Sample records for molecular beam epitaxy

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

    E-Print Network [OSTI]

    Myers, Tom

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

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

    E-Print Network [OSTI]

    Atwater, Harry

    /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

  3. Fabrication of precision high quality facets on molecular beam epitaxy material

    DOE Patents [OSTI]

    Petersen, Holly E. (Tracy, CA); Goward, William D. (Antioch, CA); Dijaili, Sol P. (Moraga, CA)

    2001-01-01T23:59:59.000Z

    Fabricating mirrored vertical surfaces on semiconductor layered material grown by molecular beam epitaxy (MBE). Low energy chemically assisted ion beam etching (CAIBE) is employed to prepare mirrored vertical surfaces on MBE-grown III-V materials under unusually low concentrations of oxygen in evacuated etching atmospheres of chlorine and xenon ion beams. UV-stabilized smooth-surfaced photoresist materials contribute to highly vertical, high quality mirrored surfaces during the etching.

  4. Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates

    E-Print Network [OSTI]

    Steckl, Andrew J.

    Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates R. Birkhahn and A grown by MBE on sapphire substrates. In this letter, we report on Er-doped GaN growth experiments on Si Er-doped -GaN thin films grown on Si 111 . The GaN was grown by molecular beam epitaxy using solid

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

    E-Print Network [OSTI]

    Feenstra, Randall

    years as a substrate for both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy of GaN of the substrate preparation and growth technique. Experimental GaN films of typically 1 mm thickness are deposited1 Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M

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

    SciTech Connect (OSTI)

    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

    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.

  7. GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY

    E-Print Network [OSTI]

    Feenstra, Randall

    1 GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY C. K. Inoki ABSTRACT We have explored the growth of GaN on porous SiC substrates by plasma-assisted molecular beam Ga droplets. Plan-view TEM observations indicate that the GaN layers grown on porous substrates

  8. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN single crystal by sodium fluxScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  9. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    doped MOCVD grown GaN on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN singleScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  10. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kushvaha, S. S., E-mail: kushvahas@nplindia.org; Pal, P.; Shukla, A. K.; Joshi, Amish G.; Gupta, Govind; Kumar, M.; Singh, S.; Gupta, Bipin K.; Haranath, D. [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)

    2014-02-15T23:59:59.000Z

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 ?m thick GaN epi-layer on sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 10{sup 8} cm{sup ?2} at 750 °C) than that of the low temperature grown sample (1.1 × 10{sup 9} cm{sup ?2} at 730 °C). A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  13. Characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Lo, Ikai; Pang, Wen-Yuan; Hsu, Yu-Chi; Hsieh, Chia-Ho; Shih, Cheng-Hung; Chou, Mitch M. C. [Department of Physics and Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Chen, Wen-Yen; Hsu, Tzu-Min [Department of Physics, National Central University, Jhong-li, Taoyuan 32001, Taiwan (China); Hsu, Gary Z. L. [United Crystal Corporation, No.243-3, Wenshan, 36061, Miaoli, Taiwan (China)

    2013-06-15T23:59:59.000Z

    The characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy on LiAlO{sub 2} substrate was studied by cathodoluminescence and photoluminescence measurements. We demonstrated that the cathodoluminescence from oblique semi-polar surfaces of mushroom-shaped GaN was much brighter than that from top polar surface due to the reduction of polarization field on the oblique semi-polar surfaces. It implies that the oblique semi-polar surface is superior for the light-emitting surface of wurtzite nano-devices.

  14. AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates

    E-Print Network [OSTI]

    Manfra, Michael J.

    PS-4 AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates Nils ABSTRACT Molecular Beam Epitaxy of GaN and related alloys is becoming a rival to the more established, and HVPE SI-GaN templates on sapphire. While sapphire and SI-Sic are established substrates for the growth

  15. Molecular beam epitaxy of n-type ZnS: A wide band gap emitter for heterojunction PV devices

    E-Print Network [OSTI]

    Atwater, Harry

    Molecular beam epitaxy of n-type ZnS: A wide band gap emitter for heterojunction PV devices Jeffrey and AZO transparent conductive oxides did not. Applications to novel PV devices incorporating low electron-ray diffraction, zinc compounds. I. INTRODUCTION The growing interest in scalable, thin-film photovoltaics (PV

  16. Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity York, 12222 Abstract: We have grown GaN on porous SiC substrates and studied the effect of substrate show that the GaN film grown on porous substrates contains open tubes and a low dislocation density

  17. High quality molecular beam epitaxial growth on patterned GaAs substrates

    SciTech Connect (OSTI)

    Smith, J.S.; Derry, P.L.; Margalit, S.; Yariv, A.

    1985-10-01T23:59:59.000Z

    In this letter we describe a procedure for high quality molecular beam epitaxy (MBE) growth over finely patterned GaAs substrates which is suitable for device fabrication requiring lateral definition of small (approx.1--2 ..mu..m) dimension. This method was used for the fabrication of index guided laser arrays. Yields of individual lasers exceeded 90%, and thresholds were uniform to 10%. Temperature and flux ratio dependence of faceting during MBE growth over patterned substrates is shown for temperatures ranging from 580 to 700 /sup 0/C and for As/Ga flux ratios from 1.4:1 to 4:1. The real index guided structure, which can be formed by a single MBE growth over a ridged substrate, is discussed. This technique should prove useful in the fabrication of devices which take advantage of unique features formed during regrowth by MBE.

  18. Fe-doped InN layers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Wang Xinqiang; Liu Shitao; Ma Dingyu; Zheng Xiantong; Chen Guang; Xu Fujun; Tang Ning; Shen Bo [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Zhang Peng; Cao Xingzhong; Wang Baoyi [State Key Laboratory of Nuclear Analysis Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Huang Sen; Chen, Kevin J. [Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology (Hong Kong); Zhou Shengqiang [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01314 Dresden (Germany); Yoshikawa, Akihiko [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2012-10-22T23:59:59.000Z

    Iron(Fe)-doped InN (InN:Fe) layers have been grown by molecular beam epitaxy. It is found that Fe-doping leads to drastic increase of residual electron concentration, which is different from the semi-insulating property of Fe-doped GaN. However, this heavy n-type doping cannot be fully explained by doped Fe-concentration ([Fe]). Further analysis shows that more unintentionally doped impurities such as hydrogen and oxygen are incorporated with increasing [Fe] and the surface is degraded with high density pits, which probably are the main reasons for electron generation and mobility reduction. Photoluminescence of InN is gradually quenched by Fe-doping. This work shows that Fe-doping is one of good choices to control electron density in InN.

  19. Molecular-beam epitaxial growth of boron-doped GaAs films

    SciTech Connect (OSTI)

    Hoke, W.E.; Lemonias, P.J.; Weir, D.G. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    GaAs films doped with boron in the 10{sup 20} cm{sup {minus}3} range were grown by solid source molecular-beam epitaxy. Lattice contractions were observed in x-ray double crystal spectra. Substitutional boron concentrations up to 1.7x10{sup 20} cm{sup {minus}3} were obtained with narrow x-ray linewidths and specular surface morphology. For a given boron flux, the substitutional concentration was dependent on growth temperature. P-type conductivity due to boron incorporation was measured in the films with hole concentration reaching 1x10{sup 19} cm{sup {minus}3}. The lattice contractions exhibited good thermal stability for rapid thermal anneals. 10 refs., 3 figs., 2 tabs.

  20. Antimony segregation in stressed SiGe heterostructures grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    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

    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.

  1. Electrical characterization of ensemble of GaN nanowires grown by the molecular beam epitaxy technique

    SciTech Connect (OSTI)

    Kolkovsky, Vl. [Technische Universität Dresden, 01062 Dresden (Germany)] [Technische Universität Dresden, 01062 Dresden (Germany); Zytkiewicz, Z. R.; Sobanska, M.; Klosek, K. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)] [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)

    2013-08-26T23:59:59.000Z

    High quality Schottky contacts are formed on GaN nanowires (NWs) structures grown by the molecular beam epitaxy technique on Si(111) substrate. The current-voltage characteristics show the rectification ratio of about 10{sup 3} and the leakage current of about 10{sup ?4} A/cm{sup 2} at room temperature. From the capacitance-voltage measurements the free carrier concentration in GaN NWs is determined as about 10{sup 16} cm{sup ?3}. Two deep levels (H200 and E280) are found in the structures containing GaN NWs. H200 is attributed to an extended defect located at the interface between the substrate and SiN{sub x} or near the sidewalls at the bottom of the NWs whereas E280 is tentatively assigned to a gallium-vacancy- or nitrogen interstitials-related defect.

  2. Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001)

    E-Print Network [OSTI]

    Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001) Wenzhi Lin, Jeongihm], but not hexagonal (wurtzite) GaN, a fast-developing semiconductor material with important technological applicationsN on wurtzite GaN(0001), by employing e-beam evaporation in an ultra-high vacuum MBE cham- ber. The FeN films

  3. Magnetotransport in MgO-based magnetic tunnel junctions grown by molecular beam epitaxy (invited)

    SciTech Connect (OSTI)

    Andrieu, S., E-mail: stephane.andrieu@univ-lorraine.fr; Bonell, F.; Hauet, T.; Montaigne, F. [Institut Jean Lamour, Nancy University/CNRS, Bd des Aiguillettes, BP239, 54506 Vandoeuvre-lès-Nancy (France); Calmels, L.; Snoeck, E. [CEMES, CNRS and Toulouse University, 29 rue Jeanne Marvig, 31055 Toulouse (France); Lefevre, P.; Bertran, F. [Synchrotron SOLEIL-CNRS, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette cedex (France)

    2014-05-07T23:59:59.000Z

    The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe{sub 1?x}V{sub x} electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe{sub 1?X}Co{sub x}/MgO/Fe{sub 1?X}Co{sub x} (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty ?1 minority spin state towards the Fermi level.

  4. Growth of GaN on Ge(111) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lieten, R. R.; Degroote, S.; Cheng, K.; Leys, M.; Kuijk, M.; Borghs, G. [MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium) and ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium); ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2006-12-18T23:59:59.000Z

    The epitaxial growth of GaN on Ge is reported. The authors found that direct growth of GaN performs exceptionally well on Ge(111) with plasma assisted molecular beam epitaxy. A streaky reflection high energy electron diffraction pattern is observed during growth. X-ray diffraction showed a rocking curve full width at half maximum of only 371 arc sec for a 38 nm GaN layer and indicates an abrupt interface between the GaN and Ge. Secondary ion mass spectrometry shows limited diffusion of Ga atoms into the Ge substrate and Ge atoms into the GaN layers. Current-voltage measurements show rectifying behavior for n-GaN on p-Ge. Their results indicate that GaN growth on Ge does not require intermediate layers, allowing the Ge substrate to be used as back contact in vertical devices. A p-n junction formed between GaN and Ge can be used in heterojunction devices.

  5. NO-assisted molecular-beam epitaxial growth of nitrogen substituted EuO

    SciTech Connect (OSTI)

    Wicks, R. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada); Altendorf, S. G.; Caspers, C.; Kierspel, H.; Sutarto, R. [II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Tjeng, L. H. [II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Max Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany); Damascelli, A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada); Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)

    2012-04-16T23:59:59.000Z

    We have investigated a method for substituting oxygen with nitrogen in EuO thin films, which is based on molecular beam epitaxy distillation with NO gas as the oxidizer. By varying the NO gas pressure, we produce crystalline, epitaxial EuO{sub 1-x}N{sub x} films with good control over the films' nitrogen concentration. In situ x-ray photoemission spectroscopy reveals that nitrogen substitution is connected to the formation Eu{sup 3+}4f{sup 6} and a corresponding decrease in the number of Eu{sup 2+}4f{sup 7}, indicating that nitrogen is being incorporated in its 3{sup -} oxidation state. While small amounts of Eu{sup 3+} in over-oxidized Eu{sub 1-{delta}}O thin films lead to a drastic suppression of the ferromagnetism, the formation of Eu{sup 3+} in EuO{sub 1-x}N{sub x} still allows the ferromagnetic phase to exist with an unaffected T{sub c}, thus providing an ideal model system to study the interplay between the magnetic f{sup 7} (J = 7/2) and the non-magnetic f{sup 6} (J = 0) states close to the Fermi level.

  6. Transition between wurtzite and zinc-blende GaN: An effect of deposition condition of molecular-beam epitaxy

    SciTech Connect (OSTI)

    Shi, B. M.; Xie, M. H.; Wu, H. S.; Wang, N.; Tong, S. Y. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tang, Hong Kong (China)

    2006-10-09T23:59:59.000Z

    GaN exists in both wurtzite and zinc-blende phases and the growths of the two on its (0001) or (111) surfaces are achieved by choosing proper deposition conditions of molecular-beam epitaxy (MBE). At low substrate temperatures but high gallium fluxes, metastable zinc-blende GaN films are obtained, whereas at high temperatures and/or using high nitrogen fluxes, equilibrium wurtzite phase GaN epilayers resulted. This dependence of crystal structure on substrate temperature and source flux is not affected by deposition rate. Rather, the initial stage nucleation kinetics plays a primary role in determining the crystallographic structures of epitaxial GaN by MBE.

  7. Polarity inversion of N-face GaN by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Wong, M.H.; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Wu Feng; Mates, Thomas E.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2008-11-01T23:59:59.000Z

    The polarity of GaN grown by plasma-assisted molecular beam epitaxy was inverted from N-face to Ga-face by simultaneously exposing the surface to Mg and activated N fluxes during a growth interruption at a reduced substrate temperature. Growth studies suggested that a Mg{sub x}N{sub y} compound was responsible for inverting the crystal. The change in polarity was verified in situ by reflection high energy electron diffraction via GaN surface reconstructions, and ex situ by convergent beam electron diffraction and KOH etch studies. The surface of the inverted material showed smooth step flow features. Ga-face high electron mobility transistors with good dc and small signal performance were fabricated on the inverted epilayers. A drain-source current of 0.84 A/mm was measured at a gate-source voltage of +1 V. Current-gain cutoff and maximum oscillation frequencies of 22 and 53 GHz, respectively, were measured in these devices. The device performance is similar to that of Ga-face transistors with comparable dimensions.

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

    E-Print Network [OSTI]

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

    2006-01-01T23:59:59.000Z

    GaN grown by molecular beam epitaxy and codoped with carbon and silicon were investigated for substratesubstrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN

  9. Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen

    E-Print Network [OSTI]

    York, Robert A.

    Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen Materials Department March 2005 Titanium dioxide TiO2, with the rutile structure was grown on 0001 oriented GaN and 0001 Al0.33Ga0.67N/GaN heterostructure field effect transistor HFET structures by molecular beam epitaxy. X

  10. High-frequency modulation of AlGaAs/GaAs lasers grown on Si substrate by molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, H.Z.; Paslaski, J.; Yariv, A.; Morkoc, H.

    1988-02-22T23:59:59.000Z

    We report on the frequency response of quantum well lasers on Si substrates grown by molecular beam epitaxy. Ridge waveguide lasers of 10 ..mu..m x 380 ..mu..m having threshold currents as low as 40 mA were used in this study. Measurements were performed up to a frequency of 4.5 GHz with a resultant modulation corner frequency of 2.5 GHz when the laser was operated about 20% above the threshold.

  11. Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures directly on sapphire substrates

    E-Print Network [OSTI]

    Manfra, Michael J.

    Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures-dimensional arrays Appl. Phys. Lett. 100, 203117 (2012) Partially filled intermediate band of Cr-doped GaN films Appl at telecommunication wavelengths J. Appl. Phys. 111, 093721 (2012) GaN epitaxy on Cu(110) by metal organic chemical

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

    SciTech Connect (OSTI)

    Krockenberger, Yoshiharu; Karimoto, Shin-ichi; Yamamoto, Hideki; Semba, Kouich [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

    2012-10-15T23:59:59.000Z

    We have investigated the formation of titanium nitride (TiN) thin films on (001) MgO substrates by molecular beam epitaxy and radio frequency acitvated nitrogen plasma. Although cubic TiN is stabile over a wide temperature range, superconducting TiN films are exclusively obtained when the substrate temperature exceeds 710 Degree-Sign C. TiN films grown at 720 Degree-Sign C show a high residual resistivity ratio of approximately 11 and the superconducting transition temperature (T{sub c}) is well above 5 K. Superconductivity has been confirmed also by magnetiztion measurements. In addition, we determined the upper critical magnetic field ({mu}{sub 0}H{sub c2}) as well as the corresponding coherence length ({xi}{sub GL}) by transport measurements under high magnetic fields. High-resolution transmission electron microscopy data revealed full in plane coherency to the substrate as well as a low defect density in the film, in agreement with a mean-free path length Script-Small-L Almost-Equal-To 106 nm, which is estimated from the residual resistivity value. The observations of reflection high energy electron diffraction intensity oscillations during the growth, distinct Laue fringes around the main Bragg peaks, and higher order diffraction spots in the reciprocal space map suggest the full controlability of the thickness of high quality superconducting TiN thin films.

  13. InAlN/GaN Bragg reflectors grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM, Universidad Politecnica de Madrid, Avda Complutense s/n, 28040 Madrid (Spain); Hosseini, D.; Peiro, F. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, SCT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2010-12-01T23:59:59.000Z

    We report on molecular beam epitaxy growth and characterization of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs), with peak reflectivity centered around 400 nm. Thanks to the well tuned ternary alloy composition, crack-free surfaces have been obtained, as confirmed by both optical and transmission electron microscopy (TEM). Their good periodicity and well-defined interfaces have been confirmed by both x-ray diffraction and TEM measurements. Peak reflectivity values as high as 60% with stop bands of 30 nm have been demonstrated. Optical measurements revealed that discrepancy between the obtained (60%) and the theoretically expected ({approx}75%) reflectivity is a consequence of significant residual absorption ({approx}35%). TEM measurements revealed the coexistence of zinc-blende and wurtzite phases, as well as planar defects, mainly in GaN. These defects are suggested as the potential source of the undesired absorption and/or scattering effects that lowered the DBRs' peak reflectivity.

  14. Molecular Dynamics Simulation of GaAs Molecular Beam Epitaxy D. A. Murdick,1

    E-Print Network [OSTI]

    Wadley, Haydn

    of Virginia, Charlottesville, Virginia 22904, USA 2 Department of Materials, University of Oxford, Oxford OX1 3PH, UK ABSTRACT The vapor deposition of epitaxial GaAs and (Ga,Mn)As thin films during far-temperature growth of Ga0.94Mn0.06As and the Mn clustering trends in as-grown films. INTRODUCTION GaAs is widely used

  15. Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Johnston, S. W. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (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); Umbel, R. [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendelloesung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 {mu}m GaAs/(100)GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 {mu}s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge.

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

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

    2012-12-01T23:59:59.000Z

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

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

    SciTech Connect (OSTI)

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

    2011-03-28T23:59:59.000Z

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

  20. Room temperature infrared photoresponse of self assembled Ge/Si (001) quantum dots grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Singha, R. K.; Manna, S.; Das, S.; Dhar, A.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2010-06-07T23:59:59.000Z

    We report on the observation of intraband near infrared (approx3.1 mum) and mid infrared (approx6.2 mum) photocurrent response at room temperature using Ge/Si self-assembled quantum dots grown by molecular beam epitaxy. Due to the bimodal size distribution and SiGe intermixing, distinguishable photoluminescence transitions are observed at 10 K, below and above the optical band gap of bulk Ge. The observed redshift in photocurrent with increasing temperature has been explained by the excitonic electric field originated due to infrared excitation at low temperatures. A good correlation between the spectral photocurrent response and photoluminescence of the quantum dots has been established.

  1. Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, Yen-Ting [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Araki, Tsutomu [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan)] [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan); Palisaitis, Justinas; Persson, Per O. Å.; Olof Holtz, Per; Birch, Jens [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Chen, Li-Chyong [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China)] [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Chen, Kuei-Hsien [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Nanishi, Yasushi [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)] [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)

    2013-11-11T23:59:59.000Z

    Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (<35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a “narrow-pass” approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.

  2. Structural characterization of ZnO films grown by molecular beam epitaxy on sapphire with MgO buffer

    SciTech Connect (OSTI)

    Pecz, B.; El-Shaer, A.; Bakin, A.; Mofor, A.-C.; Waag, A.; Stoemenos, J. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig (Germany); Physics Department, Aristotle University, University Campus, 54006 Thessaloniki (Greece)

    2006-11-15T23:59:59.000Z

    The structural characteristics of the ZnO film grown on sapphire substrate using a thin MgO buffer layer were studied using transmission electron microscopy and high-resolution x-ray diffraction. The growth was carried out in a modified plasma-molecular beam epitaxy system. The observed misfit dislocations were well confined at the sapphire overgrown interface exhibiting domain matching epitaxy, where the integral multiples of lattice constants match across the interface. The main extended defects in the ZnO film were the threading dislocations having a mean density of 4x10{sup 9} cm{sup -2}. The formation of the MgO buffer layer as well as the ZnO growth were monitored in situ by reflection high-energy electron diffraction. The very thin {approx}1 nm, MgO buffer layer can partially interdiffuse with the ZnO as well as react with the Al{sub 2}O{sub 3} substrate forming an intermediate epitaxial layer having the spinel (MgO/Al{sub 2}O{sub 3}) structure.

  3. Impact of growth conditions on vacancy-type defects in silicon-germanium structures grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Shoukri, Kareem M.; Haddara, Yaser M.; Knights, A.P.; Coleman, P.G. [Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario L8S 4K1 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Physics, University of Bath, Bath BA2 7AY (United Kingdom)

    2005-03-28T23:59:59.000Z

    Silicon-germanium layers of either 200 nm or 250 nm have been grown via molecular-beam epitaxy (MBE) on p-type (001) silicon substrates. Each sample was prepared using a unique combination of buffer-layer type, buffer-layer growth temperature, and layer Ge content. Vacancy-type defects have been identified using beam-based positron annihilation. These results, combined with those from previous work, indicate the size and concentration of defects in MBE grown SiGe layers depend strongly upon the buffer-layer growth temperature (T). For T>500 deg. C vacancy point defect concentrations are below the detectable limit of the measurement. As T is decreased to 300 deg. C, vacancy clusters form in the buffer layer and point defects appear in the SiGe film, even for a SiGe growth temperature of 500 deg. C.

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

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    The band alignment properties of atomic layer HfO{sub 2} film deposited on epitaxial (110)Ge, grown by molecular beam epitaxy, was investigated using x-ray photoelectron spectroscopy. The cross-sectional transmission electron microscopy exhibited a sharp interface between the (110)Ge epilayer and the HfO{sub 2} film. The measured valence band offset value of HfO{sub 2} relative to (110)Ge was 2.28 {+-} 0.05 eV. The extracted conduction band offset value was 2.66 {+-} 0.1 eV using the bandgaps of HfO{sub 2} of 5.61 eV and Ge bandgap of 0.67 eV. These band offset parameters and the interface chemical properties of HfO{sub 2}/(110)Ge system are of tremendous importance for the design of future high hole mobility and low-power Ge-based metal-oxide transistor devices.

  5. Gas source molecular beam epitaxy of scandium nitride on silicon carbide and gallium nitride surfaces

    SciTech Connect (OSTI)

    King, Sean W., E-mail: sean.king@intel.com; Davis, Robert F. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nemanich, Robert J. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-11-01T23:59:59.000Z

    Scandium nitride (ScN) is a group IIIB transition metal nitride semiconductor with numerous potential applications in electronic and optoelectronic devices due to close lattice matching with gallium nitride (GaN). However, prior investigations of ScN have focused primarily on heteroepitaxial growth on substrates with a high lattice mismatch of 7%–20%. In this study, the authors have investigated ammonia (NH{sub 3}) gas source molecular beam epitaxy (NH{sub 3}-GSMBE) of ScN on more closely lattice matched silicon carbide (SiC) and GaN surfaces (<3% mismatch). Based on a thermodynamic analysis of the ScN phase stability window, NH{sub 3}-GSMBE conditions of 10{sup ?5}–10{sup ?4} Torr NH{sub 3} and 800–1050?°C where selected for initial investigation. In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Rutherford backscattering measurements showed all ScN films grown using these conditions were stoichiometric. For ScN growth on 3C-SiC (111)-(?3?×??3)R30° carbon rich surfaces, the observed attenuation of the XPS Si 2p and C 1s substrate core levels with increasing ScN thickness indicated growth initiated in a layer-by-layer fashion. This was consistent with scanning electron microscopy (SEM) images of 100–200?nm thick films that revealed featureless surfaces. In contrast, ScN films grown on 3C-SiC (111)-(3?×?3) and 3C-SiC (100)-(3?×?2) silicon rich surfaces were found to exhibit extremely rough surfaces in SEM. ScN films grown on both 3C-SiC (111)-(?3?×??3)R30° and 2H-GaN (0001)-(1?×?1) epilayer surfaces exhibited hexagonal (1?×?1) low energy electron diffraction patterns indicative of (111) oriented ScN. X-ray diffraction ?-2? rocking curve scans for these same films showed a large full width half maximum of 0.29° (1047?arc sec) consistent with transmission electron microscopy images that revealed the films to be poly-crystalline with columnar grains oriented at ?15° to the [0001] direction of the 6H-SiC (0001) substrate. In-situ reflection electron energy loss spectroscopy measurements determined the band-gap for the NH{sub 3}-GSMBE ScN films to be 1.5?±?0.3 eV, and thermal probe measurements indicated all ScN films to be n-type. The four point probe sheet resistance of the ScN films was observed to increase with decreasing growth temperature and decreased with unintentional oxygen incorporation. Hg probe capacitance–voltage measurements indicated N{sub D}-N{sub A} decreased with decreasing growth temperature from 10{sup 19} to 10{sup 20}/cm{sup 3} for the lowest resistivity films to ?5?×?10{sup 16}/cm{sup 3} for the highest resistivity films. In-situ ultraviolet photoelectron spectroscopy measurements additionally showed the valence band maximum moving from 1.4 to 0.8 eV below the Fermi level with decreasing growth temperature consistent with the increased resistivity and reduction in carrier concentration. These results suggest that additional reductions in ScN carrier concentrations can be achieved via continued optimization of ScN growth conditions and selection of substrate orientation and surface termination.

  6. Effect of dislocation scattering on the transport properties of InN grown on GaN substrates by molecular beam epitaxy

    E-Print Network [OSTI]

    Effect of dislocation scattering on the transport properties of InN grown on GaN substrates on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation, optical, and transport properties of InN on GaN substrates. In this work, we have studied the MBE growth

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

    SciTech Connect (OSTI)

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

    2010-03-29T23:59:59.000Z

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

  8. Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Wu, Z. H. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Kawai, Y.; Honda, Y.; Yamaguchi, M.; Amano, H. [Graduate School of Engineering, Akasaki Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan); Fang, Y.-Y.; Chen, C. Q. [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Kondo, H.; Hori, M. [Graduate School of Engineering, Plasma Nanotechnology Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8603 (Japan)

    2011-04-04T23:59:59.000Z

    In this letter, we have investigated the structural properties of thick InGaN layers grown on GaN by plasma-assisted molecular beam epitaxy, using two growth rates of 1.0 and 3.6 A/s. A highly regular superlattice (SL) structure is found to be spontaneously formed in the film grown at 3.6 A/s but not in the film grown at 1.0 A/s. The faster grown film also exhibits superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank-Read dislocation generation mechanism within the spontaneously formed SL structure.

  9. Ultra-low resistance ohmic contacts to GaN with high Si doping concentrations grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Afroz Faria, Faiza; Guo Jia; Zhao Pei; Li Guowang; Kumar Kandaswamy, Prem; Wistey, Mark; Xing Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2012-07-16T23:59:59.000Z

    Ti/Al/Ni/Au ohmic contacts were formed on heavily doped n{sup +} metal-polar GaN samples with various Si doping concentrations grown by molecular beam epitaxy. The contact resistivity (R{sub C}) and sheet resistance (R{sub sh}) as a function of corresponding GaN free carrier concentration (n) were measured. Very low R{sub C} values (<0.09 {Omega} mm) were obtained, with a minimum R{sub C} of 0.035 {Omega} mm on a sample with a room temperature carrier concentration of {approx}5 Multiplication-Sign 10{sup 19} cm{sup -3}. Based on the systematic study, the role of R{sub C} and R{sub sh} is discussed in the context of regrown n{sup +} GaN ohmic contacts for GaN based high electron mobility transistors.

  10. Super-dense array of Ge quantum dots grown on Si(100) by low-temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Talochkin, A. B., E-mail: tal@isp.nsc.ru; Shklyaev, A. A. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Mashanov, V. I. [A.V. Rzhanov Institute of Semiconductor Physics, Lavrentyev Avenue 13, Novosibirsk 630090 (Russian Federation)

    2014-04-14T23:59:59.000Z

    Ge layer grown on Si(100) at the low temperature of ?100?°C by molecular beam epitaxy is studied using scanning tunneling microscopy and Raman spectroscopy. It is found that crystalline and pseudomorphic to the Si substrate Ge islands are formed at the initial growth stage. The islands acquire the base size of 1.2–2.6?nm and they form arrays with the super-high density of (5–8)?×?10{sup 12}?cm{sup ?2} at 1–2?nm Ge coverages. Such a density is at least 10 times higher than that of Ge “hut” clusters grown via the Stranski-Krastanov growth mode. It is shown that areas between the crystalline Ge islands are filled with amorphous Ge, which is suggested to create potential barrier for holes localized within the islands. As a result, crystalline Ge quantum dots appear being isolated from each other.

