mentioned.

C. Volpe

2008-02-22T23:59:59.000Z

258

Process for forming epitaxial perovskite thin film layers using halide precursors  

DOE Patents [OSTI]

A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

Clem, Paul G. (Albuquerque, NM); Rodriguez, Mark A. (Albuquerque, NM); Voigt, James A. (Corrales, NM); Ashley, Carol S. (Albuquerque, NM)

2001-01-01T23:59:59.000Z

259

Surface photovoltage method for the quality control of silicon epitaxial layers on sapphire  

SciTech Connect (OSTI)

The surface photovoltage method is used to study “silicon-on-sapphire” epitaxial layers with a thickness of 0.3–0.6 ?m, which are used to fabricate p-channel MOS (metal—oxide-semiconductor) transistors with improved radiation hardness. It is shown that the manner in which the photoconductivity of the epitaxial layer decays after the end of a light pulse generated by a light-emitting diode (wavelength ?400 nm) strongly depends on the density of structural defects in the bulk of the structure. This enables control over how a “silicon-on-sapphire” structure is formed to provide the manufacturing of MOS structures with optimal operating characteristics.

Yaremchuk, A. F.; Starkov, A. V.; Zaikin, A. V., E-mail: lynch0000@gmail.com [National Rsearch University MIET (Russian Federation); Alekseev, A. V. [ZAO “Telekom-STV” (Russian Federation); Sokolov, E. M. [ZAO “Epiel” (Russian Federation)

2014-12-15T23:59:59.000Z

260

Neutral particle beam intensity controller  

DOE Patents [OSTI]

The neutral beam intensity controller is based on selected magnetic defocusing of the ion beam prior to neutralization. The defocused portion of the beam is dumped onto a beam dump disposed perpendicular to the beam axis. Selective defocusing is accomplished by means of a magnetic field generator disposed about the neutralizer so that the field is transverse to the beam axis. The magnetic field intensity is varied to provide the selected partial beam defocusing of the ions prior to neutralization. The desired focused neutral beam portion passes along the beam path through a defining aperture in the beam dump, thereby controlling the desired fraction of neutral particles transmitted to a utilization device without altering the kinetic energy level of the desired neutral particle fraction. By proper selection of the magnetic field intensity, virtually zero through 100% intensity control of the neutral beam is achieved.

Dagenhart, W.K.

1984-05-29T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Pulsed ion beam source  

DOE Patents [OSTI]

An improved pulsed ion beam source having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center.

Greenly, John B. (Lansing, NY)

1997-01-01T23:59:59.000Z

262

Negligible Sample Heating from Synchrotron Infrared Beam Michael C. Martina  

E-Print Network [OSTI]

Negligible Sample Heating from Synchrotron Infrared Beam Michael C. Martina , Nelly M. Tsvetkovab of Molecular and Cellular Biology, University of California at Davis, USA Infrared (IR) spectroscopy is one can now obtain diffraction-limited spot sizes with high signal intensity in an infrared microscope

263

Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development  

SciTech Connect (OSTI)

The Los Alamos Neutron Science Center (LANSCE) is replacing Wire Scanner (WS) beam profile measurement systems. Three beam development tests have taken place to test the new wire scanners under beam conditions. These beam development tests have integrated the WS actuator, cable plant, electronics processors and associated software and have used H{sup -} beams of different beam energy and current conditions. In addition, the WS measurement-system beam tests verified actuator control systems for minimum profile bin repeatability and speed, checked for actuator backlash and positional stability, tested the replacement of simple broadband potentiometers with narrow band resolvers, and tested resolver use with National Instruments Compact Reconfigurable Input and Output (cRIO) Virtual Instrumentation. These beam tests also have verified how trans-impedance amplifiers react with various types of beam line background noise and how noise currents were not generated. This paper will describe these beam development tests and show some resulting data.

Gilpatrick, John D. [Los Alamos National Laboratory; Batygin, Yuri K. [Los Alamos National Laboratory; Gonzales, Fermin [Los Alamos National Laboratory; Gruchalla, Michael E. [Los Alamos National Laboratory; Kutac, Vincent G. [Los Alamos National Laboratory; Martinez, Derwin [Los Alamos National Laboratory; Sedillo, James Daniel [Los Alamos National Laboratory; Pillai, Chandra [Los Alamos National Laboratory; Rodriguez Esparza, Sergio [Los Alamos National Laboratory; Smith, Brian G. [Los Alamos National Laboratory

2012-05-15T23:59:59.000Z

264

Photon beam position monitor  

DOE Patents [OSTI]

A photon beam position monitor is disclosed for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade ''shadowing''. Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation. 18 figs.

Kuzay, T.M.; Shu, D.

1995-02-07T23:59:59.000Z

265

Wafer Bonding and Epitaxial Transfer of GaSb-based Epitaxy to GaAs for Monolithic Interconnection of Thermophotovoltaic Devices  

SciTech Connect (OSTI)

GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating GaAs handle wafers with SiO{sub x}/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovoltaic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO{sub x}/TiAu provides not only electrical isolation, but also high reflectivity and is used as an internal back-surface reflector. Characterization of wafer-bonded epitaxy by high-resolution x-ray diffraction and time-decay photoluminescence indicates minimal residual stress and enhancement in optical quality. 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A 10-junction device exhibited linear voltage building with an open-circuit voltage of 1.8 V.

C.A. Wang; D.A. Shiau; P.G. Murphy; P.W. O'brien; R.K. Huang; M.K. Connors; A.C. Anderson; D. Donetsky; S. Anikeev; G. Belenky; D.M. Depoy; G. Nichols

2003-06-16T23:59:59.000Z

266

Single element laser beam shaper  

DOE Patents [OSTI]

A single lens laser beam shaper for converting laser beams from any spatial profile to a flat-top or uniform spatial profile. The laser beam shaper includes a lens having two aspheric surfaces. The beam shaper significantly simplifies the overall structure in comparison with conventional 2-element systems and therefore provides great ease in alignment and reduction of cost.

Zhang, Shukui (Yorktown, VA); Michelle D. Shinn (Newport News, VA)

2005-09-13T23:59:59.000Z

267

Light beam frequency comb generator  

DOE Patents [OSTI]

A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics.

Priatko, Gordon J. (Cupertino, CA); Kaskey, Jeffrey A. (Livermore, CA)

1992-01-01T23:59:59.000Z

268

Transition from Epitaxial to Nonepitaxial Ordered Monolayers in Pyrolyzed 8CB Studied by STM  

E-Print Network [OSTI]

-ordered, epitaxial monolayers on graphite. We have found that adding two oxidation products (to mimic the effects of air oxidation or pyrolysis) changes the surface ordering of 8CB, causing it to form cell dimensions of one of the oxidation products, both pure oxidation products were found to form

Patrick, David L.

269

Growth of epitaxial tungsten oxide nanorods M.Gillet*, R. Delamare, E. Gillet  

E-Print Network [OSTI]

the grain boundaries. So the synthesis of monocristalline tungsten oxide as nanowires or nanorods amorphous tungsten oxide nanoparticles. Y.B. Li et al [18] have synthesized WO3 nanobelts and nanorods via1 Growth of epitaxial tungsten oxide nanorods M.Gillet*, R. Delamare, E. Gillet UNIVERSITE D

Paris-Sud XI, Université de

270

Improved One-dimensional Analysis of CMOS Photodiode Including Epitaxial-Substrate Junction  

E-Print Network [OSTI]

1 Improved One-dimensional Analysis of CMOS Photodiode Including Epitaxial-Substrate Junction J. S-dimensional analysis of CMOS photodiode has been derived in which the effect of the substrate, which forms a high-empirical expression exhibits a good agreement with the measured spectral response of n+ pepi photodiodes fabricated

Hornsey, Richard

271

Surface Science 415 (1998) 363375 Epitaxial growth of Cu onto Si(111) surfaces at low temperature  

E-Print Network [OSTI]

to 10 and 3 monolayers (ML), respectively. This change is attributed to the silicide formation on the Si(111)-(7�7) surface at 160 K is proposed. The changes in periodicity are due to the silicide rights reserved. Keywords: Copper; Epitaxy; Electron­solid diffraction; Metallic films; Metal

Hasegawa, Shuji

272

Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon  

E-Print Network [OSTI]

Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon H. Wang, A 2001) We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate

Wei, Qiuming

273

GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies  

E-Print Network [OSTI]

LETTERS GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies-frequency electronics3,4 and most forms of optoelectronics5,6 . However, growing large, high quality wafers implementation. More tractable, yet still difficult, problems appear in advanced electronics and optoelectronics

Rogers, John A.

274

Epitaxy of Nanocrystalline Silicon Carbide on Si(111) at Room Temperature  

E-Print Network [OSTI]

Epitaxy of Nanocrystalline Silicon Carbide on Si(111) at Room Temperature Roberto Verucchi carbide (SiC) has unique chemical, physical, and mechanical properties. A factor strongly limiting Si or plastics that cannot withstand high temperatures. Silicon carbide (SiC) has unique properties that make

Alfè, Dario

275

Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth  

DOE Patents [OSTI]

Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

Fan, John C. C. (Chestnut Hill, MA); Tsaur, Bor-Yeu (Arlington, MA); Gale, Ronald P. (Bedford, MA); Davis, Frances M. (Framingham, MA)

1986-12-30T23:59:59.000Z

276

Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth  

DOE Patents [OSTI]

Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

Fan, John C. C. (Chestnut Hill, MA); Tsaur, Bor-Yeu (Arlington, MA); Gale, Ronald P. (Bedford, MA); Davis, Frances M. (Framingham, MA)

1992-02-25T23:59:59.000Z

277

Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers  

DOE Patents [OSTI]

This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

Chang, Y. Austin (Middleton, WI); Yang, Jianhua Joshua (Madison, WI)

2008-11-11T23:59:59.000Z

278

Chlorine Etching For In-Situ Low-Temperature Silicon Surface Cleaning For Epitaxy Applications  

E-Print Network [OSTI]

. of Electrical Engineering, Princeton University, Princeton, NJ, 08544, USA Chlorine in a nitrogen ambient-situ in epitaxial reactors is typically done using hydrogen chloride (HCl) in a hydrogen ambient. However, the etch instead of hydrogen chloride to etch silicon in a hydrogen ambient (4). It was observed that the etch rate

279

Half integer quantum Hall effect in high mobility single layer epitaxial graphene  

E-Print Network [OSTI]

Half integer quantum Hall effect in high mobility single layer epitaxial graphene Xiaosong Wu,1 of is demonstrated here on a single graphene layer grown on the C-face of 4H silicon carbide. The mobility is 20 000. This is comparable to the best exfoliated graphene flakes on SiO2 and an order of magnitude larger than Si

280

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

E-Print Network [OSTI]

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

Boyer, Edmond

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

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

SciTech Connect (OSTI)

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.

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

282

Self-assembly of triangular quantum dots on (111)A substrates by droplet epitaxy  

SciTech Connect (OSTI)

We report the self-assembly of triangular GaAs quantum dots (QDs) on (111)A substrates using droplet epitaxy. Shape transition from hexagonal to triangular QDs is observed with increasing crystallizing temperature. The mechanism of the morphological change is discussed in terms of different growth rates of step edges on a (111)A substrate.

Jo, M.; Mano, T.; Abbarchi, M.; Kuroda, T. [Advanced Photonics Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakoda, K. [Advanced Photonics Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan and Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

2014-05-15T23:59:59.000Z

283

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice S. Rusponi,1  

E-Print Network [OSTI]

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice S. Rusponi affects the spectral-weight distribution of the carbon bands as well as the electronic gaps between generation electronic devices [2]. Freestanding graphene is a zero-gap semiconductor. Because most electronic

Brune, Harald

284

Determination of substrate pinning in epitaxial and supported graphene layers via Raman scattering  

E-Print Network [OSTI]

The temperature-induced shift of the Raman G line in epitaxial graphene on SiC and Ni surfaces, as well as in graphene supported on SiO[subscript 2], is investigated with Raman spectroscopy. The thermal shift rate of ...

Ferralis, Nicola

285

Perpendicular anisotropy of ultrathin epitaxial cobalt films on graphene Chi Vo-Van,1  

E-Print Network [OSTI]

of magnetism. While graphite exfoliation provides flakes of graphene of lateral size limited to at most 100 µm in applications, e.g. concerning electronic transport or photovoltaics. So far devices have relied on electrodes-metal ferromagnetic systems. In this Letter we report the optimization of the epitaxial growth of Au-capped Co

Paris-Sud XI, Université de

286

X-ray radiation effects in multilayer epitaxial graphene Jeremy Hicks1  

E-Print Network [OSTI]

1 X-ray radiation effects in multilayer epitaxial graphene Jeremy Hicks1 , Rajan Arora2 , Eleazar and after exposure to a total ionizing dose (TID) of 12 Mrad(SiO2) using a 10 keV X-ray source. While we are mostly unaffected by radiation exposure. Combined with X-ray photoelectron spectroscopy (XPS) data

287

ICFA Beam Dynamics Newsletter  

SciTech Connect (OSTI)

The Collider-Accelerator Department at Brookhaven National Laboratory is building a high-brightness 500 mA capable Energy Recovery Linac (ERL) as one of its main R&D thrusts towards eRHIC, the polarized electron - hadron collider as an upgrade of the operating RHIC facility. The ERL is in final assembly stages, with injection commisioning starting in October 2012. The objective of this ERL is to serve as a platform for R&D into high current ERL, in particular issues of halo generation and control, Higher-Order Mode (HOM) issues, coherent emissions for the beam and high-brightness, high-power beam generation and preservation. The R&D ERL features a superconducting laser-photocathode RF gun with a high quantum efficiency photoccathode served with a load-lock cathode delivery system, a highly damped 5-cell accelerating cavity, a highly flexible single-pass loop and a comprehensive system of beam instrumentation. In this ICFA Beam Dynamics Newsletter article we will describe the ERL in a degree of detail that is not usually found in regular publications. We will discuss the various systems of the ERL, following the electrons from the photocathode to the beam dump, cover the control system, machine protection etc and summarize with the status of the ERL systems.

Ben-Zvi I.; Kuczewski A.; Altinbas, Z.; Beavis, D.; Belomestnykh,; Dai, J. et al

2012-07-01T23:59:59.000Z

288

Beam Profile Monitor With Accurate Horizontal And Vertical Beam Profiles  

DOE Patents [OSTI]

A widely used scanner device that rotates a single helically shaped wire probe in and out of a particle beam at different beamline positions to give a pair of mutually perpendicular beam profiles is modified by the addition of a second wire probe. As a result, a pair of mutually perpendicular beam profiles is obtained at a first beamline position, and a second pair of mutually perpendicular beam profiles is obtained at a second beamline position. The simple modification not only provides more accurate beam profiles, but also provides a measurement of the beam divergence and quality in a single compact device.

Havener, Charles C [Knoxville, TN; Al-Rejoub, Riad [Oak Ridge, TN

2005-12-26T23:59:59.000Z

289

Grazing incidence beam expander  

SciTech Connect (OSTI)

A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

1985-01-01T23:59:59.000Z

290

Colliding neutrino beams  

E-Print Network [OSTI]

From several neutrino oscillation experiments, we understand now that neutrinos have mass. However, we really don't know what mechanism is responsible for producing this neutrino mass. Current or planned neutrino experiments utilize neutrino beams and long-baseline detectors to explore flavor mixing but do not address the question of the origin of neutrino mass. In order to answer that question, neutrino interactions need to be explored at much higher energies. This paper outlines a program to explore neutrinos and their interactions with various particles through a series of experiments involving colliding neutrino beams.

Reinhard Schwienhorst

2007-11-08T23:59:59.000Z

291

Beam Stability Complaint Form  

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 to someone6 M. Babzien, I. Ben-Zvi, P. StudyBeam History PrintBeam

292

Non-Paraxial Accelerating Beams  

E-Print Network [OSTI]

We present the spatially accelerating solutions of the Maxwell equations. Such non-paraxial beams accelerate in a circular trajectory, thus generalizing the concept of Airy beams. For both TE and TM polarizations, the beams exhibit shape-preserving bending with sub-wavelength features, and the Poynting vector of the main lobe displays a turn of more than 90 degrees. We show that these accelerating beams are self-healing, analyze their properties, and compare to the paraxial Airy beams. Finally, we present the new family of periodic accelerating beams which can be constructed from our solutions.

Ido Kaminer; Rivka Bekenstein; Jonathan Nemirovsky; Mordechai Segev

2012-02-03T23:59:59.000Z

293

Electron beam dynamics for the ISIS bremsstrahlung beam generation system  

E-Print Network [OSTI]

An electron beam transport system was designed for use in the Bremsstrahlung Beam Generation System of the Integrated Stand-off Inspection System (ISIS). The purpose of this electron transport system was to provide for ...

