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Sample records for beam epitaxy growth

  1. Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

    OpenAIRE

    2016-01-01

    In this article, we will review recent progress in the growth of topological insulator (TI) thin films by molecular beam epitaxy (MBE). The materials we focus on are the V2-VI3 family of TIs. These materials are ideally bulk insulating with surface states housing Dirac excitations which are spin-momentum locked. These surface states are interesting for fundamental physics studies (such as the search for Majorana fermions) as well as applications in spintronics and other fields. However, the m...

  2. Epitaxial film growth and metastable phases of single crystal Dy by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, K.; Homma, H.; Schuller, I.K.

    1988-04-15

    We have grown two novel epitaxial phases of dysprosium (Dy) on vanadium (V) by the molecular beam epitaxy technique. Surface structures are studied by in situ reflection high-energy electron diffraction, and bulk structures are studied by x-ray diffraction after removal from the growth chamber. The new hcp phases are approx.4% expanded uniformly in the (0001) plane and approx.9% and approx.4% expanded out of plane, along the c axes, for noninterrupted and interrupted deposition cases, respectively. We also observed (2 x 2), (3 x 3), and (4 x 4) Dy surface reconstruction patterns and a series of structural changes as the Dy film thickness increases.

  3. Gas source molecular beam epitaxial growth of GaN

    Science.gov (United States)

    Brown, Duncan W.

    1992-11-01

    Aluminum gallium nitride (AlGaN) has long been recognized as a promising radiation hard optoelectronic material. AlGaN has a wide direct band gap and therefore has potential applications in the fabrication of short wave-length devices, e.g., detectors and light-emitting diodes in the visible to ultraviolet region. Additionally, its piezoelectric properties and high acoustic velocities make it attractive for acoustic devices. The technical objective in Phase 1 was to determine if low temperature sources based on covalently bonded Group 3-nitrogen compounds could be used to prepare AlGaN films by gas source molecular beam epitaxy. The program required to investigate low temperature AlGaN source materials was separated into two parts: (1) the synthesis, purification, and pyrolysis of gallium-nitrogen adducts and aluminum-nitrogen adducts; and (2) the growth of GaN by chemical beam epitaxy. We clearly demonstrated under CBE conditions GaN(x)C(y) films could be grown using compounds with pre-existing Ga-N bonds whereas no films were formed using trimethylgallium. Dimethylgallium amide was shown to produce dramatically lower carbon content films in the presence of ammonia than did trimethylgallium in the presence of ammonia.

  4. Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

    Directory of Open Access Journals (Sweden)

    Theresa P. Ginley

    2016-11-01

    Full Text Available In this article, we will review recent progress in the growth of topological insulator (TI thin films by molecular beam epitaxy (MBE. The materials we focus on are the V2-VI3 family of TIs. These materials are ideally bulk insulating with surface states housing Dirac excitations which are spin-momentum locked. These surface states are interesting for fundamental physics studies (such as the search for Majorana fermions as well as applications in spintronics and other fields. However, the majority of TI films and bulk crystals exhibit significant bulk conductivity, which obscures these states. In addition, many TI films have a high defect density. This review will discuss progress in reducing the bulk conductivity while increasing the crystal quality. We will describe in detail how growth parameters, substrate choice, and growth technique influence the resulting TI film properties for binary and ternary TIs. We then give an overview of progress in the growth of TI heterostructures. We close by discussing the bright future for TI film growth by MBE.

  5. Growth of very large InN microcrystals by molecular beam epitaxy using epitaxial lateral overgrowth

    Energy Technology Data Exchange (ETDEWEB)

    Kamimura, J., E-mail: kamimura@pdi-berlin.de [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Kishino, K.; Kikuchi, A. [Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2015-02-28

    Very thick InN (∼40 μm) was grown by molecular beam epitaxy using the epitaxial lateral overgrowth (ELO) technique. In some regions, the ELO of InN was observed as expected, indicating an important step toward fabricating quasi-bulk InN substrates. Interestingly, most parts of the sample consist of large flat-topped microcrystals and well-faceted microstructures. This is likely due to local growth condition variations during ELO, which is supported by an experiment where ELO of InN was performed on a substrate with various stripe mask patterns. TEM characterization of a flat top InN microcrystal revealed few stacking faults and only related threading dislocations. Defect-free small faceted microcrystals were also observed. The thick InN crystals show a narrow photoluminescence spectrum with a peak at 0.679 eV and linewidth of 16.8 meV at 4 K.

  6. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan; Liu Hongxue; Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Gu, Man [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Khokhlov, Mikhail; Wolf, Stuart A. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Guilford College, Greensboro, North Carolina 27410 (United States)

    2013-01-14

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  7. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Science.gov (United States)

    Comes, Ryan; Gu, Man; Khokhlov, Mikhail; Liu, Hongxue; Lu, Jiwei; Wolf, Stuart A.

    2013-01-01

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  8. Epitaxial growth and new phase of single crystal Dy by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Kai-Yueh; Homma, Hitoshi; Schuller, I.K.

    1987-09-01

    We have grown two novel epitaxial phases of dysprosium (Dy) on vanadium (V) by molecular beam epitaxy technique. Surface and bulk structures are studied by in-situ reflection high energy electron diffraction (RHEED) and x-ray diffraction techniques. The new hcp phases are approx.4% expanded uniformly in-plane (0001), and approx.9% and approx.4% expanded out of plane along the c-axes for non-interrupted and interrupted deposition case, respectively. We also observed (2 x 2), (3 x 3), and (4 x 4) Dy surface reconstruction patterns and a series of transitions as the Dy film thickness increases. 12 refs., 3 figs.

  9. Epitaxial growth of dilute nitride-arsenide compound semiconductors by molecular beam epitaxy

    Science.gov (United States)

    Adamcyk, Martin

    InyGa1-yAs 1-xNx containing a small amount of nitrogen (x narrow bandgap semiconductor alloy that has advantageous properties for the fabrication of optoelectronic devices. In this thesis, we seek to improve the material quality of InGaAsN and GaAsN by studying how the epitaxial growth conditions affect both the structural and electronic properties of the alloy. We describe a novel RF plasma source based on a helical resonator design that was developed for the incorporation of nitrogen into GaAsN and InGaAsN thin films grown by molecular beam epitaxy. The plasma source is equipped with a baffle apparatus that decreases the ion content of the flux. We show how the structural and electronic properties of InGaAsN epilayers depend on the growth conditions. In situ light scattering measurements and atomic force microscopy show that a faceted surface morphology occurs when growth conditions increase adatom surface diffusion: slow growth rate, high substrate temperature and high V/III ratio. Large nitrogen concentrations also favour the faceted growth mode. The residual strain in relaxed InGaAsN films is found to be higher than in InGaAs epilayers having the same lattice mismatch. In situ substrate curvature measurements were used to monitor the strain state of the sample in real time during the growth. Ex situ transmission electron microscopy and x-ray diffraction measurements agree with the residual strain determined with the in situ monitor. These characterization results also indicate that threading dislocation glide is slower in InGaAsN than in InGaAs. Finally, we find that the electronic properties of InGaAsN are generally degraded with increasing nitrogen content. However, by choosing appropriate growth conditions, we demonstrate InGaAsN quantum wells with room temperature photoluminescence efficiencies that are comparable to InGaAs structures. These photoluminescence results may be related to the faceting transition that was observed during GaAsN growth. In

  10. In-situ epitaxial growth of graphene/h-BN van der Waals heterostructures by molecular beam epitaxy.

    Science.gov (United States)

    Zuo, Zheng; Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zheng, Jian-Guo; Liu, Jianlin

    2015-10-07

    Van der Waals materials have received a great deal of attention for their exceptional layered structures and exotic properties, which can open up various device applications in nanoelectronics. However, in situ epitaxial growth of dissimilar van der Waals materials remains challenging. Here we demonstrate a solution for fabricating van der Waals heterostructures. Graphene/hexagonal boron nitride (h-BN) heterostructures were synthesized on cobalt substrates by using molecular beam epitaxy. Various characterizations were carried out to evaluate the heterostructures. Wafer-scale heterostructures consisting of single-layer/bilayer graphene and multilayer h-BN were achieved. The mismatch angle between graphene and h-BN is below 1°.

  11. Molecular beam epitaxy growth of InSb1−xBix thin films

    DEFF Research Database (Denmark)

    Song, Yuxin; Wang, Shumin; Saha Roy, Ivy;

    2013-01-01

    Molecular beam epitaxy growth for InSb1−xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology...

  12. Molecular beam epitaxy growth of InSb1-xBix thin films

    DEFF Research Database (Denmark)

    Yuxin Song; Shumin Wang; Saha Roy, Ivy;

    2013-01-01

    Molecular beam epitaxy growth for InSb1-xBix thin films on (100) GaAs substrates is reported. Successful Bi incorporation for 2% is achieved, and up to 70% of the incorporated Bi atoms are at substitutional sites. The effects of growth parameters on Bi incorporation and surface morphology...

  13. Selective area growth of heterostructure bipolar transistors by metalorganic molecular beam epitaxy

    Science.gov (United States)

    Hamm, R. A.; Feygenson, A.; Ritter, D.; Wang, Y. L.; Temkin, H.; Yadvish, R. D.; Panish, M. B.

    1992-08-01

    Heterostructure bipolar transistors (HBT) have been grown by selective area epitaxy (SAE) using metalorganic molecular beam epitaxy (MOMBE). dc characteristics, comparable to those for devices grown on unprocessed substrates, were obtained after removal of the edge growth. Data is also presented for devices in which the emitter mesas were regrown by SAE into openings which had been previously defined by photolithography on a structure containing only the collector and base layers. In both cases we use an in situ cleaning process consisting of an Ar ion beam sputtering and Cl2 etching. This step results in significantly improved junction quality.

  14. InAs nanowire growth modes on Si (111) by gas source molecular beam epitaxy

    Science.gov (United States)

    Robson, M. T.; LaPierre, R. R.

    2016-02-01

    InAs nanowires (NWs) were grown on silicon substrates by gas source molecular beam epitaxy using five different growth modes: (1) Au-assisted growth, (2) positioned (patterned) Au-assisted growth, (3) Au-free growth, (4) positioned Au-assisted growth using a patterned oxide mask, and (5) Au-free selective-area epitaxy (SAE) using a patterned oxide mask. Optimal growth conditions (temperature, V/III flux ratio) were identified for each growth mode for control of NW morphology and vertical NW yield. The highest yield (72%) was achieved with the SAE method at a growth temperature of 440 °C and a V/III flux ratio of 4. Growth mechanisms are discussed for each of the growth modes.

  15. Growth of Gold-assisted Gallium Arsenide Nanowires on Silicon Substrates via Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Ramon M. delos Santos

    2008-06-01

    Full Text Available Gallium arsenide nanowires were grown on silicon (100 substrates by what is called the vapor-liquid-solid (VLS growth mechanism using a molecular beam epitaxy (MBE system. Good quality nanowires with surface density of approximately 108 nanowires per square centimeter were produced by utilizing gold nanoparticles, with density of 1011 nanoparticles per square centimeter, as catalysts for nanowire growth. X-ray diffraction measurements, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy revealed that the nanowires are epitaxially grown on the silicon substrates, are oriented along the [111] direction and have cubic zincblende structure.

  16. Epitaxial Growth of Si(111)/Er2O3(111) Structure on Si(111) by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    XU Run; TANG Min-Yan; ZHU Yan-Yan; WANG Lin-Jun

    2011-01-01

    The Si overlayers are grown by molecular beam epitaxy on atomically smllth Er2O3(111) films prepared on Si(111) substrates. Single crystalline Si overlayers are achieved and are evident due to the spot-like reflective high energy electron diffraction(RHEED) patterns and x-ray diffraction patterns. The epitaxial relationship of the Si overlayer along the surface with respect to the orientation of EreO3 and the Si substrate is as follows:overgrown Si(111)//Er2O3(111)//Si(111).The rough surface of Si overlayers, as identified by both RHEED patterns and atomic force microscopy images, indicates a three-dimensional growth mode. The reason for this is based on the interfacial energy argument. Further growth of Er2O3 films on this rough Si overlayer leads to the polycrystalline nature of the topmost Er2O3 layer.

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

    Directory of Open Access Journals (Sweden)

    S. S. Kushvaha

    2014-02-01

    Full Text Available We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm 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 × 108 cm−2 at 750 °C than that of the low temperature grown sample (1.1 × 109 cm−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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

    2014-02-15

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm 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.

  19. Adsorption-controlled growth of BiVO4 by molecular-beam epitaxy

    Directory of Open Access Journals (Sweden)

    S. Stoughton

    2013-10-01

    Full Text Available Single-phase epitaxial films of the monoclinic polymorph of BiVO4 were synthesized by reactive molecular-beam epitaxy under adsorption-controlled conditions. The BiVO4 films were grown on (001 yttria-stabilized cubic zirconia (YSZ substrates. Four-circle x-ray diffraction, scanning transmission electron microscopy (STEM, and Raman spectroscopy confirm the epitaxial growth of monoclinic BiVO4 with an atomically abrupt interface and orientation relationship (001BiVO4 ∥ (001YSZ with [100]BiVO4 ∥ [100]YSZ. Spectroscopic ellipsometry, STEM electron energy loss spectroscopy (STEM-EELS, and x-ray absorption spectroscopy indicate that the films have a direct band gap of 2.5 ± 0.1 eV.

  20. Direct growth of graphene on in situ epitaxial hexagonal boron nitride flakes by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zuo, Zheng; Liu, Jianlin, E-mail: jianlin@ece.ucr.edu [Quantum Structures Laboratory, Department of Electrical and Computer Engineering, University of California, Riverside, California 92521 (United States)

    2015-11-23

    Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850–900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes.

  1. Molecular beam epitaxy growth of germanium junctions for multi-junction solar cell applications

    Science.gov (United States)

    Masuda, T.; Faucher, J.; Lee, M. L.

    2016-11-01

    We report on the molecular beam epitaxy (MBE) growth and device characteristics of Ge solar cells. Integrating a Ge bottom cell beneath a lattice-matched triple junction stack grown by MBE could enable ultra-high efficiencies without metamorphic growth or wafer bonding. However, a diffused junction cannot be readily formed in Ge by MBE due to the low sticking coefficient of group-V molecules on Ge surfaces. We therefore realized Ge junctions by growth of homo-epitaxial n-Ge on p-Ge wafers within a standard III-V MBE system. We then fabricated Ge solar cells, finding growth temperature and post-growth annealing to be key factors for achieving high efficiency. Open-circuit voltage and fill factor values of ~0.175 V and ~0.59 without a window layer were obtained, both of which are comparable to diffused Ge junctions formed by metal-organic vapor phase epitaxy. We also demonstrate growth of high-quality, single-domain GaAs on the Ge junction, as needed for subsequent growth of III-V subcells, and that the surface passivation afforded by the GaAs layer slightly improves the Ge cell performance.

  2. ’Molecular Beam Epitaxial Growth, Characterization, and Devices of Modulated Semiconductor Structures’

    Science.gov (United States)

    1990-02-28

    on reverse if necessary and identify by block number) Key Words: Molecular Beam Epitaxv, X-ray diffraction, RHEED, GeSn , AlGaSb, Surface Structure iLb...equipment so far has been used in the study of metastable GeSn alloys grown on InP and GaSb substrates, and in analysis of the (Al, Ga)Sb material system...Homma, "Molecular beam epitaxial 6 growth of metastable GeSn alloys", Sept. 13-15, 1989, North Carolina State University, Raleigh, N.C. Also to be

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

    Directory of Open Access Journals (Sweden)

    A. Lastras-Martínez

    2014-03-01

    Full Text Available 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.

  4. An ultra-compact, high-throughput molecular beam epitaxy growth system

    Energy Technology Data Exchange (ETDEWEB)

    Baker, A. A.; Hesjedal, T. [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom); Diamond Light Source, Didcot OX11 0DE (United Kingdom); Braun, W., E-mail: w.braun@fkf.mpg.de, E-mail: fischer@createc.de; Rembold, S.; Fischer, A., E-mail: w.braun@fkf.mpg.de, E-mail: fischer@createc.de [CreaTec Fischer and Co. GmbH, Industriestr. 9, 74391 Erligheim (Germany); Gassler, G. [Dr. Gassler Electron Devices GmbH, List Str. 4, 89079 Ulm (Germany)

    2015-04-15

    We present a miniaturized molecular beam epitaxy (miniMBE) system with an outer diameter of 206 mm, optimized for flexible and high-throughput operation. The three-chamber system, used here for oxide growth, consists of a sample loading chamber, a storage chamber, and a growth chamber. The growth chamber is equipped with eight identical effusion cell ports with linear shutters, one larger port for either a multi-pocket electron beam evaporator or an oxygen plasma source, an integrated cryoshroud, retractable beam-flux monitor or quartz-crystal microbalance, reflection high energy electron diffraction, substrate manipulator, main shutter, and quadrupole mass spectrometer. The system can be combined with ultrahigh vacuum (UHV) end stations on synchrotron and neutron beamlines, or equivalently with other complex surface analysis systems, including low-temperature scanning probe microscopy systems. Substrate handling is compatible with most UHV surface characterization systems, as the miniMBE can accommodate standard surface science sample holders. We introduce the design of the system, and its specific capabilities and operational parameters, and we demonstrate the epitaxial thin film growth of magnetoelectric Cr{sub 2}O{sub 3} on c-plane sapphire and ferrimagnetic Fe{sub 3}O{sub 4} on MgO (001)

  5. An ultra-compact, high-throughput molecular beam epitaxy growth system.

    Science.gov (United States)

    Baker, A A; Braun, W; Gassler, G; Rembold, S; Fischer, A; Hesjedal, T

    2015-04-01

    We present a miniaturized molecular beam epitaxy (miniMBE) system with an outer diameter of 206 mm, optimized for flexible and high-throughput operation. The three-chamber system, used here for oxide growth, consists of a sample loading chamber, a storage chamber, and a growth chamber. The growth chamber is equipped with eight identical effusion cell ports with linear shutters, one larger port for either a multi-pocket electron beam evaporator or an oxygen plasma source, an integrated cryoshroud, retractable beam-flux monitor or quartz-crystal microbalance, reflection high energy electron diffraction, substrate manipulator, main shutter, and quadrupole mass spectrometer. The system can be combined with ultrahigh vacuum (UHV) end stations on synchrotron and neutron beamlines, or equivalently with other complex surface analysis systems, including low-temperature scanning probe microscopy systems. Substrate handling is compatible with most UHV surface characterization systems, as the miniMBE can accommodate standard surface science sample holders. We introduce the design of the system, and its specific capabilities and operational parameters, and we demonstrate the epitaxial thin film growth of magnetoelectric Cr2O3 on c-plane sapphire and ferrimagnetic Fe3O4 on MgO (001).