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

    SciTech Connect (OSTI)

    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

    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.

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

    DOE Patents [OSTI]

    Chambers, Scott A.

    2006-02-21T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  14. Influence of substrate quality on structural properties of AlGaN/GaN superlattices grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Schubert, F. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); Merkel, U.; Schmult, S. [TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany); Mikolajick, T. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany)

    2014-02-28T23:59:59.000Z

    Short-period AlGaN/GaN superlattices were established as versatile test structures to investigate the structural properties of molecular beam epitaxy (MBE)-grown GaN and AlGaN layers and their dependence on the GaN substrate quality. X-ray diffractometry data of the investigated superlattices allow access to relevant structural parameters such as aluminum mole fraction and layer thicknesses. The occurrence of theoretically predicted intense high-order satellite peaks and pronounced interface fringes in the diffraction pattern reflects abrupt interfaces and perfect 2-dimensional growth resulting in smooth surfaces. The data unambiguously demonstrate that the structural quality of the MBE grown layers is limited by the structural properties of the GaN substrate.

  15. High quality InAlN single layers lattice-matched to GaN grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM, Universidad Politecnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Rebled, J. M.; Peiro, F. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, CCiT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2011-07-18T23:59:59.000Z

    We report on properties of high quality {approx}60 nm thick InAlN layers nearly in-plane lattice-matched to GaN, grown on c-plane GaN-on-sapphire templates by plasma-assisted molecular beam epitaxy. Excellent crystalline quality and low surface roughness are confirmed by X-ray diffraction, transmission electron microscopy, and atomic force microscopy. High annular dark field observations reveal a periodic in-plane indium content variation (8 nm period), whereas optical measurements evidence certain residual absorption below the band-gap. The indium fluctuation is estimated to be {+-} 1.2% around the nominal 17% indium content via plasmon energy oscillations assessed by electron energy loss spectroscopy with sub-nanometric spatial resolution.

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

    SciTech Connect (OSTI)

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

    2013-11-18T23:59:59.000Z

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

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

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

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

    2011-01-07T23:59:59.000Z

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

  18. Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2006-07-01T23:59:59.000Z

    Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2x10{sup 6} cm{sup -2}. A threshold current density of J{sub th}{approx}1.65 kA/cm{sup 2} for the as-cleaved, gain-guided AlGaInP laser grown on SiGe/Si was obtained at the peak emission wavelength of 680 nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods.

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

    SciTech Connect (OSTI)

    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

    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.

  20. Spectroscopic and magnetic properties of Mn doped GaN epitaxial films grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Vidyasagar, R., E-mail: dr.vidyasagar1979@gmail.com [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China); Lin, Y.-T.; Tu, L.-W. [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China)] [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China)

    2012-12-15T23:59:59.000Z

    Graphical abstract: We report here that micro-Raman scattering spectrum for Mn doped GaN thin film has displayed a new peak manifested at 578 cm{sup ?1}, by which it is attributed to interior LVM originated by the incorporation of Mn ions in place of Ga sites. Mn doped GaN thin film also showed the typical negative magnetoresistance up to ?50 K, revealing that the film showed magnetic ordering of spins below 50 K. Display Omitted Highlights: ? GaN and Mn doped GaN single phase wurtzite structures grown by PAMBE. ? The phase purity of the epilayers investigated by HRXRD, HRSEM and EDX. ? The red shift in near band edge emission has been observed using micro-PL. ? A new peak related LVM at 578 cm{sup ?1} in micro-Raman scattering measurements confirmed Mn doped into GaN. ? Negative-magnetoresistance investigations have showed that the film has T{sub c} < 50 K. -- Abstract: Spectroscopic and magnetic properties of Mn doped GaN, and GaN epitaxial films have been investigated by employing micro-photoluminescence, micro-Raman, and temperature dependent magneto-resistance measurements. The HR-XRD profiles have shown that the epitaxial films are in hexagonal wurtzite structures. Morphology and composition of the films have been examined by field emission scanning electron microscopy, and energy-dispersive X-ray analysis. Micro-photoluminescence spectrum displayed a dominant near band edge emission at 362 nm, which is assigned to near band edge transition within the hexagonal structure of GaN. Raman scattering profiles showed a new vibrational mode at 578 cm{sup ?1}, which is attributed to the vacancy-related local vibrational mode of Mn occupying the Ga site. Temperature dependent negative magnetoresistance measurements provide a direct evidence of magnetic ordering below 50 K for the Mn doped GaN thin film.

  1. The study of in situ scanning tunnelling microscope characterization on GaN thin film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Yang, R.; Krzyzewski, T.; Jones, T. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)] [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2013-03-18T23:59:59.000Z

    The epitaxial growth of GaN by Plasma Assisted Molecular Beam Epitaxy was investigated by Scanning Tunnelling Microscope (STM). The GaN film was grown on initial GaN (0001) and monitored by in situ Reflection High Energy Electron Diffraction and STM during the growth. The STM characterization was carried out on different sub-films with increased thickness. The growth of GaN was achieved in 3D mode, and the hexagonal edge of GaN layers and growth gradient were observed. The final GaN was of Ga polarity and kept as (0001) orientation, without excess Ga adlayers or droplets formed on the surface.

  2. Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular-type GaN(000¯1) by MBE using a custom built Hf electron beam source and an ammonia leak. The films were). It was found that epitaxial growth of Hf is possible even at room temperature. GaN films varying in thickness

  3. Control of tensile strain and interdiffusion in Ge/Si(001) epilayers grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Luong, T. K. P.; Dau, M. T.; Zrir, M. A.; Le Thanh, V.; Petit, M. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France)] [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Stoffel, M.; Rinnert, H. [Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France)] [Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Nancy-Université, BP 70239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Ghrib, A.; El Kurdi, M.; Boucaud, P. [Institut d'Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Ba-carett. 220, 91405 Orsay (France)] [Institut d'Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Ba-carett. 220, 91405 Orsay (France); Murota, J. [Research Institute of Electrical Communications, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)] [Research Institute of Electrical Communications, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2013-08-28T23:59:59.000Z

    Tensile-strained and n-doped Ge has emerged as a potential candidate for the realization of optoelectronic devices that are compatible with the mainstream silicon technology. Tensile-strained Ge/Si epilayers can be obtained by using the difference of thermal expansion coefficients between Ge and Si. We have combined various surface, structural, and compositional characterizations to investigate the growth mode and the strain state in Ge/Si epilayers grown by molecular-beam epitaxy. The Ge growth was carried out using a two-step approach: a low-temperature growth to produce relaxed and smooth buffer layers, which is followed by a high-temperature growth to get high quality Ge layers. The existence of a substrate temperature window from 260 to 300 °C is evidenced, which allows to completely suppress the Ge/Si Stranski-Krastanov growth. As a consequence of the high temperature growth, a tensile strain lying in the range of 0.22%–0.24% is obtained. Concerning the effect of thermal annealing, it is shown that cyclic annealing may allow increasing the tensile strain up to 0.30%. Finally, we propose an approach to use carbon adsorption to suppress Si/Ge interdiffusion, which represents one of the main obstacles to overcome in order to realize pure Ge-based optoelectronic devices.

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

    SciTech Connect (OSTI)

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

    2013-10-28T23:59:59.000Z

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

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

    SciTech Connect (OSTI)

    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

    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.

  6. 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)

    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

    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.

  7. Zinc-blende (Cubic) GaN and AlGaN Layers, Structures and Bulk Crystals by Molecular Beam Epitaxy

    SciTech Connect (OSTI)

    Novikov, Sergei V.; Zainal, Norzaini; Akimov, Andrey V.; Staddon, Chris R.; Foxon, C. Thomas; Kent, Anthony J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-11-01T23:59:59.000Z

    We have studied the growth of zinc-blende GaN and AlGaN layers, structures and bulk crystals by molecular beam epitaxy (MBE). We have developed a process for growth by MBE of free-standing cubic GaN layers. Undoped thick cubic GaN films were grown on semi-insulating GaAs (001) substrates by a modified plasma-assisted molecular beam epitaxy (PA-MBE) method and were removed from the GaAs substrate after the growth. The resulting free-standing GaN wafers with thicknesses in the 30-100 {mu}m range may be used as substrates for further epitaxy of cubic GaN-based structures and devices. We have developed procedures to cleave the wafers into 10x10 mm{sup 2} square substrates and to polish them to produce epi-ready surfaces. The first GaN/InGaN LEDs on our zinc-blende GaN substrates have been demonstrated by our collaborators at Sharp Laboratories of Europe.

  8. Localized Si enrichment in coherent self-assembled Ge islands grown by molecular beam epitaxy on (001)Si single crystal

    SciTech Connect (OSTI)

    Valvo, M. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95127 Catania (Italy); Bongiorno, C.; Giannazzo, F. [IMM-CNR, VIII strada 5, 95121 Catania (Italy); Terrasi, A. [Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95127 Catania (Italy); MATIS IMM-CNR UOS Catania (Universita), via S. Sofia 64, 95123 Catania (Italy)

    2013-01-21T23:59:59.000Z

    Transmission electron microscopy (TEM), atomic force microscopy, and Rutherford backscattering spectrometry (RBS) have been used to investigate the morphology, structure, and composition of self-assembled Ge islands grown on Si (001) substrates by molecular beam epitaxy (MBE) at different temperatures. Increasing the temperature from 550 Degree-Sign C to 700 Degree-Sign C causes progressive size and shape uniformity, accompanied by enhanced Si-Ge intermixing within the islands and their wetting layer. Elemental maps obtained by energy filtered-TEM (EF-TEM) clearly show pronounced Si concentration not only in correspondence of island base perimeters, but also along their curved surface boundaries. This phenomenon is strengthened by an increase of the growth temperature, being practically negligible at 550 Degree-Sign C, while very remarkable already at 650 Degree-Sign C. The resulting island shape is affected, since this localized Si enrichment not only provides strain relief near their highly stressed base perimeters but it also influences the cluster surface energy by effective alloying, so as to form Si-enriched SiGe interfaces. Further increase to 700 Degree-Sign C causes a shape transition where more homogenous Si-Ge concentration profiles are observed. The crucial role played by local 'flattened' alloyed clusters, similar to truncated pyramids with larger bases and enhanced Si enrichment at coherently stressed interfaces, has been further clarified by EF-TEM analysis of a multi-layered Ge/Si structure containing stacked Ge islands grown at 650 Degree-Sign C. Sharp accumulation of Si has been here observed not only in proximity of the uncapped island surface in the topmost layer but also at the buried Ge/Si interfaces and even in the core of such capped Ge islands.

  9. Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kamyczek, P.; Placzek-Popko, E.; Zielony, E.; Gumienny, Z. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Zytkiewicz, Z. R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-14T23:59:59.000Z

    In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77?K–350?K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (?-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E{sub 1}?=?0.65?eV, ?{sub 1}?=?8.2 × 10{sup ?16} cm{sup 2} and E{sub 2}?=?0.58?eV, ?{sub 2}?=?2.6 × 10{sup ?15} cm{sup 2} whereas for the two low-temperature majority traps they were equal to E{sub 3}?=?0.18?eV, ?{sub 3}?=?9.7 × 10{sup ?18} cm{sup 2} and E{sub 4}?=?0.13?eV, ?{sub 4}?=?9.2 × 10{sup ?18} cm{sup 2}. The possible origin of the traps is discussed and the results are compared with data reported elsewhere.

  10. Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

    SciTech Connect (OSTI)

    Novikov, S. V.; Staddon, C. R.; Foxon, C. T.; Yu, K. M.; Broesler, R.; Hawkridge, M.; Liliental-Weber, Z.; Walukiewicz, W.; Denlinger, J.; Demchenko, I.

    2009-10-06T23:59:59.000Z

    The authors have succeeded in growing GaN1?xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As{sub 2} flux at low (as low as 100 C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x > 0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from -3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of -0.8 eV at x - 0.8. The composition dependence of the band gap of the crystalline GaN{sub 1?x}As{sub x} alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN{sub 1?x}As{sub x} with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN{sub 1?x}As{sub x} alloys have short-range ordering that resembles random crystalline GaN{sub 1?x}As{sub x} alloys. They have demonstrated the possibility of the growth of amorphous GaN{sub 1?x}As{sub x} layers with variable As content on glass substrates

  11. Near-infrared intersubband absorption in molecular-beam epitaxy-grown lattice-matched InAlN/GaN superlattices

    SciTech Connect (OSTI)

    Malis, O.; Edmunds, C. [Department of Physics, Binghamton University, Binghamton, New York 13902 (United States); Manfra, M. J.; Sivco, D. L. [Bell Laboratories, Alcatel-Lucent, Murray Hill, New Jersey 07974 (United States)

    2009-04-20T23:59:59.000Z

    Strong near-infrared intersubband absorption is observed directly at room temperature in silicon-doped lattice-matched InAlN/GaN superlattices grown by molecular-beam epitaxy on GaN templates grown by hydride vapor-phase epitaxy. X-ray diffraction characterization of the heterostructures indicates excellent layer thickness uniformity and low interface roughness. For 2-4.5 nm quantum wells, the intersubband transition energies span the technologically relevant range between 2.3 and 2.9 {mu}m. The experimental results are in good agreement with calculations of the transition energies using a conduction band offset of 1 eV and spontaneous polarization of 3 MV/cm.

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

    SciTech Connect (OSTI)

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

    2012-09-17T23:59:59.000Z

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

  13. Si (111) substrates as highly effective pseudomasks for selective growth of GaN material and devices by ammonia-molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tang, H.; Haffouz, S.; Bardwell, J.A. [Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

    2006-04-24T23:59:59.000Z

    The unique property of Si (111) as effective pseudomask substrate for selective growth of GaN by ammonia-molecular-beam epitaxy is reported. The critical nucleation temperature of GaN on Si (111) surface is found to be as low as 700 deg. C, much lower than that on sapphire or AlN surface. As a result, selective growth of GaN is possible by ammonia-molecular-beam epitaxy on Si (111) substrates using a patterned AlN buffer layer. The wide range of growth temperatures (700-900 deg. C) available for selective growth is a critical advantage for control and optimization of the facet characteristics of the selectively grown GaN patterns as required for potential fabrication of site-specific GaN or InGaN quantum dots. The demonstrated ease of selective growth of GaN on silicon has also implications in potential on-chip integration of GaN devices with silicon devices.

  14. Molecular Beam Epitaxy | EMSL

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

    hold the promise of turning sunlight into fuel. They are excellent candidates for solar hydrolysis -... Angling chromium to let oxygen through Posted: Wednesday, September...

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

    SciTech Connect (OSTI)

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

    2008-04-15T23:59:59.000Z

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

  16. Growth of In{sub 2}O{sub 3}(100) on Y-stabilized ZrO{sub 2}(100) by O-plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Bourlange, A.; Payne, D. J.; Egdell, R. G.; Foord, J. S.; Edwards, P. P.; Jones, M. O. [Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA (United Kingdom); Schertel, A. [Carl Zeiss SMT AG, Carl-Zeiss-Strasse 56, 73447 Oberkochen (Germany); Dobson, P. J. [Oxford University Begbroke Science Park, Sandy Lane, Yarnton, Kidlington, Oxon OX5 1PF (United Kingdom); Hutchison, J. L. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2008-03-03T23:59:59.000Z

    Thin films of In{sub 2}O{sub 3} have been grown on Y-stabilized ZrO{sub 2}(100) by oxygen plasma assisted molecular beam epitaxy with a substrate temperature of 650 deg. C. Ordered epitaxial growth was confirmed by high resolution transmission electron microscopy. The position of the valence band onset in the x-ray photoemission spectra of the epitaxial films is found to be inconsistent with the widely quoted value of 3.75 eV for the fundamental bandgap of In{sub 2}O{sub 3} and suggests a revised value of 2.67 eV.

  17. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect (OSTI)

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D. [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)

    2013-09-15T23:59:59.000Z

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

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

    E-Print Network [OSTI]

    Myers, Tom

    as a function of substrate temperature and dopant flux for Ga-polarity and N-polarity GaN. Incorporation GaN templates on (0001) sapphire substrates. The doped layers were grown at a rate of 0.25 µmA Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam

  19. Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(0001) by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(000¯1) by Molecular Beam Epitaxy R.Held, B.E. Ishaug, A. Parkhomovsky, A.M. Dabiran, and P (October 7, 1999) GaN(000¯1)filmsweregrownbymolecularbeamepitaxyusingammoniaandelemental

  20. Submilliampere threshold current pseudomorphic InGaAs/AlGaAs buried-heterostructure quantum well lasers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Eng, L.E.; Chen, T.R.; Sanders, S.; Zhuang, Y.H.; Zhao, B.; Yariv, A. (Department of Applied Physics, California Institute of Technology, Pasadena, California 91125 (US)); Morkoc, H. (The Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801)

    1989-10-02T23:59:59.000Z

    We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm{sup 2} at 990 nm were measured for 1540-{mu}m-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-{mu}m-wide stripe and 425-{mu}m-long cavity. With reflective coatings the best device showed 0.9 mA threshold current ({ital L}=225 {mu}m). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

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

    SciTech Connect (OSTI)

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

    2013-08-19T23:59:59.000Z

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

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  4. 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)

    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

    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.

  5. Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al{sub 2}O{sub 3} by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sobanska, Marta, E-mail: sobanska@ifpan.edu.pl; Klosek, Kamil; Borysiuk, Jolanta; Kret, Slawomir; Tchutchulasvili, Giorgi; Gieraltowska, Sylwia; Zytkiewicz, Zbigniew R. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-28T23:59:59.000Z

    We report on plasma-assisted molecular beam epitaxial growth of GaN nanowires (NWs) on Si(111) substrates with a thin amorphous Al{sub 2}O{sub 3} buffer layer deposited by atomic layer deposition. Comparison of nucleation kinetics shows that presence of amorphous Al{sub 2}O{sub 3} buffer significantly enhances spontaneous nucleation of GaN NWs. Slower nucleation was observed on partially amorphous silicon nitride films. No growth of NWs was found on sapphire substrate under the same growth conditions which we explain by a low density of defects on monocrystalline substrate surface where NWs may nucleate. Our finding shows that tuning of substrate microstructure is an efficient tool to control rate of self-induced nucleation of GaN NWs.

  6. Highly mismatched N-rich GaN{sub 1-x}Sb{sub x} films grown by low temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Yu, K. M.; Walukiewicz, W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Sarney, W. L.; Svensson, S. P. [US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)] [US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States); Novikov, S. V.; Foxon, C. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)] [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Detert, D.; Zhao, R. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States) [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Denlinger, J. D. [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Dubon, O. D. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States) [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2013-03-11T23:59:59.000Z

    We have grown N-rich, dilute Sb GaN{sub 1-x}Sb{sub x} alloys by low temperature molecular beam epitaxy. At low growth temperature of <100 Degree-Sign C the material loses crystallinity and becomes primarily amorphous with small crystallites of 2-5 nm at a Sb composition of >4 at. %. Despite the different microstructures found for GaN{sub 1-x}Sb{sub x} alloys with different composition, the absorption edge shifts continuously from 3.4 eV (GaN) to close to 1 eV for samples with Sb content >30 at. %. GaN{sub 1-x}Sb{sub x} alloys with less than 5 at. % Sb show sufficient bandgap reduction ({approx}2 eV), making them suitable for photoelectrochemical applications.

  7. High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Lang, J. R.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Neufeld, C. J.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2011-03-28T23:59:59.000Z

    High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorption measurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

  8. Surface morphology evolution of m-plane (1100) GaN during molecular beam epitaxy growth: Impact of Ga/N ratio, miscut direction, and growth temperature

    SciTech Connect (OSTI)

    Shao Jiayi; Tang Liang; Malis, Oana [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Edmunds, Colin [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Gardner, Geoff [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Manfra, Michael [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2013-07-14T23:59:59.000Z

    We present a systematic study of morphology evolution of [1100] m-plane GaN grown by plasma-assisted molecular beam epitaxy on free-standing m-plane substrates with small miscut angles towards the -c [0001] and +c [0001] directions under various gallium to nitrogen (Ga/N) ratios at substrate temperatures T = 720 Degree-Sign C and T = 740 Degree-Sign C. The miscut direction, Ga/N ratio, and growth temperature are all shown to have a dramatic impact on morphology. The observed dependence on miscut direction supports the notion of strong anisotropy in the gallium adatom diffusion barrier and growth kinetics. We demonstrate that precise control of Ga/N ratio and substrate temperature yields atomically smooth morphology on substrates oriented towards +c [0001] as well as the more commonly studied -c [0001] miscut substrates.

  9. Step-flow anisotropy of the m-plane GaN (1100) grown under nitrogen-rich conditions by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sawicka, Marta; Siekacz, Marcin; Skierbiszewski, Czeslaw [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Turski, Henryk; Krysko, Marcin; DziePcielewski, Igor; Grzegory, Izabella [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); Smalc-Koziorowska, Julita [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Warsaw University of Technology, Faculty of Material Science and Engineering, Woloska 141, PL-02-507 Warszawa (Poland)

    2011-06-15T23:59:59.000Z

    The homoepitaxial growth of m-plane (1100) GaN was investigated by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions. The surface morphologies as a function of sample miscut were studied, providing evidence for a strong growth anisotropy that is a consequence of the anisotropy of Ga adatom diffusion barriers on the m-plane surface recently calculated ab initio[Lymperakis and Neugebauer, Phys. Rev. B 79, 241308(R) (2009)]. We found that substrate miscut toward [0001] implies a step flow toward <1126> while substrate miscut toward [0001] causes formation of atomic steps either perpendicular or parallel to the [0001] direction, under N-rich conditions at 730 deg C. We describe the growth conditions for achieving atomically flat m-plane GaN layers with parallel atomic steps.

  10. Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

    SciTech Connect (OSTI)

    Furtmayr, Florian; Vielemeyer, Martin; Stutzmann, Martin; Eickhoff, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Arbiol, Jordi [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain); TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, c/ Lluis Sole i Sabaris 1-3, E-08080 Barcelona, CAT (Spain); Estrade, Sonia; Peiro, Francesca; Morante, Joan Ramon [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain)

    2008-08-01T23:59:59.000Z

    The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

  11. X-ray magnetic circular dichroism for Co{sub x}Fe{sub 4?x}N (x?=?0, 3, 4) films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Ito, Keita; Sanai, Tatsunori; Yasutomi, Yoko; Toko, Kaoru; Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Zhu, Siyuan; Kimura, Akio [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Takeda, Yukiharu; Saitoh, Yuji [Condensed Matter Science Division, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)

    2014-05-07T23:59:59.000Z

    We evaluated orbital (m{sub orb}) and spin magnetic moments (m{sub spin}) of Co{sub x}Fe{sub 4?x}N (x?=?0, 3, 4) epitaxial thin films grown by molecular beam epitaxy using x-ray magnetic circular dichroism, and discussed the dependence of these values on x. Site-averaged m{sub spin} value of Fe atoms was deduced to be 1.91??{sub B} per atom, and that of Co atoms to be 1.47??{sub B} per atom in Co{sub 3}FeN at 300?K. These values are close to 1.87??{sub B} per Fe atom in Fe{sub 4}N and 1.43??{sub B} per Co atom in Co{sub 4}N, respectively. This result implies that the Fe and Co atoms in the Co{sub 3}FeN films were located both at corner and face-centered sites in the anti-perovskite lattice. Spin magnetic moments per unit cell were decreased linearly with increasing x in Co{sub x}Fe{sub 4?x}N. This tendency is in good agreement with theory predicted by the first-principle calculation.

  12. Structural and band alignment properties of Al{sub 2}O{sub 3} on epitaxial Ge grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Advanced Devices and Sustainable Energy Laboratory (ADSEL), 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); Patra, P. K. [Department of Biomedical Engineering and Department of Mechanical Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States); Ma, A. W. K. [Department of Chemical and Biomolecular Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Aphale, A.; Macwan, I. [Department of Electrical and Computer Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States)

    2013-04-07T23:59:59.000Z

    Structural and band alignment properties of atomic layer Al{sub 2}O{sub 3} oxide film deposited on crystallographically oriented epitaxial Ge grown in-situ on (100), (110), and (111)A GaAs substrates using two separate molecular beam epitaxy chambers were investigated using cross-sectional transmission microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). High-resolution triple axis x-ray measurement demonstrated pseudomorphic and high-quality Ge epitaxial layer on crystallographically oriented GaAs substrates. The cross-sectional TEM exhibited a sharp interface between the Ge epilayer and each orientation of the GaAs substrate as well as the Al{sub 2}O{sub 3} film and the Ge epilayer. The extracted valence band offset, {Delta}E{sub v}, values of Al{sub 2}O{sub 3} relative to (100), (110), and (111) Ge orientations using XPS measurement were 3.17 eV, 3.34 eV, and 3.10 eV, respectively. Using XPS data, variations in {Delta}E{sub v} related to the crystallographic orientation were {Delta}E{sub V}(110)Ge>{Delta}E{sub V}(100)Ge{>=}{Delta}E{sub V}(111)Ge and the conduction band offset, {Delta}E{sub c}, related to the crystallographic orientation was {Delta}E{sub c}(111)Ge>{Delta}E{sub c}(110)Ge>{Delta}E{sub c}(100)Ge using the measured {Delta}E{sub v}, bandgap of Al{sub 2}O{sub 3} in each orientation, and well-known Ge bandgap of 0.67 eV. These band offset parameters are important for future application of Ge-based p- and n-channel metal-oxide field-effect transistor design.

  13. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lotsari, A.; Kehagias, Th.; Katsikini, M.; Arvanitidis, J.; Ves, S.; Komninou, Ph.; Dimitrakopulos, G. P., E-mail: gdim@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A. [Department of Physics, Microelectronics Research Group, University of Crete, P.O. Box 2208, GR 71003, Greece and IESL, FORTH, P.O. Box 1385, GR71110 Heraklion (Greece); Christofilos, D. [Physics Division, School of Technology, Aristotle University of Thessaloniki, GR54124 Thessaloniki (Greece)

    2014-06-07T23:59:59.000Z

    Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.

  14. 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)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  16. InGaP/InGaAlP double-heterostructure and multiquantum-well laser diodes grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tanaka, H.; Kawamura, Y.; Nojima, S.; Wakita, K.; Asahi, H.

    1987-03-01T23:59:59.000Z

    Room-temperature continuous-wave (cw) operation is achieved in the MBE (molecular-beam epitaxy)-grown InGaP/InGaAlP double-heterostructure (DH) visible laser diodes with a threshold current of 110 mA. The lasing wavelength and threshold current density under pulsed operation are 666 nm and as low as 3.9 kA/cm/sup 2/, respectively. This result is achieved by the introduction of H/sub 2/ into the growth chamber during growth, the continuous growth from one layer to the next layer, and the introduction of a GaAs buffer layer. InGaP/InGaAlP quantum well structures are also grown. From photoluminescence measurements, the conduction-band discontinuity ..delta..E/sub c/ is estimated to be 0.43 of the band-gap difference ..delta..E/sub g/. Furthermore, the multiquantum-well (MQW) structure is found to be stable under thermal treatment at temperatures as high as 750 /sup 0/C. Room-temperature pulsed operation of InGaP/InGaAlP MQW laser diodes is achieved for the first time. The lasing wavelength is 658 nm with a threshold current density of 7.6 kA/cm/sup 2/. cw operation is also achieved in the MQW laser diodes at -125 /sup 0/C.

  17. High-electron-mobility GaN grown on free-standing GaN templates by ammonia-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Kyle, Erin C. H., E-mail: erinkyle@umail.ucsb.edu; Kaun, Stephen W.; Burke, Peter G.; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wu, Yuh-Renn [Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei City 10617, Taiwan (China)

    2014-05-21T23:59:59.000Z

    The dependence of electron mobility on growth conditions and threading dislocation density (TDD) was studied for n{sup ?}-GaN layers grown by ammonia-based molecular beam epitaxy. Electron mobility was found to strongly depend on TDD, growth temperature, and Si-doping concentration. Temperature-dependent Hall data were fit to established transport and charge-balance equations. Dislocation scattering was analyzed over a wide range of TDDs (?2?×?10{sup 6}?cm{sup ?2} to ?2?×?10{sup 10}?cm{sup ?2}) on GaN films grown under similar conditions. A correlation between TDD and fitted acceptor states was observed, corresponding to an acceptor state for almost every c lattice translation along each threading dislocation. Optimized GaN growth on free-standing GaN templates with a low TDD (?2?×?10{sup 6}?cm{sup ?2}) resulted in electron mobilities of 1265 cm{sup 2}/Vs at 296?K and 3327 cm{sup 2}/Vs at 113?K.