Block, Robert E. (Robert Edward)

2011-01-01T23:59:59.000Z

294

Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior  

E-Print Network [OSTI]

1 Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation graphene samples performed in a wide spectral range, namely from the near signatures of the highly doped graphene layers at the interface to Si

Boyer, Edmond

295

Adatom density kinetic Monte Carlo: A hybrid approach to perform epitaxial growth simulations L. Mandreoli* and J. Neugebauer  

E-Print Network [OSTI]

.35.Fx I. INTRODUCTION Epitaxial growth is a key technique in fabricating semiconductor-based electronic deficiencies when applied to the above-mentioned topics: The first two approaches i and ii do not really bridge

296

Contribution (Poster) TNT2008 September 01-05, 2008 Oviedo-Spain  

E-Print Network [OSTI]

Contribution (Poster) TNT2008 September 01-05, 2008 Oviedo-Spain LIGHT EMITTING DIODES ON SILICON) or quantum well (QW) light-emitting diodes by molecular beam epitaxy to obtain direct band gaps on GaP grown

Boyer, Edmond

297

Condensed Matter Physics, 2011, Vol. 14, No 2, 23602: 1--11 DOI: 10.5488/CMP.14.23602  

E-Print Network [OSTI]

the mentioned parameters of the model according to the physical conditions related to concrete materials. One deposition and molecular beam epitaxy have been used in developing the Si nanomaterials (porous Si, Si

298

Growth of Cr-doped TiO Films in the Rutile and Anatase Structures...  

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

of Cr-doped TiO Films in the Rutile and Anatase Structures by Oxygen Plasma Assisted Molecular Beam Epitaxy . Growth of Cr-doped TiO Films in the Rutile and Anatase Structures by...

299

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...

300

Graduate Program Micro-and Nanostructures  

E-Print Network [OSTI]

research area. Technologies that require clean rooms, such as molecular beam epitaxy, lithography, etching but young city Paderborn in the center of Germany, it provides an excellent environment for studies

Hellebrand, Sybille

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Ion-beam technologies  

SciTech Connect (OSTI)

This compilation of figures and diagrams reviews processes for depositing diamond/diamond-like carbon films. Processes addressed are chemical vapor deposition (HFCVD, PACVD, etc.), plasma vapor deposition (plasma sputtering, ion beam sputtering, evaporation, etc.), low-energy ion implantation, and hybrid processes (biased sputtering, IBAD, biased HFCVD, etc.). The tribological performance of coatings produced by different means is discussed.

Fenske, G.R. [Argonne National Lab., IL (United States)

1993-01-01T23:59:59.000Z

302

Pulsed ion beam source  

DOE Patents [OSTI]

An improved pulsed ion beam source is disclosed having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center. 12 figs.

Greenly, J.B.

1997-08-12T23:59:59.000Z

303

Colliding beams of light  

E-Print Network [OSTI]

The stationary gravitational field of two identical counter-moving beams of pure radiation is found in full generality. The solution depends on an arbitrary function and a parameter which sets the scale of the energy density. Some of its properties are studied. Previous particular solutions are derived as subcases.

B. V. Ivanov

2002-12-28T23:59:59.000Z

304

Beam current sensor  

DOE Patents [OSTI]

A current sensor for measuring the dc component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivities in the nano-ampere range.

Kuchnir, M.; Mills, F.E.

1984-09-28T23:59:59.000Z

305

Beam current sensor  

DOE Patents [OSTI]

A current sensor for measuring the DC component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivites in the nano-ampere range.

Kuchnir, Moyses (Elmhurst, IL); Mills, Frederick E. (Elburn, IL)

1987-01-01T23:59:59.000Z

306

Neutral particle beam intensity controller  

DOE Patents [OSTI]

A neutral beam intensity controller is provided for a neutral beam generator in which a neutral beam is established by accelerating ions from an ion source into a gas neutralizer. An amplitude modulated, rotating magnetic field is applied to the accelerated ion beam in the gas neutralizer to defocus the resultant neutral beam in a controlled manner to achieve intensity control of the neutral beam along the beam axis at constant beam energy. The rotating magnetic field alters the orbits of ions in the gas neutralizer before they are neutralized, thereby controlling the fraction of neutral particles transmitted out of the neutralizer along the central beam axis to a fusion device or the like. The altered path or defocused neutral particles are sprayed onto an actively cooled beam dump disposed perpendicular to the neutral beam axis and having a central open for passage of the focused beam at the central axis of the beamline. Virtually zero therough 100% intensity control is achieved by varying the magnetic field strength without altering the ion source beam intensity or its species yield.

Dagenhart, William K. (Oak Ridge, TN)

1986-01-01T23:59:59.000Z

307

Reactions of carbon atoms in pulsed molecular beams  

SciTech Connect (OSTI)

This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

Reisler, H. [Univ. of Southern California, Los Angeles (United States)

1993-12-01T23:59:59.000Z

308

MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING  

E-Print Network [OSTI]

on 0.063" dowel pins press fit into the ends of the slideinto the center was press fit into the dividing wall as theID, 0.156" thick) are press fit into the end of the drive

Ceyer, S.T.

2010-01-01T23:59:59.000Z

309

Photodissociation of cyclic compounds in a molecular beam  

SciTech Connect (OSTI)

A discussion on the dynamics and kinematics of photofragmentation-translational spectroscopy is presented, and the results are applied to experimental studies of four cyclic compounds: hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX), s-tetrazine (ST), cyclohexene, (CHN), and 1,4-cyclohexadiene (CHDN). In infrared multiphoton dissociation (IRMPD) of RDX, the dominant primary channel is concerted triple fission to produce three CH/sub 2/N/sub 2/O/sub 2/ fragments which subsequently undergo secondary dissociation. Concerted reactions predominate over simple bond rupture not only in the number of channels, but also in the amount of products. Following /sup 1/B/sub 3u/ reverse arrow /sup 1/A/sub g/ (S/sub 1/ reverse arrow S/sub 0/) or /sup 1/B/sub 2u/ reverse arrow /sup 1/A/sub g/ (248 nm) excitation, ST reverts to the highly vibrationally excited ground electronic state through internal conversion (IC), and then decomposes into 2HCN + N/sub 2/ via concerted triple dissociation. The asymptotic angles between the N/sub 2/ and HCN groups from the center-of-mass of ST are 117.2/degree/ and 114.4/degree/ for S/sub 1/ reverse arrow S/sub 0/ and 248 nm excitation respectively.

Zhao, Xinsheng

1988-11-01T23:59:59.000Z

310

Photochemical Properties, Composition, and Structure in Molecular Beam  

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 the1 - September 2006 TheStevenAdministration Album Of FAPAC -ofTheofA

311

Gaussian Beams Enrique J. Galvez  

E-Print Network [OSTI]

Gaussian Beams Enrique J. Galvez Department of Physics and Astronomy Colgate University Copyright 2009 #12;ii #12;Contents 1 Fundamental Gaussian Beams 1 1.1 Spherical Wavefront in the Paraxial region . . . . . . . . . . . . . . . 1 1.2 Formal Solution of the Wave Equation . . . . . . . . . . . . . . . . . 3 1.2.1 Beam Spot w

Galvez, Enrique J. "Kiko"

312

Perpendicular magnetic anisotropy in epitaxially strained cobalt-ferrite (001) thin films  

SciTech Connect (OSTI)

We investigated the dependencies of both the magnetization characteristics and the perpendicular magnetic anisotropy of Co{sub x}Fe{sub 3–x}O{sub 4}(001) epitaxial films (x?=?0.5 and 0.75) on the growth conditions of the reactive magnetron sputtering process. Both saturation magnetization and the magnetic uniaxial anisotropy constant K{sub u} are strongly dependent on the reactive gas (O{sub 2}) flow rate, although there is little difference in the surface structures for all samples observed by reflection high-energy electron diffraction. In addition, certain dead-layer-like regions were observed in the initial stage of the film growth for all films. Our results suggest that the magnetic properties of Co{sub x}Fe{sub 3–x}O{sub 4} epitaxial films are governed by the oxidation state and the film structure at the vicinity of the interface.

Yanagihara, H., E-mail: yanagiha@bk.tsukuba.ac.jp; Utsumi, Y.; Niizeki, T., E-mail: t-niizeki@imr.tohoku.ac.jp; Inoue, J.; Kita, Eiji [Institute of Applied Physics, University of Tsukuba, Tsukuba 305-8573 (Japan)

2014-05-07T23:59:59.000Z

313

One-step aluminium-assisted crystallization of Ge epitaxy on Si by magnetron sputtering  

SciTech Connect (OSTI)

In this work, one-step aluminium-assisted crystallization of Ge on Si is achieved via magnetron sputtering by applying an in-situ low temperature (50?°C to 150?°C) heat treatment in between Al and Ge depositions. The effect of heat treatment on film properties and the growth mechanism of Ge epitaxy on Si are studied via X-ray diffraction, Raman and transmission electron microscopy analyses. Compared with the conventional two-step process, the one-step aluminium-assisted crystallization requires much lower thermal budget and results in pure Ge epitaxial layer, which may be suitable for use as a virtual substrate for the fabrication of III-V solar cells.

Liu, Ziheng, E-mail: ziheng.liu@unsw.edu.au; Hao, Xiaojing; Ho-Baillie, Anita; Green, Martin A. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia)

2014-02-03T23:59:59.000Z

314

Recent advances of strong-strong beam-beam simulation  

SciTech Connect (OSTI)

In this paper, we report on recent advances in strong-strong beam-beam simulation. Numerical methods used in the calculation of the beam-beam forces are reviewed. A new computational method to solve the Poisson equation on nonuniform grid is presented. This method reduces the computational cost by a half compared with the standard FFT based method on uniform grid. It is also more accurate than the standard method for a colliding beam with low transverse aspect ratio. In applications, we present the study of coherent modes with multi-bunch, multi-collision beam-beam interactions at RHIC. We also present the strong-strong simulation of the luminosity evolution at KEKB with and without finite crossing angle.

Qiang, Ji; Furman, Miguel A.; Ryne, Robert D.; Fischer, Wolfram; Ohmi,Kazuhito

2004-09-15T23:59:59.000Z

315

Metallic beam development for the Facility for Rare Isotope Beam  

SciTech Connect (OSTI)

The Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) will accelerate a primary ion beam to energies beyond 200 MeV/u using a superconducting RF linac and will reach a maximum beam power of 400 kW on the fragmentation target. The beam intensity needed from the ECR ion source is expected to be between 0.4 and 0.5 emA for most medium mass to heavy mass elements. Adding to the challenge of reaching the required intensity, an expanded list of primary beams of interest has been established based on the production rate and the number of isotope beams that could be produced with FRIB. We report here on the development done for some of the beam in the list including mercury (natural), molybdenum ({sup 98}Mo), and selenium ({sup 82}Ser)

Machicoane, Guillaume, E-mail: machicoa@nscl.msu.edu; Cole, Dallas; Leitner, Daniela; Neben, Derek; Tobos, Larry [Facility for Rare Isotope Beam, Michigan State University, East Lansing, Michigan 48824 (United States)] [Facility for Rare Isotope Beam, Michigan State University, East Lansing, Michigan 48824 (United States)

2014-02-15T23:59:59.000Z

316

Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge  

SciTech Connect (OSTI)

We demonstrate reversible carrier density control across the Dirac point (?n???10{sup 13?}cm{sup ?2}) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.

Lartsev, Arseniy; Yager, Tom; Lara-Avila, Samuel, E-mail: samuel.lara@chalmers.se; Kubatkin, Sergey [Department of Microtechnology and Nanoscience, Chalmers University of Technology, S-41296 Göteborg (Sweden); Bergsten, Tobias [SP Technical Research Institute of Sweden, S-50115 Borås (Sweden); Tzalenchuk, Alexander [National Physical Laboratory, Teddington TW110LW (United Kingdom); Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); Janssen, T. J. B. M [National Physical Laboratory, Teddington TW110LW (United Kingdom); Yakimova, Rositza [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden)

2014-08-11T23:59:59.000Z

317

Nanowire-templated lateral epitaxial growth of non-polar group III nitrides  

DOE Patents [OSTI]

A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.

Wang, George T. (Albuquerque, NM); Li, Qiming (Albuquerque, NM); Creighton, J. Randall (Albuquerque, NM)

2010-03-02T23:59:59.000Z

318

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

SciTech Connect (OSTI)

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.}

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

319

Veeco Develops a Tool to Reduce Epitaxy Costs and Increase LED Brightness  

Broader source: Energy.gov [DOE]

With the help of DOE funding, Veeco is working on reducing epitaxy costs and increasing LED efficiency by developing a physical vapor deposition (PVD) tool for depositing aluminum nitride buffer layers on LED substrates. PVD, also known as "sputtering," is an alternative to metal-organic chemical vapor deposition (MOCVD). PVD is a purely physical process that involves plasma sputter bombardment rather than a chemical reaction at the surface to be coated, as in MOCVD.

320

Axion beams at HERA?  

E-Print Network [OSTI]

If the recently observed anomaly in the PVLAS experiment is due to the axion, then the powerful beams of synchrotron photons, propagating through high magnetic field of the HERA beamline, become strong axion sources. This gives a unique opportunity of detection of the axion-photon interactions by installing a small detector in the HERA tunnel, and to corroborate the axion hypothesis within a few days of running.

K. Piotrzkowski

2007-01-09T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

InP substrate evaluation by MOVPE growth of lattice matched epitaxial layers.  

SciTech Connect (OSTI)

InP substrates form the starting point for a wide variety of semiconductor devices. The surface morphology produced during epitaxy depends critically on the starting substrate. We evaluated (1 0 0)-oriented InP wafers from three different vendors by growing thick (5 mu m) lattice-matched epilayers of InP, Gain As, and AlInAs. We assessed the surfaces with differential interference contrast microscopy and atomic force microscopy. Wafers with near singular (1 0 0) orientations produced inferior surfaces in general. Vicinal substrates with small misorientations improved the epitaxial surface for InP dramatically, reducing the density of macroscopic defects while maintaining a low RMS roughness. GaInAs and AlInAs epitaxy step-bunched forming undulations along the miscut direction. Sulfur-doped wafers were considered for singular (1 0 0) and for 0.2 degrees misorientation toward (1 1 0). We found that mound defects observed for InP and GaInAs layers on iron-doped singular wafers were absent for singular sulfur-doped wafers. These observations support the conclusion that dislocation termination at the surface and expansion of the step spiral lead to the macroscopic defects observed.

Overberg, Mark E.; Cederberg, Jeffrey George

2010-09-01T23:59:59.000Z

322

The correlation of epitaxial graphene properties and morphology of SiC (0001)  

SciTech Connect (OSTI)

The electronic properties of epitaxial graphene (EG) on SiC (0001) depend sensitively on the surface morphology of SiC substrate. Here, 2–3 layers of graphene were grown on on-axis 6H-SiC with different step densities realized through controlling growth temperature and ambient pressure. We show that epitaxial graphene on SiC (0001) with low step density and straight step edge possesses fewer point defects laying mostly on step edges and higher carrier mobility. A relationship between step density and EG mobility is established. The linear scan of Raman spectra combined with the atomic force microscopy morphology images revealed that the Raman fingerprint peaks are nearly the same on terraces, but shift significantly while cross step edges, suggesting the graphene is not homogeneous in strain and carrier concentration over terraces and step edges of substrates. Thus, control morphology of epitaxial graphene on SiC (0001) is a simple and effective method to pursue optimal route for high quality graphene and will be helpful to prepare wafer sized graphene for device applications.

Guo, Y.; Guo, L. W., E-mail: lwguo@iphy.ac.cn, E-mail: xlchen@iphy.ac.cn; Huang, J.; Jia, Y. P.; Lin, J. J.; Lu, W.; Li, Z. L. [Research and Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yang, R. [Nanoscale Physics and Devices Laboratory, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Chen, X. L., E-mail: lwguo@iphy.ac.cn, E-mail: xlchen@iphy.ac.cn [Research and Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China)

2014-01-28T23:59:59.000Z

323

Experimental study of the distribution of alloying elements after the formation of epitaxial ferrite upon cooling in a low-carbon steel  

SciTech Connect (OSTI)

The distributions of carbon and substitutional elements in a low-carbon steel during the formation of epitaxial ferrite on cooling after intercritical annealing have been studied by electron probe microanalysis (EPMA). The analysis has shown that the formation of epitaxial ferrite takes place with a partial redistribution of alloying elements between the epitaxial ferrite and the austenite. This redistribution of alloying elements causes compositional gradients in the epitaxial ferrite that lead to a different etching behaviour with respect to the intercritical ferrite. Contrary to Thermo-Calc predictions, a distinct partitioning behaviour of silicon has been observed.

Santofimia, M.J., E-mail: M.J.SantofimiaNavarro@tudelft.nl [Materials Innovation Institute (M2i), Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Kwakernaak, C.; Sloof, W.G. [Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Zhao, L. [Materials Innovation Institute (M2i), Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Sietsma, J. [Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands)

2010-10-15T23:59:59.000Z

324

Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition  

SciTech Connect (OSTI)

Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.