  6. Growth of MoO3 films by oxygen plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Altman, Eric I.; Droubay, Timothy C.; Chambers, Scott A.

    2002-07-22

    The growth of MoO₃ films on SrLaAlO₄(0 0 1), a substrate lattice-matched to b-MoO , by oxygen plasma assisted molecular beam epitaxy was characterized using reflection high-energy electron diffraction (RHEED), X-ray photoelectron spectroscopy, Xray diffraction (XRD), and atomic force and scanning tunneling microscopies (AFM and STM).It was found that the flux of reactive oxygen species to the surface was not high enough to maintain the proper stoichiometry, even at the lowest measurable deposition rates. Therefore, the films were grown by depositing Mo in small increments and then allowing the Mo to oxidize. At 675 K, the films grew epitaxially but in a three-dimensional manner. XRD of films grown under these conditions revealed atetragonal structure that has not been previously observed in bulk MoO₃ samples.

  7. Growth of CuInSe2 by molecular beam epitaxy

    Science.gov (United States)

    Grindle, S. P.; Clark, A. H.; Rezaie-Serej, S.; Falconer, E.; McNeily, J.; Kazmerski, L. L.

    1980-10-01

    Molecular beam epitaxy was used to grow CuInSe2 layers on CdS (001B) and other substrates. Epitaxial growth is obtained at a substrate temperature of 300 C. The ratio of the arrival rates of copper to indium is the key parameter governing layer stoichiometry. To produce low-resistivity p-type layers, the Cu/In arrival rate ratio must be slightly higher than that used to grow nominally stoichiometric layers. This suggests that a different defect is controlling electrical properties, rather than the copper vacancy complex which dominates bulk material. CuInSe2/CdS heterojunctions were fabricated which show a maximum solar conversion efficiency of about 5%.

  8. Effects of substrate orientation on the growth of InSb nanostructures by molecular beam epitaxy

    Science.gov (United States)

    Chou, C. Y.; Torfi, A.; Pei, C.; Wang, W. I.

    2016-05-01

    In this work, the effects of substrate orientation on InSb quantum structure growth by molecular beam epitaxy (MBE) are presented. Motivated by the observation that (411) evolves naturally as a stable facet during MBE crystal growth, comparison studies have been carried out to investigate the effects of the crystal orientation of the underlying GaSb substrate on the growth of InSb by MBE. By depositing InSb on a number of different substrate orientations, namely: (100), (311), (411), and (511), a higher nanostructure density was observed on the (411) surface compared with the other orientations. This result suggests that the (411) orientation presents a superior surface in MBE growth to develop a super-flat GaSb buffer surface, naturally favorable for nanostructure growth.

  9. Growth of CrTe thin films by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasan, M.G. [Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore); Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Hou, X.J. [Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore); Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Teo, K.L. [Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)]. E-mail: eleteokl@nus.edu.sg; Jalil, M.B.A. [Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Liew, T. [Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore); Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Chong, T.C. [Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore)

    2006-05-18

    We report the growth of Cr{sub 1-{delta}}Te films on (100) GaAs substrates using ZnTe buffer layers by solid-source molecular-beam epitaxial technique. RHEED patterns indicate a clear structural change during the initial stages of deposition. Temperature-dependent magnetization results reveal that different NiAs-related phases of Cr{sub 1-{delta}}Te can be obtained at different substrate temperatures. By varying the film thickness, a metastable zinc blende structure of CrTe could be obtained at lower substrate temperature.

  10. Molecular beam epitaxy growth and optical properties of single crystal Zn3N2 films

    Science.gov (United States)

    Wu, Peng; Tiedje, T.; Alimohammadi, H.; Bahrami-Yekta, V.; Masnadi-Shirazi, M.; Wang, Cong

    2016-10-01

    Single crystal Zn3N2 films with (100) orientation have been grown by plasma-assisted molecular beam epitaxy on MgO and A-plane sapphire substrates with in situ optical reflectance monitoring of the growth. The optical bandgap was found to be 1.25-1.28 eV and an electron Hall mobility as high as 395 cm2 V-1 s-1 was measured. The films were n-type with carrier concentrations in the 1018-1019 cm-3 range.

  11. Growth of (110) GaAs/GaAs by molecular beam epitaxy

    Science.gov (United States)

    Parechanian, L. T.; Weber, E. R.; Hierl, T. L.

    1985-04-01

    The simultaneous molecular beam epitaxy (MBE) growth of (100) and (110) GaAs/GaAs intentionally doped with Si(-1E16/cu cm) was studied as a function of substrate temperature, arsenic overpressure, and epitaxial growth rate. The films were analyzed by scanning electron and optical microscopy, liquid helium photoluminescence (PL), and electronic characterization. For the (110) epitaxial layers, an increase in morphological defect density and degradation of PL signal was observed with a lowering of the substrate temperature from 570 C. Capacitance-voltage (CV) and Hall effect measurements yield room temperature donor concentrations for the (100) films of n-7E15/ cu cm while the (110) layers exhibit electron concentrations of n-2E17/cu cm. Hall measuremtns at 77k on the (100) films show the expected mobility enhancement of Si donors, whereas the (110) epi layers become insulating or greatly compensated. This behavior suggests that room temperature conduction in the (110) films is due to a deeper donor partially compensated by an acceptor level whose concentration is of the smae order of magnitude as that of any electrically active Si. Temperature dependent Hall effect indicates that the activation energy of the deeper donor level lies -145 meV from the conduction band.

  12. Impact of growth parameters on the morphology and microstructure of epitaxial GaAs nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z.Y. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Chen, P.P., E-mail: ppchen@mail.sitp.ac.cn [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Liao, Z.M. [Materials Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Shi, S.X.; Sun, Y.; Li, T.X.; Zhang, Y.H. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China); Zou, J. [Materials Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Center for Microscopy and Microanalysis, University of Queensland, St. Lucia, QLD 4072 (Australia); Lu, W. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai 200083 (China)

    2013-12-15

    Highlights: •Defect-free wurtzite GaAs nanowires were obtained by MBE at low growth temperature. •Some GaAs nanowires grown at low temperature show the morphology of two shoulders. •High growth temperature favors the formation of nanowires with uniform diameter. •Low V/III flux ratio causes many kinked GaAs nanowires. •A phase separation of the catalyst is observed under very Ga-rich condition. -- Abstract: The effect of the growth temperature and V/III flux ratio on the morphology and microstructure of GaAs nanowires grown on GaAs (1 1 1){sub B} substrates by Au-assisted molecular beam epitaxy with solid As{sub 4} source was investigated. It has been found that a low growth temperature of 400 °C can result in defect-free wurtzite structured nanowire with syringe-like morphology, while nanowires with more homogeneous diameter can be obtained at high temperatures (500 °C and 550 °C) with many stacking faults. It was also found that, at a low V/III flux ratio, GaAs nanowires had a shrinking neck section, while a high V/III flux ratio may result in disappearance of the shrinking necking section. For the Ga very rich condition, a phase separation of the catalysts can be observed, leaving a small Au–Ga droplet covered by the outer pure Ga droplet.

  13. Investigation of the silicon ion density during molecular beam epitaxy growth

    CERN Document Server

    Eifler, G; Ashurov, K; Morozov, S

    2002-01-01

    Ions impinging on a surface during molecular beam epitaxy influence the growth and the properties of the growing layer, for example, suppression of dopant segregation and the generation of crystal defects. The silicon electron gun in the molecular beam epitaxy (MBE) equipment is used as a source for silicon ions. To use the effect of ion bombardment the mechanism of generation and distribution of ions was investigated. A monitoring system was developed and attached at the substrate position in the MBE growth chamber to measure the ion and electron densities towards the substrate. A negative voltage was applied to the substrate to modify the ion energy and density. Furthermore the current caused by charge carriers impinging on the substrate was measured and compared with the results of the monitoring system. The electron and ion densities were measured by varying the emission current of the e-gun achieving silicon growth rates between 0.07 and 0.45 nm/s and by changing the voltage applied to the substrate betw...

  14. Growth of Inclined GaAs Nanowires by Molecular Beam Epitaxy: Theory and Experiment

    Directory of Open Access Journals (Sweden)

    Tchernycheva M

    2010-01-01

    Full Text Available Abstract The growth of inclined GaAs nanowires (NWs during molecular beam epitaxy (MBE on the rotating substrates is studied. The growth model provides explicitly the NW length as a function of radius, supersaturations, diffusion lengths and the tilt angle. Growth experiments are carried out on the GaAs(211A and GaAs(111B substrates. It is found that 20° inclined NWs are two times longer in average, which is explained by a larger impingement rate on their sidewalls. We find that the effective diffusion length at 550°C amounts to 12 nm for the surface adatoms and is more than 5,000 nm for the sidewall adatoms. Supersaturations of surface and sidewall adatoms are also estimated. The obtained results show the importance of sidewall adatoms in the MBE growth of NWs, neglected in a number of earlier studies.

  15. Growth of Inclined GaAs Nanowires by Molecular Beam Epitaxy: Theory and Experiment.

    Science.gov (United States)

    Zhang, X; Dubrovskii, V G; Sibirev, N V; Cirlin, G E; Sartel, C; Tchernycheva, M; Harmand, J C; Glas, F

    2010-07-24

    The growth of inclined GaAs nanowires (NWs) during molecular beam epitaxy (MBE) on the rotating substrates is studied. The growth model provides explicitly the NW length as a function of radius, supersaturations, diffusion lengths and the tilt angle. Growth experiments are carried out on the GaAs(211)A and GaAs(111)B substrates. It is found that 20° inclined NWs are two times longer in average, which is explained by a larger impingement rate on their sidewalls. We find that the effective diffusion length at 550°C amounts to 12 nm for the surface adatoms and is more than 5,000 nm for the sidewall adatoms. Supersaturations of surface and sidewall adatoms are also estimated. The obtained results show the importance of sidewall adatoms in the MBE growth of NWs, neglected in a number of earlier studies.

  16. Epitaxial film growth study of single crystal V/Ce prepared by molecular-beam epitaxy on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Homma, H.; Yang, K.Y.; Schuller, I.K.

    1986-11-01

    The growth of epitaxial films of cerium (Ce)/vanadium (V)/on single crystal sapphires (..cap alpha..-Al/sub 2/O/sub 3/) was studied by in-situ reflection high energy electron diffraction and x-ray scattering. For the first time Ce(111) single crystal films was grown on V(110)/Al/sub 2/O/sub 3/(1120) in the Frank-van der Merwe mode. A new epitaxial orientation, different from the well known Nishiyama-Wasserman or Kurdjumov-Sachs orientations is found in the present study. Subsequent V(110) layers grow epitaxially with three equivalent domains.

  17. Molecular beam epitaxy

    CERN Document Server

    Pamplin, Brian R

    1980-01-01

    Molecular Beam Epitaxy introduces the reader to the use of molecular beam epitaxy (MBE) in the generation of III-V and IV-VI compounds and alloys and describes the semiconductor and integrated optics reasons for using the technique. Topics covered include semiconductor superlattices by MBE; design considerations for MBE systems; periodic doping structure in gallium arsenide (GaAs); nonstoichiometry and carrier concentration control in MBE of compound semiconductors; and MBE techniques for IV-VI optoelectronic devices. The use of MBE to fabricate integrated optical devices and to study semicond

  18. Hybrid molecular beam epitaxy for the growth of stoichiometric BaSnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Abhinav, E-mail: praka019@umn.edu; Dewey, John; Yun, Hwanhui; Jeong, Jong Seok; Mkhoyan, K. Andre; Jalan, Bharat, E-mail: bjalan@umn.edu [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2015-11-15

    Owing to its high room-temperature electron mobility and wide bandgap, BaSnO{sub 3} has recently become of significant interest for potential room-temperature oxide electronics. A hybrid molecular beam epitaxy (MBE) approach for the growth of high-quality BaSnO{sub 3} films is developed in this work. This approach employs hexamethylditin as a chemical precursor for tin, an effusion cell for barium, and a radio frequency plasma source for oxygen. BaSnO{sub 3} films were thus grown on SrTiO{sub 3} (001) and LaAlO{sub 3} (001) substrates. Growth conditions for stoichiometric BaSnO{sub 3} were identified. Reflection high-energy electron diffraction (RHEED) intensity oscillations, characteristic of a layer-by-layer growth mode were observed. A critical thickness of ∼1 nm for strain relaxation was determined for films grown on SrTiO{sub 3} using in situ RHEED. Scanning transmission electron microscopy combined with electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy confirmed the cube-on-cube epitaxy and composition. The importance of precursor chemistry is discussed in the context of the MBE growth of BaSnO{sub 3}.

  19. Molecular beam epitaxial growth of tungsten layers embedded in single crystal gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Harbison, J.P.; Hwang, D.M.; Levkoff, J.; Derkits G.E. Jr.

    1985-12-01

    We have been able to fabricate structures which consist of a thin (approx.10 nm) polycrystalline W film embedded in surrounding single crystalline GaAs by molecular beam epitaxy (MBE) using an electron beam evaporation source to deposit W metal in an ultrahigh vacuum MBE growth chamber. The entire deposition sequence can take place at elevated temperature (625--700 /sup 0/C) due to the nonreactive nature of W with respect to GaAs. Reflective high-energy diffraction and transmission electron microscopy indicate that the single crystal GaAs overgrowth proceeds by seeding from the GaAs layer beneath the W through spontaneously occurring perforations in the W layer.

  20. Electron beam source molecular beam epitaxial growth of analog graded Al(x)Ga(1-x)As ballistic transistors

    Science.gov (United States)

    Malik, Roger J.; Levi, Anthony F. J.

    1988-01-01

    A new method has been developed for the growth of graded band-gap Al(x)Ga(1-x)As alloys by molecular beam epitaxy which is based upon electron beam evaporation of the group III elements. The metal fluxes are measured and feedback controlled using a modulated ion gauge sensor. The system is computer controlled which allows precise programming of the Ga and Al evaporation rates. The large dynamic response of the metal sources enables growth of variable band-gap III-V alloys with arbitrary composition profiles. This new technique is demonstrated by synthesis of analog graded Al(x)Ga(1-x)As unipolar ballistic electron transistors.

  1. Investigation of the silicon ion density during molecular beam epitaxy growth

    Science.gov (United States)

    Eifler, G.; Kasper, E.; Ashurov, Kh.; Morozov, S.

    2002-05-01

    Ions impinging on a surface during molecular beam epitaxy influence the growth and the properties of the growing layer, for example, suppression of dopant segregation and the generation of crystal defects. The silicon electron gun in the molecular beam epitaxy (MBE) equipment is used as a source for silicon ions. To use the effect of ion bombardment the mechanism of generation and distribution of ions was investigated. A monitoring system was developed and attached at the substrate position in the MBE growth chamber to measure the ion and electron densities towards the substrate. A negative voltage was applied to the substrate to modify the ion energy and density. Furthermore the current caused by charge carriers impinging on the substrate was measured and compared with the results of the monitoring system. The electron and ion densities were measured by varying the emission current of the e-gun achieving silicon growth rates between 0.07 and 0.45 nm/s and by changing the voltage applied to the substrate between 0 to -1000 V. The dependencies of ion and electron densities were shown and discussed within the framework of a simple model. The charged carrier densities measured with the monitoring system enable to separate the ion part of the substrate current and show its correlation to the generation rate. Comparing the ion density on the whole substrate and in the center gives a hint to the ion beam focusing effect. The maximum ion and electron current densities obtained were 0.40 and 0.61 μA/cm2, respectively.

  2. Molecular beam epitaxy growth and magnetic properties of Cr-Co-Ga Heusler alloy films

    Directory of Open Access Journals (Sweden)

    Wuwei Feng

    2015-11-01

    Full Text Available We have re-investigated growth and magnetic properties of Cr2CoGa films using molecular beam epitaxy technique. Phase separation and precipitate formation were observed experimentally again in agreement with observation of multiple phases separation in sputtered Cr2CoGa films by M. Meinert et al. However, significant phase separation could be suppressed by proper control of growth conditions. We showed that Cr2CoGa Heusler phase, rather than Co2CrGa phase, constitutes the majority of the sample grown on GaAs(001 at 450 oC. The measured small spin moment of Cr2CoGa is in agreement with predicted HM-FCF nature; however, its Curie temperature is not as high as expected from the theoretical prediction probably due to the off-stoichiometry of Cr2CoGa and the existence of the disorders and phase separation.

  3. Molecular beam epitaxy and metalorganic chemical vapor deposition growth of epitaxial CdTe on (100) GaAs/Si and (111) GaAs/Si substrates

    Science.gov (United States)

    Nouhi, A.; Radhakrishnan, G.; Katz, J.; Koliwad, K.

    1988-01-01

    Epitaxial CdTe has been grown on both (100)GaAs/Si and (111)GaAs/Si substrates. A combination of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has been employed for the first time to achieve this growth: the GaAs layers are grown on Si substrates by MBE and the CdTe film is subsequently deposited on GaAs/Si by MOCVD. The grown layers have been characterized by X-ray diffraction, scanning electron microscopy, and photoluminescence.