  18. Growth diagram of N-face GaN (0001{sup ¯}) grown at high rate by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Okumura, Hironori, E-mail: okumura@engineering.ucsb.edu; McSkimming, Brian M.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States); Huault, Thomas; Chaix, Catherine [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)] [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)

    2014-01-06T23:59:59.000Z

    N-face GaN was grown on free-standing GaN (0001{sup ¯}) substrates at a growth rate of 1.5??m/h using plasma-assisted molecular beam epitaxy. Difference in growth rate between (0001{sup ¯}) and (0001) oriented GaN depends on nitrogen plasma power, and the (0001{sup ¯}) oriented GaN had only 70% of the growth rate of the (0001) oriented GaN at 300?W. Unintentional impurity concentrations of silicon, carbon, and oxygen were 2?×?10{sup 15}, 2?×?10{sup 16}, and 7?×?10{sup 16}?cm{sup ?3}, respectively. A growth diagram was constructed that shows the dependence of the growth modes on the difference in the Ga and active nitrogen flux, ?{sub Ga}????{sub N*}, and the growth temperature. At high ?{sub Ga}????{sub N*} (?{sub Ga}????{sub N*}), two-dimensional (step-flow and layer-by-layer) growth modes were realized. High growth temperature (780?°C) expanded the growth window of the two-dimensional growth modes, achieving a surface with rms roughness of 0.48?nm without Ga droplets.

  19. Molecular beam epitaxy and structural anisotropy of m-plane InN grown on free-standing GaN

    SciTech Connect (OSTI)

    Koblmueller, G.; Hirai, A.; Wu, F.; Gallinat, C. S.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Metcalfe, G. D.; Shen, H.; Wraback, M. [U. S. Army Research Laboratory, Sensors and Electron Devices Directorate, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2008-10-27T23:59:59.000Z

    This study reports on the growth of high-quality nonpolar m-plane [1100] InN films on free-standing m-plane GaN substrates by plasma-assisted molecular beam epitaxy. Optimized growth conditions (In/N ratio {approx}1 and T=390-430 deg. C) yielded very smooth InN films with undulated features elongated along the [1120] orientation. This directionality is associated with the underlying defect structure shown by the anisotropy of x-ray rocking curve widths parallel to the [1120] (i.e., 0.24 deg. - 0.34 deg.) and [0001] (i.e., 1.2 deg. - 2.7 deg.) orientations. Williamson-Hall analysis and transmission electron microscopy identified the mosaic tilt and lateral coherence length and their associations with different densities of dislocations and basal-plane stacking faults. Ultimately, very low band gap energies of {approx}0.67 eV were measured by optical absorption similar to the best c-plane InN.

  20. Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect (OSTI)

    Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E. [CEA-Grenoble, INAC/SP2M/NPSC, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Doisneau, B. [SIMaP, Grenoble INP, Domaine Universitaire, BP 75, 38402 Saint Martin d'Heres (France); Sarigiannidou, E. [LMGP, Grenoble INP, 3 Parvis Louis Neel, BP 257, 38016 Grenoble cedex 1 (France)

    2011-08-01T23:59:59.000Z

    We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  1. Growth kinetics of AlN and GaN films grown by molecular beam epitaxy on R-plane sapphire substrates

    SciTech Connect (OSTI)

    Chandrasekaran, R.; Moustakas, T. D. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Ozcan, A. S.; Ludwig, K. F. [Physics Department, Boston University, Boston, Massachusetts 02215 (United States); Zhou, L.; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2010-08-15T23:59:59.000Z

    This paper reports the growth by molecular beam epitaxy of AlN and GaN thin films on R-plane sapphire substrates. Contrary to previous findings that GaN grows with its (1120) A-plane parallel to the (1102) R-plane of sapphire, our results indicate that the crystallographic orientation of the III-nitride films is strongly dependent on the kinetic conditions of growth for the GaN or AlN buffer layers. Thus, group III-rich conditions for growth of either GaN or AlN buffers result in nitride films having (1120) planes parallel to the sapphire surface, and basal-plane stacking faults parallel to the growth direction. The growth of these buffers under N-rich conditions instead leads to nitride films with (1126) planes parallel to the sapphire surface, with inclined c-plane stacking faults that often terminate threading dislocations. Moreover, electron microscope observations indicate that slight miscut ({approx}0.5 deg. ) of the R-plane sapphire substrate almost completely suppresses the formation of twinning defects in the (1126) GaN films.

  2. Transport and optical properties of c-axis oriented wedge shaped GaN nanowall network grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Bhasker, H. P.; Dhar, S. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra-400076 (India); Thakur, Varun; Kesaria, Manoj; Shivaprasad, S. M. [Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Bangalore- 560064 (India)

    2014-02-21T23:59:59.000Z

    The transport and optical properties of wedge-shaped nanowall network of GaN grown spontaneously on cplane sapphire substrate by Plasma-Assisted Molecular Beam Epitaxy (PAMBE) show interesting behavior. The electron mobility at room temperature in these samples is found to be orders of magnitude higher than that of a continuous film. Our study reveals a strong correlation between the mobility and the band gap in these nanowall network samples. However, it is seen that when the thickness of the tips of the walls increases to an extent such that more than 70% of the film area is covered, it behaves close to a flat sample. In the sample with lower surface coverage (?40% and ?60%), it was observed that the conductivity, mobility as well as the band gap increase with the decrease in the average tip width of the walls. Photoluminescence (PL) experiments show a strong and broad band edge emission with a large (as high as ? 90 meV) blue shift, compared to that of a continuous film, suggesting a confinement of carriers on the top edges of the nanowalls. The PL peak width remains wide at all temperatures suggesting the existence of a high density of tail states at the band edge, which is further supported by the photoconductivity result. The high conductivity and mobility observed in these samples is believed to be due to a “dissipation less” transport of carriers, which are localized at the top edges (edge states) of the nanowalls.

  3. High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels

    SciTech Connect (OSTI)

    Koblmueller, G. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Chu, R. M.; Raman, A.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States)

    2010-02-15T23:59:59.000Z

    We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr{sub 4} to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm{sup 2}/V s and the dc drain current reached {approx}1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods.

  4. Indium and impurity incorporation in InGaN films on polar, nonpolar, and semipolar GaN orientations grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Browne, David A.; Young, Erin C.; Lang, Jordan R.; Hurni, Christophe A.; Speck, James S. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

    2012-07-15T23:59:59.000Z

    The effects of NH{sub 3} flow, group III flux, and substrate growth temperature on indium incorporation and surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. The incorporation of unintentional impurity elements (H, C, O) in InGaN films was studied as a function of growth temperature for growth on polar (0001) GaN on sapphire templates, nonpolar (1010) bulk GaN, and semipolar (1122), (2021) bulk GaN substrates. Enhanced indium incorporation was observed on both (1010) and (2021) surfaces relative to c-plane, while reduced indium incorporation was observed on (1122) for co-loaded conditions. Indium incorporation was observed to increase with decreasing growth temperature for all planes, while being relatively unaffected by the group III flux rates for a 1:1 Ga:In ratio. Indium incorporation was found to increase at the expense of a decreased growth rate for higher ammonia flows; however, smooth surface morphology was consistently observed for growth on semipolar orientations. Increased concentrations of oxygen and hydrogen were observed on semipolar and nonpolar orientations with a clear trend of increased hydrogen incorporation with indium content.

  5. Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. II. Sub-band-gap luminescence and electron irradiation effects

    SciTech Connect (OSTI)

    Robins, Lawrence H.; Bertness, Kris A.; Barker, Joy M.; Sanford, Norman A.; Schlager, John B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    2007-06-01T23:59:59.000Z

    GaN nanowires with diameters of 50-250 nm, grown by catalyst-free molecular beam epitaxy, were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 to 297 K. Both as-grown samples and dispersions of the nanowires onto other substrates were examined. The properties of the near-band-edge PL and CL spectra were discussed in Part I of this study by [Robins et al. [L. H. Robins, K. A. Bertness, J. M. Barker, N. A. Sanford, and J. B. Schlager, J. Appl. Phys. 101,113505 (2007)]. Spectral features below the band gap, and the effect of extended electron irradiation on the CL, are discussed in Part II. The observed sub-band-gap PL and CL peaks are identified as phonon replicas of the free-exciton transitions, or excitons bound to structural defects or surface states. The defect-related peaks in the nanowires are correlated with luminescence lines previously reported in GaN films, denoted the Y lines [M. A. Reshchikov and H. Morkoc, J. Appl. Phys. 97, 061301 (2005)]. The CL was partially quenched by electron beam irradiation for an extended time; the quenching was stronger for the free and shallow-donor-bound exciton peaks than for the defect-related peaks. The quenching appeared to saturate at high irradiation dose (with final intensity {approx_equal}30% of initial intensity) and was reversible on thermal cycling to room temperature. The electron irradiation-induced quenching of the CL is ascribed to charge injection and trapping phenomena.

  6. Electronic structures and magnetic moments of Co{sub 3}FeN thin films grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Ito, Keita; Sanai, Tatsunori; Yasutomi, Yoko; Toko, Kaoru; Honda, Syuta; Suemasu, Takashi [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)] [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Zhu, Siyuan; Kimura, Akio [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)] [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ueda, Shigenori [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)] [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Takeda, Yukiharu; Saitoh, Yuji [Condensed Matter Science Division, Japan Atomic Energy Agency (JAEA), 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan)] [Condensed Matter Science Division, Japan Atomic Energy Agency (JAEA), 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Imai, Yoji [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan) [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2013-12-02T23:59:59.000Z

    We evaluated electronic structures and magnetic moments in Co{sub 3}FeN epitaxial films on SrTiO{sub 3}(001). The experimentally obtained hard x-ray photoemission spectra of the Co{sub 3}FeN film have a good agreement with those calculated. Site averaged spin magnetic moments deduced by x-ray magnetic circular dichroism were 1.52 ?{sub B} per Co atom and 2.08 ?{sub B} per Fe atom at 100 K. They are close to those of Co{sub 4}N and Fe{sub 4}N, respectively, implying that the Co and Fe atoms randomly occupy the corner and face-centered sites in the Co{sub 3}FeN unit cell.

  7. Role of Ion Damage on Unintentional Ca Incorporation During the Plasma-Assisted Molecular-Beam Epitaxy Growth of Dilute Nitrides Using N2/Ar Source Gas Mixtures

    SciTech Connect (OSTI)

    Oye, M. M.; Bank, S. R.; Ptak, A. J.; Reedy, R. C.; Goorsky, M. S.; Holmes Jr., A. L.

    2008-05-01T23:59:59.000Z

    Unintentional Ca incorporation caused by Ca-contaminated substrate surfaces on as-purchased GaAs wafers are known to limit the efficiency of solar cells based on dilute nitride materials. This article focuses on further understanding the conditions and mechanisms by which these Ca impurities incorporate. Plasma-assisted molecular-beam epitaxy utilizing a 1% N{sub 2} in Ar precursor gas mixture was used to grow GaAs at 400 and 580 C, and GaN{sub 0.01}As{sub 0.99} at 400 C. Two plasma operating combinations of rf power and gas flow rate were used to generate different amounts and energies of both ions and other plasma species, while keeping nitrogen incorporation constant. The ions were characterized with a dual-grid, retarding-field ion energy analyzer, and the corresponding ion energy distributions are presented to correlate ions with Ca incorporation. When appropriate, dc-biased deflector plates were used to remove ions during growth. Secondary ion mass spectrometry was used to measure Ca in GaAs and GaN{sub 0.01}As{sub 0.99}. Ca incorporation was observed in the dilute nitride samples, but the effects of ions did not exceed other Ca incorporation mechanisms associated with defects due to both low temperature growth and nitrogen incorporation; however, different neutral active nitrogen species (atomic N and metastable N{sub 2}) may be a factor. Ca incorporation measured in GaAs grown at 400 C with a pure Ar plasma is predominantly due to defects associated with low temperature growth, as opposed to plasma damage caused by the ions. GaAs growths at 580 C without a plasma did not exhibit Ca incorporation, but growth at 580 C with ions from a pure Ar plasma caused Ca incorporation.

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

    SciTech Connect (OSTI)

    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

    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.

  9. Strain control of AlGaN/GaN high electron mobility transistor structures on silicon (111) by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Aidam, Rolf; Diwo, Elke; Rollbuehler, Nicola; Kirste, Lutz; Benkhelifa, Fouad [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

    2012-06-01T23:59:59.000Z

    This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN-based high electron mobility transistor structures grown on 4 in. Si (111) substrates. In situ measurements of wafer curvature during growth proved to be a very powerful method to analyze the buffer layer's thickness dependent strain. The Ga/N ratio at the beginning of growth of the GaN buffer layer is the critical parameter to control the compressive strain of the entire grown structure. An engineered amount of compressive strain must be designed into the structure to perfectly compensate for the tensile strain caused by differences in the thermal expansion coefficient between the epi-layer and substrate during sample cool down from growth temperatures. A maximum film thickness of 4.2 {mu}m was achieved without the formation of any cracks and a negligible bow of the wafers below 10 {mu}m. Measurement of the as-grown wafers revealed depth profiles of the charge carrier concentration comparable to values achieved on SiC substrates and mobility values of the two dimensional electron gas in the range 1230 to 1350 cm{sup 2}/Vs at a charge carrier concentration of 6.5-7 10{sup 12}/cm{sup 2}. First results on processed wafers with 2 {mu}m thick buffer layer indicate very promising results with a resistance of the buffer, measured on 200 {mu}m long contacts with 15 {mu}m pitch, in the range of R > 10{sup 9}{Omega} at 100 V and breakdown voltages up to 550 V.

  10. 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]

    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

    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.

  11. High characteristics temperature of strain-compensated 1.3 {micro}m InAsP/InGaP/InP multi-quantum well lasers grown by all solid source molecular beam epitaxy

    SciTech Connect (OSTI)

    Savolainen, P.; Toivonen, M.; Salokatve, A. [Tampere Univ. of Technology (Finland). Dept. of Physics; Asonen, H. [Tutcore Ltd., Tampere (Finland); Murison, R. [EG and G Optoelectronics Canada, Vaudreuil, Quebec (Canada)

    1996-12-31T23:59:59.000Z

    The present lasers have very good characteristic temperature values for the threshold current. In order to maintain such performance in cw mode, one should either use narrow waveguide (buried) type of laser structure or reduce the number of QWs. If the number of QW`s is reduced, total gain decreases and this should be compensated by increasing the optical confinement factor. In this paper the authors have demonstrated the suitability of InAsP/InGaP strain-compensated system for high temperature lasers emitting 1.3 {micro}m and the potential of all solid source molecular beam epitaxy for growth of optoelectronic devices.

  12. Effects of gallium doping on properties of a-plane ZnO films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Han, Seok Kyu; Lee, Hyo Sung; Lim, Dong Seok; Hong, Soon-Ku; Yoon, Nara; Oh, Dong-Cheol; Ahn, Byung Jun; Song, Jung-Hoon; Yao, Takafumi [Department of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Department of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea and Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Center for Optoelectronic Materials and Devices, Department of Defense Science and Technology, Hoseo University, Cheonan 330-713 (Korea, Republic of); Department of Physics, Kongju National University, Gongju 314-701 (Korea, Republic of); Center for Interdisciplinary Research, Tohoku University, Sendai 980-8587 (Japan)

    2011-05-15T23:59:59.000Z

    The authors report on the structural, optical, and electrical properties of Ga-doped a-plane (1120) ZnO films grown by plasma-assisted molecular beam epitaxy. Ga doping level was controlled by changing the Ga cell temperatures from 350 to 470 deg. C with an interval of 30 deg. C. With up to Ga cell temperatures of 440 deg. C, single crystalline Ga-doped a-plane ZnO films were grown; however, the sample with a Ga cell temperature of 470 deg. C showed polycrystalline features. The typical striated surface morphology normally observed from undoped ZnO films disappeared with Ga doping. ZnO films doped with Ga cell temperatures up to 440 deg. C did not show a significant change in full width at half maximum (FWHM) values of (1120) x-ray rocking curves by doping. The smallest FWHM values were 0.433 deg. ({phi}=90 deg.) and 0.522 deg. ({phi}=0 deg. ) for the sample with a Ga cell temperature of 350 deg. C. The polycrystalline ZnO film with excessive Ga doping at the Ga cell temperature of 470 deg. C showed significantly increased FWHM values. Hall measurements at room temperature (RT) revealed that electron concentration began to be saturated at the Ga cell temperature of 440 deg. C and electron mobility was drastically reduced at the Ga cell temperature of 470 deg. C. The carrier concentration of Ga-doped ZnO films were controlled from 7.2x10{sup 18} to 3.6x10{sup 20} cm{sup -3}. Anisotropic electrical properties (carrier concentration and Hall mobility) were observed in measurements by the van der Pauw method depending on the direction (c- or m-direction) for the undoped sample but not observed for the doped samples. RT photoluminescence (PL) spectra from the Ga-doped single crystalline ZnO films showed dominant near band edge (NBE) emissions with negligibly deep level emission. The NBE intensity in PL spectra increases with Ga doping.

  13. High resistivity LT-In{sub 0.47}Ga{sub 0.53}P grown by gas source molecular beam epitaxy

    SciTech Connect (OSTI)

    He, Y.; El-Masry, N.A. [North Carolina State Univ., Raleigh, NC (United States); Look, D.C. [Wright State Univ., Dayton, OH (United States)] [and others

    1993-12-01T23:59:59.000Z

    Low-temperature (LT) growth of In{sub 0.47}Ga{sub 0.53}P was carried out in the temperature range from 200 to 260{degrees}C by gas source molecular beam epitaxy using solid Ga and In and precracked PH{sub 3}. The Hall measurements of the as-grown film showed a resistivity of {approximately}10{sup 6} {Omega}-cm at room temperature whereas the annealed film (at 600{degrees}C for 1 h) had at least three orders of magnitude, higher resistivity. The Hall measurements, also, indicated activation energies of {approximately}0.5 and 0.8 eV for the as-grown and annealed samples, respectively. Double-crystal x-ray diffraction showed that the LT-InGaP films had {approximately}47% In composition. The angular separation, {Delta}{theta}, between the GaAs substrate and the as-grown LT-InGaP film on (004) reflection was increased by 20 arc-s after annealing. In order to better understand the annealing effect, a LT-InGaP film was grown on an InGaP film grown at 480{degrees}C. While annealing did not have any effect on the HT-InGaP peak position, the LT-InGaP peak was shifted toward the HT-InGaP peak, indicating a decrease in the LT-InGaP lattice parameter. Cross-sectional transmission electron microscopy indicates the presence of phase separation in LT-InGaP films, manifested in the form of a {open_quote}precipitate-like{close_quotes} microstructure. The analytical scanning transmission electron microscopy analysis of the LT-InGaP film revealed a group-V nonstoichiometric deviation of {approximately}0.5 at% P. To our knowledge, this is the first report about the growth and characterization of LT-InGaP films. 12 refs., 5 figs.

  14. Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam ABSTRACT We present the structural and surface characterization of the alloy formation of scandium gallium GaN (w-GaN) spurred much interest in related III-nitrides such as aluminium nitride (Al

  15. Two-dimensional weak anti-localization in Bi{sub 2}Te{sub 3} thin film grown on Si(111)-(7 Multiplication-Sign 7) surface by molecular beam epitaxy

    SciTech Connect (OSTI)

    Roy, Anupam; Guchhait, Samaresh; Sonde, Sushant; Dey, Rik; Pramanik, Tanmoy; Rai, Amritesh; Movva, Hema C. P.; Banerjee, Sanjay K. [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States)] [Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758 (United States); Colombo, Luigi [Texas Instruments, 12500 TI Boulevard, Dallas, Texas 75266 (United States)] [Texas Instruments, 12500 TI Boulevard, Dallas, Texas 75266 (United States)

    2013-04-22T23:59:59.000Z

    We report on low temperature transport studies of Bi{sub 2}Te{sub 3} topological insulator thin films grown on Si(111)-(7 Multiplication-Sign 7) surface by molecular beam epitaxy. A sharp increase in the magnetoresistance with magnetic field at low temperature indicates the existence of weak anti-localization. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model, and the extracted phase coherence length shows a power-law dependence with temperature indicating the existence of a two-dimensional system. An insulating ground state has also been observed at low temperature showing a logarithmic divergence of the resistance that appears to be the influence of electron-electron interaction in a two-dimensional system.

  16. Structural properties of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

    SciTech Connect (OSTI)

    Liu, X.; Leiner, J.; Dobrowolska, M.; Furdyna, J. K. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Fan, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); Zhang, Y.-H. [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Cao, H.; Chen, Y. P. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Kirby, B. J. [Center for Neutron Research, NIST, Gaithersburg, Maryland 20899 (United States)

    2011-10-24T23:59:59.000Z

    Thin films of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.

  17. 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)

    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

    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.

  18. Elimination of columnar microstructure in N-face InAlN, lattice-matched to GaN, grown by plasma-assisted molecular beam epitaxy in the N-rich regime

    SciTech Connect (OSTI)

    Ahmadi, Elaheh; Wienecke, Steven; Keller, Stacia; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Shivaraman, Ravi; Wu, Feng; Kaun, Stephen W.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-02-17T23:59:59.000Z

    The microstructure of N-face InAlN layers, lattice-matched to GaN, was investigated by scanning transmission electron microscopy and atom probe tomography. These layers were grown by plasma-assisted molecular beam epitaxy (PAMBE) in the N-rich regime. Microstructural analysis shows an absence of the lateral composition modulation that was previously observed in InAlN films grown by PAMBE. A room temperature two-dimensional electron gas (2DEG) mobility of 1100 cm{sup 2}/V s and 2DEG sheet charge density of 1.9?×?10{sup 13}?cm{sup ?2} was measured for N-face GaN/AlN/GaN/InAlN high-electron-mobility transistors with lattice-matched InAlN back barriers.

  19. Role of an ultra-thin AlN/GaN superlattice interlayer on the strain engineering of GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Shen, X. Q.; Takahashi, T.; Matsuhata, H.; Ide, T.; Shimizu, M. [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan)] [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan); Rong, X.; Chen, G.; Wang, X. Q.; Shen, B. [School of Physics, Peking University, Beijing 100871 (China)] [School of Physics, Peking University, Beijing 100871 (China)

    2013-12-02T23:59:59.000Z

    We investigate the role of an ultra-thin AlN/GaN superlattice interlayer (SL-IL) on the strain engineering of the GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy. It is found that micro-cracks limitted only at the SL-IL position are naturally generated. These micro-cracks play an important role in relaxing the tensile strain caused by the difference of the coefficient of thermal expansion between GaN and Si and keeping the residual strain in the crack-free GaN epilayers resulted from the SL-IL during the growth. The mechanism understanding of the strain modulation by the SL-IL in the GaN epilayers grown on Si substrates makes it possible to design new heterostructures of III-nitrides for optic and electronic device applications.

  20. Nucleation and Stoichiometry Dependence of rutile-TiO2(001)/GaN(0001) Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Feenstra, Randall

    the initial nucleation and the stoichiometry of rutile- TiO2(001) grown on wurtzite GaN(0001) by radio explore the growth of rutile-TiO2(001) on wurtzite GaN(0001) by oxygen plasma-assisted molecular beam) was maintained constant at 400 W. The substrates were commercially available wurtzite Ga-polar GaN(0001) grown

  1. Polarization induced hole doping in graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Li, Shibin; Zhang, Ting; Wu, Jiang; Yang, Yajie; Wang, Zhiming; Wu, Zhiming; Chen, Zhi; Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)] [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2013-02-11T23:59:59.000Z

    Polarization induced hole doping on the order of {approx}10{sup 18} cm{sup -3} is achieved in linearly graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy. Graded Al{sub x}Ga{sub 1-x}N and conventional Al{sub 0.7}Ga{sub 0.3}N layers grown on AlN are beryllium (Be) doped via epitaxial growth. The hole concentration in graded Al{sub x}Ga{sub 1-x}N:Be (x = 0.7 {approx} 1) layers demonstrates that polarization generates hole charges from Be dopant. The Al{sub 0.7}Ga{sub 0.3}N layer is not conductive owing to the absence of carriers generated from the Be dopant without the inducement of polarization. Polarization doping provides an approach to high efficiency p-type doping in high Al composition AlGaN.

  2. Structure and magnetism in strained Ge{sub 1-x-y}Sn{sub x}Mn{sub y} films grown on Ge(001) by low temperature molecular beam epitaxy

    SciTech Connect (OSTI)

    Prestat, E. [INAC, SP2M, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Karlsruher Institut fuer Technologie (KIT), Laboratorium fuer Elektronenmikroskopie, D-76128 Karlsruhe (Germany); Barski, A.; Bellet-Amalric, E.; Morel, R.; Tainoff, D.; Jain, A.; Porret, C.; Bayle-Guillemaud, P.; Jamet, M. [INAC, SP2M, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Jacquot, J.-F. [INAC, SCIB, CEA and Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France)

    2013-07-01T23:59:59.000Z

    In this letter, we study the structural and magnetic properties of Ge{sub 1-x-y}Sn{sub x}Mn{sub y} films grown on Ge(001) by low temperature molecular beam epitaxy using X-ray diffraction, high resolution transmission electron microscopy, and superconducting quantum interference device. Like in Mn doped Ge films, Mn atoms diffuse during the growth and aggregate into vertically aligned Mn-rich nanocolumns of a few nanometers in diameter. Transmission electron microscopy observations in plane view clearly indicate that the Sn incorporation is not uniform with concentration in Mn rich vertical nanocolumns lower than the detection limit of electron energy loss spectroscopy. The matrix exhibits a GeSn solid solution while there is a Sn-rich GeSn shell around GeMn nanocolumns. The magnetization in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} layers is higher than in Ge{sub 1-x}Mn{sub x} films. This magnetic moment enhancement in Ge{sub 1-x-y}Sn{sub x}Mn{sub y} is probably related to the modification of the electronic structure of Mn atoms in the nanocolumns by the Sn-rich shell, which is formed around the nanocolumns.

  3. Strain states of AlN/GaN-stress mitigating layer and their effect on GaN buffer layer grown by ammonia molecular beam epitaxy on 100-mm Si(111)

    SciTech Connect (OSTI)

    Ravikiran, L.; Radhakrishnan, K.; Agrawal, M. [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)] [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Dharmarasu, N.; Munawar Basha, S. [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)] [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)

    2013-09-28T23:59:59.000Z

    The effect of strain states of AlN/GaN-stress mitigating layer (SML) on buried crack density and its subsequent influence on the residual stresses in GaN buffer layers grown using ammonia-molecular beam epitaxy on 100-mm Si(111) substrate has been investigated. Different stages involved in the formation of buried cracks, which are crack initialization, growth of relaxed AlN layer, and subsequent lateral over growth, are identified using in-situ curvature measurements. While the increase of GaN thickness in AlN/GaN-SML enhanced its compressive strain relaxation and resulted in reduced buried crack spacing, the variation of AlN thickness did not show any effect on the crack spacing. Moreover, the decrease in the crack spacing (or increase in the buried crack density) was found to reduce the residual compression in 1st and 2nd GaN layers of AlN/GaN-SML structure. The higher buried crack density relaxed the compressive strain in 1st GaN layer, which further reduced its ability to compensate the tensile stress generated during substrate cool down, and hence resulted in lower residual compressive stress in 2nd GaN layer.

  4. Reflection high-energy electron diffraction evaluation of thermal deoxidation of chemically cleaned Si, SiGe, and Ge layers for solid-source molecular beam epitaxy

    SciTech Connect (OSTI)

    Ali, Dyan; Richardson, Christopher J. K. [Laboratory for Physical Sciences, University of Maryland, College Park, Maryland 20740 (United States)

    2012-11-15T23:59:59.000Z

    The authors present a study on the thermal evolution of the reflection high-energy electron diffraction pattern of chemically cleaned (001)-oriented Si, Ge, and SiGe surfaces, associating observed changes in the reconstructions with the desorption of known residual contaminants for Si and Ge surfaces. The implications of residual oxides prior to epitaxy on stacking fault densities in the grown films are presented. Further evidence for the two-phase nature of oxides on SiGe surfaces is provided, demonstrating that it is necessary to heat a SiGe surface up to the thermal deoxidation temperature of a Si surface to obtain stacking fault-free growth.

  5. InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular-beam epitaxy with a valved phosphorus cracker

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular; accepted 17 November 1995 The growth and device characterization of an InGaP/GaAs double-quality phosphorus-containing compounds.1­4 The growth of high-performance InGaP/ GaAs and InGaAs/InP single

  6. Chemical beam epitaxy for high efficiency photovoltaic devices

    SciTech Connect (OSTI)

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

    1994-09-01T23:59:59.000Z

    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.

  7. Molecular Beam Epitaxy, Multi-source | EMSL

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

    to form reliable, low-resistance Ohmic contacts is of critical importance to the ongoing development of oxide electronics. Most metals... The Impacts of Cation Stoichiometry and...

  8. Ion-Beam Synthesis of Epitaxial Au Nanocrystals in MgO. | EMSL

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

    relationship to MgO(100). Citation: Thevuthasan S, V Shutthanandan, CM Wang, WJ Weber, W Jiang, AS Cavanagh, J Lian, and LM Wang.2004."Ion-Beam Synthesis of Epitaxial Au...

  9. 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)

    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

    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.

  10. High-speed epitaxy using supersonic molecular jets

    SciTech Connect (OSTI)

    Eres, D.

    1990-01-01T23:59:59.000Z

    This paper discusses the use of supersonic jets of gaseous source molecules in thin films growth. Molecular jets in free form with no skimmers or collimators in the nozzle-substrate path were used in the investigation of basic film growth processes and in practical film growth applications. The Ge growth rates were found to depend linearly on the digermane jet intensity. Furthermore, the film thickness distributions showed excellent agreement with the distribution of digermane molecules in the jet. High epitaxial Ge growth rates were achieved on GaAs (100) substrates by utilizing high-intensity pulsed jets. The practical advantages and limitations of this film growth technique are evaluated, based on the results of microstructural and electrical measurements of heteroepitaxial Ge films on GaAs (100) substrates. 8 refs., 4 figs.