Chen, Z. B.; Chen, B.; Wang, Y. B.; Liao, X. Z., E-mail: xiaozhou.liao@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Lei, W. [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Tan, H. H.; Jagadish, C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Zou, J. [Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, QLD 4072 (Australia); Ringer, S. P. [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia)

2014-01-13T23:59:59.000Z

325

Understanding the Poor Resolution from Test Beam RunUnderstanding the Poor Resolution from Test Beam Run 2004 Straw Test beam results2004 Straw Test beam results  

E-Print Network [OSTI]

1 Understanding the Poor Resolution from Test Beam RunUnderstanding the Poor Resolution from Test Beam Run aah #12;2 2004 Straw Test beam results2004 Straw Test beam results ! Doc # 3308 v#3 by A. Ledovskoy " Using Data from 2004 Test Beam " Used "triplet" method for beam nominally perpendicular to Straw

326

Nondestructive Damage Detection in General Beams  

E-Print Network [OSTI]

is to provide NDE methodologies that simultaneously identify the location, the extent, and the severity of damage in general beams. By general beams, we mean beyond Euler-Bernoulli beams (i.e. slender beams) to deep beams and stubby beams whose response may...

Dincal, Selcuk

2010-12-08T23:59:59.000Z

327

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

SciTech Connect (OSTI)

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.

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

2000-07-01T23:59:59.000Z

328

Neutral Beam Excitation  

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 Contributions andDataNational Library of1, 2007Transmission toBeam Excitation of Alfv

329

BEAMS: Curiosity | Jefferson Lab  

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 Depth (AOD)ProductssondeadjustsondeadjustAboutScience Program CumulusA t i o nLiquids Reserve2015 BCPthe24-3BEAMS:

330

Decoding Photosynthesis' Molecular Mysteries  

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

Decoding Photosynthesis' Molecular Mysteries Decoding the Molecular Mysteries of Photosynthesis Understanding the inner workings of photosynthesis is key to building new man-made...

331

Particle Detector / Beam Current Transformer  

E-Print Network [OSTI]

Particle Detector / Beam Current Transformer Analysis December 8, 2009 Harold G. Kirk #12;ShotSignal,A.U. Proton Bunch Number Beam Current Transformer - 17011 0 2 4 6 8 0 2 4 6 8 10 12 14 16 18 20 Integrated Transformer Pump 187829 (au) Probe 196504 (au) Ratios: Beam Current 1.046 SF 1.019 2.9% difference #12;Shot

McDonald, Kirk

332

A pencil beam algorithm for helium ion beam therapy  

SciTech Connect (OSTI)

Purpose: To develop a flexible pencil beam algorithm for helium ion beam therapy. Dose distributions were calculated using the newly developed pencil beam algorithm and validated using Monte Carlo (MC) methods. Methods: The algorithm was based on the established theory of fluence weighted elemental pencil beam (PB) kernels. Using a new real-time splitting approach, a minimization routine selects the optimal shape for each sub-beam. Dose depositions along the beam path were determined using a look-up table (LUT). Data for LUT generation were derived from MC simulations in water using GATE 6.1. For materials other than water, dose depositions were calculated by the algorithm using water-equivalent depth scaling. Lateral beam spreading caused by multiple scattering has been accounted for by implementing a non-local scattering formula developed by Gottschalk. A new nuclear correction was modelled using a Voigt function and implemented by a LUT approach. Validation simulations have been performed using a phantom filled with homogeneous materials or heterogeneous slabs of up to 3 cm. The beams were incident perpendicular to the phantoms surface with initial particle energies ranging from 50 to 250 MeV/A with a total number of 10{sup 7} ions per beam. For comparison a special evaluation software was developed calculating the gamma indices for dose distributions. Results: In homogeneous phantoms, maximum range deviations between PB and MC of less than 1.1% and differences in the width of the distal energy falloff of the Bragg-Peak from 80% to 20% of less than 0.1 mm were found. Heterogeneous phantoms using layered slabs satisfied a {gamma}-index criterion of 2%/2mm of the local value except for some single voxels. For more complex phantoms using laterally arranged bone-air slabs, the {gamma}-index criterion was exceeded in some areas giving a maximum {gamma}-index of 1.75 and 4.9% of the voxels showed {gamma}-index values larger than one. The calculation precision of the presented algorithm was considered to be sufficient for clinical practice. Although only data for helium beams was presented, the performance of the pencil beam algorithm for proton beams was comparable. Conclusions: The pencil beam algorithm developed for helium ions presents a suitable tool for dose calculations. Its calculation speed was evaluated to be similar to other published pencil beam algorithms. The flexible design allows easy customization of measured depth-dose distributions and use of varying beam profiles, thus making it a promising candidate for integration into future treatment planning systems. Current work in progress deals with RBE effects of helium ions to complete the model.

Fuchs, Hermann; Stroebele, Julia; Schreiner, Thomas; Hirtl, Albert; Georg, Dietmar [Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, 1090 Vienna (Austria); Department of Radiation Oncology, Medical University of Vienna/AKH Vienna, 1090 Vienna (Austria) and Comprehensive Cancer Center, Medical University of Vienna/AKH Vienna, 1090 Vienna (Austria); Department of Radiation Oncology, Medical University of Vienna/AKH Vienna (Austria) and Comprehensive Cancer Center, Medical University of Vienna/AKH Vienna, 1090 Vienna (Austria); PEG MedAustron, 2700 Wiener Neustadt (Austria); Department of Nuclear Medicine, Medical University of Vienna, 1090 Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, 1090 Vienna (Austria); Department of Radiation Oncology, Medical University of Vienna/AKH Vienna, 1090 Vienna (Austria) and Comprehensive Cancer Center, Medical University of Vienna/AKH Vienna, 1090 Vienna (Austria)

2012-11-15T23:59:59.000Z

333

Beam hosing instability in overdense plasma  

SciTech Connect (OSTI)

Transverse stability of the drive beam is critical to plasma wakefield accelerators. A long, relativistic particle beam propagating in an overdense plasma is subject to beam envelope modulation and hosing (centroid displacement) instabilities. Coupled equations for the beam centroid and envelope are derived. The growth rate for beam hosing is examined including return current effects (where the beam radius is of order the plasma skin depth) in the long-beam, strongly-coupled, overdense regime.

Schroeder, C. B.; Benedetti, C.; Esarey, E.; Gruener, F. J.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Universitaet Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2012-12-21T23:59:59.000Z

334

The Gas Flow from the Gas Attenuator to the Beam Line  

SciTech Connect (OSTI)

The gas leak from the gas attenuator to the main beam line of the Linac Coherent Light Source has been evaluated, with the effect of the Knudsen molecular beam included. It has been found that the gas leak from the gas attenuator of the present design, with nitrogen as a working gas, does not exceed 10{sup -5} torr x l/s even at the highest pressure in the main attenuation cell (20 torr).

Ryutov, D.D.

2010-12-03T23:59:59.000Z

335

Broad-band beam buncher  

DOE Patents [OSTI]

A broad-band beam buncher is disclosed, comprising an evacuated housing, an electron gun therein for producing an electron beam, a buncher cavity having entrance and exit openings through which the beam is directed, grids across such openings, a source providing a positive DC voltage between the cavity and the electron gun, a drift tube through which the electron beam travels in passing through such cavity, grids across the ends of such drift tube, gaps being provided between the drift tube grids and the entrance and exit grids, a modulator for supplying an ultrahigh frequency modulating signal to the drift tube for producing velocity modulation of the electrons in the beam, a drift space in the housing through which the velocity modulated electron beam travels and in which the beam is bunched, and a discharge opening from such drift tube and having a grid across such opening through which the bunched electron beam is discharged into an accelerator or the like. The buncher cavity and the drift tube may be arranged to constitute an extension of a coaxial transmission line which is employed to deliver the modulating signal from a signal source. The extended transmission line may be terminated in its characteristic impedance to afford a broad-band response and the device as a whole designed to effect broad-band beam coupling, so as to minimize variations of the output across the response band.

Goldberg, David A. (Walnut Creek, CA); Flood, William S. (Berkeley, CA); Arthur, Allan A. (Martinez, CA); Voelker, Ferdinand (Orinda, CA)

1986-01-01T23:59:59.000Z

336

Low energy beta-beams  

E-Print Network [OSTI]

The main goal of a beta-beam facility is to determine the possible existence of CP violation in the lepton sector, the value of the third neutrino mixing angle and the mass hierarchy. Here we argue that a much broader physics case can be covered since the beta-beam concept can also be used to establish a low energy beta-beam facility. We discuss that the availability of neutrino beams in the 100 MeV energy range offers a unique opportunity to perform neutrino scattering experiments of interest for nuclear physics, for the study of fundamental interactions and of core-collapse supernova physics.

Cristina Volpe

2009-11-13T23:59:59.000Z

337

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

E-Print Network [OSTI]

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

Nabben, Reinhard

338

Atomic-Scale Investigation of Epitaxial Graphene Grown on 6H-SiC(0001) Using Scanning Tunneling Microscopy and Spectroscopy  

E-Print Network [OSTI]

Atomic-Scale Investigation of Epitaxial Graphene Grown on 6H-SiC(0001) Using Scanning Tunneling ReceiVed: June 26, 2010 Graphene was epitaxially grown on a 6H-SiC(0001) substrate by thermal the evolution of the graphene growth as a function of the temperature. We found that the evaporation of Si

Kim, Sehun

339

hal-00130698,version1-13Feb2007 Electronic structure of epitaxial graphene layers on SiC: effect of the substrate.  

E-Print Network [OSTI]

hal-00130698,version1-13Feb2007 Electronic structure of epitaxial graphene layers on SiC: effect integer quantum Hall effects expected for isolated graphene sheets. This is the case eventhough the layer-substrate epitaxy of these films implies a strong interface bond that should induce perturbations in the graphene

Paris-Sud XI, Université de

340

Ripples in epitaxial graphene on the Si-terminated SiC (0001) surface F.Varchon, P.Mallet, J.-Y.Veuillen, and L.Magaud  

E-Print Network [OSTI]

Ripples in epitaxial graphene on the Si-terminated SiC (0001) surface F.Varchon, P.Mallet, J) Interaction with a substrate can modify the graphene honeycomb lattice and thus alter its out- standing properties. This could be particularly true for epitaxial graphene where the carbon layers are grown from

Paris-Sud XI, Université de

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Doping of G Molecular Layer D  

E-Print Network [OSTI]

Metal n-SC n++ SC EF EC � 0.5 eV Metal n-SCn++ SC Raman Spectrum of Different Crystal OrientationsGe, the remaining amorphous Ge is transported through the germanide to grow epitaxially on the GaAs. ·Epitaxial

Candea, George

342

Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams  

SciTech Connect (OSTI)

Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

Siemann, R.H.; /SLAC

2011-10-24T23:59:59.000Z

343

Epitaxial ferromagnetic oxide thin films on silicon with atomically sharp interfaces  

SciTech Connect (OSTI)

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.

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

344

Fundamental optical properties of InN grown by epitaxial lateral overgrowth method  

SciTech Connect (OSTI)

Optical properties of InN grown by the epitaxial lateral overgrowth (ELO) method have been studied using photoluminescence (PL) and excitation-correlation (EC) measurements. The PL spectrum is analyzed by free-electron recombination band (FERB) model, which shows that the ELO sample has a very low background carrier concentration (n=5.5*10{sup 16}[cm{sup ?3]}). EC measurements show that the dependences of the band gap renormalization and Auger effect on the carrier concentrations are similar in spite of the different physical origins.

Kametani, Tatsuma; Kamimura, Jumpei; Inose, Yuta; Kunugita, Hideyuki; Kikuchi, Akihiko; Kishino, Katsumi; Ema, Kazuhiro [Department of Engineering and Applied Science, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

2013-12-04T23:59:59.000Z

345

Broadband electromagnetic response and ultrafast dynamics of few-layer epitaxial graphene  

SciTech Connect (OSTI)

We study the broadband optical conductivity and ultrafast carrier dynamics of epitaxial graphene in the few-layer limit. Equilibrium spectra of nominally buffer, monolayer, and multilayer graphene exhibit significant terahertz and near-infrared absorption, consistent with a model of intra- and interband transitions in a dense Dirac electron plasma. Non-equilibrium terahertz transmission changes after photoexcitation are shown to be dominated by excess hole carriers, with a 1.2-ps mono-exponential decay that refects the minority-carrier recombination time.

Choi, Hyunyong; Borondics, Ferenc; Siegel, David A.; Zhou, Shuyun Y.; Martin, Michael C.; Lanzara, Alessandra; Kaindl, Robert A.

2009-03-26T23:59:59.000Z

346

Epitaxial growth of aligned AlGalnN nanowires by metal-organic chemical vapor deposition  

DOE Patents [OSTI]

Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. <1010> M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.

Han, Jung (Woodbridge, CT); Su, Jie (New Haven, CT)

2008-08-05T23:59:59.000Z

347

Thickness dependent exchange bias in martensitic epitaxial Ni-Mn-Sn thin films  

SciTech Connect (OSTI)

A thickness dependent exchange bias in the low temperature martensitic state of epitaxial Ni-Mn-Sn thin films is found. The effect can be retained down to very small thicknesses. For a Ni{sub 50}Mn{sub 32}Sn{sub 18} thin film, which does not undergo a martensitic transformation, no exchange bias is observed. Our results suggest that a significant interplay between ferromagnetic and antiferromagnetic regions, which is the origin for exchange bias, is only present in the martensite. The finding is supported by ab initio calculations showing that the antiferromagnetic order is stabilized in the phase.

Behler, Anna [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany) [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Department of Physics, Institute for Solid State Physics, Dresden University of Technology, 01062 Dresden (Germany); Teichert, Niclas; Auge, Alexander; Hütten, Andreas [Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld (Germany)] [Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld (Germany); Dutta, Biswanath; Hickel, Tilmann [Max-Planck Institut für Eisenforschung, 40237 Düsseldorf (Germany)] [Max-Planck Institut für Eisenforschung, 40237 Düsseldorf (Germany); Waske, Anja [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany)] [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Eckert, Jürgen [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany) [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Institute of Materials Science, Dresden University of Technology, 01062 Dresden (Germany)

2013-12-15T23:59:59.000Z

348

Laser acceleration of ion beams  

E-Print Network [OSTI]

We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.

I. A. Egorova; A. V. Filatov; A. V. Prozorkevich; S. A. Smolyansky; D. B. Blaschke; M. Chubaryan

2007-02-01T23:59:59.000Z

349

Tunable source of terahertz radiation using molecular modulation  

E-Print Network [OSTI]

Tunable source of terahertz radiation using molecular modulation D. D. Yavuz* and J. J. Weber a high power and widely tunable coher- ent source of THz radiation remains a very challenging task of terahertz (THz) radiation that is based on Raman down-shifting of an infrared laser beam using highly

Yavuz, Deniz

350

Toward automated beam optics control  

SciTech Connect (OSTI)

We have begun a program aiming toward automatic control of charged-particle beam optics using artificial intelligence programming techniques. In developing our prototype, we are working with LISP machines and the KEE expert system shell. Our first goal was to develop a ''mouseable'' representation of a typical beam line. This responds actively to changes entered from the mouse or keyboard, giving an updated display of the beam line itself, its optical properties, and the instrumentation and control devices as seen by the operater. We have incorporated TRANSPORT, written in Fortran but running as a callable procedure in the LISP environment, for simulation of the beam-line optics. This paper describes the experience gained in meeting our first goal and discusses plans to extend the work so that it is usable, in realtime, on an operating beam line. 11 refs.

Silbar, R.R.; Schultz, D.E.

1987-01-01T23:59:59.000Z

351

Process for selectively patterning epitaxial film growth on a semiconductor substrate  

DOE Patents [OSTI]

Disclosed is a process for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve the first layer a sufficient amount to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Sheldon, P.; Hayes, R.E.

1984-12-04T23:59:59.000Z

352

Method of digital epitaxy by externally controlled closed-loop feedback  

DOE Patents [OSTI]

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 4 figs.

Eres, D.; Sharp, J.W.

1994-07-19T23:59:59.000Z

353

Process for selectively patterning epitaxial film growth on a semiconductor substrate  

DOE Patents [OSTI]

A process is disclosed for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve a sufficient amount of the first layer to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent to the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Sheldon, Peter (Golden, CO); Hayes, Russell E. (Boulder, CO)

1986-01-01T23:59:59.000Z

354

Anisotropy of the solid-state epitaxy of silicon carbide in silicon  

SciTech Connect (OSTI)

A new method for the solid-state synthesis of epitaxial layers is developed, in which a substrate participates in the chemical reaction and the reaction product grows not on the substrate surface, as in traditional epitaxial methods, but inside the substrate. This method offers new opportunities for elastic-energy relaxation due to a mechanism operating only in anisotropic media, specifically, the attraction of point defects formed during the chemical reaction. The attracting point centers of dilatation form relatively stable objects, dilatation dipoles, which significantly reduce the total elastic energy. It is shown that, in crystals with cubic symmetry, the most favorable arrangement of dipoles is the ?111? direction. The theory is tested by growing silicon carbide (SiC) films on Si (111) substrates by chemical reaction with carbon monoxide CO. High-quality single-crystal SiC-4H films with thicknesses of up to 100 nm are grown on Si (111). Ellipsometric analysis showed that the optical constants of the SiC-4H films are significantly anisotropic. This is caused not only by the lattice hexagonality but also by a small amount (about 2–6%) of carbon atoms remaining in the film due to dilatation dipoles. It is shown that the optical constants of the carbon impurity correspond to strongly anisotropic highly oriented pyrolytic graphite.