  4. Stochastic growth theory of molecular beam epitaxy with atom correlation effects: A Monte-Carlo master equation method

    Science.gov (United States)

    Nakayama, Hiroshi; Furuichi, Akihisa; Kita, Takashi; Nishino, Taneo

    1997-04-01

    Structural phase transition of epitaxial growing layer is quite important to understand the atomic scale mechanism of molecular beam epitaxy (MBE). GaAs and related alloy semiconductors are typical systems which show variety of such structural transitions during MBE. Structural evolution of surface reconstruction phases and an order-disorder transition in III-V alloy semiconductors are typical cases where such phase transitions appear during epitaxial processes. In this work, a stochastic theory and the Monte-Carlo simulation have been presented to describe the structural evolution of epitaxial growth in binary system. This method, known here as the 'Monte-Carlo master equation (MCME) method', couples a master equation for epitaxial growth kinetics with an Ising Hamiltonian of growing surface. The Monte-Carlo (MC) simulation of binary growing surface with atom-correlation effects has successfully revealed the evolution of atomic structure and the formation of short-range ordering (SRO) during epitaxy. This demonstrates the usefulness of the MCME method in describing the atomic-structural dynamics as compared with a conventional theory of epitaxy based on a diffusion equation and standard nucleation theory.

  5. Raman measurements of substrate temperature in a molecular beam epitaxy growth chamber.

    Science.gov (United States)

    Hutchins, T; Nazari, M; Eridisoorya, M; Myers, T M; Holtz, M

    2015-01-01

    A method is described for directly measuring the temperature of a substrate in a molecular-beam epitaxy (MBE) growth system. The approach relies on the establishment of the temperature dependence of Raman-active phonons of the substrate material using independently known calibration points across the range of interest. An unknown temperature in this range is then determined based on the Raman peak position with the substrate in situ the MBE chamber. The apparatus relies on conventional optics and Raman components. Shifting and broadening of the Raman spectrum are described based on the effects of thermal expansion and anharmonic decay. The choice of reference temperature is discussed. The method is qualified by examining the substrate temperature dependence, relative to that of a standard thermocouple, during a commonly used ramp procedure. Both temperature difference and time lag are obtained.

  6. Raman measurements of substrate temperature in a molecular beam epitaxy growth chamber

    Energy Technology Data Exchange (ETDEWEB)

    Hutchins, T.; Nazari, M.; Eridisoorya, M.; Myers, T. M.; Holtz, M., E-mail: Mark.Holtz@txstate.edu [Department of Physics, Texas State University, San Marcos, Texas 78666 (United States)

    2015-01-15

    A method is described for directly measuring the temperature of a substrate in a molecular-beam epitaxy (MBE) growth system. The approach relies on the establishment of the temperature dependence of Raman-active phonons of the substrate material using independently known calibration points across the range of interest. An unknown temperature in this range is then determined based on the Raman peak position with the substrate in situ the MBE chamber. The apparatus relies on conventional optics and Raman components. Shifting and broadening of the Raman spectrum are described based on the effects of thermal expansion and anharmonic decay. The choice of reference temperature is discussed. The method is qualified by examining the substrate temperature dependence, relative to that of a standard thermocouple, during a commonly used ramp procedure. Both temperature difference and time lag are obtained.

  7. Molecular Beam Epitaxy Growth of High Crystalline Quality LiNbO3

    Science.gov (United States)

    Tellekamp, M. Brooks; Shank, Joshua C.; Goorsky, Mark S.; Doolittle, W. Alan

    2016-12-01

    Lithium niobate is a multi-functional material with wide reaching applications in acoustics, optics, and electronics. Commercial applications for lithium niobate require high crystalline quality currently limited to bulk and ion sliced material. Thin film lithium niobate is an attractive option for a variety of integrated devices, but the research effort has been stagnant due to poor material quality. Both lattice matched and mismatched lithium niobate are grown by molecular beam epitaxy and studied to understand the role of substrate and temperature on nucleation conditions and material quality. Growth on sapphire produces partially coalesced columnar grains with atomically flat plateaus and no twin planes. A symmetric rocking curve shows a narrow linewidth with a full width at half-maximum (FWHM) of 8.6 arcsec (0.0024°), which is comparable to the 5.8 arcsec rocking curve FWHM of the substrate, while the film asymmetric rocking curve is 510 arcsec FWHM. These values indicate that the individual grains are relatively free of long-range disorder detectable by x-ray diffraction with minimal measurable tilt and twist and represents the highest structural quality epitaxial material grown on lattice mismatched sapphire without twin planes. Lithium niobate is also grown on lithium tantalate producing high quality coalesced material without twin planes and with a symmetric rocking curve of 193 arcsec, which is nearly equal to the substrate rocking curve of 194 arcsec. The surface morphology of lithium niobate on lithium tantalate is shown to be atomically flat by atomic force microscopy.

  8. Growth and characterization of GaAs layers on Si substrates by migration-enhanced molecular beam epitaxy

    Science.gov (United States)

    Kim, Jae-Hoon; Liu, John K.; Radhakrishnan, Gouri; Katz, Joseph; Sakai, Shiro

    1988-01-01

    Migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layer on Si substrates (GaAs/Si) are reported. The MEMBE growth method is described, and material properties are compared with those of normal two-step MBE-grown or in situ annealed layers. Micrographs of cross-section view transmission electron microscopy and scanning surface electron microscopy of MEMBE-grown GaAs/Si showed dislocation densities of 10 to the 7th/sq cm. AlGaAs/GaAs double heterostructures have been successfully grown on MEMBE GaAs/Si by both metalorganic chemical vapor deposition and liquid phase epitaxy.

  9. Graphitic platform for self-catalysed InAs nanowires growth by molecular beam epitaxy.

    Science.gov (United States)

    Zhuang, Qian D; Anyebe, Ezekiel A; Sanchez, Ana M; Rajpalke, Mohana K; Veal, Tim D; Zhukov, Alexander; Robinson, Benjamin J; Anderson, Frazer; Kolosov, Oleg; Fal'ko, Vladimir

    2014-01-01

    We report the self-catalysed growth of InAs nanowires (NWs) on graphite thin films using molecular beam epitaxy via a droplet-assisted technique. Through optimising metal droplets, we obtained vertically aligned InAs NWs with highly uniform diameter along their entire length. In comparison with conventional InAs NWs grown on Si (111), the graphite surface led to significant effects on the NWs geometry grown on it, i.e. larger diameter, shorter length with lower number density, which were ascribed to the absence of dangling bonds on the graphite surface. The axial growth rate of the NWs has a strong dependence on growth time, which increases quickly in the beginning then slows down after the NWs reach a length of approximately 0.8 μm. This is attributed to the combined axial growth contributions from the surface impingement and sidewall impingement together with the desorption of adatoms during the diffusion. The growth of InAs NWs on graphite was proposed following a vapour-solid mechanism. High-resolution transmission electron microscopy reveals that the NW has a mixture of pure zinc-blende and wurtzite insertions.

  10. Mapping growth windows in quaternary perovskite oxide systems by hybrid molecular beam epitaxy

    Science.gov (United States)

    Brahlek, Matthew; Zhang, Lei; Zhang, Hai-Tian; Lapano, Jason; Dedon, Liv R.; Martin, Lane W.; Engel-Herbert, Roman

    2016-09-01

    Requisite to growing stoichiometric perovskite thin films of the solid-solution A'1-xAxBO3 by hybrid molecular beam epitaxy is understanding how the growth conditions interpolate between the end members A'BO3 and ABO3, which can be grown in a self-regulated fashion, but under different conditions. Using the example of La1-xSrxVO3, the two-dimensional growth parameter space that is spanned by the flux of the metal-organic precursor vanadium oxytriisopropoxide and composition, x, was mapped out. The evolution of the adsorption-controlled growth window was obtained using a combination of X-ray diffraction, atomic force microscopy, reflection high-energy electron-diffraction (RHEED), and Rutherford backscattering spectroscopy. It is found that the stoichiometric growth conditions can be mapped out quickly with a single calibration sample using RHEED. Once stoichiometric conditions have been identified, the out-of-plane lattice parameter can be utilized to precisely determine the composition x. This strategy enables the identification of growth conditions that allow the deposition of stoichiometric perovskite oxide films with random A-site cation mixing, which is relevant to a large number of perovskite materials with interesting properties, e.g., high-temperature superconductivity and colossal magnetoresistance, that emerge in solid solution A'1-xAxBO3.

  11. Dynamic layer rearrangement during growth of layered oxide films by molecular beam epitaxy.

    Science.gov (United States)

    Lee, J H; Luo, G; Tung, I C; Chang, S H; Luo, Z; Malshe, M; Gadre, M; Bhattacharya, A; Nakhmanson, S M; Eastman, J A; Hong, H; Jellinek, J; Morgan, D; Fong, D D; Freeland, J W

    2014-09-01

    The A(n+1)B(n)O(3n+1) Ruddlesden-Popper homologous series offers a wide variety of functionalities including dielectric, ferroelectric, magnetic and catalytic properties. Unfortunately, the synthesis of such layered oxides has been a major challenge owing to the occurrence of growth defects that result in poor materials behaviour in the higher-order members. To understand the fundamental physics of layered oxide growth, we have developed an oxide molecular beam epitaxy system with in situ synchrotron X-ray scattering capability. We present results demonstrating that layered oxide films can dynamically rearrange during growth, leading to structures that are highly unexpected on the basis of the intended layer sequencing. Theoretical calculations indicate that rearrangement can occur in many layered oxide systems and suggest a general approach that may be essential for the construction of metastable Ruddlesden-Popper phases. We demonstrate the utility of the new-found growth strategy by performing the first atomically controlled synthesis of single-crystalline La3Ni2O7.

  12. Growth of SrVO{sub 3} thin films by hybrid molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, Craig; Brahlek, Matthew; Engel-Herbert, Roman, E-mail: rue2@psu.edu [Department of Material Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Moyer, Jarrett A. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Alipour, Hamideh M.; Grimley, Everett D.; LeBeau, James M. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-11-15

    The authors report the growth of stoichiometric SrVO{sub 3} thin films on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (001) substrates using hybrid molecular beam epitaxy. This growth approach employs a conventional effusion cell to supply elemental A-site Sr and the metalorganic precursor vanadium oxytriisopropoxide (VTIP) to supply vanadium. Oxygen is supplied in its molecular form through a gas inlet. An optimal VTIP:Sr flux ratio has been identified using reflection high-energy electron-diffraction, x-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy, demonstrating stoichiometric SrVO{sub 3} films with atomically flat surface morphology. Away from the optimal VTIP:Sr flux, characteristic changes in the crystalline structure and surface morphology of the films were found, enabling identification of the type of nonstoichiometry. For optimal VTIP:Sr flux ratios, high quality SrVO{sub 3} thin films were obtained with smallest deviation of the lattice parameter from the ideal value and with atomically smooth surfaces, indicative of the good cation stoichiometry achieved by this growth technique.

  13. Improvement of the crystallinity of CdTe epitaxial film grown on Si substrates by molecular beam epitaxy using the two-step growth method

    Energy Technology Data Exchange (ETDEWEB)

    Han, M.S.; Ryu, Y.S.; Song, B.K.; Kang, T.W. [Dongguk Univ., Seoul (Korea, Republic of). Dept. of Phys.; Kim, T.W. [Department of Physics, Kwangwoon University, Seoul 139-701 (Korea, Republic of)

    1997-01-05

    Molecular beam epitaxy growth of CdTe epitaxial layers on Si (100) substrates using the two-step growth method was performed to produce high-quality CdTe thin layers. The reflection high-energy electron diffraction patterns were streaky with clear Kikuchi lines, which is direct evidence for layer-by-layer two-dimensional growth of CdTe on Si. From the X-ray diffraction analysis, the grown layer was found to be a CdTe (111) epitaxial film, regardless of the film thickness. Photoluminescence (PL) measurements at 12 K showed that the defect density of the CdTe film grown on Si using two-step growth decreased in comparison with that grown using direct growth. The bound exciton appearing in the PL measurements shifted to the low energy side as the thickness of the CdTe increased. When the CdTe thickness increased from 1 to 1.8 {mu}m, the peak position of the bound exciton shifted by 7.2 meV, and the stress obtained from the exciton peak shift was -12.405 kbar. These results indicate that high quality CdTe films grown by two-step growth hold promise for applications as buffer layers for the subsequent growth of Hg{sub x}Cd{sub 1-x}Te. (orig.) 16 refs.

  14. Growth window and effect of substrate symmetry in hybrid molecular beam epitaxy of a Mott insulating rare earth titanate

    Energy Technology Data Exchange (ETDEWEB)

    Moetakef, Pouya; Zhang, Jack Y.; Raghavan, Santosh; Kajdos, Adam P.; Stemmer, Susanne [Materials Department, University of California, Santa Barbara, California, 93106-5050 (United States)

    2013-07-15

    The conditions for the growth of stoichiometric GdTiO{sub 3} thin films by molecular beam epitaxy (MBE) are investigated. It is shown that relatively high growth temperatures (>750 Degree-Sign C) are required to obtain an MBE growth window in which only the stoichiometric film grows for a range of cation flux ratios. This growth window narrows with increasing film thickness. It is also shown that single-domain films are obtained by the growth on a symmetry-matched substrate. The influence of lattice mismatch strain on the electrical and magnetic characteristics of the GdTiO{sub 3} thin film is investigated.

  15. Molecular beam epitaxy growth and magnetic properties of Cr-Co-Ga Heusler alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Wuwei, E-mail: wfeng@cugb.edu.cn; Wang, Weihua [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Zhao, Chenglong [Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Van Quang, Nguyen; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Dung, Dang Duc [Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet Road, Ha Noi (Viet Nam)

    2015-11-15

    We have re-investigated growth and magnetic properties of Cr{sub 2}CoGa films using molecular beam epitaxy technique. Phase separation and precipitate formation were observed experimentally again in agreement with observation of multiple phases separation in sputtered Cr{sub 2}CoGa films by M. Meinert et al. However, significant phase separation could be suppressed by proper control of growth conditions. We showed that Cr{sub 2}CoGa Heusler phase, rather than Co{sub 2}CrGa phase, constitutes the majority of the sample grown on GaAs(001) at 450 {sup o}C. The measured small spin moment of Cr{sub 2}CoGa is in agreement with predicted HM-FCF nature; however, its Curie temperature is not as high as expected from the theoretical prediction probably due to the off-stoichiometry of Cr{sub 2}CoGa and the existence of the disorders and phase separation.

  16. Growth of uniform CaGe2 films by alternating layer molecular beam epitaxy

    Science.gov (United States)

    Xu, Jinsong; Katoch, Jyoti; Ahmed, Adam S.; Pinchuk, Igor V.; Young, Justin R.; Johnston-Halperin, Ezekiel; Pelz, Jonathan; Kawakami, Roland K.

    2017-02-01

    Layered Zintl phase van der Waals (vdW) materials are of interest due to their strong spin-orbit coupling and potential for high mobility. Here, we report the successful growth of large area CaGe2 films, as a model of layered Zintl phase materials, on atomically flat Ge(111) substrates by molecular beam epitaxy (MBE) using an alternating layer growth (ALG) protocol. Reflection high energy electron diffraction (RHEED) patterns of the Ge buffer layer and CaGe2 indicate high quality two dimensional surfaces, which is further confirmed by atomic force microscopy (AFM), showing atomically flat and uniform CaGe2 films. The appearance of Laue oscillations in X-ray diffraction (XRD) and Kiessig fringes in the X-ray reflectivity (XRR), which are absent in co-deposited CaGe2, confirms the uniformity of the CaGe2 film and the smoothness of the interface. These results demonstrate a novel method of deposition of CaGe2 that could be also applied to other layered Zintl phase vdW materials. Also, the high quality of the CaGe2 film is promising for the exploration of novel properties of germanane.

  17. Strain relief and growth optimization of GaSb on GaP by molecular beam epitaxy.

    Science.gov (United States)

    Wang, Y; Ruterana, P; Chen, J; Desplanque, L; El Kazzi, S; Wallart, X

    2012-08-22

    In this paper, the impact of growth parameters on the strain relaxation of highly lattice mismatched (11.8%) GaSb grown on GaP substrate by molecular beam epitaxy has been investigated. The surface morphology, misfit dislocation and strain relaxation of the GaSb islands are shown to be highly related to the initial surface treatment, growth rate and temperature. More specifically, Sb-rich surface treatment is shown to promote the formation of Lomer misfit dislocations. Analysis of the misfit dislocation and strain relaxation as functions of the growth temperature and rate led to an optimal growth window for a high quality GaSb epitaxial layer on (001) GaP. With this demonstrated optimized growth, a high mobility (25,500 cm(2) V (-1) s(-1) at room temperature) AlSb/InAs heterostructure on a semi-insulating (001) GaP substrate has been achieved.

  18. Molecular beam epitaxy a short history

    CERN Document Server

    Orton, J W

    2015-01-01

    This volume describes the development of molecular beam epitaxy from its origins in the 1960s through to the present day. It begins with a short historical account of other methods of crystal growth, both bulk and epitaxial, to set the subject in context, emphasising the wide range of semiconductor materials employed. This is followed by an introduction to molecular beams and their use in the Stern-Gerlach experiment and the development of the microwave MASER.

  19. Growth and structural characterization of III-V nanowires grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dheeraj, D.L.