  11. RisR980(EN) Epitaxy, Thin films and

    E-Print Network [OSTI]

    Risø­R­980(EN) Epitaxy, Thin films and Superlattices Morten Jagd Christensen Risø National of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in structures were investigated. This thesis, "Epitaxy, Thin films and Superlattices", is written in partial

  12. 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)

    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

    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.

  13. Impacts of anisotropic lattice relaxation on crystal mosaicity and luminescence spectra of m-plane Al{sub x}Ga{sub 1-x}N films grown on m-plane freestanding GaN substrates by NH{sub 3} source molecular beam epitaxy

    SciTech Connect (OSTI)

    Hoshi, T.; Hazu, K.; Ohshita, K.; Kagaya, M.; Onuma, T.; Chichibu, S. F. [CANTech, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Fujito, K. [Optoelectronics Laboratory, Mitsubishi Chemical Corporation, 1000 Higashi-Mamiana, Ushiku 300-1295 (Japan); Namita, H. [Mitsubishi Chemical Group Science and Technology Research Center, Inc., 8-3-1 Chuo, Ami, Inashiki 300-0332 (Japan)

    2009-02-16T23:59:59.000Z

    In-plane anisotropic lattice relaxation was correlated with the crystal mosaicity and luminescence spectra for m-plane Al{sub x}Ga{sub 1-x}N films grown on a freestanding GaN substrate by NH{sub 3}-source molecular beam epitaxy. The homoepitaxial GaN film exhibited A- and B-excitonic emissions at 8 K, which obeyed the polarization selection rules. For Al{sub x}Ga{sub 1-x}N overlayers, the m-plane tilt mosaic along c-axis was the same as the substrate as far as coherent growth was maintained (x{<=}0.25). However, it became more severe than along the a-axis for lattice-relaxed films (x{>=}0.52). The results are explained in terms of anisotropic lattice and thermal mismatches between the film and the substrate. Nonetheless, all the Al{sub x}Ga{sub 1-x}N films exhibited a near-band-edge emission peak and considerably weak deep emission at room temperature.

  14. Greatly improved interfacial passivation of in-situ high ? dielectric deposition on freshly grown molecule beam epitaxy Ge epitaxial layer on Ge(100)

    SciTech Connect (OSTI)

    Chu, R. L. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Liu, Y. C.; Lee, W. C.; Huang, M. L.; Kwo, J., E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Lin, T. D.; Hong, M., E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Pi, T. W. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)

    2014-05-19T23:59:59.000Z

    A high-quality high-?/Ge interface has been achieved by combining molecule beam epitaxy grown Ge epitaxial layer and in-situ deposited high ? dielectric. The employment of Ge epitaxial layer has sucessfully buried and/or removed the residue of unfavorable carbon and native oxides on the chemically cleaned and ultra-high vacuum annealed Ge(100) wafer surface, as studied using angle-resolved x-ray photoelectron spectroscopy. Moreover, the scanning tunneling microscopy analyses showed the significant improvements in Ge surface roughness from 3.5?Å to 1?Å with the epi-layer growth. Thus, chemically cleaner, atomically more ordered, and morphologically smoother Ge surfaces were obtained for the subsquent deposition of high ? dielectrics, comparing with those substrates without Ge epi-layer. The capacitance-voltage (C-V) characteristics and low extracted interfacial trap density (D{sub it}) reveal the improved high-?/Ge interface using the Ge epi-layer approach.

  15. Nonlithographic epitaxial SnxGe1x dense nanowire arrays grown on Ge,,001...

    E-Print Network [OSTI]

    Atwater, Harry

    Nonlithographic epitaxial SnxGe1Àx dense nanowire arrays grown on Ge,,001... Regina Ragan-thick SnxGe1 x /Ge(001) epitaxial films with 0 x 0.085 by molecular-beam epitaxy. These films evolve during growth into a dense array of SnxGe1 x nanowires oriented along 001 , as confirmed by composition contrast

  16. Epitaxial GaN films by hyperthermal ion-beam nitridation of Ga droplets

    SciTech Connect (OSTI)

    Gerlach, J. W.; Ivanov, T.; Neumann, L.; Hoeche, Th.; Hirsch, D.; Rauschenbach, B. [Leibniz-Institut fuer Oberflaechenmodifizierung (IOM), D-04318 Leipzig (Germany)

    2012-06-01T23:59:59.000Z

    Epitaxial GaN film formation on bare 6H-SiC(0001) substrates via the process of transformation of Ga droplets into a thin GaN film by applying hyperthermal nitrogen ions is investigated. Pre-deposited Ga atoms in well defined amounts form large droplets on the substrate surface which are subsequently nitridated at a substrate temperature of 630 Degree-Sign C by a low-energy nitrogen ion beam from a constricted glow-discharge ion source. The Ga deposition and ion-beam nitridation process steps are monitored in situ by reflection high-energy electron diffraction. Ex situ characterization by x-ray diffraction and reflectivity techniques, Rutherford backscattering spectrometry, and electron microscopy shows that the thickness of the resulting GaN films depends on the various amounts of pre-deposited gallium. The films are epitaxial to the substrate, exhibit a mosaic like, smooth surface topography and consist of coalesced large domains of low defect density. Possible transport mechanisms of reactive nitrogen species during hyperthermal nitridation are discussed and the formation of GaN films by an ion-beam assisted process is explained.

  17. X-ray photoelectron spectroscopy of gallium nitride films grown by radical-beam gettering epitaxy

    SciTech Connect (OSTI)

    Rogozin, I. V. [Berdyansk State Pedagogical University (Ukraine)], E-mail: rogozin@bdpu.org; Kotlyarevsky, M. B. [Academy of Management and Information Technology (Ukraine)

    2007-05-15T23:59:59.000Z

    Thin GaN films were grown on GaAs(111) substrates by radical-beam gettering epitaxy. The structural quality of the films was studied by high-resolution x-ray diffraction. The chemical composition of the GaAs surface and GaN film was studied by x-ray photoelectron spectroscopy. It is shown that Ga-N and As-N bonds are formed on the GaAs surface at initial growth stages at low temperatures. The state of the film-substrate interface was studied. It was found that prolonged annealing of GaN films in nitrogen radicals shifts the composition to nitrogen excess.

  18. Point defect balance in epitaxial GaSb

    SciTech Connect (OSTI)

    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

    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.

  19. Physics with fast molecular-ion beams

    SciTech Connect (OSTI)

    Kanter, E.P.

    1980-01-01T23:59:59.000Z

    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.

  20. Counting molecular-beam grown graphene layers

    SciTech Connect (OSTI)

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

    2013-06-17T23:59:59.000Z

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

  1. Epitaxial growth of europium monoxide on diamond

    SciTech Connect (OSTI)

    Melville, A.; Heeg, T. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)] [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Mairoser, T.; Schmehl, A. [Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg (Germany)] [Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, Universitätsstraße 1, 86159 Augsburg (Germany); Fischer, M.; Gsell, S.; Schreck, M. [Institut für Physik, Universität Augsburg, D-86135 Augsburg (Germany)] [Institut für Physik, Universität Augsburg, D-86135 Augsburg (Germany); Awschalom, D. D. [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States)] [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Holländer, B.; Schubert, J. [Peter Grünberg Institute, PGI9-IT, JARA-FIT, Research Centre Jülich, D-52425 Jülich (Germany)] [Peter Grünberg Institute, PGI9-IT, JARA-FIT, Research Centre Jülich, D-52425 Jülich (Germany); Schlom, D. G. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States) [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

    2013-11-25T23:59:59.000Z

    We report the epitaxial integration of phase-pure EuO on both single-crystal diamond and on epitaxial diamond films grown on silicon utilizing reactive molecular-beam epitaxy. The epitaxial orientation relationship is (001) EuO ? (001) diamond and [110] EuO ?[100] diamond. The EuO layer is nominally unstrained and ferromagnetic with a transition temperature of 68 ± 2 K and a saturation magnetization of 5.5 ± 0.1 Bohr magnetons per europium ion on the single-crystal diamond, and a transition temperature of 67 ± 2 K and a saturation magnetization of 2.1 ± 0.1 Bohr magnetons per europium ion on the epitaxial diamond film.

  2. Yuan T. Lee's Crossed Molecular Beam Experiment

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del SolStrengtheningWildfires mayYuan T. Lee's Crossed Molecular Beam Experiment Home |

  3. Local Co Structure in Epitaxial Cox Ti-xO-x Anatase. | EMSL

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

    out to date have borne out this prediciton. One notable exception is that of Mn-doped GaN, which grows n-type by gas-source molecular beam epitaxy under certain conditions, and...

  4. Note: High density pulsed molecular beam for cold ion chemistry

    SciTech Connect (OSTI)

    Kokish, M. G.; Rajagopal, V.; Marler, J. P.; Odom, B. C., E-mail: b-odom@northwestern.edu [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

    2014-08-15T23:59:59.000Z

    A recent expansion of cold and ultracold molecule applications has led to renewed focus on molecular species preparation under ultrahigh vacuum conditions. Meanwhile, molecular beams have been used to study gas phase chemical reactions for decades. In this paper, we describe an apparatus that uses pulsed molecular beam technology to achieve high local gas densities, leading to faster reaction rates with cold trapped ions. We characterize the beam's spatial profile using the trapped ions themselves. This apparatus could be used for preparation of molecular species by reactions requiring excitation of trapped ion precursors to states with short lifetimes or for obtaining a high reaction rate with minimal increase of background chamber pressure.

  5. Molecular beam studies of reaction dynamics

    SciTech Connect (OSTI)

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

    1993-12-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    Not Available

    2011-07-01T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

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

    1993-01-01T23:59:59.000Z

    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.

  8. Multiperiod quantum-cascade nanoheterostructures: Epitaxy and diagnostics

    SciTech Connect (OSTI)

    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

    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.

  9. DYNAMICS OF INFRARED MULTIPHOTON DISSOCIATION OF SF6 BY MOLECULAR BEAM METHOD

    E-Print Network [OSTI]

    Grant, E.R.

    2010-01-01T23:59:59.000Z

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

  10. Distribution of the surface potential of epitaxial HgCdTe

    SciTech Connect (OSTI)

    Novikov, V. A., E-mail: novikovvadim@mail.ru; Grigoryev, D. V.; Bezrodnyy, D. A. [Tomsk State University, 634050, 36, Lenina Avenue, Tomsk (Russian Federation); Dvoretsky, S. A. [Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, 630090, 13, pr. Lavrentieva, Novosibirsk (Russian Federation)

    2014-09-08T23:59:59.000Z

    We studied the distribution of surface potential of the Hg{sub 1?x}Cd{sub x}Te epitaxial films grown by molecular beam epitaxy. The studies showed that the variation of the spatial distribution of surface potential in the region of the V-defect can be related to the variation of the material composition of epitaxial film. The V-defect is characterized by increased of Hg content with respect to the composition of the solid solution of Hg{sub 1?x}Cd{sub x}Te epitaxial film. In this paper, it was demonstrated that the unformed V-defects can be observed together with the macroscopic V-defects on the epitaxial film surface. These unformed V-defects can allow the creation of a complex surface potential distribution profile due to the redistribution of the solid solution composition.

  11. Optical Probing of metamagnetic phases in epitaxial EuSe

    SciTech Connect (OSTI)

    Galgano, G. D.; Henriques, A. B. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970 Sao Paulo (Brazil); Bauer, G.; Springholz, G. [Institut fuer Halbleiter und Festkoerperphysik, Johannes Kepler Universitaet Linz, 4040 Linz (Austria)

    2011-12-23T23:59:59.000Z

    EuSe is a wide gap magnetic semiconductors with a potential for applications in proof-of-concept spintronic devices. When the temperature is lowered, EuSe goes through sharp transitions between a variety of magnetic phases and is thus described as metamagnetic. The purpose of the present investigation is to correlate the magnetic order to the sharp dichroic doublet, discovered recently in high quality thin epitaxial layers of EuSe, grown by molecular beam epitaxy. We report detailed measurements of the doublet positions and intensities as a function of magnetic field in low temperatures, covering several magnetic phases.

  12. Chemical beam epitaxial growth of InP, InGaP, and InAs heterojunctions using triethylindium and bisphosphinoethane

    SciTech Connect (OSTI)

    Chin, A.; Martin, P. [General Electric Electronics Lab., Syracuse, NY (United States)] [General Electric Electronics Lab., Syracuse, NY (United States); Das, U. [Univ. of Florida, Gainesville, FL (United States)] [and others] [Univ. of Florida, Gainesville, FL (United States); and others

    1993-05-01T23:59:59.000Z

    The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices (SLS) and InGaP/InAs/InGaP quantum wells using bisphosphinoethane and tertiarybutylarsine as group V sources is reported. Mirrorlike surface morphology and excellent reflection high-energy electron diffraction patterns are observed. Room-temperature and 77 K Hall mobilities for a 2.0 {mu}m thick InP epitaxial layer are 4200 and 22 000 cm{sup 2}/V s, with carrier densities of 5.7E15 and 4.0E15 cm{sup {minus}3}, respectively. The relatively low mobility is due to a high n-type impurity concentration at the epitaxial layer-substrate interface. The full width at half-maximum linewidth of the photoluminescence spectra are 0.84, 14.6, and 16.1 meV, for InP, InGaP/InP SLS, and InGaP/InAs/InGaP quantum well, respectively. 9 refs., 5 figs., 1 tab.

  13. Evidence for graphite-like hexagonal AlN nanosheets epitaxially grown on single crystal Ag(111)

    SciTech Connect (OSTI)

    Tsipas, P.; Kassavetis, S.; Tsoutsou, D.; Xenogiannopoulou, E.; Golias, E.; Giamini, S. A.; Dimoulas, A. [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece)] [National Center for Scientific Research “Demokritos,” 15310 Athens (Greece); Grazianetti, C.; Fanciulli, M. [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy) [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, I-20126, Milano (Italy); Chiappe, D.; Molle, A. [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy)] [Laboratorio MDM, IMM-CNR, I-20864, Agrate Brianza (MB) (Italy)

    2013-12-16T23:59:59.000Z

    Ultrathin (sub-monolayer to 12 monolayers) AlN nanosheets are grown epitaxially by plasma assisted molecular beam epitaxy on Ag(111) single crystals. Electron diffraction and scanning tunneling microscopy provide evidence that AlN on Ag adopts a graphite-like hexagonal structure with a larger lattice constant compared to bulk-like wurtzite AlN. This claim is further supported by ultraviolet photoelectron spectroscopy indicating a reduced energy bandgap as expected for hexagonal AlN.

  14. Note: A helical velocity selector for continuous molecular beams

    SciTech Connect (OSTI)

    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

    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.

  15. Martensite transformation of epitaxial Ni-Ti films

    SciTech Connect (OSTI)

    Buschbeck, J.; Kozhanov, A. [Department Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 (United States); Kawasaki, J. K. [Department of Materials, University of California, Santa Barbara, CA 93106 (United States); James, R. D. [Department of Aerospace Engineering and Mechanics, University of Minnesota, Minneapolis, MN 55455 (United States); Palmstroem, C. J. [Department Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 (United States); Department of Materials, University of California, Santa Barbara, CA 93106 (United States)

    2011-05-09T23:59:59.000Z

    The structure and phase transformations of thin Ni-Ti shape memory alloy films grown by molecular beam epitaxy are investigated for compositions from 43 to 56 at. % Ti. Despite the substrate constraint, temperature dependent x-ray diffraction and resistivity measurements reveal reversible, martensitic phase transformations. The results suggest that these occur by an in-plane shear which does not disturb the lattice coherence at interfaces.

  16. Ultrathin epitaxially grown bismuth (111) membranes

    SciTech Connect (OSTI)

    Payer, T.; Rajkovic, I.; Ligges, M.; Linde, D. von der [Fachbereich Physik, Universitaet Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg (Germany); Horn-von Hoegen, M.; Meyer zu Heringdorf, F.-J. [Fachbereich Physik, Universitaet Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg (Germany); Center for Nanointegration (CeNIDE), Universitaet Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg (Germany)

    2008-09-01T23:59:59.000Z

    An ex situ cleaning and etching technique was applied to NaCl single crystals to prepare atomically flat and clean NaCl surfaces. These were used as substrates for molecular beam epitaxial growth of ultrathin continuous Bi(111) films. The high film quality - as studied with low energy electron diffraction, atomic force microscopy, and transmission electron diffraction - is attributed to the commensurate 10:7 ratio of the lattice constants. Dissolving the NaCl substrates in water allows the fabrication of freestanding 20 nm thin Bi(111) membranes of centimeter size.

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

    SciTech Connect (OSTI)

    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

    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.

  18. Investigation of Spin-Based Phenomena in Candidate Spintronic Materials by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Swartz, Adrian

    2013-01-01T23:59:59.000Z

    transport properties assuming adsorbed hydrogen induceshydrogen substantially modifies charge trans- port properties,to hydrogen-induced changes to the magnetic properties of

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

    SciTech Connect (OSTI)

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

    2013-12-01T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Cohen, Philip I.

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

  1. Surface reconstructions of cubic gallium nitride ,,001... grown by radio frequency nitrogen plasma molecular beam epitaxy

    E-Print Network [OSTI]

    observed on c-GaN 001 , depending on the growth condi- tions and the substrate. For growth of c-GaN on Ga-rich-grown GaN 001 on MgO 001 substrate. We have deduced that these variant reconstructions are com- posed of Ga; published online 27 October 2006 Cubic GaN has been grown under gallium Ga -rich growth conditions using

  2. Growth of GaN on porous SiC by molecular beam epitaxy

    E-Print Network [OSTI]

    Feenstra, Randall

    growth of high quality GaN thin films is the unavailability suitable substrates. The lack of suitable matched between the GaN and the substrate are the lattice parameter and the coefficient of thermal to the absence of high quality, large area GaN substrates. Therefore one has to resort to the heteroepitaxial

  3. Investigation of Spin-Based Phenomena in Candidate Spintronic Materials by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Swartz, Adrian

    2013-01-01T23:59:59.000Z

    applied to trivalent (Eu 3+ ) Europium oxide (Eu 2 O 3 ), wecase of divalent (Eu 2+ ) Europium monoxide, S=7/2, L=0, andmagnetic J 2 for the other europium chalcogenides (EuS,

  4. The Growth of GaN on Si by the Beam Flux Modulation

    SciTech Connect (OSTI)

    Roh, C. H.; Ha, M. W.; Song, H. J.; Choi, H. G.; Lee, J. H.; Ra, Y. W.; Hahn, C. K. [Compound Semiconductor Devices Research Center, Energy-Display R and D Division, Korea Electronics Technology Institute, Seongnam (Korea, Republic of)

    2011-12-23T23:59:59.000Z

    AlGaN/GaN HEMT structure was grown on Si (111) substrate by plasma-assisted molecular beam epitaxy (PA-MBE) using a beam flux modulation methods. In this result, it was verified that the propagation of treading dislocation (TD) due to N-rich GaN layer was effectively suppressed.

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

    SciTech Connect (OSTI)

    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

    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.

  6. Epitaxial growth of VO{sub 2} by periodic annealing

    SciTech Connect (OSTI)

    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

    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.

  7. An ultra-thin buffer layer for Ge epitaxial layers on Si

    SciTech Connect (OSTI)

    Kawano, M.; Yamada, S.; Tanikawa, K.; Miyao, M.; Hamaya, K. [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan)] [Department of Electronics, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Sawano, K. [Advanced Research Laboratories, Tokyo City University, 8-15-1 Todoroki, Tokyo 158-0082 (Japan)] [Advanced Research Laboratories, Tokyo City University, 8-15-1 Todoroki, Tokyo 158-0082 (Japan)

    2013-03-25T23:59:59.000Z

    Using an Fe{sub 3}Si insertion layer, we study epitaxial growth of Ge layers on a Si substrate by a low-temperature molecular beam epitaxy technique. When we insert only a 10-nm-thick Fe{sub 3}Si layer in between Si and Ge, epitaxial Ge layers can be obtained on Si. The detailed structural characterizations reveal that a large lattice mismatch of {approx}4% is completely relaxed in the Fe{sub 3}Si layer. This means that the Fe{sub 3}Si layers can become ultra-thin buffer layers for Ge on Si. This method will give a way to realize a universal buffer layer for Ge, GaAs, and related devices on a Si platform.

  8. Structural controlled magnetic anisotropy in Heusler L1{sub 0}-MnGa epitaxial thin films

    SciTech Connect (OSTI)

    Wang Kangkang; Lu Erdong; Smith, Arthur R. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Knepper, Jacob W.; Yang Fengyuan [Department of Physics, Ohio State University, 191 Woodruff Ave., Columbus, Ohio 43210 (United States)

    2011-04-18T23:59:59.000Z

    Ferromagnetic L1{sub 0}-MnGa thin films have been epitaxially grown on GaN, sapphire, and MgO substrates using molecular beam epitaxy. Using diffraction techniques, the epitaxial relationships are determined. It is found that the crystalline orientation of the films differ due to the influence of the substrate. By comparing the magnetic anisotropy to the structural properties, a clear correlation could be established indicating that the in-plane and out-of-plane anisotropy is directly determined by the crystal orientation of the film and could be controlled via selection of the substrates. This result could be helpful in tailoring magnetic anisotropy in thin films for spintronic applications.

  9. Growth of epitaxial iron nitride ultrathin film on zinc-blende gallium nitride

    SciTech Connect (OSTI)

    Pak, J.; Lin, W.; Wang, K.; Chinchore, A.; Shi, M.; Ingram, D. C.; Smith, A. R.; Sun, K.; Lucy, J. M.; Hauser, A. J.; Yang, F. Y. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Physics, The Ohio State University, 191 Woodruff Avenue, Columbus, Ohio 43210 (United States)

    2010-07-15T23:59:59.000Z

    The authors report the growth of iron nitride on zinc-blende gallium nitride using molecular beam epitaxy. First, zinc-blende GaN is grown on a magnesium oxide substrate having (001) orientation; second, an ultrathin layer of FeN is grown on top of the GaN layer. In situ reflection high-energy electron diffraction is used to monitor the surface during growth, and a well-defined epitaxial relationship is observed. Cross-sectional transmission electron microscopy is used to reveal the epitaxial continuity at the gallium nitride-iron nitride interface. Surface morphology of the iron nitride, similar to yet different from that of the GaN substrate, can be described as plateau valley. The FeN chemical stoichiometry is probed using both bulk and surface sensitive methods, and the magnetic properties of the sample are revealed.

  10. A crossed molecular beam study of the O(/sup 1/D/sub 2/)+CH/sub 4/ reaction

    SciTech Connect (OSTI)

    Casavecchia, P.; Buss, R.J.; Sibener, S.J.; Lee, Y.T.

    1980-12-15T23:59:59.000Z

    A cross molecular beam experiment was performed to study the O(/sup 1/D/sub 2/)+CH/sub 4/ reaction. The results show that hydrogen atom elimination reaction greatly exceeds molecular hydrogen elimination. (AIP)

  11. Investigation of Supersonic Molecular Beam Injection into the HL-1M Tokamak

    SciTech Connect (OSTI)

    Yao Lianghua; Feng Beibin; Dong Jaifu; Zhou Yan; Cui Zhengying; Cao Jianyong; Tang Nianyi; Feng Zhen; Xiao Zhenggui; Song Xianming; Hong Wenyu; Wang, Enyao; Liu Yong [Southwestern Institute of Physics (China)

    2002-07-15T23:59:59.000Z

    As a new fueling method, supersonic molecular beam injection (SMBI) has been successfully developed and used in the HL-1M tokamak and HT-7 superconducting tokamak. SMBI can enhance penetration depth and fueling efficiency. It can be considered a significant improvement over conventional gas puffing. In recent experiments, hydrogen clusters have been found in the beam produced by high working gas pressure. The hydrogen particles of the beam have penetrated into the plasma center region, in which the average velocity of the injected beam is >1200 m/s. The rate of increase of electron density for SMBI, d[bar]n{sub e}/dt, approaches that of small ice pellet injection (PI). The plasma density increases step by step after multipulse SMBI, just as with the effects of multipellet fueling. Comparison of fueling effects was made between SMBI and small ice PI in the same shot of ohmic discharge in HL-1M.

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

    E-Print Network [OSTI]

    2003-01-01T23:59:59.000Z

    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,

  13. Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

    E-Print Network [OSTI]

    Novikov, S. V.

    2011-01-01T23:59:59.000Z

    photoanode applications in hydrogen production S. V.of sunlight into hydrogen by pho- toelectrochemical ͑PEC͒is crucial for efficient hydrogen production using the PEC

  14. Temperature-dependent photoluminescence of CdZnO thin films grown by molecular-beam epitaxy

    E-Print Network [OSTI]

    Yang, Zheng

    performed on three typical CdZnO samples having pure wurtzite, pure rocksalt, and wurtzite­rocksalt mixture and analyzed based on the variable-temperature PL studies of typical wurtzite (wz) CdZnO, rocksalt (rs) Cd

  15. ScGaN Alloy Growth by Molecular Beam Epitaxy: Evidence for a Metastable Layered Hexagonal Phase

    E-Print Network [OSTI]

    range x = 0-100%. Optical and structural analysis show separate regimes of growth, namely I) wurtzite predicted a metastable wurtzite phase (w-ScN) for ScN.8 However, recently Farrer and Bellaiche have found coordination, denoted h-ScN, which can be arrived at by flattening the bilayer of the wurtzite structure

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

    E-Print Network [OSTI]

    Zhan, Ning

    2011-01-01T23:59:59.000Z

    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

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

    E-Print Network [OSTI]

    Pennycook, Steve

    ,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

  18. Operation and device applications of a valved-phosphorus cracker in solid-source molecular-beam epitaxy

    E-Print Network [OSTI]

    Woodall, Jerry M.

    and reflection high-energy electron diffraction measurements. InP and InGaP lattice matched to GaAs were grown electron microscopy. The first microwave performance (ft 44 GHz, fmax 65 GHz of an InGaP reported the growth of InGaP and InAlP by a valved cracker. High- quality InGaP and InGaAlP were grown

  19. Optical properties of InGaPN epilayer with low nitrogen content grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Kim, Kang Min [Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Nonoguchi, Shogo; Krishnamurthy, Daivasigamani; Emura, Shuichi; Hasegawa, Shigehiko; Asahi, Hajime [Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2012-09-15T23:59:59.000Z

    The effect of nitrogen concentration on the optical properties of InGaP(N) epilayer was investigated. The temperature dependence of the photoluminescence (PL) peak energy of InGaPN (N = 1%) epilayer around room temperature was found to be almost one-half of that of InGaP epilayer. The incorporation of N causes the reduction of the coupling constant for the electron-phonon interaction, leading to the reduced temperature dependence of the PL peak shift. Thermal activation energy, which is deduced from the Arrhenius plot of PL intensity, was decreased by N incorporation. The reduced PL quenching is discussed in terms of the changes in the band alignment at the InGaPN/GaAs heterointerface by the increase in the N concentration.

  20. Necessity of Ga prelayers in GaAs/Ge growth using gas-source molecular beam epitaxy

    E-Print Network [OSTI]

    in a highly defective GaAs layer.as5 Recently, InGaP light-emitting diodes have been fabricated on Si using

  1. Very high mobility two-dimensional hole gas in Si/Ge$i,-JGe structures grown by molecular beam epitaxy

    E-Print Network [OSTI]

    -dimensional elec- tron gases with mobility as high as 180 000 cm2/V s at 4.2 K,`" as well as in fabricating InGaP

  2. Specific features of kinetics of molecular beam epitaxy of compounds in the GaN-AlN system

    SciTech Connect (OSTI)

    Alekseev, A. N.; Byrnaz, A. E.; Krasovitsky, D. M.; Pavlenko, M. V.; Petrov, S. I., E-mail: support@semiteq.ru; Pogorel'sky, Yu. V.; Sokolov, I. A.; Sokolov, M. A.; Stepanov, M. V.; Shkurko, A. P.; Chalyi, V. P. [ZAO Svetlana-ROST (Russian Federation)

    2007-09-15T23:59:59.000Z

    The effect of growth conditions (V/III ratio, substrate temperature) on the properties of materials in AlN-GaN systems is discussed. A concept of the growth of the AlN/AlGaN/GaN multilayer heterostructure, which provides the improvement of crystal quality and surface morphology of the layers, is suggested and realized. The improvement of the properties of GaN in the AlN/AlGaN/GaN/AlGaN multilayer heterostructure is confirmed by a considerable increase in electron mobility in the two-dimensional electron gas formed at the upper heterointerface GaN/Al{sub 0.3}Ga{sub 0.7}N.