Kukushkin, S. A., E-mail: kukushkin_s@yahoo.com; Osipov, A. V. [Russian Academy of Sciences, Institute of Problems of Machine Science (Russian Federation)

2013-12-15T23:59:59.000Z

355

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

SciTech Connect (OSTI)

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.

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

356

Abbreviated epitaxial growth mode (AGM) method for reducing cost and improving quality of LEDs and lasers  

DOE Patents [OSTI]

The use of an abbreviated GaN growth mode on nano-patterned AGOG sapphire substrates, which utilizes a process of using 15 nm low temperature GaN buffer and bypassing etch-back and recovery processes during epitaxy, enables the growth of high-quality GaN template on nano-patterned AGOG sapphire. The GaN template grown on nano-patterned AGOG sapphire by employing abbreviated growth mode has two orders of magnitude lower threading dislocation density than that of conventional GaN template grown on planar sapphire. The use of abbreviated growth mode also leads to significant reduction in cost of the epitaxy. The growths and characteristics of InGaN quantum wells (QWs) light emitting diodes (LEDs) on both templates were compared. The InGaN QWs LEDs grown on the nano-patterned AGOG sapphire demonstrated at least a 24% enhancement of output power enhancement over that of LEDs grown on conventional GaN templates.

Tansu, Nelson; Chan, Helen M; Vinci, Richard P; Ee, Yik-Khoon; Biser, Jeffrey

2013-09-24T23:59:59.000Z

357

Asymmetric Electron Transport at Monolayer-Bilayer Heterojunctions of Epitaxial Graphene  

SciTech Connect (OSTI)

The symmetry of the graphene honeycomb lattice is a key element determining many of graphene s unique electronic properties, such as the linear energy-momentum dispersion and the suppressed backscattering 1,2. However, line defects in large-scale epitaxial graphene films, such as grain boundaries, edges, surface steps, and changes in layer thickness, often break the sublatttice symmetry and can impact transport properties of graphene profoundly 3-6. Here we report asymmetric electron transport upon polarity reversal at individual monolayer-bilayer (ML-BL) boundaries in epitaxial graphene on SiC (0001), revealed by scanning tunneling potentiometry. A greater voltage drop is observed when the current flows from BL to ML graphene than in the reverse direction, and the difference remains nearly unchanged with increasing current. This is not a typical nonlinear conductance due to electron transmission through an asymmetric potential. Rather, it indicates the opening of a dynamic energy gap at the Fermi energy due to the Coulomb interaction between the injected nonequilibrium electron density and the pseudospin polarized Friedel oscillation charge density at the boundary. This intriguing heterojunction transport behavior opens a new avenue towards novel quantum functions such as quantum switching.

Li, An-Ping [ORNL] [ORNL; Clark, Kendal W [ORNL] [ORNL; Zhang, Xiaoguang [ORNL] [ORNL; Gu, Gong [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); He, Guowei [Carnegie Mellon University (CMU)] [Carnegie Mellon University (CMU); Feenstra, Randall [Carnegie Mellon University (CMU)] [Carnegie Mellon University (CMU)

2014-01-01T23:59:59.000Z

358

Electrostatic wire stabilizing a charged particle beam  

DOE Patents [OSTI]

In combination with a charged particle beam generator and accelerator, apparatus and method are provided for stabilizing a beam of electrically charged particles. A guiding means, disposed within the particle beam, has an electric charge induced upon it by the charged particle beam. Because the sign of the electric charge on the guiding means and the sign of the particle beam are opposite, the particles are attracted toward and cluster around the guiding means to thereby stabilize the particle beam as it travels.

Prono, D.S.; Caporaso, G.J.; Briggs, R.J.

1983-03-21T23:59:59.000Z

359

Probing Organic Transistors with Infrared Beams  

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

Probing Organic Transistors with Infrared Beams Probing Organic Transistors with Infrared Beams Print Wednesday, 26 July 2006 00:00 Silicon-based transistors are well-understood,...

360

Electron beam machining using rotating and shaped beam power distribution  

DOE Patents [OSTI]

An apparatus and method are disclosed for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: (1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and (2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1,000 {micro}m (1 mm or larger), compared to the 250 {micro}m diameter of laser drilling. 5 figs.

Elmer, J.W.; O`Brien, D.W.

1996-07-09T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Electron beam machining using rotating and shaped beam power distribution  

DOE Patents [OSTI]

An apparatus and method for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: 1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and 2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1000 .mu.m (1 mm or larger), compared to the 250 .mu.m diameter of laser drilling.

Elmer, John W. (Pleasanton, CA); O'Brien, Dennis W. (Livermore, CA)

1996-01-01T23:59:59.000Z

362

Alight a beam and beaming light: A theme with variations  

SciTech Connect (OSTI)

The interaction of light (coherent and incoherent) with charged particle beams is explored in various configurations: incoherent scattering of coherent light (laser) from an incoherent particle beam (high temperature), coherent scattering of coherent light (laser) from a {open_quotes}cold{close_quotes} (bunched) beam, femtosecond generation of particle and light beams via {open_quotes}optical slicing{close_quotes} and Thomson/Compton scattering techniques, etc. The domains of ultrashort temporal duration (femtoseconds) as well as ultrashort wavelengths (x rays and shorter), with varying degrees of coherence, are explored. The relevance to a few critical areas of research in the natural sciences, e.g., ultrafast material, chemical and biological processes, protein folding, particle phase space cooling, etc. are touched upon. All the processes discussed involve proper interpretation and understanding of coherent states of matter and radiation, as well as the quality and quantity of information and energy embedded in them. {copyright} {ital 1998 American Institute of Physics.}

Chattopadhyay, S. [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California94720 (United States)] [Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California94720 (United States)

1998-05-01T23:59:59.000Z

363

A Phase Diagram of Low Temperature Epitaxial Silicon Grown by Hot-wire Chemical Vapor Deposition for Photovoltaic Devices  

E-Print Network [OSTI]

for Photovoltaic Devices Christine Esber Richardson, Brendan M. Kayes, Matthew J. Dicken, and Harry A. Atwater-grained templates is one strategy for the fast, low- temperature growth of large-grained films with hydrogen). Figure 1: Schematic of proposed photovoltaic device incorporating epitaxial Si growth on a large

Atwater, Harry

364

Inverted List Kinetic Monte Carlo with Rejection ap-plied to Directed Self-Assembly of Epitaxial Growth  

E-Print Network [OSTI]

Inverted List Kinetic Monte Carlo with Rejection ap- plied to Directed Self-Assembly of Epitaxial of subsequently deposited material using a kinetic Monte Carlo algorithm that combines the use of inverted lists finding is that the relative performance of the inverted list algorithm improves with increasing system

Schulze, Tim

365

CdTe EPITAXIAL FILMS AND THEIR PROPERTIES S. N. MAXIMOVSKY, I. P. REVOCATOVA, V. M. SALMAN,  

E-Print Network [OSTI]

161 CdTe EPITAXIAL FILMS AND THEIR PROPERTIES S. N. MAXIMOVSKY, I. P. REVOCATOVA, V. M. SALMAN, M CdTe films of p and n type conductivity with a given devia- tion of film composition from PHYSIQUE APPLIQUÃ?E TOME 12, FÃ?VRIER 1977, PAGE 161 The design of reliable CdTe nuclear radiation counters

Paris-Sud XI, Université de

366

906 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 50, NO. 4, APRIL 2003 Silicon Epitaxial Layer Recombination and  

E-Print Network [OSTI]

- sortium (SiWEDS) (Astropower, GriTek Ltd., Intel Corp., Komatsu Electronic Metals, LG Siltron, MEMC906 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 50, NO. 4, APRIL 2003 Silicon Epitaxial Layer Electronic Materials, National Renewable Energy Laboratory, Okmetic, Samsung Electronics, SUMCO, Texas

Schroder, Dieter K.

367

PUBLISHED ONLINE: 24 JULY 2011 | DOI: 10.1038/NMAT3071 Epitaxial growth of three-dimensionally  

E-Print Network [OSTI]

-dimensionally architectured optoelectronic devices Erik C. Nelson1 , Neville L. Dias2 , Kevin P. Bassett2 , Simon N. Dunham1 and Paul V. Braun1 * Optoelectronic devices have long benefited from structuring in multiple dimensions-template-directed epitaxy of group III­V materials, which enables formation of 3D structured optoelectronic devices. We

Rogers, John A.

368

Comprehensive study of the metal-insulator transition in pulsed laser deposited epitaxial VO2 thin films  

E-Print Network [OSTI]

Comprehensive study of the metal-insulator transition in pulsed laser deposited epitaxial VO2 thin properties of high-quality VO2 thin films across its metal-insulator phase transition. Detailed x-ray deposition,9 sol-gel deriving,10 sputtering,11 and pulsed laser deposition,12 the study of VO2 is reviving

Wu, Junqiao

369

Field effect in epitaxial graphene on a silicon carbide substrate Sarnoff Corporation, CN5300, Princeton, New Jersey 08543  

E-Print Network [OSTI]

deposition on the surfaces of transition metal or transition metal carbide single crystals, and the physical on a graphitized SiC surface, as opposed to highly conductive metal and metal carbide substrates that require1 Field effect in epitaxial graphene on a silicon carbide substrate Gong Gua) Sarnoff Corporation

Feenstra, Randall

370

Stress evaluation on hetero-epitaxial 3C-SiC film on (100) Si substrates R. Anzalone1,*  

E-Print Network [OSTI]

-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

Volinsky, Alex A.

371

Generation and Recombination Carrier Lifetimes in 4H SiC Epitaxial Wafers , M. J. Loboda1)  

E-Print Network [OSTI]

Generation and Recombination Carrier Lifetimes in 4H SiC Epitaxial Wafers G. Chung1) , M. J. Loboda comparative studies of recombination and carrier lifetimes in SiC. For the first time, both generation-wafer structures. The ratio of the generation to recombination lifetime is much different in SiC compared to Si

Schroder, Dieter K.

372

Circular, confined distribution for charged particle beams  

DOE Patents [OSTI]

A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location.

Garnett, Robert W. (Los Alamos, NM); Dobelbower, M. Christian (Toledo, OH)

1995-01-01T23:59:59.000Z

373

Circular, confined distribution for charged particle beams  

DOE Patents [OSTI]

A charged particle beam line is formed with magnetic optics that manipulate the charged particle beam to form the beam having a generally rectangular configuration to a circular beam cross-section having a uniform particle distribution at a predetermined location. First magnetic optics form a charged particle beam to a generally uniform particle distribution over a square planar area at a known first location. Second magnetic optics receive the charged particle beam with the generally square configuration and affect the charged particle beam to output the charged particle beam with a phase-space distribution effective to fold corner portions of the beam toward the core region of the beam. The beam forms a circular configuration having a generally uniform spatial particle distribution over a target area at a predetermined second location. 26 figs.

Garnett, R.W.; Dobelbower, M.C.

1995-11-21T23:59:59.000Z

374

Molecular information ratchets   

E-Print Network [OSTI]

In the emerging aield of molecular machines, a molecular ratchet is a chemical system that allows the positional displacement of a submolecular component of be captured and directionally relea ...

Wilson, Adam Christopher

2012-11-28T23:59:59.000Z

375

Confined energy distribution for charged particle beams  

DOE Patents [OSTI]

A charged particle beam is formed to a relatively larger area beam which is well-contained and has a beam area which relatively uniformly deposits energy over a beam target. Linear optics receive an accelerator beam and output a first beam with a first waist defined by a relatively small size in a first dimension normal to a second dimension. Nonlinear optics, such as an octupole magnet, are located about the first waist and output a second beam having a phase-space distribution which folds the beam edges along the second dimension toward the beam core to develop a well-contained beam and a relatively uniform particle intensity across the beam core. The beam may then be expanded along the second dimension to form the uniform ribbon beam at a selected distance from the nonlinear optics. Alternately, the beam may be passed through a second set of nonlinear optics to fold the beam edges in the first dimension. The beam may then be uniformly expanded along the first and second dimensions to form a well-contained, two-dimensional beam for illuminating a two-dimensional target with a relatively uniform energy deposition.

Jason, Andrew J. (Los Alamos, NM); Blind, Barbara (Los Alamos, NM)

1990-01-01T23:59:59.000Z

376

Center for Beam Physics, 1992  

SciTech Connect (OSTI)

This report contains the following information on the center for beam physics: Facilities; Organizational Chart; Roster; Profiles of Staff; Affiliates; Center Publications (1991--1993); and 1992 Summary of Activities.

Not Available

1993-06-01T23:59:59.000Z

377

Neutron beam testing of triblades  

SciTech Connect (OSTI)

PowerXCell 8i processors and Opterons in four IBM Triblades were tested at LANSCE. The hazard rate when the beam was aimed at the Opterons was higher than when it was aimed at the Cell processors.

Michalak, Sarah E [Los Alamos National Laboratory; Du Bois, Andrew J [Los Alamos National Laboratory; Storlie, Curtis B [Los Alamos National Laboratory; Rust, William N [Los Alamos National Laboratory; Du Bois, David H [Los Alamos National Laboratory; Modl, David G [Los Alamos National Laboratory; Quinn, Heather M [Los Alamos National Laboratory; Blanchard, Sean P [Los Alamos National Laboratory; Manuzzato, Andrea [UNIV DEGLI STUDI DI PADOVA ITALY

2011-01-31T23:59:59.000Z

378

STOCHASTIC COOLING FOR BUNCHED BEAMS.  

SciTech Connect (OSTI)

Problems associated with bunched beam stochastic cooling are reviewed. A longitudinal stochastic cooling system for RHIC is under construction and has been partially commissioned. The state of the system and future plans are discussed.

BLASKIEWICZ, M.

2005-05-16T23:59:59.000Z

379

Beam bunch feedback  

SciTech Connect (OSTI)

When the electromagnetic fields that are excited by the passage of a bundle of charged particles persist to act upon bunches that follow, then the motions of the bunches are coupled. This action between bunches circulating on a closed orbit can generate growing patterns of bunch excursions. Such growth can often be suppressed by feedback systems that detect the excursion and apply corrective forces to the bunches. To be addressed herein is feedback that acts on motions of the bunch body centers. In addition to being useful for suppressing the spontaneous growth of coupled-bunch motions, such feedback can be used to damp transients in bunches injected into an accelerator or storage ring; for hadrons which lack strong radiation damping, feedback is needed to avoid emittance growth through decoherence. Motions excited by noise in magnetic fields or accelerating rf can also be reduced by using this feedback. Whether the action is on motions that are transverse to the closed orbit or longitudinal, the arrangement is the same. Bunch position is detected by a pickup and that signal is processed and directed to a kicker that may act upon the same bunch or some other portion of the collective beam pattern. Transverse motion is an oscillation with angular frequency {nu}{perpendicular}{omega}{sub o} where {omega}{sub o} is the orbital frequency 2{pi}{line_integral}o. Longitudinal synchrotron oscillation occurs at frequency {omega} {sub s} = {nu}{sub s}{omega}{sub o}. The former is much more rapid, {nu}{perpendicular} being on the order of 10 while {nu}{sub s} is typically about 10{sup minus 1} to 10 {sup minus 2}.

Lambertson, G.

1995-09-01T23:59:59.000Z

380

Multiple-ion-beam time-of-flight mass spectrometer Andreas Rohrbacher and Robert E. Continettia)  

E-Print Network [OSTI]

/ionization and the molecular ions of two different proteins myoglobin and lysozyme , created by matrix assisted laser,7 and matrix assisted desorption and ionization MALDI 8­11 have become avail- able to allow the mass the samples with a robot- driven capillary,15 a scanning ion beam,16 or spatial resolu- tion was achieved

Continetti, Robert E.

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Single lens laser beam shaper  

DOE Patents [OSTI]

A single lens bullet-shaped laser beam shaper capable of redistributing an arbitrary beam profile into any desired output profile comprising a unitary lens comprising: a convex front input surface defining a focal point and a flat output portion at the focal point; and b) a cylindrical core portion having a flat input surface coincident with the flat output portion of the first input portion at the focal point and a convex rear output surface remote from the convex front input surface.