    2010-10-15

    Heterostructured semiconductor nanowires (NWs) have attracted considerable attention in recent years because of their potential in future nano-electronic and nano-photonic device applications. NWs are usually grown by vapor-liquid-solid (VLS) growth mechanism using techniques such as metal-organic vapor phase epitaxy, chemical beam epitaxy and molecular beam epitaxy (MBE). Of all the available techniques, MBE is known to be the technique which yields highest purity materials. In this study, the growth of GaAs NWs, GaAsSb NWs, as well as GaAs/GaAsSb axial and GaAs/AlGaAs radial heterostructured NWs on GaAs(111)B substrates by MBE is demonstrated. The structural and optical properties of the NWs grown are characterized by electron microscopy techniques such as scanning and transmission electron microscopy, and micro-photoluminescence, respectively. Firstly, the optimum growth conditions to obtain rod shaped GaAs NWs on GaAs(111)B substrates by MBE is determined. It has been found that in-addition to the V/III ratio and substrate temperature, buffer growth conditions also play an important role on the orientation of the NWs. The effect of V/III ratio, substrate temperature, and the arsenic species (As{sub 2}/As{sub 4}) on the morphology of GaAs NWs has been determined. Transmission electron microscopy (TEM) characterization of NWs revealed that GaAs in NW form exhibit wurtzite (WZ) crystal phase in contrast to zinc blende (ZB) phase adapted in its bulk form. Since WZ crystal phase is a metastable phase of GaAs, the WZ GaAs NWs often exhibit stacking faults. The stacking faults are known to be a detrimental problem, if not properly controlled. To gain more insight on the growth kinetics of GaAs NWs grown by MBE, several samples such as GaAs NWs grown for different time durations, and GaAs NWs with three GaAsSb inserts, where GaAsSb inserts acts as markers, have been grown. Interestingly, the growth rates of the GaAs segments and GaAsSb inserts were observed to vary

  20. Growth map for Ga-assisted growth of GaAs nanowires on Si(111) substrates by molecular beam epitaxy.

    Science.gov (United States)

    Bastiman, Faebian; Küpers, Hanno; Somaschini, Claudio; Geelhaar, Lutz

    2016-03-04

    For the Ga-assisted growth of GaAs nanowires on Si(111) substrates by molecular beam epitaxy, growth temperature, As flux, and Ga flux have been systematically varied across the entire window of growth conditions that result in the formation of nanowires. A range of GaAs structures was observed, progressing from pure Ga droplets under negligible As flux through horizontal nanowires, tilted nanowires, vertical nanowires, and nanowires without droplets to crystallites as the As flux was increased. Quantitative analysis of the resulting sample morphology was performed in terms of nanowire number and volume density, number yield and volume yield of vertical nanowires, diameter, length, as well as the number and volume density of parasitic growth. The result is a growth map that comprehensively describes all nanowire and parasitic growth morphologies and hence enables growth of nanowire samples in a predictive manner. Further analysis indicates the combination of global Ga flux and growth temperature determines the total density of all objects, whereas the global As/Ga flux ratio independently determines the resultant sample morphology. Several dependencies observed here imply that all objects present on the substrate surface, i.e. both nanowires and parasitic structures, originate from Ga droplets.

  1. Laser Molecular Beam Epitaxy Growth of BaTiO3 in Seven Thousands of Unit-Cell Layers

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan-Hong; YANG Guo-Zhen; HE Meng; ZHAO Kun; TIAN Huan-Fang; L(U) Hui-Bin; JIN Kui-Juan; CHEN Zheng-Hao; ZHOU Yue-Liang; LI Jian-Qi

    2005-01-01

    @@ BaTiO3 thin films in seven thousands of unit-cell layers have been successfully fabricated on SrTiO3 (001)substrates by laser molecular beam epitaxy. The fine streak pattern and the undamping intensity oscillation of reflection high-energy electron diffraction indicate that the BaTiO3 film was layer-by-layer epitaxial growth. The measurements of scanning electron microscopy and atomic force microscopy show that surfaces of the BaTiO3thin film are atomically smooth. The measurements of x-ray diffraction and transmission electron microscopy,as well as selected-area electron diffraction revealthat the BaTiO3 thin film is a c-oriented epitaxial crystalline structure.

  2. Thin film growth of CaFe2As2 by molecular beam epitaxy

    Science.gov (United States)

    Hatano, T.; Kawaguchi, T.; Fujimoto, R.; Nakamura, I.; Mori, Y.; Harada, S.; Ujihara, T.; Ikuta, H.

    2016-01-01

    Film growth of CaFe2As2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe2As2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch.

  3. High active nitrogen flux growth of GaN by plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    McSkimming, Brian M., E-mail: mcskimming@engineering.ucsb.edu; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Chaix, Catherine [RIBER S.A., 3a Rue Casimir Périer, BP 70083, 95873 Bezons Cedex (France)

    2015-09-15

    In the present study, the authors report on a modified Riber radio frequency (RF) nitrogen plasma source that provides active nitrogen fluxes more than 30 times higher than those commonly used for plasma assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N{sub 2} gas flow rates between 5 and 25 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux, achieved was ∼7.6 μm/h. For optimized growth conditions, the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 × 3 μm) on the order of 1 nm. Secondary ion mass spectroscopy impurity analysis demonstrates oxygen and hydrogen incorporation of 1 × 10{sup 16} and ∼5 × 10{sup 17}, respectively. In addition, the authors have achieved PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ∼100 °C greater than any previously reported PAMBE growth of GaN. This growth temperature corresponds to GaN decomposition in vacuum of more than 20 nm/min; a regime previously unattainable with conventional nitrogen plasma sources. Arrhenius analysis of the decomposition rate shows that samples with a flux ratio below stoichiometry have an activation energy greater than decomposition of GaN in vacuum while samples grown at or above stoichiometry have decreased activation energy. The activation energy of decomposition for GaN in vacuum was previously determined to be ∼3.1 eV. For a Ga/N flux ratio of ∼1.5, this activation energy was found to be ∼2.8 eV, while for a Ga/N flux ratio of ∼0.5, it was found to be ∼7.9 eV.

  4. Molecular beam epitaxial growth and structural characterization of ZnS on (001) GaAs

    Science.gov (United States)

    Benz, R. G., II; Huang, P. C.; Stock, S. R.; Summers, C. J.

    1988-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as assessed by X-ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  5. Nucleation, Growth, and Bundling of GaN Nanowires in Molecular Beam Epitaxy: Disentangling the Origin of Nanowire Coalescence.

    Science.gov (United States)

    Kaganer, Vladimir M; Fernández-Garrido, Sergio; Dogan, Pinar; Sabelfeld, Karl K; Brandt, Oliver

    2016-06-08

    We investigate the nucleation, growth, and coalescence of spontaneously formed GaN nanowires in molecular beam epitaxy combining the statistical analysis of scanning electron micrographs with Monte Carlo growth models. We find that (i) the nanowire density is limited by the shadowing of the substrate from the impinging fluxes by already existing nanowires, (ii) shortly after the nucleation stage, nanowire radial growth becomes negligible, and (iii) coalescence is caused by bundling of nanowires. The latter phenomenon is driven by the gain of surface energy at the expense of the elastic energy of bending and becomes energetically favorable once the nanowires exceed a certain critical length.

  6. In silico carbon molecular beam epitaxial growth of graphene on the h-BN substrate: carbon source effect on van der Waals epitaxy

    Science.gov (United States)

    Lee, Jonghoon; Varshney, Vikas; Park, Jeongho; Farmer, Barry L.; Roy, Ajit K.

    2016-05-01

    Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon molecular beam epitaxy (CMBE) techniques using solid carbon sublimation have reported relatively poor quality of the graphene. In this article, the CMBE growth of graphene on the h-BN substrate is numerically studied in order to identify the effect of the carbon source on the quality of the graphene film. The carbon molecular beam generated by the sublimation of solid carbon source materials such as graphite and glassy carbon is mostly composed of atomic carbon, carbon dimers and carbon trimers. Therefore, the graphene film growth becomes a complex process involving various deposition characteristics of a multitude of carbon entities. Based on the study of surface adsorption and film growth characteristics of these three major carbon entities comprising graphite vapour, we report that carbon trimers convey strong traits of vdW epitaxy prone to high quality graphene growth, while atomic carbon deposition is a surface-reaction limited process accompanied by strong chemisorption. The vdW epitaxial behaviour of carbon trimers is found to be substantial enough to nucleate and develop into graphene like planar films within a nanosecond of high flux growth simulation, while reactive atomic carbons tend to impair the structural integrity of the crystalline h-BN substrate upon deposition to form an amorphous interface between the substrate and the growing carbon film. The content of reactive atomic carbons in the molecular beam is suspected to be the primary cause of low quality graphene reported in the literature. A possible optimization of the molecular beam composition towards the synthesis of better quality graphene films is suggested.Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon

  7. Growth and characterization of molecular beam epitaxial GaAs layers on porous silicon

    Science.gov (United States)

    Lin, T. L.; Liu, J. K.; Sadwick, L.; Wang, K. L.; Kao, Y. C.

    1987-01-01

    GaAs layers have been grown on porous silicon (PS) substrates with good crystallinity by molecular beam epitaxy. In spite of the surface irregularity of PS substrates, no surface morphology deterioration was observed on epitaxial GaAs overlayers. A 10-percent Rutherford backscattering spectroscopy minimum channeling yield for GaAs-on-PS layers as compared to 16 percent for GaAs-on-Si layers grown under the same condition indicates a possible improvement of crystallinity when GaAs is grown on PS. Transmission electron microscopy reveals that the dominant defects in the GaAs-on-PS layers are microtwins and stacking faults, which originate from the GaAs/PS interface. GaAs is found to penetrate into the PS layers. n-type GaAs/p-type PS heterojunction diodes were fabricated with good rectifying characteristics.

  8. Growth of GaSb1-xBix by molecular beam epitaxy

    DEFF Research Database (Denmark)

    Song, Yuxin; Wang, Shumin; Roy, Ivy Saha;

    2012-01-01

    Molecular beam epitaxy for GaSb1-xBix is investigated in this article. The growth window for incorporation of Bi in GaSb was found. Strategies of avoiding formation of Bi droplets and enhancing Bi incorporation were studied. The Bi incorporation was confirmed by SIMS and RBS measurements. The Bi...... concentration in the samples was found to increase with increasing growth temperature and Bi flux. The position of GaSb1-xBix layer peak in XRD rocking curves is found to be correlated to Bi composition. Surface and structural properties of the samples were also investigated. Samples grown on GaSb and Ga...

  9. Effect of N2 microplasma treatment on initial growth of GaN by metal-organic molecular beam epitaxy

    Science.gov (United States)

    Suzuki, Yohei; Kusakabe, Yasuhiro; Uchiyama, Shota; Maruyama, Takahiro; Naritsuka, Shigeya; Shimizu, Kazuo

    2016-08-01

    N2 atmospheric microplasma was applied to improve the yields and reproducibility of the initial growth of GaN by metal-organic molecular beam epitaxy (MOMBE). The plasma treatment was found to be effective in cleaning the surface, and excellent flat growth was achieved even in the early stage of the growth. The effect of the air exposure after plasma treatment was also studied, and the yield of the growth was found to be largely decreased by the air exposure even after the treatment. Therefore, the oxidation of the substrate is one of main causes of the poor initial growth and the installation of the microplasma equipment in the MBE loading chamber is useful for suppressing the oxidation after the treatment. Atomic force microscopy (AFM) measurement shows that the microplasma treatment is also effective for undoing the surface double steps through etching, which is helpful for a very smooth layer-by-layer growth in the early stage of growth.

  10. Patterned growth of InGaN/GaN quantum wells on freestanding GaN grating by molecular beam epitaxy

    OpenAIRE

    Wang Yongjin; Hu Fangren; Hane Kazuhiro

    2011-01-01

    Abstract We report here the epitaxial growth of InGaN/GaN quantum wells on freestanding GaN gratings by molecular beam epitaxy (MBE). Various GaN gratings are defined by electron beam lithography and realized on GaN-on-silicon substrate by fast atom beam etching. Silicon substrate beneath GaN grating region is removed from the backside to form freestanding GaN gratings, and the patterned growth is subsequently performed on the prepared GaN template by MBE. The selective growth takes place wit...

  11. Growth of layered superconductor β-PdBi2 films using molecular beam epitaxy

    Science.gov (United States)

    Denisov, N. V.; Matetskiy, A. V.; Tupkalo, A. V.; Zotov, A. V.; Saranin, A. A.

    2017-04-01

    Bulk β-PdBi2 layered material exhibits advanced properties and is supposed to be probable topological superconductor. We present a method based on molecular beam epitaxy that allows us to grow β-PdBi2 films from a single β-PdBi2 triple layer up to the dozens of triple layers, using Bi(111) film on Si(111) as a template. The grown films demonstrate structural, electronic and superconducting properties similar to those of bulk β-PdBi2 crystals. Ability to grow the β-PdBi2 films of desired thickness opens the promising possibilities to explore fascinating properties of this advanced material.

  12. High Growth Rate Metal-Organic Molecular Beam Epitaxy for the Fabrication of GaAs Space Solar Cells

    Science.gov (United States)

    Freundlich, A.; Newman, F.; Monier, C.; Street, S.; Dargan, P.; Levy, M.

    2005-01-01

    In this work it is shown that high quality GaAs photovoltaic devices can be produced by Molecular Beam Epitaxy (MBE) with growth rates comparable to metal-organic chemical vapor deposition (MOCVD) through the subsitution of group III solid sources by metal-organic compounds. The influence the III/V flux-ratio and growth temperatures in maintaining a two dimensional layer by layer growth mode and achieving high growth rates with low residual background impurities is investigated. Finally subsequent to the study of the optimization of n- and p doping of such high growth rate epilayers, results from a preliminary attempt in the fabrication of GaAs photovoltaic devices such as tunnel diodes and solar cells using the proposed high growth rate approach are reported.

  13. Molecular beam epitaxial growth of a three-dimensional topological Dirac semimetal Na{sub 3}Bi

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yi, E-mail: YiZhang@lbl.gov [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Stanford Institute of Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Liu, Zhongkai; Shen, Zhi-Xun [Stanford Institute of Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305 (United States); Zhou, Bo [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305 (United States); Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Kim, Yeongkwan; Hussain, Zahid; Mo, Sung-Kwan, E-mail: SKMo@lbl.gov [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Chen, Yulin [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2014-07-21

    We report a molecular beam epitaxial growth of Na{sub 3}Bi single-crystal thin films on two different substrates—epitaxial bilayer graphene terminated 6H-SiC(0001) and Si(111). Using reflection high-energy electron diffraction, we found that the lattice orientation of the grown Na{sub 3}Bi thin film was rotated by 30° respect to the surface lattice orientations of these two substrates. An in-situ angle-resolved photoemission spectroscopy clearly revealed the 3-dimensional Dirac-cone band structure in such thin films. Our approach of growing Na{sub 3}Bi thin film provides a potential route for further studying its intriguing electronic properties and for fabricating it into practical devices in future.

  14. Improved control over spontaneously formed GaN nanowires in molecular beam epitaxy using a two-step growth process.

    Science.gov (United States)

    Zettler, J K; Corfdir, P; Geelhaar, L; Riechert, H; Brandt, O; Fernández-Garrido, S

    2015-11-06

    We investigate the influence of modified growth conditions during the spontaneous formation of GaN nanowires (NWs) on Si(111) in plasma-assisted molecular beam epitaxy. We find that a two-step growth approach, where the substrate temperature is increased during the nucleation stage, is an efficient method to gain control over the area coverage, average diameter, and coalescence degree of GaN NW ensembles. Furthermore, we also demonstrate that the growth conditions employed during the incubation time that precedes nanowire nucleation do not influence the properties of the final nanowire ensemble. Therefore, when growing GaN NWs at elevated temperatures or with low Ga/N ratios, the total growth time can be reduced significantly by using more favorable growth conditions for nanowire nucleation during the incubation time.

  15. Determination of Kinetic Parameters of Molecular Beam Epitaxy,

    Science.gov (United States)

    1985-04-17

    A kinetic growth model for molecular beam epitaxy (MBE) was discussed. Furthermore, high energy electron diffraction (HEED) was used as a surface...characterization method to provide evidence for this model. GaAs was used as an example to study the growth rate of molecular beam epitaxy . The relation

  16. Chemical beam epitaxy growth of AlGaAs/GaAs tunnel junctions using trimethyl aluminium for multijunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paquette, B.; DeVita, M.; Turala, A.; Kolhatkar, G.; Boucherif, A.; Jaouad, A.; Aimez, V.; Arès, R. [Institut Interdisciplinaire d' Innovation Technologique (3IT), Université de Sherbrooke, Sherbrooke, Québec (Canada); Wilkins, M.; Wheeldon, J. F.; Walker, A. W.; Hinzer, K. [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada); Fafard, S. [Cyrium Technologies Inc., Ottawa, ON (Canada)

    2013-09-27

    AlGaAs/GaAs tunnel junctions for use in high concentration multijunction solar cells were designed and grown by chemical beam epitaxy (CBE) using trimethyl aluminium (TMA) as the p-dopant source for the AlGaAs active layer. Controlled hole concentration up to 4⋅10{sup 20} cm{sup −3} was achieved through variation in growth parameters. Fabricated tunnel junctions have a peak tunneling current up to 6140 A/cm{sup 2}. These are suitable for high concentration use and outperform GaAs/GaAs tunnel junctions.

  17. Growth of GaN nanowall network on Si (111) substrate by molecular beam epitaxy.

    Science.gov (United States)

    Zhong, Aihua; Hane, Kazuhiro

    2012-12-27

    GaN nanowall network was epitaxially grown on Si (111) substrate by molecular beam epitaxy. GaN nanowalls overlap and interlace with one another, together with large numbers of holes, forming a continuous porous GaN nanowall network. The width of the GaN nanowall can be controlled, ranging from 30 to 200 nm by adjusting the N/Ga ratio. Characterization results of a transmission electron microscope and X-ray diffraction show that the GaN nanowall is well oriented along the C axis. Strong band edge emission centered at 363 nm is observed in the spectrum of room temperature photoluminescence, indicating that the GaN nanowall network is of high quality. The sheet resistance of the Si-doped GaN nanowall network along the lateral direction was 58 Ω/. The conductive porous nanowall network can be useful for integrated gas sensors due to the large surface area-to-volume ratio and electrical conductivity along the lateral direction by combining with Si micromachining.

  18. Critical issues for homoepitaxial GaN growth by molecular beam epitaxy on hydride vapor-phase epitaxy-grown GaN substrates

    Science.gov (United States)

    Storm, D. F.; Hardy, M. T.; Katzer, D. S.; Nepal, N.; Downey, B. P.; Meyer, D. J.; McConkie, Thomas O.; Zhou, Lin; Smith, David J.