  3. Indium incorporation and surface segregation during InGaN growth by molecular beam epitaxy: experiment and theory

    E-Print Network [OSTI]

    Feenstra, Randall

    of 670 C. Following the GaN growth with typical thickness of 200 nm, the substrate temperature is lowered to 580­620 C for the InGaN deposition. GaN(000 ) was grown at 720 C, on sapphire substrates, with pre-growth nitridation of the substrate performed at 1050 C and using a low-temperature GaN buffer layer grown at 550 C

  4. Correlation between structural properties and optical amplification in InGaN/GaN heterostructures grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Nabben, Reinhard

    . The lateral homogeneity can be drastically improved using a template of GaN grown on the sapphire substrate-grown heterostructures can drastically be reduced by using a template of MOVPE-GaN on the sapphire substrate, which leadsCorrelation between structural properties and optical amplification in InGaN/GaN heterostructures

  5. Growth of p-type and n-type m-plane GaN by molecular beam epitaxy

    E-Print Network [OSTI]

    McLaurin, M; Mates, T E; Wu, F; Speck, J S

    2006-01-01T23:59:59.000Z

    other more conventional substrates for GaN growth. As anbetween the GaN ?lm and the SiC substrate is considered. 19oriented GaN ?lms were grown on 6H m-plane SiC substrates

  6. Effect of Mg codoping on Eu{sup 3+} luminescence in GaN grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Takagi, Yasufumi [Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu, Shizuoka 434-8601 (Japan); Suwa, Takanobu; Sekiguchi, Hiroto; Wakahara, Akihiro [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Okada, Hiroshi [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan)

    2011-10-24T23:59:59.000Z

    The effect of Mg codoping on the Eu{sup 3+} luminescence in GaN was investigated by photoluminescence measurements. Two notable emission peaks associated with the {sup 5}D{sub 0}{yields}{sup 7}F{sub 2} transition in the Eu{sup 3+} ions were governed by Mg codopants, which corresponded to the change of the dominant peak wavelength from 622.3 to 620.3 nm with an increase in Mg concentration. An optimal amount of Mg also led to enhancement of approximately 20 times of the Eu{sup 3+} luminescence. These results indicated that the Mg codopants selectively activated the optical site of 620.3 nm emission due to the elimination of nonradiative deexcitation paths from the {sup 5}D{sub 0} state.

  7. Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices

    SciTech Connect (OSTI)

    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

    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.

  8. Photoluminescence of GaAs films grown by vacuum chemical epitaxy

    SciTech Connect (OSTI)

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

    1988-08-01T23:59:59.000Z

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

  9. Comparison of beryllium oxide and pyrolytic graphite crucibles for boron doped silicon epitaxy

    SciTech Connect (OSTI)

    Ali, Dyan; Richardson, Christopher J. K. [Laboratory for Physical Sciences, University of Maryland, College Park, Maryland 20740 (United States)

    2012-11-15T23:59:59.000Z

    This article reports on the comparison of beryllium oxide and pyrolytic graphite as crucible liners in a high-temperature effusion cell used for boron doping in silicon grown by molecular beam epitaxy. Secondary ion mass spectroscopy analysis indicates decomposition of the beryllium oxide liner, leading to significant incorporation of beryllium and oxygen in the grown films. The resulting films are of poor crystal quality with rough surfaces and broad x-ray diffraction peaks. Alternatively, the use of pyrolytic graphite crucible liners results in higher quality films.

  10. Structure and electrical properties of polycrystalline SiGe films grown by molecular beam deposition

    SciTech Connect (OSTI)

    Chistokhin, I. B., E-mail: igor@thermo.isp.nsc.ru; Gutakovskii, A. K.; Deryabin, A. S. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Division (Russian Federation)

    2007-03-15T23:59:59.000Z

    The structural and electrical properties of polycrystalline Si{sub 0.5}Ge{sub 0.5} films 150 nm thick grown by molecular beam deposition at temperatures of 200-550 deg. C on silicon substrates coated with amorphous layers of silicon oxynitride were studied. It is shown that the films consist of a mixture of amorphous and polycrystalline phases. The amorphous phase fraction decreases from {approx}50% in films deposited at 200 deg. C to zero in films grown at 550 deg. C. Subsequent 1-h annealing at a temperature of 550 deg. C results in complete solid-phase crystallization of all films. The electron transport of charge carriers in polycrystalline films occurs by the thermally activated mechanism associated with the energy barrier of {approx}0.2 eV at grain boundaries. Barrier lowering upon additional annealing of SiGe films correlates with an increase in the average grain size.

  11. 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...

  12. The chemistry of Si{sub 3}N{sub 4} and Si deposition studied using molecular beam techniques

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.; Breiland, W.G.

    1992-08-01T23:59:59.000Z

    Molecular beam techniques can be used to obtain valuable kinetic information for the chemistry of high temperature deposition processes. Molecular beam measurements of Si{sub 3}N{sub 4} deposited from SiF{sub 4} and NH{sub 3} have shown that the CVD reactor chemistry is dominated by surface reactions of the starting gases. Using a beam of heated silane, it is shown that the translational and internal energy of the gas does not influence its surface reactivity in silicon CVD. The IRIS (Imaging of Radicals Interacting with Surfaces) technique for measuring the surface reactivity of radicals during deposition is also discussed with examples (SiH, SiO and NH). 5 refs., 4 figs.

  13. The chemistry of Si sub 3 N sub 4 and Si deposition studied using molecular beam techniques

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.; Breiland, W.G.

    1992-01-01T23:59:59.000Z

    Molecular beam techniques can be used to obtain valuable kinetic information for the chemistry of high temperature deposition processes. Molecular beam measurements of Si{sub 3}N{sub 4} deposited from SiF{sub 4} and NH{sub 3} have shown that the CVD reactor chemistry is dominated by surface reactions of the starting gases. Using a beam of heated silane, it is shown that the translational and internal energy of the gas does not influence its surface reactivity in silicon CVD. The IRIS (Imaging of Radicals Interacting with Surfaces) technique for measuring the surface reactivity of radicals during deposition is also discussed with examples (SiH, SiO and NH). 5 refs., 4 figs.

  14. Superconducting epitaxial thin films of CeNi{sub x}Bi{sub 2} with a bismuth square net structure

    SciTech Connect (OSTI)

    Buckow, Alexander; Kupka, Katharina; Retzlaff, Reiner; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2012-10-15T23:59:59.000Z

    We have grown highly epitaxial and phase pure thin films of the arsenic-free pnictide compound CeNi{sub x}Bi{sub 2} on (100) MgO substrates by reactive molecular beam epitaxy (RMBE). X-ray diffraction and reflection high-energy electron diffraction of the films confirm the ZrCuSiAs structure with a Bi square net layer. Superconductivity was observed in magnetization and resistivity measurements for x= 0.75 to 0.93 in these CeNi{sub x}Bi{sub 2} thin films with the highest critical temperature of 4.05 K and a resistive transition width of 0.1 K for x= 0.86. Our results indicate that thin film deposition by RMBE provides a tool to synthesize high-quality pnictide superconductors of the novel 112 type.

  15. Pellet and Molecular Beam Injection Fueling on the HL-1M Tokamak

    SciTech Connect (OSTI)

    Xiao Zhenggui; Li Bo; Li Li; Liu Dequan; Yao Lianghua; Dong Jiafu; Guo Gancheng; Deng Zhongchao; Zheng Yinjia; Hong Wenyu; Yan Longwen; Liu Yi; Liu Yong; Wang, Enyao [Southwestern Institute of Physics (China)

    2003-01-15T23:59:59.000Z

    The Eight-shot Pellet Injector (EPI) and Molecular Beam Injector (MBI) as new plasma fueling methods have been developed and installed on the HL-1M tokamak for fueling experiments. The main structures and characteristics of the fueling device and the typical fueling experimental results with EPI and the MBI are reported. In these experiments, typical responses of plasma in discharges with PI and MBI are the peaked density profile Q{sub n} n{sub e}(0)/<(n{sub e})> of >1.65 for MBI and of 2 for PI. The improvement of confinement time E is usually better than 10 to 30% of Gas Puffing (GP) discharge in the same operation condition. In addition, the penetration depth and deposition region of fueling particles, the variance of soft X-ray sawteeth, the rotation and flow of plasma in edge region as well as the photographing of ablation clouds with PI and MBI are compared and presented in this paper.

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

    SciTech Connect (OSTI)

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

    1996-12-31T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

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

    1994-12-31T23:59:59.000Z

    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.

  18. Interface roughening and defect nucleation during solid phase epitaxy regrowth of doped and intrinsic Si{sub 0.83}Ge{sub 0.17} alloys

    SciTech Connect (OSTI)

    D'Angelo, D.; Piro, A. M.; Terrasi, A.; Grimaldi, M. G.; Mirabella, S.; Bongiorno, C. [MATIS CNR-INFM and Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, 95123 Catania (Italy); CNR-IMM, Sezione di Catania, Stradale Primosole 50, 95121 Catania (Italy)

    2007-05-15T23:59:59.000Z

    Metastable pseudomorphic Si{sub 0.83}Ge{sub 0.17} with thickness of 135 nm was deposited on (001) Si substrate by molecular beam epitaxy and amorphized to a depth of {approx}360 nm, using 3x10{sup 15} cm{sup -2} Ge ions at 270 keV. Samples were regrown by solid phase epitaxy in the 500-600 degree sign C temperature range. The regrowth rate was measured in situ by time resolved reflectivity, while the structure of the epilayers was investigated by transmission electron microscopy. Three regions can be distinguished in SiGe after solid phase epitaxy, independent of the annealing temperature: (1) a 20 nm defect-free layer close to the original crystal-amorphous interface, (2) a middle region with a high density of planar defects, and (3) a layer with dislocations and stacking faults extending up to the surface. The activation energy of the SiGe solid phase epitaxy is equal to the activation energy of Si except in the middle region. The amorphous-crystal interface evolution was studied by transmission electron microscopy of partially regrown samples. In order to study the effects of dopants, some samples were also implanted with B{sup +} and Sb{sup +} ions. At the ion projected range (125 nm for both implants) the regrowth rate increases by a factor of 3 with respect to the unimplanted SiGe, but the defect-free layer again is found to be about 20 nm in all cases. Moreover, the activation energy of the solid phase epitaxy regrowth process does not depend on dopant introduction, while the only observable effect of B or Sb incorporation is a smoothness of the amorphous-crystal interface during solid phase epitaxy.

  19. Epitaxial Cr on n-SrTiO3(001)—An ideal Ohmic contact ....

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

    beam epitaxy are shown to result in an ordered interface with Cr bound to O in the terminal TiO2 layer, no reduction of the SrTiO3, and a near-perfect Ohmic contact. Cr...

  20. Temperature-controlled epitaxy of In{sub x}Ga{sub 1-x}N alloys and their band gap bowing

    SciTech Connect (OSTI)

    Liu, S. T.; Wang, X. Q.; Chen, G.; Zhang, Y. W.; Feng, L.; Huang, C. C.; Xu, F. J.; Tang, N.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Sang, L. W.; Sumiya, M. [Wide Bandgap Material Group, National Institute for Materials Science, 305-0044, Tsukuba (Japan)

    2011-12-01T23:59:59.000Z

    In{sub x}Ga{sub 1-x}N alloys (0 {<=} x {<=} 1) have been grown on GaN/sapphire templates by molecular beam epitaxy. Growth temperature controlled epitaxy was proposed to modulate the In composition so that each In{sub x}Ga{sub 1-x}N layer was grown at a temperature as high as possible and thus their crystalline quality was improved. The bandgap energies of the In{sub x}Ga{sub 1-x}N alloys have been precisely evaluated by optical transmission spectroscopy, where the effect of residual strain and electron concentration (the Burstein-Moss effect) on the bandgap energy shift has been considered. Finally, a bowing parameter of {approx}1.9 {+-} 0.1 eV has been obtained by the well fitting In-composition dependent bandgap energy.

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

    SciTech Connect (OSTI)

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

    1986-02-17T23:59:59.000Z

    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%.

  2. Epitaxial thin films

    DOE Patents [OSTI]

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

    2006-04-25T23:59:59.000Z

    Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

  3. Effects of long jumps, reversible aggregation, and Meyer-Neldel rule on submonolayer epitaxial growth

    E-Print Network [OSTI]

    Rochefort, Alain

    Effects of long jumps, reversible aggregation, and Meyer-Neldel rule on submonolayer epitaxial with an embedded-atom-method molecular-dynamics study that the compensation law or the Meyer-Neldel rule MNR could

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  6. A hybrid epitaxy method for InAs on GaP

    SciTech Connect (OSTI)

    Chen, A.; Yulius, A.; Woodall, J. M.; Broadbridge, C.C. [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States); Department of Physics, Southern Connecticut State University, New Haven, Connecticut 06515 (United States)

    2004-10-18T23:59:59.000Z

    The interface formation mechanism during the molecular-beam epitaxy (MBE) of InAs/GaP has been studied with the aid of the In-Ga-P phase diagram. It is discovered that an initial dissolution and crystallization process similar to liquid phase epitaxy (LPE) may happen at sufficiently high temperature, resulting in a graded composition at the interface. Consequently, 'parasitic LPE/MBE' is the name for this hybrid form of MBE. High-resolution TEM images confirm the existence of the interfacial layer in the sample grown at high temperature. The graded interface smears out the band offset and leads to a nonrectifying heterojunction. Low-temperature (LT) MBE growth can turn off the LPE component, enabling the growth of an abrupt interface. Based on this 'LPE/MBE' model, a LT MBE technique is developed to grow an abrupt InAs/InGaP interface for heterojunction power Schottky rectifiers. The LT InAs/InGaP heterojunction demonstrates nearly ideal Schottky rectifier characteristics, while the sample grown at high temperature shows resistive ohmic characteristics. The LT InAs/InGaP Schottky diode also demonstrates good stability with respect to anneal temperature, similar to the InAs/GaP heterojunctions.

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

    SciTech Connect (OSTI)

    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

    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.

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

    E-Print Network [OSTI]

    New Mexico, University of

    . 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

  9. 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]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    for indicator lamp application, but the LED structure can befor indicator lamp application, but the LED structure can beLEDs are the ultimate goal to replace incandescent and fluorescent lamps

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

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

    2009-04-06T23:59:59.000Z

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

  12. ecent developments in molecular beam epitaxial growth of group IV semiconductors devices has led to a renewed interest in SiGe heterostructures. This effort is motivated

    E-Print Network [OSTI]

    Abbondandolo, Alberto

    to a renewed interest in SiGe heterostructures. This effort is motivated Rmainly by the goal of integrating Valence and conduction band dispersion around the Gpoint of a double Si/Ge QW system grown on cubic Si. Ge originate from the splitting of the Ge confined light hole bands. Electronic states of Si-Ge based

  13. 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]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    on metamorphic growth of InGaP layers on GaP substrates, astemperature amber photoluminescence from InGaP QWs, grownon a metamorphic InGaP layer. References: Fred Shubert E. ,

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

    SciTech Connect (OSTI)

    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

    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.

  15. Optical phonon modes in InGaN/GaN dot-in-a-wire heterostructures grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Titus, J.; Perera, A. G. U. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States)] [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Nguyen, H. P. T.; Mi, Z. [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)] [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)

    2013-03-25T23:59:59.000Z

    We report on the studies of optical phonon modes in nearly defect-free GaN nanowires embedded with intrinsic InGaN quantum dots by using oblique angle transmission infrared spectroscopy. These phonon modes are dependent on the nanowire fill-factor, doping densities of the nanowires, and the presence of InGaN dots. These factors can be applied for potential phonon based photodetectors whose spectral responses can be tailored by varying a combination of these three parameters. The optical anisotropy along the growth (c-) axis of the GaN nanowire contributes to the polarization agility of such potential photodetectors.

  16. Substrate nitridation induced modulations in transport properties of wurtzite GaN/p-Si (100) heterojunctions grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Bhat, Thirumaleshwara N.; Rajpalke, Mohana K.; Krupanidhi, S. B. [Materials Research Centre, Indian Institute of Science, Bangalore- 560012 (India); Roul, Basanta; Kumar, Mahesh [Materials Research Centre, Indian Institute of Science, Bangalore- 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore-560013 (India)

    2011-11-01T23:59:59.000Z

    Phase pure wurtzite GaN films were grown on Si (100) substrates by introducing a silicon nitride layer followed by low temperature GaN growth as buffer layers. GaN films grown directly on Si (100) were found to be phase mixtured, containing both cubic ({beta}) and hexagonal ({alpha}) modifications. The x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy studies reveal that the significant enhancement in the structural as well as in the optical properties of GaN films grown with silicon nitride buffer layer grown at 800 deg. C when compared to the samples grown in the absence of silicon nitride buffer layer and with silicon nitride buffer layer grown at 600 deg. C. Core-level photoelectron spectroscopy of Si{sub x}N{sub y} layers reveals the sources for superior qualities of GaN epilayers grown with the high temperature substrate nitridation process. The discussion has been carried out on the typical inverted rectification behavior exhibited by n-GaN/p-Si heterojunctions. Considerable modulation in the transport mechanism was observed with the nitridation conditions. The heterojunction fabricated with the sample of substrate nitridation at high temperature exhibited superior rectifying nature with reduced trap concentrations. Lowest ideality factors ({approx}1.5) were observed in the heterojunctions grown with high temperature substrate nitridation which is attributed to the recombination tunneling at the space charge region transport mechanism at lower voltages and at higher voltages space charge limited current conduction is the dominating transport mechanism. Whereas, thermally generated carrier tunneling and recombination tunneling are the dominating transport mechanisms in the heterojunctions grown without substrate nitridation and low temperature substrate nitridation, respectively.

  17. 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]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    ? G, Kcal/mol GaP GaN AlN o Substrate temperature, C Figurenm-thick GaN 0.006 P 0.994 layer on substrate temperature.substrate temperature for Reactions formation of AlP, GaP, GaN and

  18. 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]

    Davis, H. Floyd

    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

  19. 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)

    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

    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.

  20. 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)

    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

    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.

  1. Point contact Andreev spectroscopy of epitaxial Co{sub 2}FeSi Heusler alloys on GaAs (001)

    SciTech Connect (OSTI)

    Lehmann, Hauke; Merkt, Ulrich; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Scholtyssek, Jan M. [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Institut fuer Elektrische Messtechnik und Grundlagen der Elektrotechnik, Technische Universitaet Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Herrmann, Claudia; Herfort, Jens [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2011-09-15T23:59:59.000Z

    The predicted half-metallicity of Co{sub 2}FeSi in combination with its high Curie temperature of above 980 K makes this Heusler alloy interesting for spinelectronics. Thin Co{sub 2}FeSi films are grown by molecular-beam epitaxy on GaAs (001) with a close lattice match. We present a study of point-contact measurements on different films, varying in thickness between 18 nm and 48 nm and in substrate temperature during deposition between 100 deg. C and 300 deg. C. Transport spin polarizations at the Fermi level are determined from differential conductance curves obtained by point-contact Andreev-reflection spectroscopy. A maximum transport spin polarization of about 60% is measured for a 18 nm thin Co{sub 2}FeSi film grown at 200 deg. C.

  2. Interfacial band alignment and structural properties of nanoscale TiO{sub 2} thin films for integration with epitaxial crystallographic oriented germanium

    SciTech Connect (OSTI)

    Jain, N.; Zhu, Y.; Hudait, M. K., E-mail: mantu.hudait@vt.edu [Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Varghese, R.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2014-01-14T23:59:59.000Z

    We have investigated the structural and band alignment properties of nanoscale titanium dioxide (TiO{sub 2}) thin films deposited on epitaxial crystallographic oriented Ge layers grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy. The TiO{sub 2} thin films deposited at low temperature by physical vapor deposition were found to be amorphous in nature, and high-resolution transmission electron microscopy confirmed a sharp heterointerface between the TiO{sub 2} thin film and the epitaxially grown Ge with no traceable interfacial layer. A comprehensive assessment on the effect of substrate orientation on the band alignment at the TiO{sub 2}/Ge heterointerface is presented by utilizing x-ray photoelectron spectroscopy and spectroscopic ellipsometry. A band-gap of 3.33?±?0.02?eV was determined for the amorphous TiO{sub 2} thin film from the Tauc plot. Irrespective of the crystallographic orientation of the epitaxial Ge layer, a sufficient valence band-offset of greater than 2?eV was obtained at the TiO{sub 2}/Ge heterointerface while the corresponding conduction band-offsets for the aforementioned TiO{sub 2}/Ge system were found to be smaller than 1?eV. A comparative assessment on the effect of Ge substrate orientation revealed a valence band-offset relation of ?E{sub V}(100)?>??E{sub V}(111)?>??E{sub V}(110) and a conduction band-offset relation of ?E{sub C}(110) >??E{sub C}(111)?>??E{sub C}(100). These band-offset parameters are of critical importance and will provide key insight for the design and performance analysis of TiO{sub 2} for potential high-? dielectric integration and for future metal-insulator-semiconductor contact applications with next generation of Ge based metal-oxide field-effect transistors.

  3. Quasi-zero lattice mismatch and band alignment of BaTiO{sub 3} on epitaxial (110)Ge

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y.; Jain, N. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Zhou, Y.; Priya, S [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-07-14T23:59:59.000Z

    Growth, structural, and band alignment properties of pulsed laser deposited amorphous BaTiO{sub 3} on epitaxial molecular beam epitaxy grown (110)Ge layer, as well as their utilization in low power transistor are reported. High-resolution x-ray diffraction demonstrated quasi-zero lattice mismatch of BaTiO{sub 3} on (110)Ge. Cross-sectional transmission electron microscopy micrograph confirms the amorphous nature of BaTiO{sub 3} layer as well as shows a sharp heterointerface between BaTiO{sub 3} and Ge with no traceable interfacial layer. The valence band offset, {Delta}E{sub v}, of 1.99 {+-} 0.05 eV at the BaTiO{sub 3}/(110)Ge heterointerface is measured using x-ray photoelectron spectroscopy. The conduction band offset, {Delta}E{sub c}, of 1.14 {+-} 0.1 eV is calculated using the bandgap energies of BaTiO{sub 3} of 3.8 eV and Ge of 0.67 eV. These band offset parameters for carrier confinement and the interface chemical properties of the BaTiO{sub 3}/(110)Ge system are significant advancement towards designing Ge-based p-and n-channel metal-oxide semiconductor field-effect transistors for low-power application.

  4. Molecular Beam Kinetics | EMSL

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

    desorption... The Deposition Angle-Dependent Density of Amorphous Solid Water Films. The index of refraction and thickness of amorphous solid water (ASW) films are determined...

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

    SciTech Connect (OSTI)

    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

    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.

  6. A crossed molecular beams study of the reaction of the ethynyl radical )) with allene (H2CCCH2(X1

    E-Print Network [OSTI]

    Kaiser, Ralf I.

    molecular hydrogen (H2),8,9 molecular oxygen (O2),10 and water (H2O)11 via hydrocarbons 2,12­16 to nitrogen role in the synthesis of polyynes, polycyclic aromatic hydrocarbons (PAHs), and soot particles;1 (PAHs) and aerosol particles.22,23 Since the macroscopic alteration of combustion systems and planetary

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

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

    2014-11-21T23:59:59.000Z

    Tailored metal alloy thin film-oxide interfaces generated using molecular beam epitaxial (MBE) deposition of alloy thin films on a single crystalline oxide substrate can be used for detailed studies of irradiation damage response on the interface structure. However presence of nanoscale phase separation in the MBE grown alloy thin films can impact the metal-oxide interface structure. Due to nanoscale domain size of such phase separation it is very challenging to characterize by conventional techniques. Therefor laser assisted atom probe tomography (APT) was utilized to study the phase separation in epitaxial Cr0.61Mo0.39, Cr0.77Mo0.23, and Cr0.32V0.68 alloy thin films grown by MBE on MgO(001) single crystal substrates. Statistical analysis, namely frequency distribution analysis and Pearson coefficient analysis of experimental data was compared with similar analyses conducted on simulated APT datasets with known extent of phase separation. Thus the presence of phase separation in Cr-Mo films, even when phase separation was not clearly observed by x-ray diffraction, and the absence of phase separation in the Cr-V film were thus confirmed.

  9. Testing epitaxial Co{sub 1.5}Fe{sub 1.5}Ge(001) electrodes in MgO-based magnetic tunnel junctions

    SciTech Connect (OSTI)

    Neggache, A. [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre lès Nancy (France); Synchrotron SOLEIL-CNRS, L'Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette (France); Hauet, T.; Petit-Watelot, S.; Boulet, P.; Andrieu, S., E-mail: stephane.andrieu@univ-lorraine.fr [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre lès Nancy (France); Bertran, F.; Le Fèvre, P.; Ohresser, P. [Synchrotron SOLEIL-CNRS, L'Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette (France); Devolder, T. [Institut d'Electronique Fondamentale, CNRS, UMR 8622, 91405 Orsay (France); Mewes, C. [Department of Physics and Astronomy/Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Maat, S.; Childress, J. R. [San Jose Research Center, HGST, a Western Digital company, San Jose, California 95135 (United States)

    2014-06-23T23:59:59.000Z

    The ability of the full Heusler alloy Co{sub 1.5}Fe{sub 1.5}Ge(001) (CFG) to be a Half-Metallic Magnetic (HMM) material is investigated. Epitaxial CFG(001) layers were grown by molecular beam epitaxy. The results obtained using electron diffraction, X-ray diffraction, and X-ray magnetic circular dichroism are consistent with the full Heusler structure. The pseudo-gap in the minority spin density of state typical in HMM is examined using spin-resolved photoemission. Interestingly, the spin polarization found to be negative at E{sub F} in equimolar CoFe(001) is observed to shift to positive values when inserting Ge in CoFe. However, no pseudo-gap is found at the Fermi level, even if moderate magnetization and low Gilbert damping are observed as expected in HMM materials. Magneto-transport properties in MgO-based magnetic tunnel junctions using CFG electrodes are investigated via spin and symmetry resolved photoemission.

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

    SciTech Connect (OSTI)

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

    2014-12-03T23:59:59.000Z

    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.

  11. Atomic-Level Simulations of Epitaxial Recrystallization andAmorphous...

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

    Simulations of Epitaxial Recrystallization and Amorphous-to-Crystalline Transition in 4H-SiC. Atomic-Level Simulations of Epitaxial Recrystallization and Amorphous-to-Crystalline...

  12. Smoothing of Si{sub 0.7}Ge{sub 0.3} virtual substrates by gas-cluster-ion beam

    SciTech Connect (OSTI)

    Chen, H.; Chen, F.; Wang, X.M.; Yu, X.K.; Liu, J.R.; Ma, K.B.; Chu, W.K.; Cheng, H.H.; Yu, I.S.; Ho, Y.T.; Horng, K.Y. [Department of Physics and Texas Center for Superconductivity at University of Houston, University of Houston, Houston, Texas 77204 (United States); Center for Condensed Matter Sciences and Institute of Electronic Engineering, National Taiwan University, Taipei, Taiwan (China); Chung-Shan Institute of Science and Technology, Tao-Yuan, Taiwan (China)

    2005-09-05T23:59:59.000Z

    The planarization of the SiGe virtual substrate surface is crucial for the fabrication of high-performance strained-Si metal-oxide-semiconductor field-effect transistors. In this letter, we report on the smoothing of the inherently crosshatched rough surfaces of SiGe deposited by molecular beam epitaxy on Si substrates by gas cluster ion beams. Atomic force microscopy measurements show that the average surface roughness (R{sub a}) of the SiGe layer could be reduced considerably from 3.2 to 0.7 nm without any crosshatched pattern. Rutherford backscattering in combination with channeling was used to study the damage produced by cluster bombardment. No visible surface damage was observed for the normal-incidence smoothed SiGe with postsmoothing glancing angle cluster ion beam etching.

  13. 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)

    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

    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.

  14. Ion beam processing of advanced electronic materials

    SciTech Connect (OSTI)

    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

    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)

  15. Absolute infrared vibrational band intensities of molecular ions determined by direct laser absorption spectroscopy in fast ion beams

    SciTech Connect (OSTI)

    Keim, E.R.; Polak, M.L.; Owrutsky, J.C.; Coe, J.V.; Saykally, R.J. (Department of Chemistry, University of California, Berkeley, CA (USA))

    1990-09-01T23:59:59.000Z

    The technique of direct laser absorption spectroscopy in fast ion beams has been employed for the determination of absolute integrated band intensities ({ital S}{sup 0}{sub {ital v}}) for the {nu}{sub 3} fundamental bands of H{sub 3}O{sup +} and NH{sup +}{sub 4}. In addition, the absolute band intensities for the {nu}{sub 1} fundamental bands of HN{sup +}{sub 2} and HCO{sup +} have been remeasured. The values obtained in units of cm{sup {minus}2} atm{sup {minus}1} at STP are 1880(290) and 580(90) for the {nu}{sub 1} fundamentals of HN{sup +}{sub 2} and HCO{sup +}, respectively; and 4000(800) and 1220(190) for the {nu}{sub 3} fundamentals of H{sub 3}O{sup +} and NH{sup +}{sub 4}, respectively. Comparisons with {ital ab} {ital initio} results are presented.

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

    SciTech Connect (OSTI)

    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

    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}.