Liu, Chuyu (Newport News, VA); Zhang, Shukui (Yorktown, VA)

2011-10-04T23:59:59.000Z

382

Enhanced photosensitivity of electro-oxidized epitaxial graphene Mikhail E. Itkis,1  

E-Print Network [OSTI]

, photoconductivity in graphene was detected using a laser beam focused at regions adjacent to the metal electrodes . The electrical contacts to the channels were formed by e-beam evaporation of 10 nm Pd and 100 nm Au layers by applying +0.8 V to the test channel working electrode against a Pt wire electrode inserted

383

Polarity-inverted ScAlN film growth by ion beam irradiation and application to overtone acoustic wave (000-1)/(0001) film resonators  

SciTech Connect (OSTI)

Polarity inversion in wurtzite film is generally achieved by the epitaxial growth on a specific under-layer. We demonstrate polarity inversion of c-axis oriented ScAlN films by substrate ion beam irradiation without using buffer layer. Substrate ion beam irradiation was induced by either sputtering a small amount of oxide (as a negative ion source) onto the cathode or by applying a RF bias to the substrate. Polarity of the films was determined by a press test and nonlinear dielectric measurement. Second overtone thickness extensional mode acoustic resonance and suppression of fundamental mode resonance, indicating complete polarity inversion, were clearly observed in bilayer highly oriented (000-1)/(0001) ScAlN film.

Suzuki, Masashi; Yanagitani, Takahiko, E-mail: yana@nitech.ac.jp [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Odagawa, Hiroyuki [Kumamoto National College of Technology, Kumamoto 861-1102 (Japan)

2014-04-28T23:59:59.000Z

384

Much simplified ion-beam assisted deposition-TiN template for high-performance coated conductors  

SciTech Connect (OSTI)

A much simplified template, i.e., two nonsuperconducting layers between the superconducting YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and the polycrystalline metal substrate, has been developed for high-performance coated conductors by using biaxially aligned TiN as a seed layer. A combination of a thin TiN ({approx}10 nm by ion-beam assisted deposition) layer and an epitaxial buffer LaMnO{sub 3} layer ({approx}120 nm) allows us to grow epitaxial YBCO films with values of full width at half-maximum around 3.5 deg. and 1.7 deg. for the {phi}-scan of (103) and rocking curve of (005) YBCO, respectively. The YBCO films grown on electropolished polycrystalline Hastelloy using this two-layer template exhibited a superconducting transition temperature of 89.5 K, a critical current density of 1.2 MA/cm{sup 2} at 75.5 K, and an {alpha} value (proportional factor of critical current density J{sub c}{approx}H{sup -}{alpha}) of around 0.33, indicating a high density of pinning centers and an absence of weak links.

Xiong, J. [Division of Materials Physics and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Matias, V.; Zhai, J. Y.; Maiorov, B.; Trugman, D.; Jia, Q. X. [Division of Materials Physics and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Wang, H. [Department of Electrical and Computer Engineering, Texas A and M University, College Station, Texas 77843-3128 (United States); Tao, B. W.; Li, Y. R. [State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2010-10-15T23:59:59.000Z

385

Electron beam diagnostic for profiling high power beams  

DOE Patents [OSTI]

A system for characterizing high power electron beams at power levels of 10 kW and above is described. This system is comprised of a slit disk assembly having a multitude of radial slits, a conducting disk with the same number of radial slits located below the slit disk assembly, a Faraday cup assembly located below the conducting disk, and a start-stop target located proximate the slit disk assembly. In order to keep the system from over-heating during use, a heat sink is placed in close proximity to the components discussed above, and an active cooling system, using water, for example, can be integrated into the heat sink. During use, the high power beam is initially directed onto a start-stop target and after reaching its full power is translated around the slit disk assembly, wherein the beam enters the radial slits and the conducting disk radial slits and is detected at the Faraday cup assembly. A trigger probe assembly can also be integrated into the system in order to aid in the determination of the proper orientation of the beam during reconstruction. After passing over each of the slits, the beam is then rapidly translated back to the start-stop target to minimize the amount of time that the high power beam comes in contact with the slit disk assembly. The data obtained by the system is then transferred into a computer system, where a computer tomography algorithm is used to reconstruct the power density distribution of the beam.

Elmer, John W. (Danville, CA); Palmer, Todd A. (Livermore, CA); Teruya, Alan T. (Livermore, CA)

2008-03-25T23:59:59.000Z

386

Preparation of silicon substrates for gallium-arsenide solar cells by electron-beam-pulse processing. Annual technical report, March 15, 1980-March 15, 1981  

SciTech Connect (OSTI)

In the past year a process has been developed for creating high-quality epitaxial layers of germanium on silicon substrates using rapid heating and cooling with a pulsed electron beam. This single-crystal germanium coating is the key to the production of high efficiency GaAs solar cells on low-cost silicon substrates in an economical manner. Thin (less than or equal to 1 ..mu..m) layers of Ge have been deposited on Si wafers by chemical vapor deposition (CVD) in single-crystal form or by vacuum evaporation in amorphous or polycrystalline form. The CVD films have given the best results, with good crystallinity and electrical properties as deposited. A persistent problem with surface roughness in the as-deposited films has been overcome by pulsed electron beam melting of the near-surface region in time periods on the order of a microsecond. The brief molten period smooths the surface features without compromising the crystallinity, electrical properties, or interfacial abruptness of the Ge film. These layers are of a quality suitable for further evaluation by GaAs growth and cell processing in the next phase of the program. Pulsed electron beam processing also serves a vital function for the evaporated Ge films, which are melted by the beam and recrystallized on the Si substrates, epitaxial single crystal Ge layers result from amorphous or polycrystalline starting films. To date results have not been as satisfactory as for CVD films; contamination from several sources has been identified as a problem. Many of these sources have been eliminated, so that a decision on the intrinsic limitations of the evaporated film approach should be made in the near future.

Tobin, S.P.

1981-05-01T23:59:59.000Z

387

Evolution of (001) and (111) facets for selective epitaxial growth inside submicron trenches  

SciTech Connect (OSTI)

The evolution of (001) and (111) facets for the epitaxial growth inside submicron trenches is systematically studied in this report. The analysis with the method of “Lagrange multiplier” indicates the equilibrium crystal shape. In the case of non-equilibrium without external fluxes, we employed the “weighted mean curvature” method to mathematically model the inter-facet migration rate for two extreme kinetic cases: “surface diffusion limited” and “surface attachment/detachment limited.” Coupled with external supply of atoms, the self-limited behavior of facet size is theoretically predicted. Moreover, we find that the self-limited stable facet size in trenches of different widths has a specific relationship determined by the surface energy ratio, kinetic rate ratio, and isolated growth rate difference. The two limited cases could be discriminated according to the mathematical fitting of one exponent in this relationship based on the stable facet size in trenches of different widths.

Jiang, S., E-mail: jiang@imec.be; Heyns, M., E-mail: marc.heyns@imec.be [IMEC, Kapeldreef 75, B-3001 Heverlee (Belgium); Department of Metallurgy and Materials Engineering, KULeuven, Kasteelpark Arenberg 44-bus 2450, B-3001 Heverlee (Belgium); Merckling, C.; Guo, W.; Waldron, N.; Caymax, M. [IMEC, Kapeldreef 75, B-3001 Heverlee (Belgium); Vandervorst, W. [IMEC, Kapeldreef 75, B-3001 Heverlee (Belgium); Department of Physics and Astronomy, KULeuven, Celestijnenlaan 200D-bus 2418, B-3001 Heverlee (Belgium); Seefeldt, M. [Department of Metallurgy and Materials Engineering, KULeuven, Kasteelpark Arenberg 44-bus 2450, B-3001 Heverlee (Belgium)

2014-01-14T23:59:59.000Z

388

Identification of dominant scattering mechanism in epitaxial graphene on SiC  

SciTech Connect (OSTI)

A scheme of identification of scattering mechanisms in epitaxial graphene (EG) on SiC substrate is developed and applied to three EG samples grown on SiC (0001), (112{sup ¯}0), and (101{sup ¯}0) substrates. Hall measurements combined with defect detection technique enable us to evaluate the individual contributions to the carrier scatterings by defects and by substrates. It is found that the dominant scatterings can be due to either substrate or defects, dependent on the substrate orientations. The EG on SiC (112{sup ¯}0) exhibits a better control over the two major scattering mechanisms and achieves the highest mobility even with a high carrier concentration, promising for high performance graphene-based electronic devices. The method developed here will shed light on major aspects in governing carrier transport in EG to harness it effectively.

Lin, Jingjing; Guo, Liwei, E-mail: lwguo@iphy.ac.cn, E-mail: chenx29@aphy.iphy.ac.cn; Jia, Yuping; Huang, Jiao; Guo, Yu; Li, Zhilin; Chen, Xiaolong, E-mail: lwguo@iphy.ac.cn, E-mail: chenx29@aphy.iphy.ac.cn [Research and Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Yang, Rong; Wu, Shuang; Zhang, Guangyu [Nanoscale Physics and Devices Laboratory, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)

2014-05-05T23:59:59.000Z

389

Epitaxial lift-off of quantum dot enhanced GaAs single junction solar cells  

SciTech Connect (OSTI)

InAs/GaAs strain-balanced quantum dot (QD) n-i-p solar cells were fabricated by epitaxial lift-off (ELO), creating thin and flexible devices that exhibit an enhanced sub-GaAs bandgap current collection extending into the near infrared. Materials and optical analysis indicates that QD quality after ELO processing is preserved, which is supported by transmission electron microscopy images of the QD superlattice post-ELO. Spectral responsivity measurements depict a broadband resonant cavity enhancement past the GaAs bandedge, which is due to the thinning of the device. Integrated external quantum efficiency shows a QD contribution to the short circuit current density of 0.23?mA/cm{sup 2}.

Bennett, Mitchell F.; Bittner, Zachary S.; Forbes, David V.; Hubbard, Seth M., E-mail: smhsps@rit.edu [Rochester Institute of Technology, Rochester, New York 14623 (United States); Rao Tatavarti, Sudersena; Wibowo, Andree; Pan, Noren; Chern, Kevin [MicroLink Devices, Inc., Niles, Illinois 60714 (United States)] [MicroLink Devices, Inc., Niles, Illinois 60714 (United States); Phillip Ahrenkiel, S. [South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States)] [South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States)

2013-11-18T23:59:59.000Z

390

Epitaxial two-dimensional nitrogen atomic sheet in GaAs  

SciTech Connect (OSTI)

We have grown an epitaxial two-dimensional nitrogen (N) atomic sheet in GaAs by using the site-controlled N ?-doping technique. We observed a change of the electronic states in N ?-doped GaAs from the isolated impurity centers to the delocalized impurity band at 1.49?eV with increasing N-doping density. According to the excitation-power- and temperature-dependent photoluminescence (PL) spectra, the emission related to localized levels below the impurity band edge was dominant at low excitation power and temperature, whereas the effects of the localized levels can be neglected by increasing the excitation power and temperature. Furthermore, a clear Landau shift of the PL-peak energy was observed at several Tesla in the Faraday configuration, in contrast to the case in the impurity limit.

Harada, Yukihiro, E-mail: y.harada@eedept.kobe-u.ac.jp; Yamamoto, Masuki; Baba, Takeshi; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

2014-01-27T23:59:59.000Z

391

Nanoporous films for epitaxial growth of single crystal semiconductor materials : final LDRD report.  

SciTech Connect (OSTI)

This senior council Tier 1 LDRD was focused on exploring the use of porous growth masks as a method for defect reduction during heteroepitaxial crystal growth. Initially our goal was to investigate porous silica as a growth mask, however, we expanded the scope of the research to include several other porous growth masks on various size scales, including mesoporous carbon, photolithographically patterned SU-8 and carbonized SU-8 structures. Use of photolithographically defined growth templates represents a new direction, unique in the extensive literature of patterned epitaxial growth, and presents the possibility of providing a single step growth mask. Additional research included investigation of pore viability via electrochemical deposition into high aspect ratio photoresist. This project was a small footprint research effort which, nonetheless, produced significant progress towards both the stated goal as well as unanticipated research directions.

Rowen, Adam M.; Koleske, Daniel David; Fan, Hongyou; Brinker, C. Jeffrey; Burckel, David Bruce; Williams, John Dalton; Arrington, Christian L.; Steen, William Arthur

2007-10-01T23:59:59.000Z

392

Achieving clean epitaxial graphene surfaces suitable for device applications by improved lithographic process  

SciTech Connect (OSTI)

It is well-known that the performance of graphene electronic devices is often limited by extrinsic scattering related to resist residue from transfer, lithography, and other processes. Here, we report a polymer-assisted fabrication procedure that produces a clean graphene surface following device fabrication by a standard lithography process. The effectiveness of this improved lithography process is demonstrated by examining the temperature dependence of epitaxial graphene-metal contact resistance using the transfer length method for Ti/Au (10?nm/50?nm) metallization. The Landauer-Buttiker model was used to explain carrier transport at the graphene-metal interface as a function of temperature. At room temperature, a contact resistance of 140 ?-?m was obtained after a thermal anneal at 523?K for 2?hr under vacuum, which is comparable to state-of-the-art values.

Nath, A., E-mail: anath@gmu.edu; Rao, M. V. [George Mason University, 4400 University Dr., Fairfax, Virginia 22030 (United States); Koehler, A. D.; Jernigan, G. G.; Wheeler, V. D.; Hite, J. K.; Hernández, S. C.; Robinson, Z. R.; Myers-Ward, R. L.; Eddy, C. R.; Gaskill, D. K. [U.S. Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, D.C. 20375 (United States); Garces, N. Y. [Sotera Defense Solutions, 2200 Defense Hwy. Suite 405, Crofton, Maryland 21114 (United States)

2014-06-02T23:59:59.000Z

393

Nufact 2008 The Beta Beam WP Beta beam R&D status  

E-Print Network [OSTI]

Nufact 2008 The Beta Beam WP Nufact 08 1 Beta beam R&D status Elena Wildner, CERN on behalf of the Beta Beam Study Group EURISOL/Euronu #12;Nufact 2008 The Beta Beam WP Nufact08Nufact08 Outline Recall, EURISOL Ion Production Loss Management Improvements New Program, EuroNu 2 #12;Nufact 2008 The Beta Beam WP

McDonald, Kirk

394

A Timoshenko beam theory with pressure corrections for layered orthotropic beams  

E-Print Network [OSTI]

A Timoshenko beam theory with pressure corrections for layered orthotropic beams Graeme J. Kennedya of Michigan, Ann Arbor, MI 48109, USA Abstract A Timoshenko beam theory for layered orthotropic beams and rotation variables that provide the kinematic description of the beam, stress and strain moments used

Papalambros, Panos

395

Molecular electrostatic potentials by systematic molecular fragmentation  

SciTech Connect (OSTI)

A simple method is presented for estimating the molecular electrostatic potential in and around molecules using systematic molecular fragmentation. This approach estimates the potential directly from the electron density. The accuracy of the method is established for a set of organic molecules and ions. The utility of the approach is demonstrated by estimating the binding energy of a water molecule in an internal cavity in the protein ubiquitin.

Reid, David M.; Collins, Michael A. [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)] [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)

2013-11-14T23:59:59.000Z

396

Structured epitaxial graphene: growth and properties Yike Hu1, Ming Ruan1, Zelei Guo1, Rui Dong1, James Palmer1, John Hankinson1,  

E-Print Network [OSTI]

1 Structured epitaxial graphene: growth and properties Yike Hu1 Abstract Graphene is generally considered to be a strong candidate to succeed. Currently demonstrated viable graphene devices are essentially limited to micron

Paris-Sud XI, Université de

397

Relaxation of crystal lattice parameters and structural ordering in In{sub x}Ga{sub 1-x}As epitaxial alloys  

SciTech Connect (OSTI)

Epitaxial In{sub x}Ga{sub 1-x}As/GaAs(100) heterostructures grown by the MOC-hydride method with a considerable lattice mismatch are studied by X-ray diffraction and scanning electron microscopy. The relaxation coefficient of the crystal lattice of the epitaxial alloy is calculated and the deformation energy is evaluated. It is shown that, at a concentration of the In atoms in metal sublattice close to x = 0.5, the superstructural phase formed on the surface of the epitaxial In{sub x}Ga{sub 1-x}As alloy is the InGaAs{sub 2} compound with a layered tetragonal crystal lattice and ordered arrangement of the atoms of the metal sublattice in the growth plane of the epitaxial film.