    2016-12-01

    While the heteroepitaxial growth of gallium nitride-based materials and devices on substrates such as SiC, sapphire, and Si has been well-documented, the lack of a cost-effective source of bulk GaN crystals has hindered similar progress on homoepitaxy. Nevertheless, freestanding GaN wafers are becoming more widely available, and there is great interest in growing GaN films and devices on bulk GaN substrates, in order to take advantage of the greatly reduced density of threading dislocations, particularly for vertical devices. However, homoepitaxial GaN growth is far from a trivial task due to the reactivity and different chemical sensitivities of N-polar (000_1) and Ga-polar (0001) GaN surfaces, which can affect the microstructure and concentrations of impurities in homoepitaxial GaN layers. In order to achieve high quality, high purity homoepitaxial GaN, it is necessary to investigate the effect of the ex situ wet chemical clean, the use of in situ cleaning procedures, the sensitivity of the GaN surface to thermal decomposition, and the effect of growth temperature. We review the current understanding of these issues with a focus on homoepitaxial growth of GaN by molecular beam epitaxy (MBE) on c-plane surfaces of freestanding GaN substrates grown by hydride vapor phase epitaxy (HVPE), as HVPE-grown substrates are most widely available. We demonstrate methods for obtaining homoepitaxial GaN layers by plasma-assisted MBE in which no additional threading dislocations are generated from the regrowth interface and impurity concentrations are greatly reduced.

  19. Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Satapathy, D.K.

    2005-12-19

    The present work is devoted to the growth of the ferromagnetic metal MnAs on the semiconductor GaAs by molecular-beam epitaxy (MBE). The MnAs thin films are deposited on GaAs by molecular-beam epitaxy (MBE). Grazing incidence diffraction (GID) and reflection high-energy electron diffraction (RHEED) are used in situ to investigate the nucleation, evolution of strain, morphology and interfacial structure during the MBE growth. Four stages of the nucleation process during growth of MnAs on GaAs(001) are revealed by RHEED azimuthal scans. GID shows that further growth of MnAs films proceed via the formation of relaxed islands at a nominal thickness of 2.5 ML which increase in size and finally coalesce to form a continuous film. Early on, an ordered array of misfit dislocations forms at the interface releasing the misfit strain even before complete coalescence occurs. The fascinating complex nucleation process of MnAs on GaAs(0 0 1) contains elements of both Volmer-Weber and Stranski-Krastanov growth. A nonuniform strain amounting to 0.66%, along the [1 -1 0] direction and 0.54%, along the [1 1 0] direction is demonstrated from x-ray line profile analysis. A high correlation between the defects is found along the GaAs[1 1 0] direction. An extremely periodic array of misfit dislocations with a period of 4.95{+-}0.05 nm is formed at the interface along the [1 1 0] direction which releases the 7.5% of misfit. The inhomogeneous strain due to the periodic dislocations is confined at the interface within a layer of 1.6 nm thickness. The misfit along the [1 -1 0] direction is released by the formation of a coincidence site lattice. (orig.)

  20. Position-controlled growth of GaN nanowires and nanotubes on diamond by molecular beam epitaxy.

    Science.gov (United States)

    Schuster, Fabian; Hetzl, Martin; Weiszer, Saskia; Garrido, Jose A; de la Mata, María; Magen, Cesar; Arbiol, Jordi; Stutzmann, Martin

    2015-03-11

    In this work the position-controlled growth of GaN nanowires (NWs) on diamond by means of molecular beam epitaxy is investigated. In terms of growth, diamond can be seen as a model substrate, providing information of systematic relevance also for other substrates. Thin Ti masks are structured by electron beam lithography which allows the fabrication of perfectly homogeneous GaN NW arrays with different diameters and distances. While the wurtzite NWs are found to be Ga-polar, N-polar nucleation leads to the formation of tripod structures with a zinc-blende core which can be efficiently suppressed above a substrate temperature of 870 °C. A variation of the III/V flux ratio reveals that both axial and radial growth rates are N-limited despite the globally N-rich growth conditions, which is explained by the different diffusion behavior of Ga and N atoms. Furthermore, it is shown that the hole arrangement has no effect on the selectivity but can be used to force a transition from nanowire to nanotube growth by employing a highly competitive growth regime.

  1. Patterned growth of InGaN/GaN quantum wells on freestanding GaN grating by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Wang Yongjin

    2011-01-01

    Full Text Available Abstract We report here the epitaxial growth of InGaN/GaN quantum wells on freestanding GaN gratings by molecular beam epitaxy (MBE. Various GaN gratings are defined by electron beam lithography and realized on GaN-on-silicon substrate by fast atom beam etching. Silicon substrate beneath GaN grating region is removed from the backside to form freestanding GaN gratings, and the patterned growth is subsequently performed on the prepared GaN template by MBE. The selective growth takes place with the assistance of nanoscale GaN gratings and depends on the grating period P and the grating width W. Importantly, coalescences between two side facets are realized to generate epitaxial gratings with triangular section. Thin epitaxial gratings produce the promising photoluminescence performance. This work provides a feasible way for further GaN-based integrated optics devices by a combination of GaN micromachining and epitaxial growth on a GaN-on-silicon substrate. PACS 81.05.Ea; 81.65.Cf; 81.15.Hi.

  2. Molecular Beam Epitaxial Growth of ZnO on Si Substrate Using Ozone as an Oxygen Source

    Science.gov (United States)

    Fujita, Miki; Kawamoto, Noriaki; Tatsumi, Tomohiko; Yamagishi, Katsumi; Horikoshi, Yoshiji

    2003-01-01

    Epitaxial ZnO films have been grown on Si (111) substrates by molecular beam epitaxy using ozone as an oxygen source. An initial deposition of a Zn layer followed by its oxidation produces a superior template for the subsequent ZnO growth. The reflection high-energy electron diffraction measurement suggests that the initial Zn layer and ZnO film are rotated by 30° with respect to the Si substrate orientation. The X-ray diffraction measurement reveals that the as-grown ZnO films are strongly c-oriented and include no rotational domains. Although there exists a small trace of ZnO (10\\bar{1}1) domains, it easily disappears upon annealing at 1100°C for 1 min after growth. Low-temperature photoluminescence measurements indicate that the emission property is improved significantly after annealing. The bound-exciton emission at 3.354 eV is dominant and its full-width at half maximum is as small as 11 meV.

  3. Shadowing and mask opening effects during selective-area vapor-liquid-solid growth of InP nanowires by metalorganic molecular beam epitaxy.

    Science.gov (United States)

    Kelrich, A; Calahorra, Y; Greenberg, Y; Gavrilov, A; Cohen, S; Ritter, D

    2013-11-29

    Indium phosphide nanowires were grown by metalorganic molecular beam epitaxy using the selective-area vapor-liquid-solid method. We show experimentally and theoretically that the size of the annular opening around the nanowire has a major impact on nanowire growth rate. In addition, we observed a considerable reduction of the growth rate in dense two-dimensional arrays, in agreement with a calculation of the shadowing of the scattered precursors. Due to the impact of these effects on growth, they should be considered during selective-area vapor-liquid-solid nanowire epitaxy.

  4. Plasma-assisted molecular beam epitaxy growth of ZnSnN2

    Science.gov (United States)

    Feldberg, Nathaniel; Aldous, James; Yao, Yuan; Tanveer, Imtiaz; Keen, Benjamin; Linhart, Wojciech; Veal, Tim; Song, Young-Wook; Reeves, Roger; Durbin, Steve

    2012-02-01

    The Zn-IV-nitrides are a promising series of ``earth abundant element'' semiconductors with a predicted band gap range of 0.6 eV to 5.4 eV, which, like the (Al,Ga,In)N family, spans the entire visible solar spectrum. Considering this alternative family has a number of advantages, including the avoidance of indium, the price of which has varied almost an order of magnitude over the past decade, and surface electron accumulation which is present in the In-rich alloys. Not all members of this family have yet been synthesized, in particular ZnSnN2, the most important member for PV with its predicted band gap of approximately 2 eV. We have successfully grown a series of these films using plasma-assisted molecular beam epitaxy using elemental Zn and Sn sources. In this report, we discuss the relationship between process parameters and microstructure, as well as stoichiometry as determined by Rutherford backscattering spectrometry. Additionally, we provide preliminary estimates for its bandgap energy based on photoluminescence and optical absorption.

  5. Numerical approximations for the molecular beam epitaxial growth model based on the invariant energy quadratization method

    Science.gov (United States)

    Yang, Xiaofeng; Zhao, Jia; Wang, Qi

    2017-03-01

    The Molecular Beam Epitaxial model is derived from the variation of a free energy, that consists of either a fourth order Ginzburg-Landau double well potential or a nonlinear logarithmic potential in terms of the gradient of a height function. One challenge in solving the MBE model numerically is how to develop proper temporal discretization for the nonlinear terms in order to preserve energy stability at the time-discrete level. In this paper, we resolve this issue by developing a first and second order time-stepping scheme based on the "Invariant Energy Quadratization" (IEQ) method. The novelty is that all nonlinear terms are treated semi-explicitly, and the resulted semi-discrete equations form a linear system at each time step. Moreover, the linear operator is symmetric positive definite and thus can be solved efficiently. We then prove that all proposed schemes are unconditionally energy stable. The semi-discrete schemes are further discretized in space using finite difference methods and implemented on GPUs for high-performance computing. Various 2D and 3D numerical examples are presented to demonstrate stability and accuracy of the proposed schemes.

  6. Atomic Layer Epitaxy of h-BN(0001) Multilayers on Co(0001) and Molecular Beam Epitaxy Growth of Graphene on h-BN(0001)/Co(0001).

    Science.gov (United States)

    Driver, M Sky; Beatty, John D; Olanipekun, Opeyemi; Reid, Kimberly; Rath, Ashutosh; Voyles, Paul M; Kelber, Jeffry A

    2016-03-22

    The direct growth of hexagonal boron nitride (h-BN) by industrially scalable methods is of broad interest for spintronic and nanoelectronic device applications. Such applications often require atomically precise control of film thickness and azimuthal registry between layers and substrate. We report the formation, by atomic layer epitaxy (ALE), of multilayer h-BN(0001) films (up to 7 monolayers) on Co(0001). The ALE process employs BCl3/NH3 cycles at 600 K substrate temperature. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that this process yields an increase in h-BN average film thickness linearly proportional to the number of BCl3/NH3 cycles, with BN layers in azimuthal registry with each other and with the Co(0001) substrate. LEED diffraction spot profile data indicate an average BN domain size of at least 1900 Å. Optical microscopy data indicate the presence of some domains as large as ∼20 μm. Transmission electron microscopy (TEM) and ambient exposure studies demonstrate macroscopic and microscopic continuity of the h-BN film, with the h-BN film highly conformal to the Co substrate. Photoemission data show that the h-BN(0001) film is p-type, with band bending near the Co/h-BN interface. Growth of graphene by molecular beam epitaxy (MBE) is observed on the surface of multilayer h-BN(0001) at temperatures of 800 K. LEED data indicate azimuthal graphene alignment with the h-BN and Co(0001) lattices, with domain size similar to BN. The evidence of multilayer BN and graphene azimuthal alignment with the lattice of the Co(0001) substrate demonstrates that this procedure is suitable for scalable production of heterojunctions for spintronic applications.

  7. Effects of growth temperature and device structure on GaP solar cells grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Vaisman, M.; Tomasulo, S.; Masuda, T.; Lang, J. R.; Faucher, J.; Lee, M. L. [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States)

    2015-02-09

    Gallium phosphide (GaP) is an attractive candidate for wide-bandgap solar cell applications, possessing the largest bandgap of the III-arsenide/phosphides without aluminum. However, GaP cells to date have exhibited poor internal quantum efficiency (IQE), even for photons absorbed by direct transitions, motivating improvements in material quality and device structure. In this work, we investigated GaP solar cells grown by molecular beam epitaxy over a range of substrate temperatures, employing a much thinner emitter than in prior work. Higher growth temperatures yielded the best solar cell characteristics, indicative of increased diffusion lengths. Furthermore, the inclusion of an AlGaP window layer improved both open-circuit voltage and short wavelength IQE.

  8. Molecular beam epitaxial growth and characterization of Al(Ga)N nanowire deep ultraviolet light emitting diodes and lasers

    Science.gov (United States)

    Mi, Z.; Zhao, S.; Woo, S. Y.; Bugnet, M.; Djavid, M.; Liu, X.; Kang, J.; Kong, X.; Ji, W.; Guo, H.; Liu, Z.; Botton, G. A.

    2016-09-01

    We report on the detailed molecular beam epitaxial growth and characterization of Al(Ga)N nanowire heterostructures on Si and their applications for deep ultraviolet light emitting diodes and lasers. The nanowires are formed under nitrogen-rich conditions without using any metal catalyst. Compared to conventional epilayers, Mg-dopant incorporation is significantly enhanced in nearly strain- and defect-free Al(Ga)N nanowire structures, leading to efficient p-type conduction. The resulting Al(Ga)N nanowire LEDs exhibit excellent performance, including a turn-on voltage of ∼5.5 V for an AlN nanowire LED operating at 207 nm. The design, fabrication, and performance of an electrically injected AlGaN nanowire laser operating in the UV-B band is also presented.

  9. Molecular Beam Epitaxial Growth of Heterostructures to Study Quantum Interference Phenomena

    Science.gov (United States)

    1990-01-01

    MBE growth and regrowth of heterostructures for quantum interference transistors and a detailed study of the physical mechanisms and the limitations imposed by them in such devices. We have investigated in detail the suitability of the MBE regrowth process for such applications. Very encouraging progress has been made. The performance characteristics of dual-channel quantum interference devices grown in our laboratory and defined by e-beam lithography have been measured and reported. From this work it is clear that to achieve enhanced performance and to demonstrate a large

  10. Effects of growth temperature on nonpolar a-plane InN grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Rajpalke, Mohana K.; Bhat, Thirumaleshwara N.; Krupanidhi, S.B. [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India); Roul, Basanta [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore-560013 (India); Kumar, Mahesh [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India); Centre of Excellence in Information and Communication Technology, Indian Institute of Technology, Jodhpur-342011 (India); Sinha, Neeraj [Office of Principal Scientific Advisor, Government of India, New Delhi 110011 (India); Department of Materials Science, Gulbarga University, Gulbarga 585 106 (India); Jali, V.M. [Department of Physics, Gulbarga University, Gulbarga 585 106 (India)

    2014-04-15

    Nonpolar a-plane InN films were grown on r-plane sapphire substrate by plasma assisted molecular beam epitaxy with GaN underlayer. Effect of growth temperature on structural, morphological, and optical properties has been studied. The growth of nonpolar a-plane (1 1 -2 0) orientation was confirmed by high resolution X-ray diffraction study. The film grown at 500 C shows better crystallinity with the rocking curve FWHM 0.67 and 0.85 along [0 0 0 1] and [1 -1 0 0] directions, respectively. Scanning electron micrograph shows formation of Indium droplets at higher growth temperature. Room tem-perature absorption spectra show growth temperature dependent band gap variation from 0.74-0.81 eV, consistent with the expected Burstein-Moss effect. The rectifying behaviour of the I-V curve indicates the existence of Schottky barrier at the InN and GaN interface. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Isolation and control of voids and void-hillocks during molecular beam epitaxial growth of HgCdTe

    Science.gov (United States)

    Chandra, D.; Aqariden, F.; Frazier, J.; Gutzler, S.; Orent, T.; Shih, H. D.

    2000-06-01

    Formation of small voids and defect complexes involving small voids during the molecular beam epitaxial growth of mercury cadmium telluride on cadmium zinc telluride was investigated. Some of these defects were demonstrated to form away from the substrate-epi interface. Other defects were demonstrated to close before reaching the top surface without leaving any perturbations on the surface, thus remaining completely hidden. The voids, which formed away from the substrate-epifilm fixed interface, nucleated on defects introduced into the film already grown, leading to the formation of defect complexes, unlike the voids which nucleated at the substrate-epifilm fixed interface. These defect complexes are decorated with high density dislocation nests. The voids which closed before reaching the film surface usually also nucleated slightly away from the film-substrate interface, continued to replicate for a while as the growth progressed, but then relatively rapidly closed off at a significant depth from the film surface. These voids also appeared to form defect complexes with other kinds of defects. Correlations between these materials defects and performance of individual vertically integrated photodiode (VIP) devices were demonstrated, where the relative location of these defects with respect to the junction boundary appears to be particularly important. Elimination or reduction of fluctuations in relative flux magnitudes or substrate temperature, more likely during multi-composition layer growth, yielded films with significantly lower defect concentrations.

  12. Controllable Growth of Vertical Heterostructure GaTe(x)Se(1-x)/Si by Molecular Beam Epitaxy.

    Science.gov (United States)

    Liu, Shanshan; Yuan, Xiang; Wang, Peng; Chen, Zhi-Gang; Tang, Lei; Zhang, Enze; Zhang, Cheng; Liu, Yanwen; Wang, Weiyi; Liu, Cong; Chen, Chen; Zou, Jin; Hu, Weida; Xiu, Faxian

    2015-08-25

    Two dimensional (2D) alloys, especially transition metal dichalcogenides, have attracted intense attention owing to their band-gap tunability and potential optoelectrical applications. Here, we report the controllable synthesis of wafer-scale, few-layer GaTexSe1-x alloys (0 ≤ x ≤ 1) by molecular beam epitaxy (MBE). We achieve a layer-by-layer growth mode with uniform distribution of Ga, Te, and Se elements across 2 in. wafers. Raman spectroscopy was carried out to explore the composition-dependent vibration frequency of phonons, which matches well with the modified random-element-isodisplacement model. Highly efficient photodiode arrays were also built by depositing few-layer GaTe0.64Se0.36 on n-type Si substrates. These p-n junctions have steady rectification characteristics with a rectifying ratio exceeding 300 and a high external quantum efficiency around 50%. We further measured more devices on MBE-grown GaTexSe1-x/Si heterostructures across the full range to explore the composition-dependent external quantum efficiency. Our study opens a new avenue for the controllable growth of 2D alloys with wafer-scale homogeneity, which is a prominent challenge in 2D material research.

  13. Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

    Science.gov (United States)

    Yang, H. F.; Liu, Z. T.; Fan, C. C.; Yao, Q.; Xiang, P.; Zhang, K. L.; Li, M. Y.; Liu, J. S.; Shen, D. W.

    2016-08-01

    By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO3 and iso-polarity LaAlO3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO3 (111) substrate was more suitable than Nb-doped SrTiO3. In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO3 based superlattices.

  14. Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    H. F. Yang

    2016-08-01

    Full Text Available By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001- and (111-orientated polar LaNiO3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO3 and iso-polarity LaAlO3 substrates were chosen to achieve high-quality (001-orientated films in a layer-by-layer growth mode. For largely polar (111-orientated films, we showed that iso-polarity LaAlO3 (111 substrate was more suitable than Nb-doped SrTiO3. In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO3 based superlattices.