  17. Vacancy-type defects in In{sub x}Ga{sub 1-x}N alloys probed using a monoenergetic positron beam

    SciTech Connect (OSTI)

    Uedono, A.; Watanabe, T. [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Ishibashi, S. [Nanosystem Research Institute (NRI) 'RICS,' National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Wang, X. Q.; Liu, S. T.; Chen, G.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Sang, L. W.; Sumiya, M. [Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan)

    2012-07-01T23:59:59.000Z

    Native defects in In{sub x}Ga{sub 1-x}N grown by plasma-assisted molecular beam epitaxy were probed by a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured, and these were compared with results obtained using first-principles calculation. The defect concentration increased with increasing In composition x and reached the maximum at x = 0.44{approx}0.56. A clear correlation between the line-width of photoluminescence and the defect concentration was obtained. The major defect species detected by positron annihilation was identified as cation vacancies coupled with multiple nitrogen vacancies (V{sub N}s), and their introduction mechanism is discussed in terms of the strain energy due to bond-length/angle distortions and the suppression of the V{sub N} formation energy by neighboring In atoms.

  18. 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)

    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

    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.

  19. Gas-source molecular-beam epitaxy of InGaP and GaAs on strained-relaxed Ge{sub x}Si{sub 1-x}/Si

    SciTech Connect (OSTI)

    Kuo, J.M.; Fitzgerald, E.A.; Xie, Y.H. [AT& T Bell Lab., Murray Hill, NJ (United States)] [and others] [AT& T Bell Lab., Murray Hill, NJ (United States); and others

    1993-05-01T23:59:59.000Z

    Lattice-matched GaAs and InGaP structures on strain-relieved Ge/graded GeSi/Si without increasing the threading dislocation density at the III-V/Ge interface have been successfully grown. The results show that exposure of the Ge surface to As{sub 2} produces a drastic change in the step structure of the Ge surface. Subsequent exposure to Ga and continuation of growth invariably produces three-dimensional growth and a high threading dislocation density at the GaAs/Ge interface. However, exposure of the Ge surface to Ga does not appear to change the Ge step structure, and subsequent growth of GaAs leads to near two-dimensional growth and no massive increase in threading dislocation density at the GaAs/Ge interface as in the case of As{sub 2} exposure. InGaP light-emitting homojunction diodes have been fabricated on the relaxed Ge/graded GeSi/Si. Room-temperature operation was achieved with a surface-emitting output power of {approximately} 10 mW/cm{sup 2}. The best dislocation density achieved was 5x10{sup 6}-10{sup 7} cm{sup {minus}2} in the InGaP/GaAs/Ge/graded GeSi/Si structure. 9 refs., 3 figs.

  20. 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...

  1. algaassb epitaxial layers: Topics by E-print Network

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

    Daniel 3 van der Waals Epitaxy of InAs Nanowires Vertically Aligned on Single-Layer Graphene Engineering Websites Summary: -organic vapor-phase epitaxy Hybrid junctions composed...

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

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

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

  3. Epitaxial graphene on silicon carbide: Introduction to structured graphene

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    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

  4. Chemical vapor deposition of epitaxial silicon

    DOE Patents [OSTI]

    Berkman, Samuel (Florham Park, NJ)

    1984-01-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  6. Dual ion beam assisted deposition of biaxially textured template layers

    DOE Patents [OSTI]

    Groves, James R.; Arendt, Paul N.; Hammond, Robert H.

    2005-05-31T23:59:59.000Z

    The present invention is directed towards a process and apparatus for epitaxial deposition of a material, e.g., a layer of MgO, onto a substrate such as a flexible metal substrate, using dual ion beams for the ion beam assisted deposition whereby thick layers can be deposited without degradation of the desired properties by the material. The ability to deposit thicker layers without loss of properties provides a significantly broader deposition window for the process.

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

    SciTech Connect (OSTI)

    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

    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.

  8. 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)

    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

    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.

  9. ORIGINAL PAPER Epitaxial Stabilization of Face Selective Catalysts

    E-Print Network [OSTI]

    Marks, Laurence D.

    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

  10. 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...

  11. Structure-property Relationships in Pure and Doped Epitaxial...

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

    Structure-property Relationships in Pure and Doped Epitaxial Tungsten Trioxide Thin Films Principal Investigator Yingge Du (EMSL) Co-Investigators Ping Yang (EMSL), Rama S. Vemuri...

  12. Electron holography of devices with epitaxial layers

    SciTech Connect (OSTI)

    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

    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.

  13. Covalent Functionalization of Epitaxial Graphene by Azidotrimethylsilane Junghun Choi,

    E-Print Network [OSTI]

    Kim, Sehun

    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

  14. ccsd00001676, Epitaxy and growth of titanium bu er layers

    E-Print Network [OSTI]

    ccsd­00001676, version 1 ­ 16 Jun 2004 Epitaxy and growth of titanium bu#11;er layers on Al 2 O 3 de Lourmel, 75015 Paris, France Abstract The structure and growth of thin #12;lms of titanium on #11 [2110] and Ti[1010] k Al 2 O 3 [1100] epitaxy of the #11; phase of titanium reported before for thick

  15. Luminosity and beam-beam

    E-Print Network [OSTI]

    Papotti, G; Trad, G

    We report on observations on luminosity evolution and beam-beam interaction from the 2011 physics run. Extrapolations for 2012 are attempted and a list of desired studies and machine developments is included.

  16. Atomic-scale Structural Characterizations of Functional Epitaxial Thin Films

    E-Print Network [OSTI]

    Zhu, Yuanyuan

    2013-06-03T23:59:59.000Z

    ................................................................ 10 1.3.1 Superconducting FeSe0.5Te0.5 epitaxial films........................................ 10 1.3.2 YBa2Cu3O7-x(YBCO) epitaxial thin films and flux-pinning effects ...... 14 1.3.3 Perovskite oxide epitaxial thin films... ...................................... 22 Figure 1.9. (a) Schematic illustration of ABO3 perovskite structure. (b) The corner -sharing oxygen octahedra in perovskite structure. . ................................... 23 Figure 1.10. (a) A HRTEM micrograph,67 (b) a Cs-corrected HRTEM image...

  17. Self-doping effects in epitaxially grown graphene

    E-Print Network [OSTI]

    Siegel, David A.

    2009-01-01T23:59:59.000Z

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

  18. Vacancy-type defects in Er-doped GaN studied by a monoenergetic positron beam

    SciTech Connect (OSTI)

    Uedono, A.; Shaoqiang, C.; Jongwon, S.; Ito, K.; Nakamori, H.; Honda, N.; Tomita, S.; Akimoto, K.; Kudo, H. [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, 305-8573 (Japan); Ishibashi, S. [Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8568 (Japan)

    2008-05-15T23:59:59.000Z

    A relationship between intra-4f transitions of Er and vacancy-type defects in Er-doped GaN was studied by using a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured for Er-doped GaN grown by molecular beam epitaxy. A clear correlation between the defect concentration and the photoluminescence (PL) intensity was observed. The major defect species detected by positrons was identified as a Ga vacancy V{sub Ga}, and its concentration increased with increasing Er concentration [Er]. For the sample with [Er]=3.3 at. %, the maximum integrated intensity of PL was observed. The V{sub Ga} concentration was above 10{sup 18} cm{sup -3} and additional vacancies such as divacancies started to be introduced at this Er concentration. For the sample with higher [Er], the PL intensity decreased, and the mean size of vacancies decreased due to an introduction of precipitates and/or metastable phases.

  19. Two-dimensional imaging of laser-induced fluorescence: OH in a plasma-generated molecular beam scattering from a silicon surface

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States)

    1996-02-01T23:59:59.000Z

    Low-temperature plasmas are used for a wide variety of materials processing applications, especially in the fabrication of microelectronic devices. Thus plasma processes, such as etching, deposition, and cleaning, are the subject of much current research. However, achieving a detailed understanding of such systems, especially for computer simulations, requires a great deal of kinetic information about the physics and chemistry. One particular aspect, the reactions of radicals generated in the plasma at the surfaces of the substrates, is important in determining the performance of a plasma process. However, such reactions are not well studied because there are few experimental techniques available that can directly probe them. Here, two-dimensional (2-D) imaging is a significant improvement to the IRIS (imaging of radicals interacting with surfaces) technique for measuring the reactivity of plasma-generated radicals at surfaces. Several interesting phenomena resulting from the effects of saturation of the optical transition and of molecular translation during the radiative lifetime of OH have now been observed directly.

  20. 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....

  1. Electrical transport properties of Ti-doped Fe2O3(0001) epitaxial...

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

    Electrical transport properties of Ti-doped Fe2O3(0001) epitaxial films. Electrical transport properties of Ti-doped Fe2O3(0001) epitaxial films. Abstract: The electrical transport...

  2. Structure And Radiation Damage Behavior Of Epitaxial CrxMo1-x...

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

    And Radiation Damage Behavior Of Epitaxial CrxMo1-x Alloy Thin Films On MgO. Structure And Radiation Damage Behavior Of Epitaxial CrxMo1-x Alloy Thin Films On MgO. Abstract:...

  3. Piloting epitaxy with ellipsometry as an in-situ sensor technology

    E-Print Network [OSTI]

    Warnick, Sean C. (Sean Charles)

    2003-01-01T23:59:59.000Z

    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 ...

  4. 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

  5. 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)...

  6. Electronic properties of H and D doped ZnO epitaxial films. ...

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

    of H and D doped ZnO epitaxial films. Abstract: ZnO epitaxial films grown by pulsed laser deposition in an ambient of H2 or D2 exhibit qualitatively different electronic...

  7. THIN FILM EPITAXY WITH OR WITHOUT SLOPE SELECTION BO LI AND JIAN-GUO LIU

    E-Print Network [OSTI]

    Soatto, Stefano

    THIN FILM EPITAXY WITH OR WITHOUT SLOPE SELECTION BO LI AND JIAN-GUO LIU Abstract. Two nonlinear diffusion equations for thin film epitaxy, with or without slope se- lection, are studied in this work = - · h 1 + | h|2 + h (1.1) and th = - · 1 - | h|2 h + h (1.2) that model epitaxial growth of thin films

  8. Switchable diode effect and ferroelectric resistive switching in epitaxial BiFeO3 thin films

    E-Print Network [OSTI]

    Tian, Weidong

    Switchable diode effect and ferroelectric resistive switching in epitaxial BiFeO3 thin films Can observed in epitaxial multiferroic BiFeO3 BFO thin films. The forward direction of the rectifying current the switchable diode effect and the ferroelectric resistive switching in epitaxially BFO thin films. BFO thin

  9. Growth and Characterization of Epitaxial Oxide Thin Films

    E-Print Network [OSTI]

    Garg, Ashish

    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...

  10. Process for growing epitaxial gallium nitride and composite wafers

    DOE Patents [OSTI]

    Weber, Eicke R.; Subramanya, Sudhir G.; Kim, Yihwan; Kruger, Joachim

    2003-05-13T23:59:59.000Z

    A novel growth procedure to grow epitaxial Group III metal nitride thin films on lattice-mismatched substrates is proposed. Demonstrated are the quality improvement of epitaxial GaN layers using a pure metallic Ga buffer layer on c-plane sapphire substrate. X-ray rocking curve results indicate that the layers had excellent structural properties. The electron Hall mobility increases to an outstandingly high value of .mu.>400 cm.sup.2 /Vs for an electron background concentration of 4.times.10.sup.17 cm.sup.-3.

  11. Timothy C Droubay | EMSL

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

    molecular beam epitaxy system is designed to enable the growth of crystalline metal, alloy... Pulsed Laser Deposition EMSL's pulsed laser deposition (PLD) system is...

  12. American Recovery and Reinvestment Act | EMSL

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

    imaging as well as next-generation oxygen-plasma assisted molecular beam epitaxy Microfluidics manipulation and manufacturing. Learn more detail about Recovery Act Instruments...

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

    SciTech Connect (OSTI)

    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

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

  14. Epitaxial growth of AlN films via plasma-assisted atomic layer epitaxy

    SciTech Connect (OSTI)

    Nepal, N.; Qadri, S. B.; Hite, J. K.; Mahadik, N. A.; Mastro, M. A.; Eddy, C. R. Jr. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States)] [U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

    2013-08-19T23:59:59.000Z

    Thin AlN layers were grown at 200–650 °C by plasma assisted atomic layer epitaxy (PA-ALE) simultaneously on Si(111), sapphire (1120), and GaN/sapphire substrates. The AlN growth on Si(111) is self-limited for trimethyaluminum (TMA) pulse of length > 0.04 s, using a 10 s purge. However, the AlN nucleation on GaN/sapphire is non-uniform and has a bimodal island size distribution for TMA pulse of ?0.03 s. The growth rate (GR) remains almost constant for T{sub g} between 300 and 400 °C indicating ALE mode at those temperatures. The GR is increased by 20% at T{sub g} = 500 °C. Spectroscopic ellipsometry (SE) measurement shows that the ALE AlN layers grown at T{sub g} ? 400 °C have no clear band edge related features, however, the theoretically estimated band gap of 6.2 eV was measured for AlN grown at T{sub g} ? 500 °C. X-ray diffraction measurements on 37 nm thick AlN films grown at optimized growth conditions (T{sub g} = 500 °C, 10 s purge, 0.06 s TMA pulse) reveal that the ALE AlN on GaN/sapphire is (0002) oriented with rocking curve full width at the half maximum (FWHM) of 670 arc sec. Epitaxial growth of crystalline AlN layers by PA-ALE at low temperatures broadens application of the material in the technologies that require large area conformal growth at low temperatures with thickness control at the atomic scale.

  15. Thermoelectric power factor in semiconductors with buried epitaxial semimetallic nanoparticles

    E-Print Network [OSTI]

    Bowers, John

    Thermoelectric power factor in semiconductors with buried epitaxial semimetallic nanoparticles J. M, mobility, and Seebeck coefficient of these materials and discuss their potential for use in thermoelectric on thermoelectric materials has focused on the ability of heterostructures and quantum con- finement to increase

  16. Continuum Theory of Epitaxial Crystal Growth, I Abstract 1 Introduction

    E-Print Network [OSTI]

    with appropriate boundary conditions at the continuum level to describe the growth ... epitaxial, i.e. layer by layer growth of a crystalline thin lm on a suitably ...... [13] Mullins W.W., Theory of Thermal Grooving, J. Appl. Phys., 28(1957), 333{

  17. 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.

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

    DOE Patents [OSTI]

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

    2013-02-19T23:59:59.000Z

    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.

  19. CROSSED MOLECULAR BEAM STUDIES OF CHEMILUMINESCENT REACTIONS

    E-Print Network [OSTI]

    Kahler, Carol Cuzens

    2013-01-01T23:59:59.000Z

    inch thick quartz plate (ESCO Optics grade Sl-UV) pressedis varied. ird lens (G) (ESCO Optics, fused silica, 2 inch·I~UV, The fourth lens (H) (ESCO Optics, fused silica, grade

  20. CROSSED MOLECULAR BEAM STUDIES OF CHEMILUMINESCENT REACTIONS

    E-Print Network [OSTI]

    Kahler, Carol Cuzens

    2013-01-01T23:59:59.000Z

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

  1. Dudley Herschbach: Chemical Reactions and Molecular Beams

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisitingContract ManagementDiscovering HowAna MooreDrought-induced treeDryDudley

  2. Yuan T. Lee and Molecular Beam Studies

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del SolStrengtheningWildfires may

  3. Accelerator beam profile analyzer

    DOE Patents [OSTI]

    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

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

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

    SciTech Connect (OSTI)

    Biedermann, Laura Butler

    2009-09-01T23:59:59.000Z

    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.

  5. Beam Status

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItem NotEnergy,ARMForms About Batteries Batteries An error occurred. TryRing CurrentBeam

  6. 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWP TWPAlumniComplex historian ...BESFor Users LiveBattling birdBeam

  7. 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWP TWPAlumniComplex historian ...BESFor Users LiveBattlingBeam

  8. Beam geometry selection using sequential beam addition

    SciTech Connect (OSTI)

    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

    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.

  9. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    DOE Patents [OSTI]

    Goyal, Amit

    2013-07-09T23:59:59.000Z

    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.

  10. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    DOE Patents [OSTI]

    Goyal, Amit (Knoxville, TN)

    2012-07-24T23:59:59.000Z

    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.

  11. Hidden Ferromagnetic Secondary Phases in Cobalt-doped ZnO Epitaxial...

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

    ZnO Epitaxial Thin Films. Abstract: The quest to discover a dilute magnetic semiconductor which is ferromagnetic at room temperature has led to extensive research on...

  12. InAlAs EPITAXIAL GROWTH FOR WIDE BAND GAP SOLAR CELLS Marina S. Leite

    E-Print Network [OSTI]

    Atwater, Harry

    concentrator cells made of metamorphic InGaP/GaAs/InGaAs can achieve > 41 % by using metamorphic epitaxial

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

    E-Print Network [OSTI]

    Woodall, Jerry M.

    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

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

    E-Print Network [OSTI]

    Sheldon, Nathan D.

    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

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

    E-Print Network [OSTI]

    Gall, Daniel

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

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

    E-Print Network [OSTI]

    Boyer, Edmond

    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

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

    E-Print Network [OSTI]

    Recanati, Catherine

    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

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

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    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

  19. Silicon epitaxy below 200C: Towards thin crystalline solar cells R. Carioua,b

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Silicon epitaxy below 200°C: Towards thin crystalline solar cells R. Carioua,b , R. Ruggeria,c , P spectroscopic ellipsometry and HRTEM measurements. Moreover, we build heterojunction solar cells with intrinsic of current devices. KEYWORDS Silicon epitaxy, RF-PECVD, low temperature, thin crystalline solar cells

  20. Epitaxial ternary nitride thin films prepared by a chemical solution method

    SciTech Connect (OSTI)

    Luo, Hongmei [Los Alamos National Laboratory; Feldmann, David M [Los Alamos National Laboratory; Wang, Haiyan [TEXAS A& M; Bi, Zhenxing [TEXAS A& M

    2008-01-01T23:59:59.000Z

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

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

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    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

  2. Effect of functionalization on the electrostatic charging, tunneling, and Raman spectroscopy of epitaxial graphene

    E-Print Network [OSTI]

    of epitaxial graphene Jeongmin Hong, Sandip Niyogi, Elena Bekyarova, Mikhail E. Itkis, Palanisamy Ramesh graphene Appl. Phys. Lett. 101, 111602 (2012); 10.1063/1.4752443 Evidences of electrochemical graphene (2012); 10.1063/1.4725489 Pinned and unpinned epitaxial graphene layers on SiC studied by Raman

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

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

    Demaurex, Bénédicte; Bartlome, Richard; Seif, Johannes P.; Geissbühler, Jonas; Alexander, Duncan T.; Jeangros, Quentin; Ballif, Christophe; De Wolf, Stefaan

    2014-08-07T23:59:59.000Z

    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 frommore »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.« less

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

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

    Demaurex, Bénédicte; Bartlome, Richard; Seif, Johannes P.; Geissbühler, Jonas; Alexander, Duncan T.; Jeangros, Quentin; Ballif, Christophe; De Wolf, Stefaan

    2014-08-07T23:59:59.000Z

    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.

  5. Neutral beam dump with cathodic arc titanium gettering

    SciTech Connect (OSTI)

    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

    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.

  6. Substrate doping effects on Raman spectrum of epitaxial graphene on SiC R. Yang, Q. S. Huang, X. L. Chen, G. Y. Zhang,a

    E-Print Network [OSTI]

    Wang, Wei Hua

    Substrate doping effects on Raman spectrum of epitaxial graphene on SiC R. Yang, Q. S. Huang, X. L; published online 2 February 2010 In this paper, we reported a Raman scattering study of epitaxial graphene to the epitaxial graphene. We found that the charge carrier type and concentration of epitaxial graphene can

  7. AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN

    E-Print Network [OSTI]

    York, Robert A.

    AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN 1 epitaxially on AlGaN/GaN HFET structures by molecular beam epitaxy (MBE). Growth was first performed on GaN templates to establish epitaxial growth conditions. X-ray diffraction showed [001] TiO2 || [1010]GaN

  8. Molecular phosphorus ion source for semiconductor technology

    SciTech Connect (OSTI)

    Gushenets V. I.; Hershcovitch A.; Bugaev, A.S.; Oks, E.M.; Kulevoy, T.V.

    2012-02-15T23:59:59.000Z

    This paper presents results on the generation of molecular phosphorus ion beams in a hot filament ion source. Solid red phosphorous is evaporated mainly as tetra-atomic molecules up to a temperature of 800 C. Thus, one of the main conditions for producing maximum P{sub 4}{sup +} fraction in the beam is to keep the temperature of the phosphorous oven, the steam line and the discharge chamber walls no greater than 800 C. The prior version of our ion source was equipped with a discharge chamber cooling system. The modified source ensured a P{sub 4}{sup +} ion beam current greater than 30% of the total beam current.

  9. Apparatus for externally controlled closed-loop feedback digital epitaxy

    DOE Patents [OSTI]

    Eres, Djula (Knoxville, TN); Sharp, Jeffrey W. (Knoxville, TN)

    1996-01-01T23:59:59.000Z

    A method and apparatus for digital epitaxy. 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.

  10. Apparatus for externally controlled closed-loop feedback digital epitaxy

    DOE Patents [OSTI]

    Eres, D.; Sharp, J.W.

    1996-07-30T23:59:59.000Z

    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.

  11. Epitaxially grown sputtered LaAlO sub 3 films

    SciTech Connect (OSTI)

    Lee, A.E.; Platt, C.E.; Burch, J.F.; Simon, R.W. (TRW Space Technology Group, Redondo Beach, CA (USA)); Goral, J.P.; Al-Jassim, M.M. (Solar Energy Research Institute, Golden, CO (USA))

    1990-11-05T23:59:59.000Z

    We have grown crystalline thin films of LaAlO{sub 3} using off-axis rf sputtering from a single stoichiometric target. The films grow epitaxially on SrTiO{sub 3} and LaAlO{sub 3} (100) substrates as well as on YBa{sub 2}Cu{sub 3}O{sub 7} thin films. We report on the growth conditions used to make these films, the properties of the films, and the properties of bilayer and trilayer structures containing both LaAlO{sub 3} and YBa{sub 2}Cu{sub 3}O{sub 7} films. Transmission electron microscopy cross-sectional and x-ray diffraction analyses indicate that all the constituent films in the multilayers grow epitaxially and that the interfaces between the films are sharply defined. Preliminary transport measurements on these multilayers show that LaAlO{sub 3} can be used for dielectric layers in a variety of high-temperature superconductor electronic circuits.

  12. Magnetismo Molecular (Molecular Magentism)

    SciTech Connect (OSTI)

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

    2010-07-01T23:59:59.000Z

    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.

  13. Beam position monitor

    DOE Patents [OSTI]

    Alkire, Randy W.; Rosenbaum, Gerold; Evans, Gwyndaf

    2003-07-22T23:59:59.000Z

    An apparatus for determining the position of an x-ray beam relative to a desired beam axis. Where the apparatus is positioned along the beam path so that a thin metal foil target intersects the x-ray beam generating fluorescent radiation. A PIN diode array is positioned so that a portion of the fluorescent radiation is intercepted by the array resulting in an a series of electrical signals from the PIN diodes making up the array. The signals are then analyzed and the position of the x-ray beam is determined relative to the desired beam path.

  14. BEAMS3D Neutral Beam Injection Model

    SciTech Connect (OSTI)

    Lazerson, Samuel

    2014-04-14T23:59:59.000Z

    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.

  15. Center for Beam Physics

    E-Print Network [OSTI]

    Chattopadhyay, S.

    2010-01-01T23:59:59.000Z

    interactions, ultra-high intensity lasers, 3D Laser Imagingconcepts, ultra-high intensity lasers, x-ray generation,interests: Ultra-high vacuum, particle beam and laser beam

  16. Epitaxial Growth and Characterization of Silicon Carbide Films

    SciTech Connect (OSTI)

    Dhanaraj,G.; Dudley, M.; Chen, Y.; Ragothamachar, B.; Wu, B.; Zhang, H.

    2006-01-01T23:59:59.000Z

    Silicon carbide (SiC) epitaxial layers have been grown in a chemical vapor deposition (CVD) system designed and fabricated in our laboratory. Silicon tetrachloride-propane as well as silane-propane were used as precursor gases. The hot zone was designed based on simulation by using numerical modeling. Growth rates up to 200 {mu}m could be achieved. A new growth-assisted hydrogen etching was developed to show the distribution of the micropipes present in the substrate. Higher growth rate was observed on off-axis (0 0 0 1) 4 H SiC compared to the on-axis (0 0 0 1) wafer and growth mechanism was explained.

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

    E-Print Network [OSTI]

    doped p-type (100) crystalline silicon substrates. We have studied the effect of the epitaxial intrinsic The photovoltaic industry has been growing with astonishing rates over the past years, but expansion plans

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

    E-Print Network [OSTI]

    doped p-type (100) crystalline silicon substrates. We have studied the effect of the epitaxial intrinsic-2263" DOI : 10.1016/j.solmat.2011.03.038 #12;2 1. Introduction The photovoltaic industry has been growing

  19. Geometric control of kinetic pathways: Characterizing equilibrium in epitaxial growth Paul N. Patrone1,2

    E-Print Network [OSTI]

    Milchberg, Howard

    with those of kinetic Monte Carlo simulations. PACS number(s): Epitaxial growth involves a competition? Our goal in this Letter is to provide a criterion, in the context of a tractable model, that indicates

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

    E-Print Network [OSTI]

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

    2011-01-01T23:59:59.000Z

    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 ...

  1. Epitaxial growth of NiTiO3 with a distorted ilmenite structure...

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

    growth of NiTiO3 with a distorted ilmenite structure. Epitaxial growth of NiTiO3 with a distorted ilmenite structure. Abstract: MTiO3 (M Fe, Mn, Ni) compounds have received...

  2. Layer resolved magnetic domain imaging of epitaxial heterostructures in large applied magnetic fields

    E-Print Network [OSTI]

    Zohar, S.; Choi, Y.; Love, D. M.; Mansell, R.; Barnes, C. H. W.; Keavney, D. J.; Rosenberg, R. A.

    2015-02-19T23:59:59.000Z

    We use X-ray Excited Luminescence Microscopy to investigate the elemental and layer resolved magnetic reversal in an interlayer exchange coupled (IEC) epitaxial Fe/Cr wedge/Co heterostructure. The transition from strongly coupled parallel Co...

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

    E-Print Network [OSTI]

    Bi, Lei

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

  4. Origin of transverse magnetization in epitaxial Cu/Ni/Cu nanowire arrays

    E-Print Network [OSTI]

    Ciria, M.

    The patterning-induced changes in the magnetic anisotropy and hysteresis of epitaxial (100)-oriented Cu/Ni(9, 10, 15 nm)/Cu planar nanowires have been quantified. When the Ni films are patterned into lines, strain relaxation ...

  5. 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.

  6. Enhanced Magnetism in Epitaxial SrRuO3 Thin Films

    E-Print Network [OSTI]

    Grutter, A.J.

    2010-01-01T23:59:59.000Z

    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+

  7. Effective lifetimes exceeding 300 ?s in gettered p-type epitaxial kerfless silicon for photovoltaics

    E-Print Network [OSTI]

    Powell, D. M.

    We evaluate defect concentrations and investigate the lifetime potential of p-type single-crystal kerfless silicon produced via epitaxy for photovoltaics. In gettered material, low interstitial iron concentrations (as low ...

  8. Epitaxial Growth and Microstructure of Cu2O Nanoparticle/thin...

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

    The grown layer was dominated by Cu2O phase, possessing an epitaxial orientation with the substrate such that: Cu2O001STO001 and Cu2O(100)STO(100). Cu2O film...

  9. Center for Beam Physics

    E-Print Network [OSTI]

    Chattopadhyay, S.

    2010-01-01T23:59:59.000Z

    FEL Collaboration: Photocathode/SCRF Collaboration: Two-BeamUniversity on Photocathode/ SCRF technology, LBNL-BNL on

  10. Beam Dynamics for ARIA

    E-Print Network [OSTI]

    Ekdahl, Carl

    2015-01-01T23:59:59.000Z

    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.

  11. Speckle Patterns with Atomic and Molecular de Broglie Waves

    SciTech Connect (OSTI)

    Patton, Forest S.; Deponte, Daniel P.; Kevan, Stephen D. [Department of Physics, University of Oregon, Eugene, Oregon 97403-1274 (United States); Elliott, Greg S. [Department of Physics, University of Puget Sound, Tacoma, Washington 98416 (United States)

    2006-07-07T23:59:59.000Z

    We have developed a nozzle source that delivers a continuous beam of atomic helium or molecular hydrogen having a high degree of transverse coherence and with adequate optical brightness to enable new kinds of experiments. Using this source we have measured single slit diffraction patterns and the first ever speckle-diffraction patterns using atomic and molecular de Broglie waves. Our results suggest fruitful application of coherent matter beams in dynamic scattering and diffractive imaging at short wavelength and with extreme surface sensitivity.

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

    E-Print Network [OSTI]

    Furman, Miguel

    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

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

    E-Print Network [OSTI]

    Furman, Miguel

    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

  14. Pulsed-electron-beam melting of Fe

    SciTech Connect (OSTI)

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

    1981-01-01T23:59:59.000Z

    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.