Seredin, P. V., E-mail: paul@phys.vsu.ru; Glotov, A. V.; Domashevskaya, E. P. [Voronezh State University (Russian Federation); Arsentyev, I. N., E-mail: arsentyev@mail.ioffe.ru; Vinokurov, D. A. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Stankevich, A. L.; Tarasov, I. S. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2010-08-15T23:59:59.000Z

398

Microstructure and Mechanics of Superconductor Epitaxy via the Chemical Solution Deposition Method  

SciTech Connect (OSTI)

Executive Summary: Initially the funds were sufficient funds were awarded to support one graduate student and one post-doc. Lange, though other funds, also supported a graduate intern from ETH Zurich, Switzerland for a period of 6 months. The initial direction was to study the chemical solution deposition method to understand the microstructural and mechanical phenomena that currently limit the production of thick film, reliable superconductor wires. The study was focused on producing thicker buffer layer(s) on Ni-alloy substrates produced by the RABiTS method. It focused on the development of the microstructure during epitaxy, and the mechanical phenomena that produce cracks during dip-coating, pyrolysis (decomposition of precursors during heating), crystallization and epitaxy. The initial direction of producing thicker layers of a know buffer layer material was redirected by co-workers at ORNL, in an attempt to epitaxially synthesize a potential buffer layer material, LaMnO3, via the solution route. After a more than a period of 6 months that showed that the LaMnO3 reacted with the Ni-W substrate at temperatures that could produce epitaxy, reviewers at the annual program review strongly recommended that the research was not yielding positive results. The only positive result presented at the meeting was that much thicker films could be produce by incorporating a polymer into the precursor that appeared to increase the precursor’s resistance to crack growth. Thus, to continue the program, the objectives were changed to find compositions with the perovskite structure that would be a) chemically compatible with either the Ni-W RABiTS or the MgO IBAD Ni-alloy substrates, and produce a better lattice parameter fit between either of the two substrates. At the start of the second year, the funding was reduced to 2/3’s of the first year level, which required the termination of the post-doc after approximately 5 months into the second year. From then on, further funding was intermittent to say the least, and funding to support the student and the research expenses has to be supplemented by Lange’s gift funds. During the first part of the second year, strontium zirconate was identified as an alternative to lanthanum manganite as a buffer layer for use on the IBAD MgO superconducting wire. A lattice parameter of 4.101 Angstroms offers a reduced lattice mismatch between the MgO and SrZrO3. Studies were focused on investigating hybrid precursor routes, combining Sr acetate with a number of different Zr alkoxides. Initial results from heat treating precursors to form powders are positive with the formation of orthorhombic SrZrO3 at temperatures between 800°C and 1100°C under a reducing atmosphere of Ar – 5% H2. Buffer layer research on RABiTS substrates were centered on GdAlO3 (3.71 Å) and YAlO3 (3.68 Å) buffer layer materials. Powder experiments in YAlO3 have shown the perovskite phase to be metastable at processing temperatures below 1500 °C. Experiments involving spin coating of YAlO3 precursors have found significant problems involved with wettability of the YAlO3 precursor (Yttrium acetate, Aluminum tri-sec butoxide, DI water and Formic Acid) on RABiTS substrates; this, and the demise of the funds precluded further research using YAlO3. The diminished funds for the second year, and the small, tricked funds during the third year lead to a redirection of the student to another research area., and a stop to any experimental achievements that were much too ambition relative to the available funds. The only positive results obtained during this latter period was the understanding why two dissimilar structures could result in an epitaxial relation. It was shown that two rules of crystal chemistry, cation/anion coordination and charge balance, could be applied to understand the epitaxy of SrTiO3 on Ni c(2 X 2)S, TiO2 (anatase) on LaAlO3, TiO2 (rutile) on r-plane Al2O3, and Zr1-x(Yx)O2 on (0001) Al2O3. This new understanding of the interface between two dissimilar structures has important implications that include the buff

Frederick F. Lange

2006-11-30T23:59:59.000Z

399

Realizing in-plane surface diffraction by x-ray multiple-beam diffraction with large incidence angle  

SciTech Connect (OSTI)

Based on rigorous dynamical-theory calculations, we demonstrate the principle of an x-ray multiple-beam diffraction (MBD) scheme that overcomes the long-lasting difficulties of high-resolution in-plane diffraction from crystal surfaces. This scheme only utilizes symmetric reflection geometry with large incident angles but activates the out-of-plane and in-plane diffraction processes simultaneously and separately in the continuous MBD planes. The in-plane diffraction is realized by detoured MBD, where the intermediate diffracted waves propagate parallel to the surface, which corresponds to an absolute Bragg surface diffraction configuration that is extremely sensitive to surface structures. A series of MBD diffraction and imaging techniques may be developed from this principle to study surface/interface (misfit) strains, lateral nanostructures, and phase transitions of a wide range of (pseudo)cubic crystal structures, including ultrathin epitaxial films and multilayers, quantum dots, strain-engineered semiconductor or (multi)ferroic materials, etc.

Huang, Xian-Rong, E-mail: xiahuang@aps.anl.gov; Gog, Thomas; Assoufid, Lahsen [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Peng, Ru-Wen, E-mail: rwpeng@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Siddons, D. P. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2014-11-03T23:59:59.000Z

400

Development of Production PVD-AIN Buffer Layer System and Processes to Reduce Epitaxy Costs and Increase LED Efficiency  

SciTech Connect (OSTI)

The DOE has set aggressive goals for solid state lighting (SSL) adoption, which require manufacturing and quality improvements for virtually all process steps leading to an LED luminaire product. The goals pertinent to this proposed project are to reduce the cost and improve the quality of the epitaxial growth processes used to build LED structures. The objectives outlined in this proposal focus on achieving cost reduction and performance improvements over state-of-the-art, using technologies that are low in cost and amenable to high efficiency manufacturing. The objectives of the outlined proposal focus on cost reductions in epitaxial growth by reducing epitaxy layer thickness and hetero-epitaxial strain, and by enabling the use of larger, less expensive silicon substrates and would be accomplished through the introduction of a high productivity reactive sputtering system and an effective sputtered aluminum-nitride (AlN) buffer/nucleation layer process. Success of the proposed project could enable efficient adoption of GaN on-silicon (GaN/Si) epitaxial technology on 150mm silicon substrates. The reduction in epitaxy cost per cm{sup 2} using 150mm GaN-on-Si technology derives from (1) a reduction in cost of ownership and increase in throughput for the buffer deposition process via the elimination of MOCVD buffer layers and other throughput and CoO enhancements, (2) improvement in brightness through reductions in defect density, (3) reduction in substrate cost through the replacement of sapphire with silicon, and (4) reduction in non-ESD yield loss through reductions in wafer bow and temperature variation. The adoption of 150mm GaN/Si processing will also facilitate significant cost reductions in subsequent wafer fabrication manufacturing costs. There were three phases to this project. These three phases overlap in order to aggressively facilitate a commercially available production GaN/Si capability. In Phase I of the project, the repeatability of the performance was analyzed and improvements implemented to the Veeco PVD-AlN prototype system to establish a specification and baseline PVD-AlN films on sapphire and in parallel the evaluation of PVD AlN on silicon substrates began. In Phase II of the project a Beta tool based on a scaled-up process module capable of depositing uniform films on batches of 4”or 6” diameter substrates in a production worthy operation was developed and qualified. In Phase III, the means to increase the throughput of the PVD-AlN system was evaluated and focused primarily on minimizing the impact of the substrate heating and cooling times that dominated the overall cycle time.

Cerio, Frank

2013-09-14T23:59:59.000Z

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401

Physics Opportunities with Meson Beams  

E-Print Network [OSTI]

Over the past two decades, meson photo- and electro-production data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even nonexistent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state of-the-art meson-beam facility needs to be constructed. The present paper summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.

Briscoe, William J; Haberzettl, Helmut; Manley, D Mark; Naruki, Megumi; Strakovsky, Igor I; Swanson, Eric S

2015-01-01T23:59:59.000Z

402

Effect of Beam-Beam Interactions on Stability of Coherent Oscillations in a Muon Collider  

SciTech Connect (OSTI)

In order to achieve peak luminosity of a muon collider in the 10{sup 34}/cm{sup 2}/s range the number of muons per bunch should be of the order of a few units of 10{sup 12} rendering the beam-beam parameter as high as 0.1 per IP. Such strong beam-beam interaction can be a source of instability if the working point is chosen close to a coherent beam-beam resonance. On the other hand, the beam-beam tunespread can provide a mechanism of suppression of the beam-wall driven instabilities. In this report the coherent instabilities driven by beam-beam and beam-wall interactions are studied with the help of BBSS code for the case of 1.5 TeV c.o.m muon collider.

Alexahin, Y.; /Fermilab; Ohmi, K.; /KEK, Tsukuba

2012-05-01T23:59:59.000Z

403

Survey of Collective Instabilities and Beam-Plasma Interactions in Intense Heavy Ion Beams  

E-Print Network [OSTI]

H. Qin, Phys. Rev. ST Accel. Beams 4, 104401 (2001). [30] S.Davidson, Phys. Rev. ST Accel. Beams 5, 021001 (2002). [31]Channell, Phys. Rev. ST Accel. Beams 2, 074401 (1999); [32

Davidson, Ronald C.

2009-01-01T23:59:59.000Z

404

Nonparaxial Mathieu and Weber accelerating beams  

E-Print Network [OSTI]

We demonstrate both theoretically and experimentally nonparaxial Mathieu and Weber accelerating beams, generalizing the concept of previously found accelerating beams. We show that such beams bend into large angles along circular, elliptical or parabolic trajectories but still retain nondiffracting and self-healing capabilities. The circular nonparaxial accelerating beams can be considered as a special case of the Mathieu accelerating beams, while an Airy beam is only a special case of the Weber beams at the paraxial limit. Not only generalized nonparaxial accelerating beams open up many possibilities of beam engineering for applications, but the fundamental concept developed here can be applied to other linear wave systems in nature, ranging from electromagnetic and elastic waves to matter waves.

Peng Zhang; Yi Hu; Tongcang Li; Drake Cannan; Xiaobo Yin; Roberto Morandotti; Zhigang Chen; Xiang Zhang

2012-10-23T23:59:59.000Z

405

Finding beam focus errors automatically  

SciTech Connect (OSTI)

An automated method for finding beam focus errors using an optimization program called COMFORT-PLUS. The steps involved in finding the correction factors using COMFORT-PLUS has been used to find the beam focus errors for two damping rings at the SLAC Linear Collider. The program is to be used as an off-line program to analyze actual measured data for any SLC system. A limitation on the application of this procedure is found to be that it depends on the magnitude of the machine errors. Another is that the program is not totally automated since the user must decide a priori where to look for errors. (LEW)

Lee, M.J.; Clearwater, S.H.; Kleban, S.D.

1987-01-01T23:59:59.000Z

406

Shimmed electron beam welding process  

DOE Patents [OSTI]

A modified electron beam welding process effects welding of joints between superalloy materials by inserting a weldable shim in the joint and heating the superalloy materials with an electron beam. The process insures a full penetration of joints with a consistent percentage of filler material and thereby improves fatigue life of the joint by three to four times as compared with the prior art. The process also allows variable shim thickness and joint fit-up gaps to provide increased flexibility for manufacturing when joining complex airfoil structures and the like.

Feng, Ganjiang (Clifton Park, NY); Nowak, Daniel Anthony (Alplaus, NY); Murphy, John Thomas (Niskayuna, NY)

2002-01-01T23:59:59.000Z

407

Transverse beam shape measurements of intense proton beams using optical transition radiation  

SciTech Connect (OSTI)

A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

Scarpine, Victor E.; /Fermilab

2012-03-01T23:59:59.000Z

408

Pulsed laser deposition of epitaxial yttrium iron garnet films with low Gilbert damping and bulk-like magnetization  

SciTech Connect (OSTI)

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.

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

409

Magnetic anisotropies in epitaxial Fe{sub 3}O{sub 4}/GaAs(100) patterned structures  

SciTech Connect (OSTI)

Previous studies on epitaxial Fe{sub 3}O{sub 4} rings in the context of spin-transfer torque effect have revealed complicated and undesirable domain structures, attributed to the intrinsic fourfold magnetocrystalline anisotropy in the ferrite. In this Letter, we report a viable solution to this problem, utilizing a 6-nm-thick epitaxial Fe{sub 3}O{sub 4} thin film on GaAs(100), where the fourfold magnetocrystalline anisotropy is negligible. We demonstrate that in the Fe{sub 3}O{sub 4} planar wires patterned from our thin film, such a unique magnetic anisotropy system has been preserved, and relatively simple magnetic domain configurations compared to those previous reports can be obtained.

Zhang, W., E-mail: xiaotur@gmail.com; Zhang, D.; Yuan, S. J.; Huang, Z. C.; Zhai, Y. [Department of Physics, Southeast University, Nanjing 211189 (China); Wong, P. K. J. [NanoElectronics Group, MESA Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede (Netherlands); Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Wu, J. [Department of Physics, University of York, York YO10 5DD (United Kingdom); Xu, Y. B. [Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York, YO10 5DD (United Kingdom)

2014-10-15T23:59:59.000Z

410

Blinking suppression of CdTe quantum dots on epitaxial graphene and the analysis with Marcus electron transfer  

SciTech Connect (OSTI)

We have prepared epitaxial graphene by a Si sublimation method from 4H-SiC. Single-particle spectroscopy of CdTe quantum dots (QDs) on epitaxial graphene covered with polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG) showed the suppression of luminescence blinking and ?10 times decreased luminescence intensity as compared with those on a glass. The electronic coupling constant, H{sub 01}, between CdTe QDs and graphene was calculated to be (3.3?±?0.4)?×?10{sup 2?}cm{sup ?1} in PVP and (3.7?±?0.8)?×?10{sup 2?}cm{sup ?1} in PEG based on Marcus theory of electron transfer and Tang-Marcus model of blinking with statistical distribution.

Hirose, Takuya; Tamai, Naoto, E-mail: tamai@kwansei.ac.jp [Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan); Kutsuma, Yasunori; Kurita, Atsusi; Kaneko, Tadaaki [Department of Physics, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan)

2014-08-25T23:59:59.000Z

411

Epitaxial growth of CdTe oriented thin films, infrared characterization and possible applications to photo-voltaic cells  

E-Print Network [OSTI]

573 Epitaxial growth of CdTe oriented thin films, infrared characterization and possible décembre 1979, accepté le 12 décembre 1979) Résumé. 2014 Des films minces orientés de CdTe, d de CdTe cubique dont la face (111), polie mécaniquement et décapée chimiquement, est préalablement

Paris-Sud XI, Université de

412

Anomalous thickness-dependent strain states and strain-tunable magnetization in Zn-doped ferrite epitaxial films  

SciTech Connect (OSTI)

A series of Zn{sub x}Fe{sub 3?x}O{sub 4} (ZFO, x?=?0.4) thin films were epitaxially deposited on single-crystal (001)-SrTiO{sub 3} (STO) substrates by radio frequency magnetron sputtering. The anomalous thickness-dependent strain states of ZFO films were found, i.e., a tensile in-plane strain exists in the thinner ZFO film and which monotonously turns into compressive in the thicker films. Considering the lattice constant of bulk ZFO is bigger than that of STO, this strain state cannot be explained in the conventional framework of lattice-mismatch-induced strain in the hetero-epitaxial system. This unusual phenomenon is proposed to be closely related to the Volmer-Weber film growth mode in the thinner films and incorporation of the interstitial atoms into the island's boundaries during subsequent epitaxial growth of the thicker films. The ZFO/STO epitaxial film is found in the nature of magnetic semiconductor by transport measurements. The in-plane magnetization of the ZFO/STO films is found to increase as the in-plane compressive strain develops, which is further proved in the (001)-ZFO/PMN-PT film where the film strain state can be in situ controlled with applied electric field. This compressive-strain-enhanced magnetization can be attributed to the strain-mediated electric-field-induced in-plane magnetic anisotropy field enhancement. The above results indicate that strain engineering on magnetic oxide semiconductor ZFO films is promising for novel oxide-electronic devices.

Yang, Y. J.; Bao, J.; Gao, C., E-mail: zlluo@ustc.edu.cn, E-mail: cgao@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026 (China); CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Yang, M. M.; Luo, Z. L., E-mail: zlluo@ustc.edu.cn, E-mail: cgao@ustc.edu.cn; Hu, C. S.; Chen, X. C.; Pan, G. Q. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huang, H. L. [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zhang, S.; Wang, J. W.; Li, P. S.; Liu, Y.; Zhao, Y. G. [Department of Physics and State Key Laboratory of New Ceramics, Fine Processing, Tsinghua University, Beijing 100084 (China); Jiang, T.; Liu, Y. K.; Li, X. G. [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science, Technology of China, Hefei, Anhui 230026 (China)

2014-05-07T23:59:59.000Z

413

State-to-state dynamics of molecular energy transfer  

SciTech Connect (OSTI)

The goal of this research program is to elucidate the elementary dynamical mechanisms of vibrational and rotational energy transfer between molecules, at a quantum-state resolved level of detail. Molecular beam techniques are used to isolate individual molecular collisions, and to control the kinetic energy of collision. Lasers are used both to prepare specific quantum states prior to collision by stimulated-emission pumping (SEP), and to measure the distribution of quantum states in the collision products by laser-induced fluorescence (LIF). The results are interpreted in terms of dynamical models, which may be cast in a classical, semiclassical or quantum mechanical framework, as appropriate.

Gentry, W.R.; Giese, C.F. [Univ. of Minnesota, Minneapolis (United States)

1993-12-01T23:59:59.000Z

414

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

SciTech Connect (OSTI)

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.

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

415

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

SciTech Connect (OSTI)

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.

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

416

accidental beam loss: Topics by E-print Network  

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

interaction of fields induced by the beam with their environment. Beam current transformers as well as beam position monitors are based on this principle. The signals induced...