  15. Growth and characterization of molecular beam epitaxy-grown Bi2Te3-xSex topological insulator alloys

    Science.gov (United States)

    Tung, Y.; Chiang, Y. F.; Chong, C. W.; Deng, Z. X.; Chen, Y. C.; Huang, J. C. A.; Cheng, C.-M.; Pi, T.-W.; Tsuei, K.-D.; Li, Z.; Qiu, H.

    2016-02-01

    We report a systematic study on the structural and electronic properties of Bi2Te3-xSex topological insulator alloy grown by molecular beam epitaxy (MBE). A mixing ratio of Bi2Se3 to Bi2Te3 was controlled by varying the Bi:Te:Se flux ratio. X-ray diffraction and Raman spectroscopy measurements indicate the high crystalline quality for the as-grown Bi2Te3-xSex films. Substitution of Te by Se is also revealed from both analyses. The surfaces of the films exhibit terrace-like quintuple layers and their size of the characteristic triangular terraces decreases monotonically with increasing Se content. However, the triangular terrace structure gradually recovers as the Se content further increases. Most importantly, the angle-resolved photoemission spectroscopy results provide evidence of single-Dirac-cone like surface states in which Bi2Te3-xSex with Se/Te-substitution leads to tunable surface states. Our results demonstrate that by fine-tuned MBE growth conditions, Bi2Te3-xSex thin film alloys with tunable topological surface states can be obtained, providing an excellent platform for exploring the novel device applications based on this compound.

  16. Growth of polar and non-polar nitride semiconductor quasi-substrates by hydride vapor phase epitaxy for the development of optoelectronic devices by molecular beam epitaxy

    Science.gov (United States)

    Moldawer, Adam Lyle

    The family of nitride semiconductors has had a profound influence on the development of optoelectronics for a large variety of applications. However, as of yet there are no native substrates commercially available that are grown by liquid phase methods as with Si and GaAs. As a result, the majority of electronic and optoelectronic devices are grown heteroepitaxially on sapphire and SiC. This PhD research addresses both the development of polar and non-polar GaN and AIN templates by Hydride Vapor Phase Epitaxy (HVPE) on sapphire and SiC substrates, as well as the growth and characterization of optoelectronic devices on these templates by molecular beam epitaxy (MBE). Polar and non-polar GaN templates have been grown in a vertical HVPE reactor on the C- and R-planes of sapphire respectively. The growth conditions have been optimized to allow the formation for thick (50um) GaN templates without cracks. These templates were characterized structurally by studying their surface morphologies by SEM and AFM, and their structure through XRD and TEM. The polar C-plane GaN templates were found to be atomically smooth. However, the surface morphology of the non-polar GaN films grown on the R-plane of sapphire were found to have a facetted surface morphology, with the facets intersecting at 120° angles. This surface morphology reflects an equilibrium growth, since the A-plane of GaN grows faster than the M-planes of GaN due to the lower atomic density of the plane. For the development of deep-UV optoelectronics, it is required to grow AIGaN quantum wells on AIN templates. However, since AIN is a high melting point material, such templates have to be grown at higher temperatures, close to half the melting point of the material (1500 °C). As these temperatures cannot be easily obtained by traditional furnace heating, an HVPE reactor has been designed to heat the substrate inductively to these temperatures. This apparatus has been used to grow high-quality, transparent AIN films

  17. Perspective: Oxide molecular-beam epitaxy rocks!

    Directory of Open Access Journals (Sweden)

    Darrell G. Schlom

    2015-06-01

    Full Text Available Molecular-beam epitaxy (MBE is the “gold standard” synthesis technique for preparing semiconductor heterostructures with high purity, high mobility, and exquisite control of layer thickness at the atomic-layer level. Its use for the growth of multicomponent oxides got off to a rocky start 30 yr ago, but in the ensuing decades, it has become the definitive method for the preparation of oxide heterostructures too, particularly when it is desired to explore their intrinsic properties. Examples illustrating the unparalleled achievements of oxide MBE are given; these motivate its expanding use for exploring the potentially revolutionary states of matter possessed by oxide systems.

  18. Perspective: Oxide molecular-beam epitaxy rocks!

    Energy Technology Data Exchange (ETDEWEB)

    Schlom, Darrell G., E-mail: schlom@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

    2015-06-01

    Molecular-beam epitaxy (MBE) is the “gold standard” synthesis technique for preparing semiconductor heterostructures with high purity, high mobility, and exquisite control of layer thickness at the atomic-layer level. Its use for the growth of multicomponent oxides got off to a rocky start 30 yr ago, but in the ensuing decades, it has become the definitive method for the preparation of oxide heterostructures too, particularly when it is desired to explore their intrinsic properties. Examples illustrating the unparalleled achievements of oxide MBE are given; these motivate its expanding use for exploring the potentially revolutionary states of matter possessed by oxide systems.

  19. Submicron FETs Using Molecular Beam Epitaxy.

    Science.gov (United States)

    1979-08-01

    C NISMIMOTO N0001-77-C-0655 UNCLASSIFIED NLIiiII/mlum.. varian SUBMICRON FETs USING MOLECULAR BEAM EPITAXY 00 ANNUAL REPORT NO. 2 (August 1978...Ohmic Contacts to Highly Doped n-type GaAs Layers Grown by Molecular Beam Epitaxy (MBE) for Field-Effect Trans- istors," J. Appl. Phys. 50, 951 (1979...36 ’A, References (Cont.) 8. D. M. Collins, "The Use of SnTe as the Source of Donor Impurities in GaAs Grown by Molecular Beam Epitaxy ," Appl. Phys

  20. Growth and characterization of metamorphic InAs/GaSb tunnel heterojunction on GaAs by molecular beam epitaxy

    Science.gov (United States)

    Liu, Jheng-Sin; Clavel, Michael B.; Pandey, Rahul; Datta, Suman; Meeker, Michael; Khodaparast, Giti A.; Hudait, Mantu K.

    2016-06-01

    The structural, morphological, optical, and electrical transport characteristics of a metamorphic, broken-gap InAs/GaSb p-i-n tunnel diode structure, grown by molecular beam epitaxy on GaAs, were demonstrated. Precise shutter sequences were implemented for the strain-balanced InAs/GaSb active layer growth on GaAs, as corroborated by high-resolution X-ray analysis. Cross-sectional transmission electron microscopy and detailed micrograph analysis demonstrated strain relaxation primarily via the formation of 90° Lomer misfit dislocations (MDs) exhibiting a 5.6 nm spacing and intermittent 60° MDs at the GaSb/GaAs heterointerface, which was further supported by a minimal lattice tilt of 180 arc sec observed during X-ray analysis. Selective area diffraction and Fast Fourier Transform patterns confirmed the full relaxation of the GaSb buffer layer and quasi-ideal, strain-balanced InAs/GaSb heteroepitaxy. Temperature-dependent photoluminescence measurements demonstrated the optical band gap of the GaSb layer. Strong optical signal at room temperature from this structure supports a high-quality material synthesis. Current-voltage characteristics of fabricated InAs/GaSb p-i-n tunnel diodes measured at 77 K and 290 K demonstrated two bias-dependent transport mechanisms. The Shockley-Read-Hall generation-recombination mechanism at low bias and band-to-band tunneling transport at high bias confirmed the p-i-n tunnel diode operation. This elucidated the importance of defect control in metamorphic InAs/GaSb tunnel diodes for the implementation of low-voltage and high-performance tunnel field effect transistor applications.

  1. Foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires on Si (111) by molecular-beam epitaxy.

    Science.gov (United States)

    So, Hyok; Pan, Dong; Li, Lixia; Zhao, Jianhua

    2017-03-01

    Epitaxial high-quality InAs/InSb axial heterostructure nanowires are of great interest due to their distinct advantages in fundamental research as well as applications in semiconductor electronic and quantum devices. Currently, nearly all the growth of InAs/InSb axial heterostructure nanowires is assisted with foreign catalysts such as Au, and work on foreign-catalyst-free growth of InAs/InSb axial heterostructure nanowires is lacking. Here we report on the growth of InAs/InSb axial heterostructure nanowires on Si (111) substrates by molecular-beam epitaxy without using any foreign catalysts. The Sb/In beam equivalent pressure (BEP) ratio is found to have important influence on the heterostructure nanowire morphology, and InSb nanowires can be epitaxially grown on InAs nanowire stems with a hexagonal prism and nanosheet-like shapes when the Sb/In BEP ratio varies from 10 to 20. Transmission electron microscopy studies reveal that the InAs nanowire stems have a mixture of zincblende (ZB) and wurtzite (WZ) crystal structures, while InSb nanowire parts have a pure ZB crystal structure free of stacking faults. Composition analysis of axial heterostructure nanowires provides clear evidence that the InSb nanowires are epitaxially grown on InAs nanowires in an In self-assisted vapor-liquid-solid manner. This study paves a new route for growing narrow-gap semiconductor heterostructures with strong spin-orbit interaction for the study of topological states, and the growth manner presented here is expected to be used to grow other In-based axial heterostructure nanowires.

  2. Very low-temperature epitaxial growth of Mn{sub 5}Ge{sub 3} and Mn{sub 5}Ge{sub 3}C{sub 0.2} films on Ge(111) using molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Petit, Matthieu, E-mail: matthieu.petit@univ-amu.fr [Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille (France); Michez, Lisa [Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille (France); Dutoit, Charles-Emmanuel; Bertaina, Sylvain; Dolocan, Voicu O. [Aix-Marseille Université, CNRS, IM2NP UMR7334, 13397 Cedex 20 Marseille (France); Heresanu, Vasile [Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille (France); Stoffel, Mathieu [Université de Lorraine, UMR CNRS 7198, Institut Jean Lamour, BP 70239, 54506 Vandeuvre-lès-Nancy (France); Le Thanh, Vinh [Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille (France)

    2015-08-31

    C-doped Mn{sub 5}Ge{sub 3} compound is ferromagnetic at temperature up to 430 K. Hence it is a potential spin injector into group-IV semiconductors. Segregation and diffusion of Mn at the Mn{sub 5}Ge{sub 3}/Ge interface could severely hinder the efficiency of the spin injection. To avoid these two phenomena we investigate the growth of Mn{sub 5}Ge{sub 3} and C-doped Mn{sub 5}Ge{sub 3} films on Ge(111) substrates by molecular beam epitaxy at room-temperature. The reactive deposition epitaxy method is used to deposit these films. Reflection high energy electron diffraction, X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy indicate that the crystalline quality is very high. Magnetic characterizations by superconducting quantum interference device and ferromagnetic resonance reinforce the structural analysis results on the thin film quality. - Highlights: • Epitaxial Mn{sub 5}Ge{sub 3} and C-doped Mn{sub 5}Ge{sub 3} films grown on Ge(111) at room temperature. • Mn{sub 5}Ge{sub 3} and C-doped Mn{sub 5}Ge{sub 3} films grown by reactive deposition epitaxy. • RHEED, XRD and TEM measurements show a very high crystallinity. • Magnetic measurements support the structural analysis in the crystalline quality. • Ferromagnetic resonance linewidth is very narrow (3.5 mT at RT)

  3. Native-oxide-based selective area growth of InP nanowires via metal-organic molecular beam epitaxy mediated by surface diffusion.

    Science.gov (United States)

    Calahorra, Yonatan; Greenberg, Yaakov; Cohen, Shimon; Ritter, Dan

    2012-06-22

    The growth of InP nanowires on an InP(111) B substrate is reported. The substrate native oxide was not removed from the surface prior to growth. Nanowires were grown at 400 °C from gold catalysts in a selective area manner, without bulk growth. Unlike SiO(2)-based metal-organic molecular beam epitaxy selective area growth, the growth reported here is mediated by surface diffusion with a characteristic diffusion length of 4 μm, about an order of magnitude larger than values for diffusion on bare substrates. A pre-growth heating treatment at 450 °C was found to increase the yield of nanowire nucleation from the gold catalysts.

  4. Silicon Holder For Molecular-Beam Epitaxy

    Science.gov (United States)

    Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.

    1993-01-01

    Simple assembly of silicon wafers holds silicon-based charge-coupled device (CCD) during postprocessing in which silicon deposited by molecular-beam epitaxy. Attains temperatures similar to CCD, so hotspots suppressed. Coefficients of thermal expansion of holder and CCD equal, so thermal stresses caused by differential thermal expansion and contraction do not develop. Holder readily fabricated, by standard silicon processing techniques, to accommodate various CCD geometries. Silicon does not contaminate CCD or molecular-beam-epitaxy vacuum chamber.

  5. Nanostructure formation during relatively high temperature growth of Mn-doped GaAs by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Del Río-De Santiago, A.; Méndez-García, V.H. [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico); Martínez-Velis, I.; Casallas-Moreno, Y.L. [Physics Department, CINVESTAV-IPN, Apdo. Postal 14470 D. F. México, México (Mexico); López-Luna, E. [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico); Yu Gorbatchev, A. [IICO-UASLP, Av. Karakorum 1470, Lomas 4a. Sección, San Luis Potosí, S.L.P. 78210, México (Mexico); López-López, M. [Physics Department, CINVESTAV-IPN, Apdo. Postal 14470 D. F. México, México (Mexico); Cruz-Hernández, E., E-mail: esteban.cruz@uaslp.mx [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico)

    2015-04-01

    Highlights: • The formation of different kind of nanostructures in GaMnAs layers depending on Mn concentration at relative HT-MBE is reported. In this Mn% range, it is found the formation of nanogrooves, nanoleaves, and nanowires. • It is shown the progressive photoluminescence transitions from purely GaAsMn zinc blende (for Mn% = 0.01) to a mixture of zinc blende and wurtzite GaAsMn (for Mn% = 0.2). • A critical thickness for the Mn catalyst effect was determined by RHEED. - Abstract: In the present work, we report on molecular beam epitaxy growth of Mn-doped GaAs films at the relatively high temperature (HT) of 530 °C. We found that by increasing the Mn atomic percent, Mn%, from 0.01 to 0.2, the surface morphology of the samples is strongly influenced and changes from planar to corrugated for Mn% values from 0.01 to 0.05, corresponding to nanostructures on the surface with dimensions of 200–300 nm and with the shape of leave, to nanowire-like structures for Mn% values above 0.05. From reflection high-energy electron diffraction patterns, we observed the growth mode transition from two- to three-dimensional occurring at a Mn% exceeding 0.05. The optical and electrical properties were obtained from photoluminescence (PL) and Hall effect measurements, respectively. For the higher Mn concentration, besides the Mn related transitions at approximately 1.41 eV, PL spectra sharp peaks are present between 1.43 and 1.49 eV, which we related to the coexistence of zinc blende and wurtzite phases in the nanowire-like structures of this sample. At Mn% of 0.04, an increase of the carrier mobility up to a value of 1.1 × 10{sup 3} cm{sup 2}/Vs at 77 K was found, then decreases as Mn% is further increased due to the strengthening of the ionized impurity scattering.

  6. Molecular beam epitaxy growth of GaAs/InAs core-shell nanowires and fabrication of InAs nanotubes.

    Science.gov (United States)

    Rieger, Torsten; Luysberg, Martina; Schäpers, Thomas; Grützmacher, Detlev; Lepsa, Mihail Ion

    2012-11-14

    We present results about the growth of GaAs/InAs core-shell nanowires (NWs) using molecular beam epitaxy. The core is grown via the Ga droplet-assisted growth mechanism. For a homogeneous growth of the InAs shell, the As(4) flux and substrate temperature are critical. The shell growth starts with InAs islands along the NW core, which increase in time and merge giving finally a continuous and smooth layer. At the top of the NWs, a small part of the core is free of InAs indicating a crystal phase selective growth. This allows a precise measurement of the shell thickness and the fabrication of InAs nanotubes by selective etching. The strain relaxation in the shell occurs mainly via the formation of misfit dislocations and saturates at ~80%. Additionally, other types of defects are observed, namely stacking faults transferred from the core or formed in the shell, and threading dislocations.

  7. Selective-area growth of GaN nanowires on SiO2-masked Si (111) substrates by molecular beam epitaxy

    Science.gov (United States)

    Kruse, J. E.; Lymperakis, L.; Eftychis, S.; Adikimenakis, A.; Doundoulakis, G.; Tsagaraki, K.; Androulidaki, M.; Olziersky, A.; Dimitrakis, P.; Ioannou-Sougleridis, V.; Normand, P.; Koukoula, T.; Kehagias, Th.; Komninou, Ph.; Konstantinidis, G.; Georgakilas, A.

    2016-06-01

    We analyze a method to selectively grow straight, vertical gallium nitride nanowires by plasma-assisted molecular beam epitaxy (MBE) at sites specified by a silicon oxide mask, which is thermally grown on silicon (111) substrates and patterned by electron-beam lithography and reactive-ion etching. The investigated method requires only one single molecular beam epitaxy MBE growth process, i.e., the SiO2 mask is formed on silicon instead of on a previously grown GaN or AlN buffer layer. We present a systematic and analytical study involving various mask patterns, characterization by scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy, as well as numerical simulations, to evaluate how the dimensions (window diameter and spacing) of the mask affect the distribution of the nanowires, their morphology, and alignment, as well as their photonic properties. Capabilities and limitations for this method of selective-area growth of nanowires have been identified. A window diameter less than 50 nm and a window spacing larger than 500 nm can provide single nanowire nucleation in nearly all mask windows. The results are consistent with a Ga diffusion length on the silicon dioxide surface in the order of approximately 1 μm.