  15. III International Conference on SiGe(C) Epitaxy and Heterostructures, NM, Mar. 2003 SiGe Single-Hole Transistor Fabricated by AFM Oxidation and Epitaxial Regrowth

    E-Print Network [OSTI]

    III International Conference on SiGe(C) Epitaxy and Heterostructures, NM, Mar. 2003 110 SiGe Single, West Lafayette, IN 47907, U.S.A. Nanodevices on Si/SiGe heterostructures are of growing interest [1 the performance of the devices. In this paper, we demonstrate a reproducible single-hole transistor SiGe device

  16. Epitaxial {tau} phase MnAl thin films on MgO (001) with thickness-dependent magnetic anisotropy

    SciTech Connect (OSTI)

    Cui Yishen; Chen Wei [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Yin Wenjing; Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2011-11-15T23:59:59.000Z

    In this study, ferromagnetic MnAl films were prepared by alternating Al/Mn quasi-monolayer deposition using a novel biased target ion beam deposition (BTIBD) technique. XRD results showed that the magnetic {tau} phase was well formed in MnAl thin films ({approx}10 nm), which grew epitaxially on single crystal MgO (001) substrates. The optimized saturation magnetization was {approx}394 emu/cc. Furthermore, we observed a thickness-dependent uniaxial anisotropy in ferromagnetic MnAl films, which was attributed to the change of the tetragonal lattice distortion as a function of film thickness. The relationship between the film thicknesses and saturation magnetizations suggested the existence of a magnetically dead layer {approx}2.7 nm with an extrapolated saturation moment around 523 emu/cc ({approx}1.90 {mu}{sub B}/Mn). This value has exceeded the experimental value in bulk materials and is close to the theoretically predicted magnetization ({approx}1.975 {mu}{sub B}/Mn).

  17. Methods of Beam Cooling

    E-Print Network [OSTI]

    Sessler, A. M.

    2008-01-01T23:59:59.000Z

    of Optical Stochastic Cooling", presented at PAC, (1995).1991). Hangst, J. , "Laser Cooling of a Stored Ion Beam - ATheorem and Phase Space Cooling", Proceedings of the

  18. Broad beam ion implanter

    DOE Patents [OSTI]

    Leung, Ka-Ngo (Hercules, CA)

    1996-01-01T23:59:59.000Z

    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.

  19. Courses on Beam Physics

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

    is an incomplete listing of course available for beam physics. United States Particle Accelerator School The US Particle Accelerator School provides educational programs in the...

  20. Controlled epitaxial graphene growth within removable amorphous carbon corrals

    SciTech Connect (OSTI)

    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

    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.

  1. Epitaxial growth in dislocation-free strained asymmetric alloy films

    SciTech Connect (OSTI)

    Desai, Rashmi C.; Kim, Ho Kwon; Chatterji, Apratim; Ngai, Darryl; Chen Si; Yang Nan [Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7 (Canada)

    2010-06-15T23:59:59.000Z

    Epitaxial growth in strained asymmetric, dislocation-free, coherent, alloy films is explored. Linear-stability analysis is used to theoretically analyze the coupled instability arising jointly from the substrate-film lattice mismatch (morphological instability) and the spinodal decomposition mechanism. Both the static and growing films are considered. Role of various parameters in determining stability regions for a coherent growing alloy film is investigated. In addition to the usual parameters: lattice mismatch {epsilon}, solute-expansion coefficient {eta}, growth velocity V, and growth temperature T, we consider the alloy asymmetry arising from its mean composition. The dependence of elastic moduli on composition fluctuations and the coupling between top surface and underlying bulk of the film also play important roles. The theory is applied to group III-V films such as GaAsN, InGaN, and InGaP and to group IV Si-Ge films at temperatures below the bare critical temperature T{sub c} for strain-free spinodal decomposition. The dependences of various material parameters on mean concentration and temperature lead to significant qualitative changes.

  2. Production of a beam of highly vibrationally excited CO using perturbations

    E-Print Network [OSTI]

    Bartels, Nils

    An intense molecular beam of CO (X[superscript 1]?[superscript +]) in high vibrational states (v = 17, 18) was produced by a new approach that we call PUMP – PUMP – PERTURB and DUMP. The basic idea is to access high ...

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

    E-Print Network [OSTI]

    Gall, Daniel

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

  4. Laser beam generating apparatus

    DOE Patents [OSTI]

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

    1994-02-15T23:59:59.000Z

    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.

  5. Laser beam generating apparatus

    DOE Patents [OSTI]

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

    1993-12-28T23:59:59.000Z

    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.

  6. B13+: Photodriven Molecular Wankel Engine

    SciTech Connect (OSTI)

    Zhang, Jin; Sergeeva, Alina P.; Sparta, Manuel; Alexandrova, Anastassia N.

    2012-07-09T23:59:59.000Z

    Synthetic molecular motors that are capable of delivering controlled movement upon energy input are one of the key building blocks in nanomachinery. The major energy sources of molecular motors are from chemical reactions, photon beams, or electric current, which are converted into mechanical forces through the excitation of the electronic states of the molecule. The energy scale of the electronic excitation is normally two orders of magnitude larger than the molecular vibrational frequencies. To reduce the heat dissipation and increase the energy utilization efficiency, a motor running purely on the electronic ground-state (GS) potential energy surfaces is highly desirable.

  7. First Beam to FACET

    SciTech Connect (OSTI)

    Erickson, R.; Clarke, C.; Colocho, W.; Decker, F.-J.; Hogan, M.; Kalsi, S.; Lipkowitz, N.; Nelson, J.; Phinney, N.; Schuh, P.; Sheppard, J.; Smith, H.; Smith, T.; Stanek, M.; Turner, J.; Warren, J.; Weathersby, S.; Wienands, U.; Wittmer, W.; Woodley, M.; Yocky, G.; /SLAC

    2011-12-13T23:59:59.000Z

    The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new Facility for Advanced Accelerator Experimental Tests (FACET) while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). On June 23, 2011, the first electron beam was transported through this new facility. Commissioning of FACET is in progress. On June 23, 2011, an electron beam was successfully transported through the new FACET system to a dump in Sector 20 in the linac tunnel. This was achieved while the last third of the linac, operating from the same control room, but with a separate injector system, was providing an electron beam to the Linac Coherent Light Source (LCLS), demonstrating that concurrent operation of the two facilities is practical. With the initial checkout of the new transport line essentially complete, attention is now turning toward compressing the electron bunches longitudinally and focusing them transversely to support a variety of accelerator science experiments.

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

    DOE Patents [OSTI]

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

    2009-10-13T23:59:59.000Z

    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.

  9. STOCHASTIC COOLING OF BUNCHED BEAMS

    E-Print Network [OSTI]

    Bisognano, J.J.

    2010-01-01T23:59:59.000Z

    March 11-13, 1981 STOCHASTIC COOLING OF BUNCHED BEAMS J.J.W-7406-BW-48 STOCHASTIC COOLING OF BUNCHED BEAMS* J.J.longitudinal stochastic cooling of bunched particle beams.

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

    SciTech Connect (OSTI)

    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

    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.

  11. 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

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

    SciTech Connect (OSTI)

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

    2009-02-01T23:59:59.000Z

    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.

  13. Ion beam lithography system

    DOE Patents [OSTI]

    Leung, Ka-Ngo

    2005-08-02T23:59:59.000Z

    A maskless plasma-formed ion beam lithography tool provides for patterning of sub-50 nm features on large area flat or curved substrate surfaces. The system is very compact and does not require an accelerator column and electrostatic beam scanning components. The patterns are formed by switching beamlets on or off from a two electrode blanking system with the substrate being scanned mechanically in one dimension. This arrangement can provide a maskless nano-beam lithography tool for economic and high throughput processing.

  14. Sandia Energy - Molecular Geochemistry

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

    molecular spectroscopy, and molecular simulation to complex multicomponent and multiphase systems; particular emphasis on the use of molecular simulation and various...

  15. Molecular phosphorus ion source for semiconductor technology

    SciTech Connect (OSTI)

    Gushenets, V. I.; Bugaev, A. S.; Oks, E. M. [Institute of High Current Electronics SB RAS, Tomsk 634055 (Russian Federation); Hershcovitch, A. [Brookhaven National Laboratory, Upton, New York 11973 (United States); Kulevoy, T. V. [Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation)

    2012-02-15T23:59:59.000Z

    This paper presents results on the generation of molecular phosphorus ion beams in a hot filament ion source. Solid red phosphorous is evaporated mainly as tetra-atomic molecules up to a temperature of 800 deg. C. Thus, one of the main conditions for producing maximum P{sub 4}{sup +} fraction in the beam is to keep the temperature of the phosphorous oven, the steam line and the discharge chamber walls no greater than 800 deg. C. The prior version of our ion source was equipped with a discharge chamber cooling system. The modified source ensured a P{sub 4}{sup +} ion beam current greater than 30% of the total beam current.

  16. Coherent beam-beam mode in the LHC

    E-Print Network [OSTI]

    Buffat, X; Giachino, R; Herr, W; Papotti, G; Pieloni, T; White, S

    2014-01-01T23:59:59.000Z

    Observations of single bunch beam-beam coherent modes during dedicated experiments in the LHC are presented. Their role in standard operation for physics is discussed and, in particular, candidates of beam-beam coherent mode driven unstable by the machine impedance are presented.

  17. Focused ion beam system

    DOE Patents [OSTI]

    Leung, K.; Gough, R.A.; Ji, Q.; Lee, Y.Y.

    1999-08-31T23:59:59.000Z

    A focused ion beam (FIB) system produces a final beam spot size down to 0.1 {mu}m or less and an ion beam output current on the order of microamps. The FIB system increases ion source brightness by properly configuring the first (plasma) and second (extraction) electrodes. The first electrode is configured to have a high aperture diameter to electrode thickness aspect ratio. Additional accelerator and focusing electrodes are used to produce the final beam. As few as five electrodes can be used, providing a very compact FIB system with a length down to only 20 mm. Multibeamlet arrangements with a single ion source can be produced to increase throughput. The FIB system can be used for nanolithography and doping applications for fabrication of semiconductor devices with minimum feature sizes of 0.1 m or less. 13 figs.

  18. Final focus test beam

    SciTech Connect (OSTI)

    Not Available

    1991-03-01T23:59:59.000Z

    This report discusses the following: the Final Focus Test Beam Project; optical design; magnets; instrumentation; magnetic measurement and BPM calibration; mechanical alignment and stabilization; vacuum system; power supplies; control system; radiation shielding and personnel protection; infrastructure; and administration.

  19. Pulsed ion beam source

    DOE Patents [OSTI]

    Greenly, John B. (Lansing, NY)

    1997-01-01T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  1. LHC beam behaviour

    E-Print Network [OSTI]

    Herr, W

    2010-01-01T23:59:59.000Z

    An attempt is made to extract information on the LHC beam behaviour and dynamics from the observations made during the first runs in 2009. Although no systematic studies have been made, some basic properties can be established and in particular the observations in the presence of two beams and in collision are studied. They are analyzed in view of the foreseen runs at higher energy and possible improvements are proposed.

  2. Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development

    SciTech Connect (OSTI)

    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

    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.

  3. Photon beam position monitor

    DOE Patents [OSTI]

    Kuzay, T.M.; Shu, D.

    1995-02-07T23:59:59.000Z

    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.

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

    E-Print Network [OSTI]

    Brune, Harald

    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

  5. GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies

    E-Print Network [OSTI]

    Rogers, John A.

    LETTERS GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies and high electron mobilities. Examples range from effi- cient photovoltaic devices1,2 to radio and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic

  6. Local deformations and incommensurability of high quality epitaxial graphene on a weakly interacting transition metal

    E-Print Network [OSTI]

    parameter mismatch when cooling down the sample from the graphene preparation temperature to the measurement to the preparation conditions. All these effects are consistent with initial growth and subsequent pining of grapheneLocal deformations and incommensurability of high quality epitaxial graphene on a weakly

  7. Role of pseudospin in quasiparticle interferences in epitaxial probed by high resolution scanning tunneling microscopy

    E-Print Network [OSTI]

    Boyer, Edmond

    Role of pseudospin in quasiparticle interferences in epitaxial graphene, probed by high resolution of freedom emerging in graphene as a direct consequence of its honeycomb atomic structure, is responsible to provide a clear understanding of how such graphene's pseudospin impacts the quasiparticle interferences

  8. Embedded epitaxial growth of low-threshold GaInAsP/InP injection lasers

    SciTech Connect (OSTI)

    Chen, P.C.; Yu, K.L.; Margalit, S.; Yariv, A.

    1981-03-01T23:59:59.000Z

    Single-growth liquid-phase embedded epitaxy in the GaInAsP/InP system is described, and a new heterostructure laser is grown using this technique. These lasers exhibit excellent current and optical confinement. Threshold currents as low as 45 mA are achieved for a laser with 4-..mu..m-wide active region.

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

    DOE Patents [OSTI]

    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

    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.

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

    DOE Patents [OSTI]

    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

    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.

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

    E-Print Network [OSTI]

    Ferralis, Nicola

    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 ...

  12. Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

    DOE Patents [OSTI]

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

    2008-11-11T23:59:59.000Z

    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.

  13. 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

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

    SciTech Connect (OSTI)

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

    2012-06-01T23:59:59.000Z

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

  15. REVIEW OF SCIENTIFIC INSTRUMENTS 82, 023908 (2011) Calorimetry of epitaxial thin films

    E-Print Network [OSTI]

    Hellman, Frances

    2011-01-01T23:59:59.000Z

    REVIEW OF SCIENTIFIC INSTRUMENTS 82, 023908 (2011) Calorimetry of epitaxial thin films David W 2011; accepted 22 January 2011; published online 24 February 2011) Thin film growth allows. Microcalorimetry and nanocalorimetry techniques exist for the measurements of thin films but rely on an amorphous

  16. ccsd-00001676,version1-16Jun2004 Epitaxy and growth of titanium buffer layers

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ccsd-00001676,version1-16Jun2004 Epitaxy and growth of titanium buffer layers on Al2O3(0001) E Paris, France Abstract The structure and growth of thin films of titanium on -Al2O3 at room temperature of the phase of titanium reported before for thick films prepared at high temperature. The other structure can

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

    E-Print Network [OSTI]

    Boyer, Edmond

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

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

    E-Print Network [OSTI]

    Wei, Qiuming

    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

  19. 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

  20. Stress analysis of selective epitaxial growth of GaN Q. K. K. Liua)

    E-Print Network [OSTI]

    Nabben, Reinhard

    Stress analysis of selective epitaxial growth of GaN Q. K. K. Liua) Bereich Theoretische Physik Stress distributions in selectively overgrown self-organized GaN hexagonal pyramids have been analyzed in the literature and an effective lattice mismatch between the GaN and the substrate that was determined from

  1. Aligned Epitaxial SnO2 Nanowires on Sapphire: Growth and Device Applications

    E-Print Network [OSTI]

    Zhou, Chongwu

    process. Substrate guided growth of semiconducting nanowires has been successfully demonstrated for GaN-plane, M-plane, and R-plane sapphire substrates. These parallel nanowires can reach 100 m in length the direction of nanowire growth by using the epitaxial relation between the nanowire and the substrate combines

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

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    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

  3. Single element laser beam shaper

    DOE Patents [OSTI]

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

    2005-09-13T23:59:59.000Z

    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.

  4. Molecular Science Computing | EMSL

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

    Scientific Capabilities Molecular Science Computing Overview Cell Isolation and Systems Analysis Deposition and Microfabrication Mass Spectrometry Microscopy Molecular Science...

  5. Optical investigations of surface processes in GaP heteroepitaxy on silicon under pulsed chemical beam epitaxy conditions*

    E-Print Network [OSTI]

    Dietz, Nikolaus

    was exposed to individual pulses of the precursors triethylgallium TEG and tertiarybutylphosphine TBP, or less likely, of TEG fragments, that occurs with TEG exposure. The optical data also show that TBP dealkylation occurs essentially instantaneously upon arrival at the surface, and that TEG dealkylation

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

    E-Print Network [OSTI]

    Boyer, Edmond

    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

  7. Materials at UC Santa Barbara Ranked in the top two programs in the country for research impact and citations, materials research at UC

    E-Print Network [OSTI]

    Akhmedov, Azer

    as semiconductors · Soft cellular materials · Nanostructured materials by molecular beam epitaxy Solid chemistry to synthesize conjugated polymer composites for use in photovoltaic and optoelectronic devices in energy efficiency in Buildings, Lighting, Computing, Electronics & Photonics, Energy Production & Storage

  8. 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...

  9. 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...

  10. 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

  11. Sandia National Laboratories: gallium nitride

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

    and Systems Dept.) recently published the article "Band offsets of La2O3 on (0001) GaN grown by reactive molecular-beam epitaxy" in Applied Physics Letters outlining research...

  12. ICFA Beam Dynamics Newsletter

    SciTech Connect (OSTI)

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

    2012-07-01T23:59:59.000Z

    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.

  13. Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test

    SciTech Connect (OSTI)

    Jana, M.R.; Bross, A.; Chung, M.; Greer, S.; Johnstone, C.; Kobilarcik, T.; Koizumi, G.; Leonova, M.; Moretti, A.; Popovic, M.; Schwartz, T.; /Fermilab /IIT, Chicago /PDT, Torino

    2012-05-15T23:59:59.000Z

    Recent High Pressure RF (HPRF) cavity experiment at MuCool Test Area (MTA) has used 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces the electrons. These electrons consume RF power inside the cavity. Number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is {approx} 1200. The measurement of beam position and profile are necessary. MTA is flammable gas (Hydrogen) hazard zone so we have developed a passive beam diagnostic instrument using Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. Neutral density filter was used to avoid saturation of CCD camera. Image data is filtered and fitted with Gaussian function to compute the beam size. The beam profile obtained from scintillation screen shall be compared with multi-wire beam profile.

  14. Beam Profile Monitor With Accurate Horizontal And Vertical Beam Profiles

    DOE Patents [OSTI]

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

    2005-12-26T23:59:59.000Z

    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.

  15. Grazing incidence beam expander

    SciTech Connect (OSTI)

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

    1985-01-01T23:59:59.000Z

    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.

  16. Beam characteristics of energy-matched flattening filter free beams

    SciTech Connect (OSTI)

    Paynter, D.; Weston, S. J.; Cosgrove, V. P. [St James Institute of Oncology The Leeds Teaching Hospitals NHS Trust, Medical Physics, Leeds LS9 7TF (United Kingdom)] [St James Institute of Oncology The Leeds Teaching Hospitals NHS Trust, Medical Physics, Leeds LS9 7TF (United Kingdom); Evans, J. A. [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds (United Kingdom)] [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds (United Kingdom); Thwaites, D. I. [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds, United Kingdom and Institute of Medical Physics, School of Physics, University of Sydney (Australia)] [LIGHT Institute University of Leeds Leeds LS2 9JT, Division of Medical Physics, Leeds, United Kingdom and Institute of Medical Physics, School of Physics, University of Sydney (Australia)

    2014-05-15T23:59:59.000Z

    Purpose: Flattening filter free (FFF) linear accelerators can increase treatment efficiency and plan quality. There are multiple methods of defining a FFF beam. The Elekta control system supports tuning of the delivered FFF beam energy to enable matching of the percentage depth-dose (PDD) of the flattened beam at 10 cm depth. This is compared to FFF beams where the linac control parameters are identical to those for the flattened beam. All beams were delivered on an Elekta Synergy accelerator with an Agility multi-leaf collimator installed and compared to the standard, flattened beam. The aim of this study is to compare “matched” FFF beams to both “unmatched” FFF beams and flattened beams to determine the benefits of matching beams. Methods: For the three modes of operation 6 MV flattened, 6 MV matched FFF, 6 MV unmatched FFF, 10 MV flattened, 10 MV matched FFF, and 10 MV unmatched FFF beam profiles were obtained using a plotting tank and were measured in steps of 0.1 mm in the penumbral region. Beam penumbra was defined as the distance between the 80% and 20% of the normalized dose when the inflection points of the unflattened and flattened profiles were normalized with the central axis dose of the flattened field set as 100%. PDD data was obtained at field sizes ranging from 3 cm × 3 cm to 40?cm × 40 cm. Radiation protection measurements were additionally performed to determine the head leakage and environmental monitoring through the maze and primary barriers. Results: No significant change is made to the beam penumbra for FFF beams with and without PDD matching, the maximum change in penumbra for a 10 cm × 10 cm field was within the experimental error of the study. The changes in the profile shape with increasing field size are most significant for the matched FFF beam, and both FFF beams showed less profile shape variation with increasing depth when compared to flattened beams, due to consistency in beam energy spectra across the radiation field. The PDDs of the FFF beams showed less variation with field size, the d{sub max} value was deeper for the matched FFF beam than the FFF beam and deeper than the flattened beam for field sizes greater than 5 cm × 5 cm. The head leakage when using the machine in FFF mode is less than half that for a flattened beam, but comparable for both FFF modes. The radiation protection dose-rate measurements show an increase of instantaneous dose-rates when operating the machines in FFF mode but that increase is less than the ratio of MU/min produced by the machine. Conclusions: The matching of a FFF beam to a flattened beam at a depth of 10 cm in water by increasing the FFF beam energy does not reduce any of the reported benefits of FFF beams. Conversely, there are a number of potential benefits resulting from matching the FFF beam; the depth of maximum dose is deeper, the out of field dose is potentially reduced, and the beam quality and penetration more closely resembles the flattened beams currently used in clinical practice, making dose distributions in water more alike. Highlighted in this work is the fact that some conventional specifications and methods for measurement of beam parameters such as penumbra are not relevant and further work is required to address this situation with respect to “matched” FFF beams and to determine methods of measurement that are not reliant on an associated flattened beam.

  17. 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

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

    E-Print Network [OSTI]

    Boyer, Edmond

    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

  19. Molecular Foundry

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOne of

  20. Molecular Foundry

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOne

  1. Molecular Foundry

    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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOnItemResearch > The EnergyCenterDioxide Capture inFacility AMFInnovationMolecularOneThe

  2. Research Updates: Epitaxial strain relaxation and associated interfacial reconstructions: The driving force for creating new structures with integrated functionality

    E-Print Network [OSTI]

    Zhu, Yuanyuan; Chen, Aiping; Zhou, Honghui; Zhang, Wenrui; Narayan, Jagdish; MacManus-Driscoll, Judith L.; Jia, Quanxi; Wang, Haiyan

    2013-11-11T23:59:59.000Z

    epitaxial growth model. © 2013 Author(s). All article content, except where other- wise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4828936] Perovskite oxides exhibit very rich physical... can be controlled by substrate selection. It plays a vital role in tailoring the functionalities of perovskite thin films such as optical, electrical, and magnetic properties, and understanding the epitaxial strain relaxation in oxide thin film is thus...

  3. Observation of Coherent Beam-beam Effects in the LHC

    E-Print Network [OSTI]

    Buffat, X; Giachino, R; Herr, W; Papotti, G; Pieloni, T; Calaga, R; White, S M

    2011-01-01T23:59:59.000Z

    Early collisions in the LHC with a very limited number of bunches with high intensities indicated the presence of coherent beam-beam driven oscillations. Here we discuss the experimental results and compare with the expectations.

  4. Electron beam dynamics for the ISIS bremsstrahlung beam generation system

    E-Print Network [OSTI]

    Block, Robert E. (Robert Edward)

    2011-01-01T23:59:59.000Z

    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 ...

  5. Heavy Oil Upgrading from Electron Beam (E-Beam) Irradiation 

    E-Print Network [OSTI]

    Yang, Daegil

    2011-02-22T23:59:59.000Z

    hydrocarbons. Second, we studied the energy transfer mechanism of E-Beam upgrading to optimize the process. Third, we conducted a preliminary economic analysis based on energy consumption and compared the economics of E-Beam upgrading with conventional...

  6. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    Detector chamber. (Q) Main chamber ion pump- (S) Rotation (from ion pumps. (A) Buffer chamber ion pump feedthrough. (B) Quadrupole chamber ion pump feedthrough. (C) Coolant

  7. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    temperature cycling and since the chambers are difficult to access and view in the -Un­ completed condition, the construction and welding

  8. MOLECULAR BEAM PHOTOIONIZATION AND GAS-SURFACE SCATTERING

    E-Print Network [OSTI]

    Ceyer, S.T.

    2010-01-01T23:59:59.000Z

    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

  9. Reactions of carbon atoms in pulsed molecular beams

    SciTech Connect (OSTI)

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

    1993-12-01T23:59:59.000Z

    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.

  10. CROSSED MOLECULAR BEAM STUDIES OF UN-IMOLECULAR REACTION DYNAMICS

    E-Print Network [OSTI]

    Buss, R.J.

    2010-01-01T23:59:59.000Z

    Cambridge, Mass. , 1972. R. J. Buss and Y. T. Lee, FaradayS. J. Sibener, R. J. Buss, and Y. T. Lee, Xlth Inter­S. J. Sibener, R. J. Buss, and Y. T. Lee, Rev. Sci.

  11. Pulsed ion beam source

    DOE Patents [OSTI]

    Greenly, J.B.

    1997-08-12T23:59:59.000Z

    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.

  12. Colliding beams of light

    E-Print Network [OSTI]

    B. V. Ivanov

    2002-12-28T23:59:59.000Z

    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.

  13. Ion-beam technologies

    SciTech Connect (OSTI)

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

    1993-01-01T23:59:59.000Z

    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.

  14. The Cooling of Particle Beams

    E-Print Network [OSTI]

    Sessler, Andrew M.

    2008-01-01T23:59:59.000Z

    67, 15. Hangst, J "Laser Cooling of a Stored Ion Beam - ATheorem an.d Phase Space Cooling", Proceedings of theWorkshop on Beam Cooling and Related Topics, Montreaux, CERN

  15. Hadron beams session-summary

    SciTech Connect (OSTI)

    Terwilliger, K.M. (University of Michigan, Ann Arbor, MI 48109-1120, USA (US))

    1989-05-05T23:59:59.000Z

    The status of presently operating polarized beams at Fermilab, the AGS, and KEK is discussed. Other schemes such as Siberian Snakes and self-polarization of a beam in situ are briefly analyzed.(AIP)

  16. Laser beam pulse formatting method

    DOE Patents [OSTI]

    Daly, T.P.; Moses, E.I.; Patterson, R.W.; Sawicki, R.H.

    1994-08-09T23:59:59.000Z

    A method for formatting a laser beam pulse using one or more delay loops is disclosed. The delay loops have a partially reflective beam splitter and a plurality of highly reflective mirrors arranged such that the laser beam pulse enters into the delay loop through the beam splitter and circulates therein along a delay loop length defined by the mirrors. As the laser beam pulse circulates within the delay loop a portion thereof is emitted upon each completed circuit when the laser beam pulse strikes the beam splitter. The laser beam pulse is thereby formatted into a plurality of sub-pulses. The delay loops are used in combination to produce complex waveforms by combining the sub-pulses using additive waveform synthesis. 8 figs.

  17. Pseudo-rotational epitaxy of self-assembled octadecyltrichlorosilane monolayers on sapphire (0001)

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

    Steinruck, H. -G. [Univ. of Erlangen-Nurnberg, Erlangen (Germany); Ocko, B. M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Magerl, A. [Univ. of Erlangen-Nurnberg, Erlangen (Germany); Deutsch, M. [Bar-Ilan Univ., Ramat-Gan (Israel)

    2014-10-01T23:59:59.000Z

    The structure of octadecyltrichlorosilane self-assembled monolayers (SAMs) on sapphire (0001) was studied by Å-resolution surface-specific x-ray scattering methods. The monolayer was found to consist of three sublayers where the outermost layer corresponds to vertically oriented, closely packed alkyl tails. Laterally, the monolayer is hexagonally packed and exhibits pseudorotational epitaxy to the sapphire, manifested by a broad scattering peak at zero relative azimuthal rotation, with long powderlike tails. The lattice mismatch of ~1% – 3% to the sapphire’s and the different length scale introduced by the lateral Si-O-Si bonding prohibit positional epitaxy. However, the substrate induces an intriguing increase in the crystalline coherence length of the SAM’s powderlike crystallites when rotationally aligned with the sapphire’s lattice. The increase correlates well with the rotational dependence of the separation of corresponding substrate-monolayer lattice sites.

  18. Pseudo-rotational epitaxy of self-assembled octadecyltrichlorosilane monolayers on sapphire (0001)

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

    Steinruck, H. -G.; Ocko, B. M.; Magerl, A.; Deutsch, M.

    2014-10-01T23:59:59.000Z

    The structure of octadecyltrichlorosilane self-assembled monolayers (SAMs) on sapphire (0001) was studied by Å-resolution surface-specific x-ray scattering methods. The monolayer was found to consist of three sublayers where the outermost layer corresponds to vertically oriented, closely packed alkyl tails. Laterally, the monolayer is hexagonally packed and exhibits pseudorotational epitaxy to the sapphire, manifested by a broad scattering peak at zero relative azimuthal rotation, with long powderlike tails. The lattice mismatch of ~1% – 3% to the sapphire’s and the different length scale introduced by the lateral Si-O-Si bonding prohibit positional epitaxy. However, the substrate induces an intriguing increase in themore »crystalline coherence length of the SAM’s powderlike crystallites when rotationally aligned with the sapphire’s lattice. The increase correlates well with the rotational dependence of the separation of corresponding substrate-monolayer lattice sites.« less

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

    SciTech Connect (OSTI)

    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

    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.