417

On Gaussian Beams Described by Jacobi's Equation  

E-Print Network [OSTI]

Gaussian beams describe the amplitude and phase of rays and are widely used to model acoustic propagation. This paper describes four new results in the theory of Gaussian beams. (1) A new version of the ?ervený equations ...

Smith, Steven T.

418

Electron Beam--21st Century Food Technology  

E-Print Network [OSTI]

This publication explains electron beam irradiation technology to consumers, industry professionals and government officials. Electron beam irradiation is a method of treating food and other products for pathogens that might jeopardize food safety....

Vestal, Andy

2003-03-07T23:59:59.000Z

419

Autogenerator of beams of charged particles  

DOE Patents [OSTI]

An autogenerating apparatus provides secondary intense relativistic current beam pulses in response to an injected beam pulse. One or more electromagnetic energy storage devices are provided in conjunction with gaps along a beam propagation path for the injected beam pulse. For injected beam pulses which are no longer than double the transit time of electromagnetic waves within the storage devices (which may be resonant cavities), distinct secondary beam pulses are generated by each of the energy storage devices. The beam propagation path, together with the one or more gaps provided therein, operates as a pulse forming transmission line cavity, in which the separate cavities associated with the gaps provide delays for electromagnetic waves generated at the gaps. After doubly traversing the cavity, the electromagnetic waves cause the gap to generate the secondary beam pulses, which are thus delayed by a time interval equal to the double transit time for the induced wave within the cavity.

Adler, R.J.; Mazarakis, M.G.; Miller, R.M.; Shope, S.L.; Smith, D.L.

1983-10-31T23:59:59.000Z

420

Transport of elliptic intense charged -particle beams  

E-Print Network [OSTI]

The transport theory of high-intensity elliptic charged-particle beams is presented. In particular, the halo formation and beam loss problem associated with the high space charge and small-aperture structure is addressed, ...

Zhou, J. (Jing), 1978-

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Adaptive phase measurements for narrowband squeezed beams  

E-Print Network [OSTI]

We have previously [Phys. Rev. A 65, 043803 (2002)] analyzed adaptive measurements for estimating the continuously varying phase of a coherent beam, and a broadband squeezed beam. A real squeezed beam must have finite photon flux N and hence can be significantly squeezed only over a limited frequency range. In this paper we analyze adaptive phase measurements of this type for a realistic model of a squeezed beam. We show that, provided it is possible to suitably choose the parameters of the beam, a mean-square phase uncertainty scaling as (N/kappa)^{-5/8} is possible, where kappa is the linewidth of the beam resulting from the fluctuating phase. This is an improvement over the (N/kappa)^{-1/2} scaling found previously for coherent beams. In the experimentally realistic case where there is a limit on the maximum squeezing possible, the variance will be reduced below that for coherent beams, though the scaling is unchanged.

Dominic W. Berry; Howard M. Wiseman

2006-03-22T23:59:59.000Z

422

Autogenerator of beams of charged particles  

DOE Patents [OSTI]

An autogenerating apparatus provides secondary intense relativistic current beam pulses in response to an injected beam pulse. One or more electromagnetic energy storage devices are provided in conjunction with gaps along a beam propagation path for the injected beam pulse. For injected beam pulses which are no longer than double the transit time of electromagnetic waves within the storage devices (which may be resonant cavities), distinct secondary beam pulses are generated by each of the energy storage devices. The beam propagation path, together with the one or more gaps provided therein, operates as a pulse forming transmission line cavity, in which the separate cavities associated with the gaps provide delays for electromagnetic waves generated at the gaps. After doubly traversing the cavity, the electromagnetic waves cause the gap to generate the secondary beam pulses, which are thus delayed by a time interval equal to the double transit time for the induced wave within the cavity.

Adler, Richard J. (Albuquerque, NM); Mazarakis, Michael G. (Albuquerque, NM); Miller, Robert B. (Albuquerque, NM); Shope, Steven L. (Albuquerque, NM); Smith, David L. (Albuquerque, NM)

1986-01-01T23:59:59.000Z

423

Physical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering  

SciTech Connect (OSTI)

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.

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

424

Site control technique for quantum dots using electron beam induced deposition  

SciTech Connect (OSTI)

To develop simple and high throughput sit definition technique for quantum dots (QDs), the electron beam induced deposition (EBID) method was used as desorption guide of phosphorus atoms form InP substrate. As the results one or a few indium (In) droplets (DLs) were created in the carbon grid pattern by thermal annealing at a temperature of 450°C for 10 min in the ultra high vacuum condition. The size of In DLs was larger than QDs, but arsenide DLs by molecular beam in growth chamber emitted wavelength of 1.028?m at 50K by photoluminescence measurement.

Iizuka, Kanji; Jung, JaeHun; Yokota, Hiroshi [Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro, Minami-saitama, Saitama 3458501 (Japan)

2014-05-15T23:59:59.000Z

425

Physics with energetic radioactive ion beams  

SciTech Connect (OSTI)

Beams of short-lived, unstable nuclei have opened new dimensions in studies of nuclear structure and reactions. Such beams also provide key information on reactions that take place in our sun and other stars. Status and prospects of the physics with energetic radioactive beams are summarized.

Henning, W.F.

1996-12-31T23:59:59.000Z

426

Gaussian beams in inhomogeneous anisotropic layered structures  

E-Print Network [OSTI]

Gaussian beams in inhomogeneous anisotropic layered structures Vlastislav Cerven´y 1 ) and Ivan@ig.cas.cz. Summary Gaussian beams concentrated close to rays of high-frequency seismic body waves prop- agating in an inhomogeneous anisotropic layered structure are studied. The amplitude profiles of the Gaussian beam along

Cerveny, Vlastislav

427

A Generalized Vlasov Theory for Composite Beams  

E-Print Network [OSTI]

A Generalized Vlasov Theory for Composite Beams Wenbin Yu, Department of Mechanical and Aerospace-0150 Abstract A generalized Vlasov theory for composite beams with arbitrary geometric and material sectional properties is developed based on the variational asymptotic beam sectional analysis. Instead of invoking ad

Yu, Wenbin

428

Stability design of long precast concrete beams  

E-Print Network [OSTI]

Stability design of long precast concrete beams T. J. Stratford, BA, MEng, C. J. Burgoyne BA, MSc needed for design engineers to check the stability of precast concrete beams when simply supported loads can be determined and how estimates can be made of the eect of imperfections both in the beam

Burgoyne, Chris

429

Lateral stability of long precast concrete beams  

E-Print Network [OSTI]

Lateral stability of long precast concrete beams T. J. Stratford, BA, BEng, and C. J. Burgoyne, BA, MSc, CEng, MICE & Modern precast concrete bridge beams are becoming increasingly long and slender, making them more susceptible to buckling failure. This paper shows that once the beam is positioned

Burgoyne, Chris

430

Laser Telecommunication timeLaser beam  

E-Print Network [OSTI]

Laser Telecommunication Experiment Laser time Laser beam intensity timeLaser beam Laser battery Laser connected to a circuit without a modulator. Bottom graph illustrates what happen when a modulating signal is superimposed to the DC voltage driving the laser Laser beam intensity DC Input voltage DC

La Rosa, Andres H.

431

BEAM COUPLING IMPEDANCE STUDIES ON THE LHC FP420 MULTI-POCKET BEAM PIPE PROTOTYPE  

E-Print Network [OSTI]

BEAM COUPLING IMPEDANCE STUDIES ON THE LHC FP420 MULTI-POCKET BEAM PIPE PROTOTYPE F. Roncarolo , R LHC beam pipe in which two pockets hosting the detectors introduce an abrupt cross-section variation of the pipe. During the FP420 proposed operation, each station is moved towards the beam as close as 5 mm ( 15

432

Interface control of surface photochemical reactivity in ultrathin epitaxial ferroelectric films  

SciTech Connect (OSTI)

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.

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

433

Kinetics of CO adsorption on epitaxial (111)Cu on (111)Pd thin films  

SciTech Connect (OSTI)

CO adsorption has been studied on (111)Cu/Pd thin-film surfaces grown epitaxially on mica in UHV of base pressure 5 x 10/sup -11/ Torr. Auger electron spectroscopy investigations of the growth of Cu on (111)Pd films showed that layer growth occurred. The Kelvin probe, work function method was used to monitor the CO adsorption at 298 K as a function of Cu overlayer thickness. It was found that very thin Cu overlayers had a drastic effect on saturation CO coverage: one monolayer of copper reduced the saturation CO coverage by /similar to/95%. For the pure (111)Pd thin-film surface, the data showed that the rate of CO adsorption changes when the CO fractional coverage approaches /similar to/0.4. This result is most likely due to the previously reported change in CO superlattice structure that occurs with increasing coverage. The kinetic adsorption data for various bilayers were interpreted in terms of a first-order Kisliuk mobile precursor model.

Oral, B.; Kothari, R.; Vook, R.W.

1989-05-01T23:59:59.000Z

434

Hydride vapor phase epitaxy and characterization of high-quality ScN epilayers  

SciTech Connect (OSTI)

The heteroepitaxial growth of ScN films was investigated on various substrates by hydride vapor phase epitaxy (HVPE). Single crystalline mirror-like ScN(100) and ScN(110) layers were successfully deposited on r- and m-plane sapphire substrates, respectively. Homogeneous stoichiometric films (N/Sc ratio 1.01?±?0.10) up to 40??m in thickness were deposited. Their mosaicity drastically improved with increasing the film thickness. The band gap was determined by optical methods to be 2.06?eV. Impurity concentrations including H, C, O, Si, and Cl were investigated through energy dispersive X-ray spectrometry and secondary ion mass spectrometry. As a result, it was found that the presence of impurities was efficiently suppressed in comparison with that of HVPE-grown ScN films reported in the past, which was possible thanks to the home-designed corrosion-free HVPE reactor. Room-temperature Hall measurements indicated that the residual free electron concentrations ranged between 10{sup 18}–10{sup 20}?cm{sup ?3}, which was markedly lower than the reported values. The carrier mobility increased monotonically with the decreasing in carrier concentration, achieving the largest value ever reported, 284?cm{sup 2}?V{sup ?1}?s{sup ?1} at n?=?3.7?×?10{sup 18}?cm{sup ?3}.

Oshima, Yuichi, E-mail: OSHIMA.Yuichi@nims.go.jp; Víllora, Encarnación G.; Shimamura, Kiyoshi [Environment and Energy Materials Research Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2014-04-21T23:59:59.000Z

435

Electronic structure of fully epitaxial Co2TiSn thin films  

SciTech Connect (OSTI)

In this article we report on the properties of thin films of the full Heusler compound Co{sub 2}TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600 C. The films are well ordered in the L2{sub 1} structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 {mu}{sub B} on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L{sub 3,2} edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co{sub 2}TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.

Meinert, Markus; Schmalhorst, Jan; Wulfmeier, Hendrik; Reiss, Gunter; Arenholz, Elke; Graf, Tanja; Felser, Claudia

2010-10-28T23:59:59.000Z

436

VAV Reheat Versus Active Chilled Beams and DOAS  

E-Print Network [OSTI]

Andrey. Don’t Turn Active Beams Into Expensive Diffusers,added costs of the piping and beams for ACBs are simply too1. Simmonds, Peter. To Beam or not To Beam? , Engineered

Stein, Jeff; Taylor, Steven

2013-01-01T23:59:59.000Z

437

Neutron beam testing of triblades  

SciTech Connect (OSTI)

Four IBM Triblades were tested in the Irradiation of Chips and Electronics facility at the Los Alamos Neutron Science Center. Triblades include two dual-core Opteron processors and four PowerXCell 8i (Cell) processors. The Triblades were tested in their field configuration while running different applications, with the beam aimed at the Cell processor or the Opteron running the application. Testing focused on the Cell processors, which were tested while running five different applications and an idle condition. While neither application nor Triblade was statistically important in predicting the hazard rate, the hazard rate when the beam was aimed at the Opterons was significantly higher than when it was aimed at the Cell processors. In addition, four Cell blades (one in each Triblade) suffered voltage shorts, leading to their inoperability. The hardware tested is the same as that in the Roadrunner supercomputer.

Michalak, Sarah E [Los Alamos National Laboratory; Du Bois, Andrew J [Los Alamos National Laboratory; Storlie, Curtis B [Los Alamos National Laboratory; Rust, William N [Los Alamos National Laboratory; Du Bois, David H [Los Alamos National Laboratory; Modl, David G [Los Alamos National Laboratory; Quinn, Heather M [Los Alamos National Laboratory; Blanchard, Sean P [Los Alamos National Laboratory; Manuzzato, Andrea [UNIV DEGLI STUDI DI PADOVA ITALY

2010-12-16T23:59:59.000Z

438

The MICE Muon Beam Line  

SciTech Connect (OSTI)

In the Muon Ionization Cooling Experiment (MICE) at RAL, muons are produced and transported in a dedicated beam line connecting the production point (target) to the cooling channel. We discuss the main features of the beamline, meant to provide muons with momenta between 140 MeV/c and 240 MeV/c and emittances up to 10 mm rad, which is accomplished by means of a diffuser. Matching procedures to the MICE cooling channel are also described. In summer 2010 we performed an intense data taking campaign to finalize the calibration of the MICE Particle Identification (PID) detectors and the understanding of the beam line, which completes the STEPI phase of MICE. We highlight the main results from these data.

Apollonio, Marco [High Energy Physics Group, Department of Physics, Imperial College London SW7 2AZ (United Kingdom)

2011-10-06T23:59:59.000Z

439

Oxygen ion-beam microlithography  

DOE Patents [OSTI]

A method of providing and developing a resist on a substrate for constructing integrated circuit (IC) chips includes the following steps: of depositing a thin film of amorphous silicon or hydrogenated amorphous silicon on the substrate and exposing portions of the amorphous silicon to low-energy oxygen ion beams to oxidize the amorphous silicon at those selected portions. The nonoxidized portions are then removed by etching with RF-excited hydrogen plasma. Components of the IC chip can then be constructed through the removed portions of the resist. The entire process can be performed in an in-line vacuum production system having several vacuum chambers. Nitrogen or carbon ion beams can also be used.

Tsuo, Y. Simon (Lakewood, CO)

1991-01-01T23:59:59.000Z

440

X-ray beam finder  

DOE Patents [OSTI]

An X-ray beam finder for locating a focal spot of an X-ray tube includes a mass of X-ray opaque material having first and second axially-aligned, parallel-opposed faces connected by a plurality of substantially identical parallel holes perpendicular to the faces and a film holder for holding X-ray sensitive film tightly against one face while the other face is placed in contact with the window of an X-ray head.

Gilbert, H.W.

1983-06-16T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

A relation between surface oxide and oxygen-defect complexes in solid-phase epitaxial Si regrown from ion-beam-amorphized Si layers  

E-Print Network [OSTI]

of Applied Physics, California Institute of Technology, Pasadena, California 91125 Stefano Rassiga and Kelvin positron annihilation spectroscopy, secondary-ion mass spectroscopy, and Monte Carlo simulations. The O was used to measure the incorporation of O atoms in the Si sub- strate, predicted by Monte Carlo TRIM 8

Atwater, Harry

442

A relation between surface oxide and oxygen-defect complexes in solid-phase epitaxial Si regrown from ion-beam-amorphized Si layers  

SciTech Connect (OSTI)

We present a direct evidence that ion implantation through thin ({<=}5 nm) surface oxide layers is a source of O impurities, which form O-defect complexes during thermal treatment. The impurity-defect complexes are identified by correlating the results from positron annihilation spectroscopy, secondary-ion mass spectroscopy, and Monte Carlo simulations. The O atoms are introduced in the bulk by multiple recoil implantation by the primary ions. The signatures of large V{sub m}O{sub n} formations are observed at 800 degree sign C, which implies the existence of smaller species at lower temperatures. (c) 2000 American Institute of Physics.

Petkov, Mihail P. [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States)] [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States); Chen, Claudine M. [Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States); Atwater, Harry A. [Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States); Rassiga, Stefano [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States)] [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States); Lynn, Kelvin G. [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States)] [Department of Physics, Washington State University, Pullman, Washington 99163-2814 (United States)

2000-03-13T23:59:59.000Z

443

Molecular heat pump  

E-Print Network [OSTI]

We propose a novel molecular device that pumps heat against a thermal gradient. The system consists of a molecular element connecting two thermal reservoirs that are characterized by different spectral properties. The pumping action is achieved by applying an external force that periodically modulates molecular levels. This modulation affects periodic oscillations of the internal temperature of the molecule and the strength of its coupling to each reservoir resulting in a net heat flow in the desired direction. The heat flow is examined in the slow and fast modulation limits and for different modulation waveforms, thus making it possible to optimize the device performance.

Dvira Segal; Abraham Nitzan

2005-10-11T23:59:59.000Z

444

Accelerated molecular dynamics methods  

SciTech Connect (OSTI)

The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.