  8. Influence of growth temperature on laser molecular beam epitaxy and properties of GaN layers grown on c-plane sapphire

    Science.gov (United States)

    Dixit, Ripudaman; Tyagi, Prashant; Kushvaha, Sunil Singh; Chockalingam, Sreekumar; Yadav, Brajesh Singh; Sharma, Nita Dilawar; Kumar, M. Senthil

    2017-04-01

    We have investigated the influence of growth temperature on the in-plane strain, structural, optical and mechanical properties of heteroepitaxially grown GaN layers on sapphire (0001) substrate by laser molecular beam epitaxy (LMBE) technique in the temperature range 500-700 °C. The GaN epitaxial layers are found to have a large in-plane compressive stress of about 1 GPa for low growth temperatures but the strain drastically reduced in the layer grown at 700 °C. The nature of the in-plane strain has been analyzed using high resolution x-ray diffraction, atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL) measurements. From AFM, a change in GaN growth mode from grain to island is observed at the high growth temperature above 600 °C. A blue shift of 20-30 meV in near band edge PL emission line has been noticed for the GaN layers containing the large in-plane strain. These observations indicate that the in-plane strain in the GaN layers is dominated by a biaxial strain. Using nanoindentation, it is found that the indentation hardness and Young's modulus of the GaN layers increases with increasing growth temperature. The results disclose the critical role of growth mode in determining the in-plane strain and mechanical properties of the GaN layers grown by LMBE technique.

  9. Defect-free zinc-blende structured InAs nanowires realized by in situ two V/III ratio growth in molecular beam epitaxy.

    Science.gov (United States)

    Zhang, Zhi; Lu, Zhen-Yu; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-08-07

    In this study, we devised a two-V/III-ratio procedure to control the Au-assisted growth of defect-free InAs nanowires in molecular beam epitaxy. The demonstrated two V/III ratio procedure consists of a first high V/III ratio growth step to prepare the nanowire foundation on the substrate surface, followed by a low V/III ratio step to induce the nanowire growth. By manipulating the V/III ratios in different steps, we have achieved the controlled growth of pure defect-free zinc-blende structured InAs nanowires on the GaAs {1̄1̄1̄} substrates. This study provides an approach to control not only the crystal structure of semiconductor nanowires, but also their structural qualities.

  10. Growth and characterization of InP ringlike quantum-dot molecules grown by solid-source molecular beam epitaxy.

    Science.gov (United States)

    Jevasuwan, Wipakorn; Boonpeng, Poonyasiri; Panyakeow, Somsak; Ratanathammaphan, Somchai

    2010-11-01

    In this paper, we have studied the fabrication of InP ringlike quantum-dot molecules on GaAs(001) substrate grown by solid-source molecular beam epitaxy using droplet epitaxy technique and the effect of In deposition rate on the physical and optical properties of InP ringlike quantum-dot molecules. The In deposition rate is varied from 0.2 ML/s to 0.4, 0.8 and 1.6 ML/s. The surface morphology and cross-section were examined by ex-situ atomic force microscope and transmission electron microscope, respectively. The increasing of In deposition rate results in the decreasing of outer and inner diameters of InP ringlike quantum-dot molecules and height of InP quantum dots but increases the InP quantum dot and ringlike quantum-dot molecule densities. The photoluminescence peaks of InP ringlike quantum-dot molecules are blue-shifted and FWHM is narrower when In deposition rate is bigger.

  11. Low-temperature growth of Ge{sub 1} {sub -x}Sn{sub x} thin films with strain control by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lin Hai, E-mail: hailin@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, California, 94305 (United States); Chen, Robert; Huo Yijie; Kamins, Theodore I.; Harris, James S. [Department of Electrical Engineering, Stanford University, Stanford, California, 94305 (United States)

    2012-03-30

    High-quality Ge{sub 1-x}Sn{sub x} thin films on InGaAs buffer layers have been demonstrated using low-temperature growth by molecular beam epitaxy. X-ray diffraction and secondary ion mass spectrometry are used to determine the strain and Sn concentration. Up to 10.5% Sn has been incorporated into the Ge{sub 1-x}Sn{sub x} thin film without Sn precipitation, as verified by transmission electron microscopy. Roughened surfaces are found for tensile strained Ge{sub 1-x}Sn{sub x} layers. - Highlights: Black-Right-Pointing-Pointer GeSn alloys were grown by molecular beam epitaxy with up to 10.5% Sn. Black-Right-Pointing-Pointer Unstrained GeSn alloys have high crystal quality. Black-Right-Pointing-Pointer Consistent Sn concentration was obtained from two different methods. Black-Right-Pointing-Pointer The growth of tensile strained GeSn results in a roughened surface.

  12. Large-area growth of multi-layer hexagonal boron nitride on polished cobalt foils by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Xu, Zhongguang; Tian, Hao; Khanaki, Alireza; Zheng, Renjing; Suja, Mohammad; Liu, Jianlin

    2017-01-01

    Two-dimensional (2D) hexagonal boron nitride (h-BN), which has a similar honeycomb lattice structure to graphene, is promising as a dielectric material for a wide variety of potential applications based on 2D materials. Synthesis of high-quality, large-size and single-crystalline h-BN domains is of vital importance for fundamental research as well as practical applications. In this work, we report the growth of h-BN films on mechanically polished cobalt (Co) foils using plasma-assisted molecular beam epitaxy. Under appropriate growth conditions, the coverage of h-BN layers can be readily controlled by growth time. A large-area, multi-layer h-BN film with a thickness of 5~6 nm is confirmed by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. In addition, the size of h-BN single domains is 20~100 μm. Dielectric property of as-grown h-BN film is evaluated by characterization of Co(foil)/h-BN/Co(contact) capacitor devices. Breakdown electric field is in the range of 3.0~3.3 MV/cm, which indicates that the epitaxial h-BN film has good insulating characteristics. In addition, the effect of substrate morphology on h-BN growth is discussed regarding different domain density, lateral size, and thickness of the h-BN films grown on unpolished and polished Co foils. PMID:28230178

  13. Growth by molecular beam epitaxy and properties of inclined GaN nanowires on Si(001) substrate.

    Science.gov (United States)

    Borysiuk, J; Zytkiewicz, Z R; Sobanska, M; Wierzbicka, A; Klosek, K; Korona, K P; Perkowska, P S; Reszka, A

    2014-04-04

    The growth mode and structural and optical properties of novel type of inclined GaN nanowires (NWs) grown by plasma-assisted MBE on Si(001) substrate were investigated. We show that due to a specific nucleation mechanism the NWs grow epitaxially on the Si substrate without any Si(x)N(y) interlayer, first in the form of zinc-blende islands and then as double wurtzite GaN nanorods with Ga-polarity. X-ray measurements show that orientation of these nanowires is epitaxially linked to the symmetry of the substrate so that [0001] axis of w-GaN nanowire is directed along the [111]Si axis. This is different from commonly observed behavior of self-induced GaN NWs that are N-polar and grow perpendicularly to the surface of nitridized silicon substrate independently on its orientation. The inclined NWs exhibit bright luminescence of bulk donor-bound excitons (D(0)X) at 3.472 eV and exciton-related peak at 3.46 eV having a long lifetime (0.7 ns at 4 K) and observable up to 50 K.

  14. Alloy formation during molecular beam epitaxy growth of Si-doped InAs nanowires on GaAs[111]B.

    Science.gov (United States)

    Davydok, Anton; Rieger, Torsten; Biermanns, Andreas; Saqib, Muhammad; Grap, Thomas; Lepsa, Mihail Ion; Pietsch, Ullrich

    2013-08-01

    Vertically aligned InAs nanowires (NWs) doped with Si were grown self-assisted by molecular beam epitaxy on GaAs[111]B substrates covered with a thin SiO x layer. Using out-of-plane X-ray diffraction, the influence of Si supply on the growth process and nanostructure formation was studied. It was found that the number of parasitic crystallites grown between the NWs increases with increasing Si flux. In addition, the formation of a Ga0.2In0.8As alloy was observed if the growth was performed on samples covered by a defective oxide layer. This alloy formation is observed within the crystallites and not within the nanowires. The Ga concentration is determined from the lattice mismatch of the crystallites relative to the InAs nanowires. No alloy formation is found for samples with faultless oxide layers.

  15. Impact of growth and annealing conditions on the parameters of Ge/Si(001) relaxed layers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yurasov, D. V., E-mail: Inquisitor@ipm.sci-nnov.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Bobrov, A. I. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Daniltsev, V. M.; Novikov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Pavlov, D. A. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Skorokhodov, E. V.; Shaleev, M. V.; Yunin, P. A. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2015-11-15

    Influence of the Ge layer thickness and annealing conditions on the parameters of relaxed Ge/Si(001) layers grown by molecular beam epitaxy via two-stage growth is investigated. The dependences of the threading dislocation density and surface roughness on the Ge layer thickness, annealing temperature and time, and the presence of a hydrogen atmosphere are obtained. As a result of optimization of the growth and annealing conditions, relaxed Ge/Si(001) layers which are thinner than 1 μm with a low threading dislocation density on the order of 10{sup 7} cm{sup –2} and a root mean square roughness of less than 1 nm are obtained.

  16. Optimization of nitrogen plasma source parameters by measurements of emitted light intensity for growth of GaN by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Klosek, K.; Sobanska, M.; Tchutchulashvili, G.; Zytkiewicz, Z.R., E-mail: zytkie@ifpan.edu.pl; Teisseyre, H.; Klopotowski, L.

    2013-05-01

    A comprehensive analysis of operating parameters of Addon RF nitrogen plasma source was made in order to determine how a ratio of different active nitrogen species depends on operating parameters of the source such as supplied power and nitrogen flow. We show that output signal of the optical sensor that measures intensity of the light emitted by the plasma is a direct measure of the amount of active nitrogen available for growth. Results of optical emission spectroscopy and measurements of growth kinetics show that nitrogen excited metastable molecules are the species mainly contributing to the growth of GaN under Ga-rich conditions. A procedure is presented allowing to find an optimal conditions of the plasma cell for high-quality GaN growth. Under these conditions the nitrogen flux contains maximum amount of excited metastable molecules and minimal amount of ionic and atomic nitrogen species to minimize GaN lattice damage, even at high growth rates. - Highlights: ► Operating parameters of Addon radio-frequency nitrogen plasma source studied ► Their influence on molecular beam epitaxy (MBE) growth of GaN analyzed ► MBE growth rate of GaN well correlates with output of the plasma emission sensor. ► Optical emission spectroscopy measurements of the nitrogen plasma made ► Nitrogen excited molecules mainly contribute to plasma-assisted MBE growth of GaN.

  17. Growth of GaAs{sub 1−x}Bi{sub x} by molecular beam epitaxy: Trade-offs in optical and structural characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jincheng; Kim, Tong-Ho; Jiao, Wenyuan; Kong, Wei; Brown, April S. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Forghani, Kamran [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Collar, Kristen [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Kuech, Thomas F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2014-07-28

    Recent work has shown that Bi incorporation increases during molecular beam epitaxy (MBE) when surface processes are kinetically limited through increased growth rate. Herein we explore how the structural and optical properties of GaAs{sub 1−x}Bi{sub x} films are modified when grown under conditions with varying degrees of kinetic limitations realized through growth temperature and growth rate changes. Within the typical window of MBE growth conditions for GaAs{sub 1−x}Bi{sub x}, we compare films with similar (∼3%) compositions grown under conditions of reduced kinetic limitations, i.e., relatively low gallium supersaturation achieved at higher temperatures (∼350 °C) and lower growth rates (∼0.5 μm/h), to those grown farther from equilibrium, specifically, higher supersaturation achieved at lower growth temperatures (∼290 °C) and higher growth rates (∼1.4 μm/h). Both the x-ray diffraction full width at half maximum of the omega-2theta scan and the 300 K photoluminescence intensity increase when samples are grown under less kinetically limited conditions. We interpret these findings in relation to the incorporation of Bi-related microstructural defects that are more readily formed during less kinetically limited growth. These defects lead to enhanced luminescence efficiency due to the spatial localization of carriers.

  18. Instrumentation for Epitaxial Growth of Complex Oxides

    Science.gov (United States)

    2015-12-17

    P.O. Box 12211 Research Triangle Park, NC 27709-2211 epitaxy, molecular beam epitaxy, oxide heterostructures REPORT DOCUMENTATION PAGE 11. SPONSOR...The installation of this shielding was founded to dramatically increase the beam stability and mitigate intensity fluctuations. The RHEED source has

  19. Reflectance-anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Gallegos, J.; Lastras-Martinez, A.; Lastras-Martinez, L.F. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico); Balderas-Navarro, R.E. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico); Facultad de Ciencias, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico)

    2008-07-01

    Reflectance-Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E{sub 1} optical transition as a probe. We follow the kinetics of the deposition of GaAs and In{sub 0.3}Ga{sub 0.7}As on GaAs(001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As{sub 4} or As{sub 2} flux pressure of 5 x 10{sup -6} Torr. Clear RA-oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga-As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Columnar growth of CoSi2 on Si(111), Si(100) and Si(110) by molecular beam epitaxy

    Science.gov (United States)

    Fathauer, R. W.; Nieh, C. W.; Xiao, Q. F.; Hashimoto, Shin

    1990-01-01

    Codeposition of silicon and cobalt on heated silicon substrates in ratios several times the silicide stoichiometry is found to result in epitaxial columns of CoSi2 surrounded by a matrix of epitaxial silicon. For (111)-oriented wafers, nearly cylindrical columns are formed, where both columns and surrounding silicon are defect free, as deduced from transmission electron microscopy. Independent control of the column diameter and separation is possible, and diameters of 27-135 nm have been demonstrated.

  1. Two-step growth of high quality Bi{sub 2}Te{sub 3} thin films on Al{sub 2}O{sub 3} (0001) by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, S. E.; Huo, Y.; Harris, J. S. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Li, S. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Zhou, B.; Chen, Y. L. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Department of Physics, University of Oxford, Parks Road, OX1 3PU Oxford (United Kingdom); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2013-04-29

    Large-area topological insulator Bi{sub 2}Te{sub 3} thin films were grown on Al{sub 2}O{sub 3} (0001) using a two-temperature step molecular beam epitaxy growth process. By depositing a low temperature nucleation layer to serve as a template for high temperature epitaxial film growth, a high quality terrace-step surface morphology with a significant reduction in three-dimensional defect structures was achieved. X-ray diffraction measurements indicate that high crystalline quality Bi{sub 2}Te{sub 3} layers were grown incoherently by van der Waals epitaxy using this technique. Angle resolved photoemission spectroscopy measurements verified the integrity of this growth method by confirming the presence of metallic surface states on cleaved two-step Bi{sub 2}Te{sub 3} samples.

  2. Growth of single-crystal columns of CoSi2 embedded in epitaxial Si on Si(111) by molecular beam epitaxy

    Science.gov (United States)

    Fathauer, R. W.; Nieh, C. W.; Xiao, Q. F.; Hashimoto, Shin

    1989-01-01

    The codeposition of Si and Co on a heated Si(111) substrate is found to result in epitaxial columns of CoSi2 if the Si:Co ratio is greater than approximately 3:1. These columns are surrounded by an Si matrix which shows bulk-like crystalline quality based on transmission electron microscopy and ion channeling. This phenomenon has been studied as functions of substrate temperature and Si:Co ratio. Samples with columns ranging in average diameter from approximately 25 to 130 nm have been produced.

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

    Science.gov (United States)

    Rutkowski, M M; McNicholas, K M; Zeng, Zhaoquan; Brillson, L J

    2013-06-01

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

  4. Initial growth stages of Si–Ge–Sn ternary alloys grown on Si (100) by low-temperature molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tuktamyshev, A. R., E-mail: tuktamyshev@isp.nsc.ru; Mashanov, V. I.; Timofeev, V. A.; Nikiforov, A. I.; Teys, S. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-12-15

    Temperature dependence of the critical thickness of the transition from two-dimensional to threedimensional growth of the Ge{sub 1–5x}Si{sub 4x}Sn{sub x} films grown on Si (100) by molecular-beam epitaxy in the temperature range 150–450°C has been experimentally determined. This dependence is nonmonotonic and is similar to that of the critical thickness for the transition from two-dimensional to three-dimensional growth in the case of the deposition of pure Ge on Si (100) and is caused by a change in the mechanism of two-dimensional growth. Data on the average size and the density of islands, and the ratio between the height of the islands and their lateral size are obtained by the methods of atomic force microscopy and scanning tunneling microscopy. As the growth temperature is increased from 200 to 400°C, the average size of the nanoislands increases from 4.7 to 23.6 nm.

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

    Science.gov (United States)

    Rutkowski, M. M.; McNicholas, K. M.; Zeng, Zhaoquan; Brillson, L. J.

    2013-06-01

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

  6. Direct growth of GaN on off-oriented SiC (0001) by molecular-beam epitaxy for GaN/SiC heterojunction bipolar transistor

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Y.; Kimoto, T. [Department of Electronic Science and Engineering, Kyoto University Katsura Campus, Nishikyo-ku, Kyoto, 615-8510 (Japan); Suda, J. [Department of Electronic Science and Engineering, Kyoto University Katsura Campus, Nishikyo-ku, Kyoto, 615-8510 (Japan); PRESTO, Japan Science and Technology Agency (JST) Kawaguchi, Saitama 332-0012 (Japan)

    2005-05-01

    Direct growth of GaN on misoriented 4H- and 6H-SiC (0001) Si-face substrates and electrical characteristics of n-GaN/p-SiC heterojunction mesa diodes are presented. GaN was grown by molecular-beam epitaxy (MBE) using elemental Ga and rf plasma-excited active nitrogen. SiC substrates misoriented 8 toward the [11-20] direction were used in this study. The surfaces of MBE-grown GaN layers have wavy features with peak-to-valley height of 30 nm. These features originated from the substrate misorientation. It was found that step bunching and large faceting along [01-10] and [10-10] directions occurred during the growth of GaN. Lowering the growth temperature suppresses large faceting, and results in reduction of the peak-to-valley height to 3 nm. However, the surface still has the same undulating features (on a smaller length scale). Mesa diodes were fabricated from the grown GaN layers. The correlation between the diode electrical characteristics and GaN growth conditions is discussed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Molecular Beam Epitaxy Growth of Superconducting Ba1-xKxFe2As2 and SmFeAs(O,F) Films

    Science.gov (United States)

    Ueda, Shinya; Takeda, Soichiro; Takano, Shiro; Mitsuda, Akihiro; Naito, Michio

    2012-01-01

    We report the molecular beam epitaxy (MBE) growth of the iron-based superconductors, Ba1-xKxFe2As2 and SmFeAs(O,F). In the growth of Ba1-xKxFe2As2 films, the key to incorporating volatile K in films is low-temperature (≤350 °C) growth in reduced As flux. The highest Tc thus far obtained is Tcon (Tcend) = 38.0 K (35.8 K). In the growth of superconducting SmFeAs(O,F), we adopted two methods. In the first method, we first grew pristine SmFeAsO films, and subsequently introduced F into the films by diffusion from an overlayer of SmF3. In the second method, we grew as-grown superconducting SmFeAs(O,F) films by coevaporating Sm, SmF3, Fe, and As. Thus far, better results have been obtained by the first F diffusion method. The films prepared by F diffusion showed Tcon (Tcend) = 56.5 K (55.3 K), whereas the as-grown films showed Tcon (Tcend) = 51.5 K (48.0 K).