  20. Proximity-induced giant spin-orbit interaction in epitaxial graphene on topological insulator

    E-Print Network [OSTI]

    Jin, Kyung-Hwan

    2015-01-01T23:59:59.000Z

    Heterostructures of Dirac materials such as graphene and topological insulators provide interesting platforms to explore exotic quantum states of electrons in solids. Here we study the electronic structure of graphene-Sb2Te3 heterostructure using density functional theory and tight-binding methods. We show that the epitaxial graphene on Sb2Te3 turns into quantum spin-Hall phase due to its proximity to the topological insulating Sb2Te3. It is found that the epitaxial graphene develops a giant spin-orbit gap of about ~20 meV, which is about three orders of magnitude larger than that of pristine graphene. We discuss the origin of such enhancement of the spin-orbit interaction and possible outcomes of the spin-Hall phase in graphene.

  1. Effect of buffer layer growth temperature on epitaxial GaN films deposited by magnetron sputtering

    SciTech Connect (OSTI)

    Mohanta, P.; Singh, D.; Kumar, R.; Ganguli, T.; Srinivasa, R. S.; Major, S. S. [Center For Research in Nano-Technology and Science (India); Semiconductor Laser Section, RRCAT, Indore-452013 (India); Department of Metallurgical Engineering and Materials Science (India); Department of Physics, Indian Institute of Technology Bombay, Mumbai - 400076 (India)

    2012-06-05T23:59:59.000Z

    Epitaxial GaN films were deposited by reactive sputtering of a GaAs target in 100 % nitrogen at 700 deg. C on ZnO buffer layers grown at different substrate temperatures over sapphire substrates. High resolution X-ray diffraction measurements and the corresponding analysis show that the growth temperature of buffer layers significantly affects the micro-structural parameters of GaN epilayer, such as lateral coherence length, tilt and twist, while the vertical coherence length remains unaffected. The optimum substrate temperature for buffer layer growth has been found to be 300 deg. C. High epitaxial quality GaN film grown on such a buffer layer exhibited micro strain of 1.8x10{sup -4} along with screw and edge type dislocation densities of 7.87x10{sup 9} and 1.16x10{sup 11}, respectively.

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

    SciTech Connect (OSTI)

    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

    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.

  3. 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.

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

    DOE Patents [OSTI]

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

    2010-03-02T23:59:59.000Z

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  6. Epitaxial growth of zinc blende and wurtzitic allied nitride thin films on (001) silicon

    E-Print Network [OSTI]

    Moustakas, Theodore

    hasbeenreported to be grown on ,@SiCand MgO( 100) substrates,"'which are closely lat- tice matchedto &GaN, and on GaAs substrate,"*" which has a significant mismatch to P-GaN. Growth of GaN onto silicon expansioncoefficient,it is rather difficult to epitaxially grow GaN on Si substrate. Early attempts have led

  7. Epitaxial Growth of InGaN Nanowire Arrays for Light Emitting Diodes

    E-Print Network [OSTI]

    Yang, Peidong

    from the substrate. Ni/Au (20 nm / 20 nm) contacts were deposited on the p-GaN substrate in a geometryS1 Epitaxial Growth of InGaN Nanowire Arrays for Light Emitting Diodes Christopher Hahn, Zhaoyu. The straight line represents the Vegard's law correlation between GaN (c = 5.188 Å) and InN (c = 5.709 Å). (b

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

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  10. Nanoscale molecularly imprinted polymers and method thereof

    DOE Patents [OSTI]

    Hart, Bradley R. (Brentwood, CA); Talley, Chad E. (Brentwood, CA)

    2008-06-10T23:59:59.000Z

    Nanoscale molecularly imprinted polymers (MIP) having polymer features wherein the size, shape and position are predetermined can be fabricated using an xy piezo stage mounted on an inverted microscope and a laser. Using an AMF controller, a solution containing polymer precursors and a photo initiator are positioned on the xy piezo and hit with a laser beam. The thickness of the polymeric features can be varied from a few nanometers to over a micron.

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

    SciTech Connect (OSTI)

    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

    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.

  12. Epitaxial europium oxide on Ni(100) with single-crystal quality

    SciTech Connect (OSTI)

    Foerster, Daniel F.; Klinkhammer, Juergen; Busse, Carsten; Altendorf, Simone G.; Michely, Thomas; Hu Zhiwei; Chin Yiying; Tjeng, L. H.; Coraux, Johann; Bourgault, Daniel [II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Strasse 77, D-50937 Koeln (Germany); II. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Strasse 77, D-50937 Koeln, Germany and Max Planck Institute for Chemical Physics of Solids, Noethnitzerstr. 40, D-01187 Dresden (Germany); Institut Neel, CNRS-UJF, 25 rue des Martyrs, F-38042 Grenoble Cedex 9 (France)

    2011-01-15T23:59:59.000Z

    High quality epitaxy of EuO on Ni(100) is developed in an in situ scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) study. A careful selection of the initial growth parameters is decisive to obtain a surface oxide suitable for the subsequent epitaxy of single phase EuO(100). After the creation of a three layer thick coalesced oxide film for the subsequent growth a distillation technique is applied. Appropriate annealing of films with up to 100 nm thickness generates sufficient conductivity for STM and electron spectroscopies. Oxygen vacancies are directly imaged by STM. They are of decisive importance for the metal-to-insulator transition around the temperature of the ferromagnetic-to-paramagnetic transition. A fast relaxation of the initial biaxial strain observed by LEED leaves little hope for an increase of the Curie temperature through epitaxial compression. Ex situ x-ray adsorption spectroscopy and magneto-optical Kerr effect microscopy measurements of thicker films are consistent with the stoichiometric single phase EuO with bulk properties.

  13. Recent advances of strong-strong beam-beam simulation

    SciTech Connect (OSTI)

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

    2004-09-15T23:59:59.000Z

    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.

  14. Metallic beam development for the Facility for Rare Isotope Beam

    SciTech Connect (OSTI)

    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

    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)

  15. Results of long-range beam-beam studies - scaling with beam separation and intensity

    E-Print Network [OSTI]

    Assmann, R; Buffat, X; Calaga, R; Giachino, R; Herr, W; Metral, E; Papotti, G; Pieloni, T; Roy, G; Trad, G; Kaltchev, D; CERN. Geneva. ATS Department

    2012-01-01T23:59:59.000Z

    We studied possible limitations due to the long-range beam-beam effects in the LHC. With a large number of bunches and collisions in all interaction points, we have reduced the crossing angles to enhance long-range beam-beam effects to evaluate their influence on dynamic aperture and losses. Different beta* and intensities have been used in two dedicated experiments and allow the test of the expected scaling laws.

  16. Ion beam generating apparatus

    DOE Patents [OSTI]

    Brown, Ian G. (1088 Woodside Rd., Berkeley, CA 94708); Galvin, James (2 Commodore #276, Emeryville, CA 94608)

    1987-01-01T23:59:59.000Z

    An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam.

  17. Ion beam generating apparatus

    DOE Patents [OSTI]

    Brown, I.G.; Galvin, J.

    1987-12-22T23:59:59.000Z

    An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam. 10 figs.

  18. Stationary nonlinear Airy beams

    SciTech Connect (OSTI)

    Lotti, A. [Dipartimento di Fisica e Matematica, Universita del'Insubria, Via Valleggio 11, I-22100 Como (Italy); Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Faccio, D. [Dipartimento di Fisica e Matematica, Universita del'Insubria, Via Valleggio 11, I-22100 Como (Italy); School of Engineering and Physical Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Couairon, A. [Centre de Physique Theorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Papazoglou, D. G. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Materials Science and Technology Department, University of Crete, GR-71003 Heraklion (Greece); Panagiotopoulos, P.; Tzortzakis, S. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Abdollahpour, D. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1527, GR-71110 Heraklion (Greece); Physics Department, University of Crete, GR-71003 Heraklion (Greece)

    2011-08-15T23:59:59.000Z

    We demonstrate the existence of an additional class of stationary accelerating Airy wave forms that exist in the presence of third-order (Kerr) nonlinearity and nonlinear losses. Numerical simulations and experiments, in agreement with the analytical model, highlight how these stationary solutions sustain the nonlinear evolution of Airy beams. The generic nature of the Airy solution allows extension of these results to other settings, and a variety of applications are suggested.

  19. Axion beams at HERA?

    E-Print Network [OSTI]

    K. Piotrzkowski

    2007-01-09T23:59:59.000Z

    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.

  20. Molecular Science Computing | EMSL

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

    Molecular Science Computing Overview Cell Isolation and Systems Analysis Deposition and Microfabrication Mass Spectrometry Microscopy Molecular Science Computing NMR and EPR...

  1. 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

  2. Plasma-beam traps and radiofrequency quadrupole beam coolers

    SciTech Connect (OSTI)

    Maggiore, M., E-mail: mario.maggiore@lnl.infn.it; Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S. [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy)] [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy); Caruso, A.; Longhitano, A. [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy)] [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy); Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M. [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)] [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)

    2014-02-15T23:59:59.000Z

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

  3. Thermodynamic Theory of Epitaxial Alloys: First-Principles Mixed-Basis Cluster Expansion of (In,Ga)N Alloy Film

    SciTech Connect (OSTI)

    Liu, J. Z.; Zunger, A.

    2009-01-01T23:59:59.000Z

    Epitaxial growth of semiconductor alloys onto a fixed substrate has become the method of choice to make high quality crystals. In the coherent epitaxial growth, the lattice mismatch between the alloy film and the substrate induces a particular form of strain, adding a strain energy term into the free energy of the alloy system. Such epitaxial strain energy can alter the thermodynamics of the alloy, leading to a different phase diagram and different atomic microstructures. In this paper, we present a general-purpose mixed-basis cluster expansion method to describe the thermodynamics of an epitaxial alloy, where the formation energy of a structure is expressed in terms of pair and many-body interactions. With a finite number of first-principles calculation inputs, our method can predict the energies of various atomic structures with an accuracy comparable to that of first-principles calculations themselves. Epitaxial (In, Ga)N zinc-blende alloy grown on GaN(001) substrate is taken as an example to demonstrate the details of the method. Two (210) superlattice structures, (InN){sub 2}/(GaN){sub 2} (at x = 0.50) and (InN){sub 4}/(GaN){sub 1} (at x = 0.80), are identified as the ground state structures, in contrast to the phase-separation behavior of the bulk alloy.

  4. Observations of beam-beam effects at the LHC

    E-Print Network [OSTI]

    Papotti, G; Herr, W; Giachino, R; Pieloni, T

    2014-01-01T23:59:59.000Z

    This paper introduces a list of observations related to the beam-beam interaction that were collected over the first years of LHC proton physics operation (2010-12). Beam-beam related effects not only have been extensively observed and recorded, but have also shaped the operation of the LHC for high-intensity proton running in a number of ways: the construction of the filling scheme, the choice of luminosity levelling techniques, measures to mitigate instabilities, and the choice of settings for improving performance (e.g. to reduce losses), among others.

  5. Precision Absolute Beam Current Measurement of Low Power Electron Beam

    SciTech Connect (OSTI)

    Ali, M. M.; Bevins, M. E.; Degtiarenko, P.; Freyberger, A.; Krafft, G. A.

    2012-11-01T23:59:59.000Z

    Precise measurements of low power CW electron beam current for the Jefferson Lab Nuclear Physics program have been performed using a Tungsten calorimeter. This paper describes the rationale for the choice of the calorimeter technique, as well as the design and calibration of the device. The calorimeter is in use presently to provide a 1% absolute current measurement of CW electron beam with 50 to 500 nA of average beam current and 1-3 GeV beam energy. Results from these recent measurements will also be presented.

  6. 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: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's Possible for Renewable Energy:Nanowire Solar541,9337, 2011 at3, Issue 30 NewNetworks,Beam

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

    E-Print Network [OSTI]

    Kim, Sehun

    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

  8. Effect of surfactant Sb on In incorporation and thin film morphology of InGaN layers grown by organometallic vapor phase epitaxy

    E-Print Network [OSTI]

    Simons, Jack

    was interpreted as due to a surfactant-induced change of surface phase on the InGaN films. & 2013 Elsevier B of GaN and InN [2]. These problems con- tribute to material defects, inhomogeneous alloying, and phase the lateral epitaxial overgrowth (LEO) of GaN by organome- tallic vapor phase epitaxy (OMVPE). A change

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

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    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

  10. 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]

    Paris-Sud XI, Université de

    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

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

  12. Silicon Epitaxial Regrowth Passivation of SiGe Nanostructures Pattered by AFM Xiang-Zheng Bo, Leonid P. Rokhinson, and J. C. Sturm

    E-Print Network [OSTI]

    Silicon Epitaxial Regrowth Passivation of SiGe Nanostructures Pattered by AFM Oxidation Xiang@princeton.edu ABSTRACT SiGe quantum devices were demonstrated by AFM oxidation and selective wet etching with features temperature regrowth of epitaxial silicon over strained SiGe has been tested. The silicon regrowth on Si0.8Ge0

  13. PHYSICAL REVIEW B VOLUME 52, NUMBER 23 15 DECEMBER 1995-I Properties of the yellow luminescence in undoped GaN epitaxial layers

    E-Print Network [OSTI]

    Nabben, Reinhard

    Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten masks: A method to map the free-carrier concentration of thick GaN samples A. Kaschner,a) A. Hoffmann properties of two epitaxial-laterally overgrown GaN structures with tungsten masks in 1100 and 1120 direction

  14. The influence of substrate surface preparation on LP MOVPE GaN epitaxy on differently oriented 4H-SiC substrates

    E-Print Network [OSTI]

    Ozbay, Ekmel

    The influence of substrate surface preparation on LP MOVPE GaN epitaxy on differently oriented 4H preparation and off-cut of 4H-SiC substrates on morphological and structural properties of GaN grown by low-SiC is most suitable for GaN epitaxy and that substrate etching improves the surface morphology of epilayer

  15. Beam characterization by wavefront sensor

    DOE Patents [OSTI]

    Neal, D.R.; Alford, W.J.; Gruetzner, J.K.

    1999-08-10T23:59:59.000Z

    An apparatus and method are disclosed for characterizing an energy beam (such as a laser) with a two-dimensional wavefront sensor, such as a Shack-Hartmann lenslet array. The sensor measures wavefront slope and irradiance of the beam at a single point on the beam and calculates a space-beamwidth product. A detector array such as a charge coupled device camera is preferably employed. 21 figs.

  16. Beam emittance measurements at Fermilab

    SciTech Connect (OSTI)

    Wendt, Manfred; Eddy, Nathan; Hu, Martin; Scarpine, Victor; Syphers, Mike; Tassotto, Gianni; Thurman-Keup, Randy; Yang, Ming-Jen; Zagel, James; /Fermilab

    2008-01-01T23:59:59.000Z

    We give short overview of various beam emittance measurement methods, currently applied at different machine locations for the Run II collider physics program at Fermilab. All these methods are based on beam profile measurements, and we give some examples of the related instrumentation techniques. At the end we introduce a multi-megawatt proton source project, currently under investigation at Fermilab, with respect to the beam instrumentation challenges.

  17. Low energy beta-beams

    E-Print Network [OSTI]

    Cristina Volpe

    2009-11-13T23:59:59.000Z

    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.

  18. First LHC Beams in ATLAS

    E-Print Network [OSTI]

    Krieger, P

    2009-01-01T23:59:59.000Z

    This is a talk on the ATLAS single beam running, to be given on February 9th at the Aspen Winter Conference.

  19. ANL Beams and Applications Seminar

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

    characterization of the laser and electron beams of the Cornell Energy Recovery Linac Heng Li Cornell University June 18 Interbeam Scattering Studies at CesrTA Michael Ehrlichman...

  20. Broad-band beam buncher

    DOE Patents [OSTI]

    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

    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.

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

    SciTech Connect (OSTI)

    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

    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.

  2. Single-growth embedded epitaxy AlGaAs injection lasers with extremely low threshold currents

    SciTech Connect (OSTI)

    Katz, J.; Margalit, S.; Wilt, D.; Chen, P.C.; Yariv, A.

    1980-12-01T23:59:59.000Z

    A new type of strip-geometry AlGaAs double-heterostructure laser with an embedded optical waveguide has been developed. The new structure is fabricated using a single step of epitaxial growth. Lasers with threshold currents as low as 9.5 mA (150 ..mu..m long) were obtained. These lasers exhibit operation in a single spatial and longitudinal mode, have differential quantum efficiencies exceeding 45%, and a characteristic temperature of 175/sup 0/ C. They emit more than 12 mW/facet of optical power without any kinks.

  3. Effect of Oxygen Adsorption on the Local Properties of Epitaxial Graphene on SiC (0001)

    E-Print Network [OSTI]

    Mathieu, C; Mentes, T O; Pallecchi, E; Locatelli, A; Latil, S; Belkhou, R; Ouerghi, A

    2015-01-01T23:59:59.000Z

    The effect of oxygen adsorption on the local structure and electronic properties of monolayer graphene grown on SiC(0001) has been studied by means of Low Energy Electron Microscopy (LEEM), microprobe Low Energy Electron Diffraction (\\muLEED) and microprobe Angle Resolved Photoemission (\\muARPES). We show that the buffer layer of epitaxial graphene on SiC(0001) is partially decoupled after oxidation. The monitoring of the oxidation process demonstrates that the oxygen saturates the Si dangling bonds, breaks some Si-C bonds at the interface and intercalates the graphene layer. Accurate control over the oxidation parameters enables us to tune the charge density modulation in the layer.

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

    SciTech Connect (OSTI)

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

    2009-03-26T23:59:59.000Z

    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.

  5. Fundamental optical properties of InN grown by epitaxial lateral overgrowth method

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

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

    2014-07-07T23:59:59.000Z

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

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

    DOE Patents [OSTI]

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

    2008-08-05T23:59:59.000Z

    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.

  8. NEUTRAL-BEAM INJECTION

    SciTech Connect (OSTI)

    Kunkel, W.B.

    1980-06-01T23:59:59.000Z

    The emphasis in the preceding chapters has been on magnetic confinement of high temperature plasmas. The question of production and heating of such plasmas has been dealt with relatively more briefly. It should not be inferred, however, that these matters must therefore be either trivial or unimportant. A review of the history reveals that in the early days all these aspects of the controlled fusion problem were considered to be on a par, and were tackled simultaneously and with equal vigor. Only the confinement problem turned out to be much more complex than initially anticipated, and richer in challenge to the plasma physicist than the questions of plasma production and heating. On the other hand, the properties of high-temperature plasmas and plasma confinement can only be studied experimentally after the problems of production and of heating to adequate temperatures are solved. It is the purpose of this and the next chapter to supplement the preceding discussions with more detail on two important subjects: neutral-beam injection and radio-frequency heating. These are the major contenders for heating in present and future tokamak and mirror fusion experiments, and even in several proposed reactors. For neutral beams we emphasize here the technology involved, which has undergone a rather remarkable development. The physics of particle and energy deposition in the plasma, and the discussion of the resulting effects on the confined plasma, have been included in previous chapters, and some experimental results are quoted there. Other heating processes of relevance to fusion are mentioned elsewhere in this book, in connection with the experiments where they are used: i.e. ohmic heating, adiabatic compression heating, and alpha-particle heating in Chapter 3 by H.P. Furth; more ohmic heating in Chapter 7, and shock-implosion heating, laser heating, and relativistic-electron beam heating in Chapter 8, both by W. E. Quinn. These methods are relatively straightforward in their physics and their technology, or in any case they are considered to be adequately covered by these other authors.

  9. Laser acceleration of ion beams

    E-Print Network [OSTI]

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

    2007-02-01T23:59:59.000Z

    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.

  10. Head-on beam-beam collisions with high intensities and long range beam-beam studies in the LHC

    E-Print Network [OSTI]

    Albert, M; Assmann, R; Buffat, X; Calaga, R; Cornelis, K; Fitterer, M; Giachino, R; Herr, W; Miyamoto, R; Norman, L; Papotti, G; Pieloni, T; Ponce, L; Redaelli, S; Schaumann, M; Trad, G; Wollmann, D

    2011-01-01T23:59:59.000Z

    In two experiments we studied possible limitations due to the beam-beam effects in the LHC. In the first experiment we collided high intensity bunches head-on to explore the region for high luminosity collisions. In the second test we reduced the crossing angle in the presence of long range encounters to increase their effects.

  11. Toward automated beam optics control

    SciTech Connect (OSTI)

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

    1987-01-01T23:59:59.000Z

    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.

  12. Method of digital epitaxy by externally controlled closed-loop feedback

    DOE Patents [OSTI]

    Eres, D.; Sharp, J.W.

    1994-07-19T23:59:59.000Z

    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.

  13. Process for selectively patterning epitaxial film growth on a semiconductor substrate

    DOE Patents [OSTI]

    Sheldon, P.; Hayes, R.E.

    1984-12-04T23:59:59.000Z

    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.

  14. Asymmetric Electron Transport at Monolayer-Bilayer Heterojunctions of Epitaxial Graphene

    SciTech Connect (OSTI)

    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

    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.

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

    SciTech Connect (OSTI)

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

    2013-09-24T23:59:59.000Z

    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.

  16. Delivering High IntensityDelivering High Intensity Proton Beam:Proton Beam

    E-Print Network [OSTI]

    McDonald, Kirk

    11 Delivering High IntensityDelivering High Intensity Proton Beam:Proton Beam: Lessons for the NextFACT08NuFACT08 ­­ 4 July4 July S. ChildressS. Childress ­­ Proton BeamsProton Beams 22 Presentation OutlinePresentation Outline Key Proton Beam ConsiderationsKey Proton Beam Considerations The First

  17. Molecular information ratchets 

    E-Print Network [OSTI]

    Wilson, Adam Christopher

    2012-11-28T23:59:59.000Z

    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 ...

  18. Laser beam alignment apparatus and method

    DOE Patents [OSTI]

    Gruhn, Charles R. (Martinez, CA); Hammond, Robert B. (Los Alamos, NM)

    1981-01-01T23:59:59.000Z

    The disclosure relates to an apparatus and method for laser beam alignment. Thermoelectric properties of a disc in a laser beam path are used to provide an indication of beam alignment and/or automatic laser alignment.

  19. EMSL - Molecular Science Computing

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

    computing Resources and Techniques Molecular Science Computing - Sophisticated and integrated computational capabilities, including scientific consultants, software, Cascade...

  20. Electrostatic wire stabilizing a charged particle beam

    DOE Patents [OSTI]

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

    1983-03-21T23:59:59.000Z

    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.

  1. Epitaxial ordering of a perylenetetracarboxylic diimide-melamine supramolecular network driven by the Au,,111...-,,22 3... reconstruction

    E-Print Network [OSTI]

    Castell, Martin

    Epitaxial ordering of a perylenetetracarboxylic diimide-melamine supramolecular network driven. Castell1,b 1 Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom 2 Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands

  2. Epitaxial growth and thermal stability of Fe{sub 4}N film on TiN buffered Si(001) substrate

    SciTech Connect (OSTI)

    Xiang, H.; Shi, F.-Y.; Voyles, P. M.; Chang, Y. A. [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Rzchowski, M. S. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2011-04-01T23:59:59.000Z

    Epitaxial Fe{sub 4}N thin films were grown on TiN buffered Si(001) substrate by dc reactive sputtering deposition at different substrate temperatures. Fe{sub 4}N films epitaxially grew on TiN within the substrate temperature range from 250 to 350 deg. C. Lower than 250 deg. C there will be some other Fe{sub x}N compounds formed and higher than 400 deg. C there will be only Fe left. Fe{sub 4}N is metastable and the postannealing process in vacuum will decompose Fe{sub 4}N film to Fe. However, introducing 30% N{sub 2} in the postannealing atmosphere can stabilize the Fe{sub 4}N up to 350 deg. C in the (Ar,N{sub 2}) gas mixture. The surface roughness of the epitaxial Fe{sub 4}N films decreases with film thickness. There is in-plane biaxial magnetic anisotropy of epitaxial Fe{sub 4}N(001) on Si(001) with the [100] easy direction.

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

    E-Print Network [OSTI]

    Volinsky, Alex A.

    -power, high- frequency and high-temperature electronics due its outstanding electrical and thermal properties determines the final wafer bow, which has important implications with regard to the processing, the epitaxial of the impact that the growth rate has on the residual stress, wafer bow and film crystallinity of LPCVD-grown 3

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

    E-Print Network [OSTI]

    Atwater, Harry

    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

  5. In situ magnetic a.nd structural analysis of epitaxial NisoFezothin films for spin-valve heterostructures

    E-Print Network [OSTI]

    Atwater, Harry

    In situ magnetic a.nd structural analysis of epitaxial NisoFezothin films for spin-valve-coupling and giant magnetoresistance (.GMRj in NiseFez,,/Cu multilayers' and spin-valves.' To date, all" Furthermore, FeMn, which is typically used in spin valves to exchange bias one of the ferromagnetic layers

  6. Nanocomposites of Semimetallic ErAs Nanoparticles Epitaxially Embedded within InGaAlAs-based Semiconductors for Thermoelectric Materials

    E-Print Network [OSTI]

    GaAlAs-based Semiconductors for Thermoelectric Materials J.M.O. Zide', G. Zeng2, J.H. Bahk2, W. Kim3, S. L. Singer3, DAs nanoparticles which are epitaxially embedded within InGaAlAs-based semiconductors. The properties. In one geometry, barriers of InGaAlAs, a wider bandgap semiconductor, are introduced into an Er

  7. Carbon incorporation for strain compensation during solid phase epitaxial recrystallization of SiGe on Si at 500600 C

    E-Print Network [OSTI]

    Florida, University of

    Carbon incorporation for strain compensation during solid phase epitaxial recrystallization of SiGe in the MBE grown SiGe layers prior to regrowth at moderate temperatures 500­700 °C has three main effects­10 and photodetectors.11,12 The addition of germa- nium to silicon allows the resulting SiGe layer to have a reduced

  8. SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography and silicon epitaxial-regrowth

    E-Print Network [OSTI]

    Rokhinson, Leonid

    SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography; published online 10 November 2006 A SiGe quantum dot single-hole transistor passivated by silicon epitaxial are reproducible, in sharp contrast with the noisy and irreproducible I-V characteristics of unpassivated SiGe

  9. Yellow-green strained-InGaP quantum-well epitaxial-transparent-substrate light emitting diodes

    E-Print Network [OSTI]

    Yellow-green strained-InGaP quantum-well epitaxial-transparent-substrate light emitting diodes L March 2004 We present a strained-InGaP quantum-well light emitting diode LED operating in the green that InGaP alloys in this composition range are not lattice-matched to any traditional substrate material

  10. Terahertz studies of carrier dynamics and dielectric response of n-type, freestanding epitaxial GaN

    E-Print Network [OSTI]

    Terahertz studies of carrier dynamics and dielectric response of n-type, freestanding epitaxial GaN conductivity and dielectric function of GaN by terahertz time-domain spectroscopy. Transmission measurements are performed on an n-type, 180- m-thick, freestanding GaN crystal. Frequency dependent electron dynamics, power

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

    E-Print Network [OSTI]

    Continetti, Robert E.

    /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

  12. MEASUREMENT OF BEAM CHARACTERISTICS FOR PHOTO- ELECTRON BEAM...

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

    electron beam is expected to be used in a wide field, such as X-ray generation by inverse Compton scattering, pulse radiolysis, etc. The laser driven photo cathode rf gun system is...

  13. Electron beam machining using rotating and shaped beam power distribution

    DOE Patents [OSTI]

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

    1996-07-09T23:59:59.000Z

    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.

  14. Electron beam machining using rotating and shaped beam power distribution

    DOE Patents [OSTI]

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

    1996-01-01T23:59:59.000Z

    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.

  15. Alight a beam and beaming light: A theme with variations

    SciTech Connect (OSTI)

    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

    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.}

  16. Thermal stresses in laminated beams

    E-Print Network [OSTI]

    Marcano, Victor Manuel

    1983-01-01T23:59:59.000Z

    Stresses Acting on a Section of the Laminated Beam -------- 15 5. Loading Geometry and Material Characteristics of the Test Problem 21 6. Simply-Supported Beam with a Sinusoidal Load--------- 30 7. Shear Stress Distribution for a Simply- Supported... 24. Normal Stress Distribution for a Cantilever Laminated Beam, T-Z sinzx/L --------------- 58 m. i 25. Axial Stress Distribution for a Cantilever Laminated Bearq, T-T (2z/8+1) 2 mi 27. Normal Stress Distribution for ("/L) ? ---- 6O 2 a...

  17. Thermal stresses in laminated beams 

    E-Print Network [OSTI]

    Marcano, Victor Manuel

    1983-01-01T23:59:59.000Z

    Stresses Acting on a Section of the Laminated Beam -------- 15 5. Loading Geometry and Material Characteristics of the Test Problem 21 6. Simply-Supported Beam with a Sinusoidal Load--------- 30 7. Shear Stress Distribution for a Simply- Supported... 24. Normal Stress Distribution for a Cantilever Laminated Beam, T-Z sinzx/L --------------- 58 m. i 25. Axial Stress Distribution for a Cantilever Laminated Bearq, T-T (2z/8+1) 2 mi 27. Normal Stress Distribution for ("/L) ? ---- 6O 2 a...

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

    SciTech Connect (OSTI)

    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

    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.

  19. Circular, confined distribution for charged particle beams

    DOE Patents [OSTI]

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

    1995-11-21T23:59:59.000Z

    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.

  20. Circular, confined distribution for charged particle beams

    DOE Patents [OSTI]

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

    1995-01-01T23:59:59.000Z

    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.