Perez, Danny [Los Alamos National Laboratory

2011-01-04T23:59:59.000Z

445

Carbon Fiber Damage in Accelerator Beam  

E-Print Network [OSTI]

Carbon fibers are commonly used as moving targets in Beam Wire Scanners. Because of their thermomechanical properties they are very resistant to particle beams. Their strength deteriorates with time due to radiation damage and low-cycle thermal fatigue. In case of high intensity beams this process can accelerate and in extreme cases the fiber is damaged during a single scan. In this work a model describing the fiber temperature, thermionic emission and sublimation is discussed. Results are compared with fiber damage test performed on SPS beam in November 2008. In conclusions the limits of Wire Scanner operation on high intensity beams are drawn.

Sapinski, M; Guerrero, A; Koopman, J; Métral, E

2009-01-01T23:59:59.000Z

446

W-Band Sheet Beam Klystron Design  

SciTech Connect (OSTI)

Sheet beam devices provide important advantages for very high power, narrow bandwidth RF sources like accelerator klystrons [1]. Reduced current density and increased surface area result in increased power capabi1ity, reduced magnetic fields for focusing and reduced cathode loading. These advantages are offset by increased complexity, beam formation and transport issues and potential for mode competition in the ovennoded cavities and drift tube. This paper will describe the design issues encountered in developing a 100 kW peak and 2 kW average power sheet beam k1ystron at W-band including beam formation, beam transport, circuit design, circuit fabrication and mode competition.

Scheitrum, G.; Caryotakis, G.; Burke, A.; Jensen, A.; Jongewaard, E.a Krasnykh, A.; Neubauer, M.; Phillips, R.; Rauenbuehler, K.; /SLAC

2011-11-11T23:59:59.000Z

447

Electron beam generation in Tevatron electron lenses  

SciTech Connect (OSTI)

New type of high perveance electron guns with convex cathode has been developed. Three guns described in this article are built to provide transverse electron current density distributions needed for Electron Lenses for beam-beam compensation in the Tevatron collider. The current distribution can be controlled either by the gun geometry or by voltage on a special control electrode located near cathode. We present the designs of the guns and report results of beam measurements on the test bench. Because of their high current density and low transverse temperature of electrons, electron guns of this type can be used in electron cooling and beam-beam compensation devices.

Kamerdzhiev, V.; Kuznetsov, G.; Shiltsev, V.; Solyak, N.; /Fermilab; Tiunov, M.; /Novosibirsk, IYF

2006-08-01T23:59:59.000Z

448

Scattering apodizer for laser beams  

DOE Patents [OSTI]

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Summers, M.A.; Hagen, W.F.; Boyd, R.D.

1984-01-01T23:59:59.000Z

449

Scattering apodizer for laser beams  

DOE Patents [OSTI]

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Summers, Mark A. (Livermore, CA); Hagen, Wilhelm F. (Livermore, CA); Boyd, Robert D. (Livermore, CA)

1985-01-01T23:59:59.000Z

450

Particle beam injector system and method  

DOE Patents [OSTI]

Methods and devices enable coupling of a charged particle beam to a radio frequency quadrupole accelerator. Coupling of the charged particle beam is accomplished, at least in-part, by relying on of sensitivity of the input phase space acceptance of the radio frequency quadrupole to the angle of the input charged particle beam. A first electric field across a beam deflector deflects the particle beam at an angle that is beyond the acceptance angle of the radio frequency quadrupole. By momentarily reversing or reducing the established electric field, a narrow portion of the charged particle beam is deflected at an angle within the acceptance angle of the radio frequency quadrupole. In another configuration, beam is directed at an angle within the acceptance angle of the radio frequency quadrupole by the first electric field and is deflected beyond the acceptance angle of the radio frequency quadrupole due to the second electric field.

Guethlein, Gary

2013-06-18T23:59:59.000Z

451

Paraxial Light Beams with Angular Momentum  

E-Print Network [OSTI]

Fundamental and applied concepts concerning the ability of light beams to carry a certain mechanical angular momentum with respect to the propagation axis are reviewed and discussed. Following issues are included: Historical reference; Angular momentum of a paraxial beam and its constituents; Spin angular momentum and paradoxes associated with it; Orbital angular momentum; Circularly-spiral beams: examples and methods of generation; Orbital angular momentum and the intensity moments; Symmetry breakdown and decomposition of the orbital angular momentum; Mechanical models of the vortex light beams; Mechanical action of the beam angular momentum; Rotational Doppler effect, its manifestation in the image rotation; Spectrum of helical harmonics and associated problems; Non-collinear rotational Doppler effect; Properties of a beam forcedly rotating around its own axis. Research prospects and ways of practical utilization of optical beams with angular momentum.

A. Bekshaev; M. Soskin; M. Vasnetsov

2008-01-15T23:59:59.000Z

452

Theory of Molecular Machines. I. Channel Capacity of Molecular Machines  

E-Print Network [OSTI]

Theory of Molecular Machines. I. Channel Capacity of Molecular Machines running title: Channel Capacity of Molecular Machines Thomas D. Schneider version = 5.76 of ccmm.tex 2004 Feb 3 Version 5.67 was submitted 1990 December 5 Schneider, T. D. (1991). Theory of molecular machines. I. Channel capacity

Schneider, Thomas D.

453

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum wells to colloidal CdSe/ZnS core/shell quantum dots  

E-Print Network [OSTI]

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum n a l f o r p h y s i c s New Journal of Physics White light generation by resonant nonradiative white-light-generating nonradiative energy transfer (ET) from epitaxial quantum wells (QWs) to colloidal

Demir, Hilmi Volkan

454

Simple Low-Frequency Beam Pickup  

SciTech Connect (OSTI)

Detection of the field induced by a beam outside of the beam pipe can be used as a beam diagnostic. Wires placed in longitudinal slots in the outside wall of the beam pipe can be used as a beam pickup. This has a very small beam-coupling impedance and avoids complications of having a feedthrough. The signal can be reasonably high at low frequencies. We present a field waveform at the outer side of a beam pipe, obtained as a result of calculations and measurements. We calculate the beam-coupling impedance due to a long longitudinal slot in the resistive wall and the signal induced in a wire placed in such a slot and shielded by a thin screen from the beam. These results should be relevant for impedance calculations of the slot in an antechamber and for slots in the PEP-II distributed ion pump screens. The design of the low-frequency beam position monitor is very simple. It can be used in storage rings, synchrotron light sources, and free electron lasers, like LINAC coherent light source.

Novokhatski, A.; Heifets, S.; /SLAC; Aleksandrov, A.; /Oak Ridge

2011-10-12T23:59:59.000Z

455

Optics of electron beam in the Recycler  

SciTech Connect (OSTI)

Electron cooling of 8.9 GeV/c antiprotons in the Recycler ring (Fermilab) requires high current and good quality of the DC electron beam. Electron trajectories of {approx}0.2 A or higher DC electron beam have to be parallel in the cooling section, within {approx}0.2 mrad, making the beam envelope cylindrical. These requirements yielded a specific scheme of the electron transport from a gun to the cooling section, with electrostatic acceleration and deceleration in the Pelletron. Recuperation of the DC beam limits beam losses at as tiny level as {approx}0.001%, setting strict requirements on the return electron line to the Pelletron and a collector. To smooth the beam envelope in the cooling section, it has to be linear and known at the transport start. Also, strength of the relevant optic elements has to be measured with good accuracy. Beam-based optic measurements are being carried out and analyzed to get this information. They include beam simulations in the Pelletron, differential optic (beam response) measurements and simulation, beam profile measurements with optical transition radiation, envelope measurements and analysis with orifice scrapers. Current results for the first half-year of commissioning are presented. Although electron cooling is already routinely used for pbar stacking, its efficiency is expected to be improved.

Burov, Alexey V.; Kazakevich, G.; Kroc, T.; Lebedev, V.; Nagaitsev, S.; Prost, L.; Pruss, S.; Shemyakin, A.; Sutherland, M.; Tiunov, M.; Warner, A.; /Fermilab

2005-11-01T23:59:59.000Z

456

Using neutral beams as a light ion beam probe (invited)  

SciTech Connect (OSTI)

By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfvén eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique.

Chen, Xi, E-mail: chenxi@fusion.gat.com [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831 (United States); Heidbrink, W. W. [University of California Irvine, Irvine, California 92697 (United States); Van Zeeland, M. A.; Pace, D. C.; Petty, C. C.; Fisher, R. K. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Kramer, G. J.; Nazikian, R. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Austin, M. E. [University of Texas at Austin, Austin, Texas 78712 (United States); Hanson, J. M. [Columbia University, New York, New York 10027 (United States); Zeng, L. [University of California Los Angeles, Los Angeles, California 90095 (United States)

2014-11-15T23:59:59.000Z

457

Self-organization during growth of ZrN/SiN{sub x} multilayers by epitaxial lateral overgrowth  

SciTech Connect (OSTI)

ZrN/SiN{sub x} nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiN{sub x} thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiN{sub x} is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiN{sub x}—known to take place on TiN(001)—on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiN{sub x} deposition, the material segregates to form surface precipitates in discontinuous layers for SiN{sub x} thicknesses ?6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiN{sub x} precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiN{sub x} in samples deposited at 800 °C with up to 6 Å thick SiN{sub x} layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1–3 nm large SiN{sub x} precipitates along apparent column boundaries in the epitaxial ZrN.

Fallqvist, A.; Fager, H.; Hultman, L.; Persson, P. O. Å. [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)] [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Ghafoor, N. [Nanostructured Materials, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)] [Nanostructured Materials, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)

2013-12-14T23:59:59.000Z

458

Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications  

SciTech Connect (OSTI)

Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nanoelectromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro-channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.

Rodak, L.E.; Kuchibhatla, S.; Famouri, P.; Ting, L.; Korakakis, D.

2008-01-01T23:59:59.000Z

459

Recent progress in GaInAsSb thermophotovoltaics grown by organometallic vapor phase epitaxy  

SciTech Connect (OSTI)

Studies on the materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for thermophotovoltaic (TPV) devices are reviewed. Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The overall material quality of these alloys depends on growth temperature, In content, V/III ratio, substrate misorientation, and to a lesser extent, growth rate. A mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for GaInAsSb layers with peak emission in the wavelength range between 2 and 2.5 {micro}m. The crystal quality improves for growth temperature decreasing from 575 to 525 C, and with decreasing In content, as based on epilayer surface morphology and low temperature PL spectra. A trend of smaller full width at half-maximum for low temperature PL spectra is observed as the growth rate is increased from 1.5 to 2.5 and 5 {micro}m/h. In general, GaInAsSb layers grown on (100) GaSb substrates with a 6{degree} toward (111)B misorientation exhibited overall better material quality than layers grown on the more standard substrate (100)2{degree} toward (110). Consistent growth of high performance lattice-matched GaInAsSb TPV devices is also demonstrated.

Wang, C.A.; Choi, H.K.; Oakley, D.C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-06-01T23:59:59.000Z

460

Characterization of recombination processes in epitaxial thin films and substrates for antimonide based thermophotovoltaic devices  

SciTech Connect (OSTI)

Recombination processes in antimonide-based materials for thermophotovoltaic (TPV) devices have been investigated using a radio-frequency (RF) photoreflectance technique, in which a Nd-YAG pulsed laser is used to excite excess carriers, and the short-pulse response and photoconductivity decay are monitored with an inductively-coupled non-contacting RF probe. Double-capped lattice-matched GaInAsSb organometallic vapor phase epitaxy (OMVPE)--grown layers on GaSb substrates have been used to evaluate bulk lifetime and surface recombination velocity with different layer thicknesses. With an active layer doping of 2 {times} 10{sup 17} cm{sup {minus}3}, effective bulk lifetimes of 95 ns and surface recombination velocities of 1,900 cm/s have been obtained. As the laser intensity is increased the lifetime decreases, which may be indicative of radiative recombination under these high level injection conditions. Similar measurements have been taken on both commercially available GaSb boules as well as in-house grown quaternary GaInAsSb boules. A two-step decay is observed with the quaternary boules, an initial decay of nominally 15 ns which is relatively independent of laser intensity and a second decay of 30--60 ns which increases with decreasing laser intensity. This behavior may be indicative of free charge separation as a result of short-range ordering in the quaternary crystals. GaSb boules, both commercially available and those grown in-house, exhibit more classical characteristics.

Saroop, S.; Borrego, J.; Gutmann, R.; Dutta, P.; Ostrogorsky, A. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Integrated Electronics and Electronics Manufacturing; Charache, G. [Lockheed Martin Inc., Schenectady, NY (United States); Wang, C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.

1998-06-01T23:59:59.000Z

Note: This page contains sample records for the topic "molecular beam epitaxy" from the National Library of EnergyBeta (NLEBeta).
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461

Low Emittance Electron Beam Studies  

SciTech Connect (OSTI)

We have studied the properties of a low emittance electron beam produced by laser pulses incident onto an rf gun photocathode. The experiments were carried out at the A0 photoinjector at Fermilab. Such beam studies are necessary for fixing the design of new Linear Colliders as well as for the development of Free Electron Lasers. An overview of the A0 photoinjector is given in Chapter 1. In Chapter 2 we describe the A0 photoinjector laser system. A stable laser system is imperative for reliable photoinjector operation. After the recent upgrade, we have been able to reach a new level of stability in the pulse-to-pulse fluctuations of the pulse amplitude, and of the temporal and transverse profiles. In Chapter 3 we present a study of transverse emittance versus the shape of the photo-cathode drive-laser pulse. For that purpose a special temporal profile laser shaping device called a pulse-stacker was developed. In Chapter 4 we discuss longitudinal beam dynamics studies using a two macro-particle bunch; this technique is helpful in analyzing pulse compression in the magnetic chicane, as well as velocity bunching effects in the rf-gun and the 9-cell accelerating cavity. In Chapter 5 we introduce a proposal for laser acceleration of electrons. We have developed a laser functioning on the TEM*{sub 01} mode, a mode with a longitudinal electric field component which is suitable for such a process. Using this technique at energies above 40 MeV, one would be able to observe laser-based acceleration.

Tikhoplav, Rodion; /Rochester U.; ,

2006-04-01T23:59:59.000Z

462

Near-Infrared Photoluminescence Enhancement in Ge/CdS and Ge/ZnS Core/Shell Nanocrystals: Utilizing IV/II-VI Semiconductor Epitaxy  

SciTech Connect (OSTI)

Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a common strategy employed in the synthesis of highly luminescent II–VI, III–V and IV–VI semiconductor quantum dots. Here, we use relatively unexplored IV/II–VI epitaxy as a way to enhance the photoluminescence and improve the optical stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS nanocrystals. The presence of an epitaxial II–VI shell greatly enhances the near-infrared photoluminescence and improves the photoluminescence stability of Ge. Ge/II–VI nanocrystals are reproducibly 1–3 orders of magnitude brighter than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II–VI nanocrystals. We expect this synthetic IV/II–VI epitaxial approach will lead to further studies into the optoelectronic behavior and practical applications of Si and Ge-based nanomaterials.

Guo, Yijun [Ames Laboratory; Rowland, Clare E [Argonne National Laboratory; Schaller, Richard D [Argonne National Laboratory; Vela, Javier [Ames Laboratory

2014-08-26T23:59:59.000Z

463

Protective laser beam viewing device  

DOE Patents [OSTI]

A protective laser beam viewing system or device including a camera selectively sensitive to laser light wavelengths and a viewing screen receiving images from the laser sensitive camera. According to a preferred embodiment of the invention, the camera is worn on the head of the user or incorporated into a goggle-type viewing display so that it is always aimed at the area of viewing interest to the user and the viewing screen is incorporated into a video display worn as goggles over the eyes of the user.

Neil, George R.; Jordan, Kevin Carl

2012-12-18T23:59:59.000Z

464

Nuclear astrophysics and electron beams  

SciTech Connect (OSTI)

Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei.

Schwenk, A. [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany)

2013-11-07T23:59:59.000Z

465

Proton beam therapy control system  

DOE Patents [OSTI]

A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

Baumann, Michael A; Beloussov, Alexandre V; Bakir, Julide; Armon, Deganit; Olsen, Howard B; Salem, Dana

2013-06-25T23:59:59.000Z

466

Proton beam therapy control system  

DOE Patents [OSTI]

A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

Baumann, Michael A; Beloussov, Alexandre V; Bakir, Julide; Armon, Deganit; Olsen, Howard B; Salem, Dana

2013-12-03T23:59:59.000Z

467

Proton beam therapy control system  

DOE Patents [OSTI]

A tiered communications architecture for managing network traffic in a distributed system. Communication between client or control computers and a plurality of hardware devices is administered by agent and monitor devices whose activities are coordinated to reduce the number of open channels or sockets. The communications architecture also improves the transparency and scalability of the distributed system by reducing network mapping dependence. The architecture is desirably implemented in a proton beam therapy system to provide flexible security policies which improve patent safety and facilitate system maintenance and development.

Baumann, Michael A. (Riverside, CA); Beloussov, Alexandre V. (Bernardino, CA); Bakir, Julide (Alta Loma, CA); Armon, Deganit (Redlands, CA); Olsen, Howard B. (Colton, CA); Salem, Dana (Riverside, CA)

2008-07-08T23:59:59.000Z

468