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-06-15

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

  9. Thin film growth of a topological crystal insulator SnTe on the CdTe (111) surface by molecular beam epitaxy

    Science.gov (United States)

    Ishikawa, Ryo; Yamaguchi, Tomonari; Ohtaki, Yusuke; Akiyama, Ryota; Kuroda, Shinji

    2016-11-01

    We report molecular beam epitaxial growth of a SnTe (111) layer on a CdTe template, fabricated by depositing it on a GaAs (111)A substrate, instead of BaF2 which has been conventionally used as a substrate. By optimizing temperatures for the growth of both SnTe and CdTe layers and the SnTe growth rate, we could obtain SnTe layers of the single phase grown only in the (111) orientation and of much improved surface morphology from the viewpoint of the extension and the flatness of flat regions, compared to the layers grown on BaF2. In this optimal growth condition, we have also achieved a low hole density of the order of 1017 cm-3 at 4 K, the lowest value ever reported for SnTe thin films without additional doping. In the magnetoresistance measurement on this optimized SnTe layer, we observe characteristic negative magneto-conductance which is attributed to the weak antilocalization effect of the two-dimensional transport in the topological surface state.

  10. Growth of free-standing bulk wurtzite AlxGa1-xN layers by molecular beam epitaxy using a highly efficient RF plasma source

    Science.gov (United States)

    Novikov, S. V.; Staddon, C. R.; Sahonta, S.-L.; Oliver, R. A.; Humphreys, C. J.; Foxon, C. T.

    2016-12-01

    The recent development of group III nitrides allows researchers world-wide to consider AlGaN based light emitting diodes as a possible new alternative deep ultra-violet light source for surface decontamination and water purification. In this paper we will describe our recent results on plasma-assisted molecular beam epitaxy (PA-MBE) growth of free-standing wurtzite AlxGa1-xN bulk crystals using the latest model of Riber's highly efficient nitrogen RF plasma source. We have achieved AlGaN growth rates up to 3 μm/h. Wurtzite AlxGa1-xN layers with thicknesses up to 100 μm were successfully grown by PA-MBE on 2-inch and 3-inch GaAs (111)B substrates. After growth the GaAs was subsequently removed using a chemical etch to achieve free-standing AlxGa1-xN wafers. Free-standing bulk AlxGa1-xN wafers with thicknesses in the range 30-100 μm may be used as substrates for further growth of AlxGa1-xN-based structures and devices. High Resolution Scanning Transmission Electron Microscopy (HR-STEM) and Convergent Beam Electron Diffraction (CBED) were employed for detailed structural analysis of AlGaN/GaAs (111)B interface and allowed us to determine the N-polarity of AlGaN layers grown on GaAs (111)B substrates. The novel, high efficiency RF plasma source allowed us to achieve free-standing AlxGa1-xN layers in a single day's growth, making this a commercially viable process.

  11. Growth of pseudomorphic structures through organic epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kaviyil, Sreejith Embekkat; Sassella, Adele; Borghesi, Alessandro [Department of Materials Science, Universita degli Studi di Milano Bicocca, Via R. Cozzi 53, I-20125 Milan (Italy); Campione, Marcello [Department of Earth and Environmental Sciences, Universita degli Studi di Milano Bicocca, Piazza della Scienza 4, I-20126 Milan (Italy); Su Genbo; He Youping [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Science, Fuzhou 350002 (China); Chen Chenjia [Department of Physics, Peking University, Beijing 100871 (China)

    2012-12-14

    The control of molecular orientation in thin solid film phases of organic semiconductors is a basic factor for the exploitation of their physical properties for optoelectronic devices. We compare structural and optical properties of thin films of the organic semiconductor {alpha}-quarterthiophene grown by molecular beam epitaxy on different organic substrates. We show how epitactic interactions, characteristic of the surface of organic crystals, can drive the orientation of the crystalline overlayer and the selection of specific polymorphs and new pseudomorphic phases. We identify a key role in this phenomenon played by the marked groove-like corrugations present in some organic crystal surfaces. Since different polymorphs possess rather different performance in terms of, e.g., charge carrier mobility, this strategy is demonstrated to allow for the growth of oriented phases with enhanced physical properties, while keeping the substrate at room temperature. These results provide useful guidelines for the design of technological substrates for organic epitaxy and they substantiate the adoption of an organic epitaxy approach for the fabrication of optoelectronic devices based on thin films of organic semiconductors.

  12. Effects of Ga ion irradiation on growth of GaN on SiN substrates by electron cyclotron resonance-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, J. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan) and Center for Quantum Science and Technology under Extreme Conditions, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan) and CREST-JST, Kawaguchi Center Building, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan)]. E-mail: yanagisawa@ee.es.osaka-u.ac.jp; Matsumoto, H. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Fukuyama, T. [Department of Electronics, Information and Communication Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585 (Japan); Shiraishi, Y. [Department of Electronics, Information and Communication Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585 (Japan); Yodo, T. [Department of Electronics, Information and Communication Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585 (Japan); Akasaka, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan)

    2007-04-15

    The possibility of forming GaN layers on Ga-implanted SiN surfaces was investigated using electron cyclotron resonance-assisted molecular beam epitaxy (MBE). It is found that the GaN layer initially formed on the SiN surface by Ga implantation at room temperature was amorphous-like, but become to polycrystalline after annealing at 650 deg. C for 3 min in vacuum. After the MBE growth of GaN, a grain structure of h-GaN was observed on the Ga-implanted SiN surface. The crystallinity of the GaN grown was, however, decreased upon increasing the Ga ion fluence on the SiN surface, which might be due, at least partly, to the formation of Ga clusters by the excess Ga implanted. The present results indicate the possibility of forming patterned GaN layers on SiN by selective Ga implantation on the SiN substrate, using a focused ion beam.

  13. Buffer-layer enhanced crystal growth of BaB{sub 6} (1 0 0) thin films on MgO (1 0 0) substrates by laser molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Yushi; Yamauchi, Ryosuke; Arai, Hideki; Tan, Geng [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Tsuchimine, Nobuo; Kobayashi, Susumu [Toshima Manufacturing Company Limited, 1414 Shimonomoto, Higashimatsuyama-shi, Saitama 355-0036 (Japan); Saeki, Kazuhiko; Takezawa, Nobutaka [Department of Materials Technology, Industrial Technology Center of Tochigi Prefecture, 367-1 Karinuma, Utsunomiya-shi, Tochigi 321-3224 (Japan); Mitsuhashi, Masahiko; Kaneko, Satoru [Kanagawa Industrial Technology Center, Kanagawa Prefectural Government, 705-1 Shimo-Imaizumi, Ebina, Kanagawa 243-0435 (Japan); Yoshimoto, Mamoru, E-mail: yoshimoto.m.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Patent Attorney, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan)

    2012-02-01

    Crystalline BaB{sub 6} (1 0 0) thin films can be fabricated on MgO (1 0 0) substrates by inserting a 2-3 nm-thick epitaxial SrB{sub 6} (1 0 0) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB{sub 6} (1 0 0)/SrB{sub 6} (1 0 0)/MgO (1 0 0) with the single domain of the epitaxial relationship. Conversely, BaB{sub 6} thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB{sub 6} thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB{sub 6} epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90 Multiplication-Sign 10{sup -1} {Omega} cm at room temperature.

  14. Effects of in situ annealing of GaAs(100) substrates on the subsequent growth of InAs quantum dots by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Cortes, H; Mejia-Garcia, C [Escuela Superior de Fisica y Matematicas del IPN, UPALM, Edif. 9, Col. Lindavista, Mexico DF 07738 (Mexico); Mendez-GarcIa, V H; Vazquez-Cortes, D [Coordinacion para la Innovacion y la Aplicacion de la Ciencia y la TecnologIa, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis PotosI, S L P 78000 (Mexico); Rojas-Ramirez, J S; Contreras-Guerrero, R; RamIrez-Lopez, M; Martinez-Velis, I; Lopez-Lopez, M, E-mail: mlopez@fis.cinvestav.mx [Physics Department, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, Mexico DF 07000 (Mexico)

    2010-04-02

    In the present work, we study the growth by molecular beam epitaxy of InAs self-assembling quantum dots (SAQDs) on GaAs(100) substrates subjected to an in situ annealing treatment. The annealing process consists of the exposition of the GaAs buffer layer surface to high temperatures for a few seconds with the shutter of an arsenic Knudsen cell closed. The purpose of the annealing is to obtain a better uniformity of the SAQD sizes. In our study we prepared different samples using the Stranski-Krastanov growth method to obtain InAs/GaAs(100) quantum dot samples with different annealing times and temperatures. Their structural and optical properties were studied by reflection high-energy electron diffraction (RHEED), high-resolution scanning electron microscopy (HRSEM), atomic force microscopy (AFM), and photoreflectance spectroscopy (PR). According to the results of AFM and HRSEM, by the thermal treatment we obtained a better distribution of quantum dot sizes in comparison with a reference sample with no treatment. The PR spectra from 0.9 to 1.35 eV presented two transitions associated with SAQDs. The energy transitions were obtained by fitting the PR spectra using the third derivative model.

  15. Effects of RF plasma parameters on the growth of InGaN/GaN heterostructures using plasma-assisted molecular beam epitaxy

    CERN Document Server

    Shim Kyu Ha; Kim, K H; Hong, S U; Cho, K I; Lee, H G; Kim, J

    1999-01-01

    The effects of rf plasma power on the structural/optical properties of GaN-based nitride epilayers grown by plasma-assisted molecular beam epitaxy have been investigated. Atomic force microscopy and high-resolution x-ray diffraction analyses revealed that the sharp interface of In sub 0 sub . sub 2 Ga sub 0 sub . sub 8 N/GaN heterostructures could be obtained by suppressing the surface roughening at high rf power. photoluminescence data suggest that the formation of damaged subsurface due to energetic particles was alleviated in the InGaN growth in comparison with the GaN growth. In our experimental set-up, the rf power of 400 W appeared to properly suppress the 3D island formation without causing defects at the subsurface of In sub 0 sub . sub 2 Ga sub 0 sub . sub 8 N. The phenomena associated with the indium incorporation could be explained by an inequality with two kinetic processes of the surface diffusion and the plasma stimulated desorption.

  16. Selective area growth of In(Ga)N/GaN nanocolumns by molecular beam epitaxy on GaN-buffered Si(111): from ultraviolet to infrared emission.

    Science.gov (United States)

    Albert, S; Bengoechea-Encabo, A; Sánchez-García, M A; Kong, X; Trampert, A; Calleja, E

    2013-05-03

    Selective area growth of In(Ga)N/GaN nanocolumns was performed on GaN-buffered Si(111) substrates by plasma-assisted molecular beam epitaxy. Undoped and Si-doped GaN buffer layers were first grown on Si(111) substrates, showing photoluminescence excitonic emission without traces of other low energy contributions, in particular, the yellow band. The GaN buffer surface roughness (between 10 and 14 nm, the rms value in a 10 × 10 μm(2) area) was low enough to allow the fabrication of a thin (7 nm thick) well defined Ti nanohole mask, for the selective area growth. Ordered In(Ga)N/GaN nanocolumns emitting from the ultraviolet (3.2 eV) to the infrared (0.78 eV) were obtained. The morphology and the emission efficiency of the In(Ga)N/GaN nanocolumns emitting at a given wavelength could be substantially improved by tuning the In/Ga and total III/N ratios. An estimated internal quantum efficiency of 36% was derived from photoluminescence data for green emitting nanocolumns.

  17. Impact of P/In flux ratio and epilayer thickness on faceting for nanoscale selective area growth of InP by molecular beam epitaxy.

    Science.gov (United States)

    Fahed, M; Desplanque, L; Coinon, C; Troadec, D; Wallart, X

    2015-07-24

    The impact of the P/In flux ratio and the deposited thickness on the faceting of InP nanostructures selectively grown by molecular beam epitaxy (MBE) is reported. Homoepitaxial growth of InP is performed inside 200 nm wide stripe openings oriented either along a [110] or [1-10] azimuth in a 10 nm thick SiO2 film deposited on an InP(001) substrate. When varying the P/In flux ratio, no major shape differences are observed for [1-10]-oriented apertures. On the other hand, the InP nanostructure cross sections strongly evolve for [110]-oriented apertures for which (111)B facets are more prominent and (001) ones shrink for large P/In flux ratio values. These results show that the growth conditions allow tailoring the nanocrystal shape. They are discussed in the framework of the equilibrium crystal shape model using existing theoretical calculations of the surface energies of different low-index InP surfaces as a function of the phosphorus chemical potential, directly related to the P/In ratio. Experimental observations strongly suggest that the relative (111)A surface energy is probably smaller than the calculated value. We also discuss the evolution of the nanostructure shape with the InP-deposited thickness.

  18. Selective area growth of In(Ga)N/GaN nanocolumns by molecular beam epitaxy on GaN-buffered Si(111): from ultraviolet to infrared emission

    Science.gov (United States)

    Albert, S.; Bengoechea-Encabo, A.; Sánchez-García, M. A.; Kong, X.; Trampert, A.; Calleja, E.

    2013-05-01

    Selective area growth of In(Ga)N/GaN nanocolumns was performed on GaN-buffered Si(111) substrates by plasma-assisted molecular beam epitaxy. Undoped and Si-doped GaN buffer layers were first grown on Si(111) substrates, showing photoluminescence excitonic emission without traces of other low energy contributions, in particular, the yellow band. The GaN buffer surface roughness (between 10 and 14 nm, the rms value in a 10 × 10 μm2 area) was low enough to allow the fabrication of a thin (7 nm thick) well defined Ti nanohole mask, for the selective area growth. Ordered In(Ga)N/GaN nanocolumns emitting from the ultraviolet (3.2 eV) to the infrared (0.78 eV) were obtained. The morphology and the emission efficiency of the In(Ga)N/GaN nanocolumns emitting at a given wavelength could be substantially improved by tuning the In/Ga and total III/N ratios. An estimated internal quantum efficiency of 36% was derived from photoluminescence data for green emitting nanocolumns.

  19. Molecular-beam epitaxial growth of tensile-strained and n-doped Ge/Si(001) films using a GaP decomposition source

    Energy Technology Data Exchange (ETDEWEB)

    Luong, T.K.P. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Ghrib, A. [Institut d' Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Bât. 220, F-91405 Orsay (France); Dau, M.T.; Zrir, M.A. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Stoffel, M. [Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 70239, F-54506 Vandoeuvre-lès-Nancy Cedex (France); Le Thanh, V., E-mail: lethanh@cinam.univ.mrs.fr [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); Daineche, R. [Aix-Marseille Université, CNRS IM2NP-UMR 6242, F-13397 Marseille Cedex 20 (France); Le, T.G.; Heresanu, V.; Abbes, O.; Petit, M. [Aix-Marseille Université, CNRS CINaM-UMR 7325, F-13288 Marseille Cedex 09 (France); El Kurdi, M.; Boucaud, P. [Institut d' Electronique Fondamentale, CNRS UMR 8622, Université Paris-Sud, Bât. 220, F-91405 Orsay (France); Rinnert, H. [Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, Nancy-Université, BP 70239, F-54506 Vandoeuvre-lès-Nancy Cedex (France); Murota, J. [Res. Inst. Elec. Comm., Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-04-30

    We have combined numerous characterization techniques to investigate the growth of tensile-strained and n-doped Ge films on Si(001) substrates by means of solid-source molecular-beam epitaxy. The Ge growth was carried out using a two-step growth method: a low-temperature growth to produce strain relaxed and smooth buffer layers, followed by a high-temperature growth to get high crystalline quality Ge layers. It is shown that the Ge/Si Stranski–Krastanov growth mode can be completely suppressed when the growth is performed at substrate temperatures ranging between 260 °C and 300 °C. X-ray diffraction measurements indicate that the Ge films grown at temperatures of 700–770 °C are tensile-strained with typical values lying in the range of 0.22–0.24%. Cyclic annealing allows further increase in the tensile strain up to 0.30%, which represents the highest value ever reported in the Ge/Si system. n-Doping of Ge was carried out using a GaP decomposition source. It is shown that heavy n-doping levels are obtained at low substrate temperatures (210–250 °C). For a GaP source temperature of 725 °C and a substrate temperature of 210 °C, a phosphorus concentration of about 10{sup 19} cm{sup −3} can be obtained. Photoluminescence measurements reveal an intensity enhancement of about 16 times of the direct band gap emission and display a redshift of 25 meV that can be attributed to band gap narrowing due to a high n-doping level. Finally, we discuss about growth strategies allowing optimizing the Ge growth/doping process for optoelectronic applications. - Highlights: • We investigate the effect of tensile strain and n-doping on Ge optical properties. • We show that cyclic annealing allows getting a tensile strain up to 0.30% in Ge. • n-Doping of Ge/Si films is performed using a GaP decomposition source. • We show that n-doping is more important to enhance the photoluminescence intensity. • We present new growth strategies to develop Ge

  20. Silicon/Germanium Molecular Beam Epitaxy

    OpenAIRE

    2006-01-01

    Molecular Beam Epitaxy (MBE) is a well-established method to grow low-dimensional structures for research applications. MBE has given many contributions to the rapid expanding research-area of nano-technology and will probably continuing doing so. The MBE equipment, dedicated for Silicon/Germanium (Si/Ge) systems, at Karlstads University (Kau) has been studied and started for the first time. In the work of starting the system, all the built in interlocks has been surveyed and connected, and t...

  1. Effects of growth temperature on high-quality In0.2Ga0.8N layers by plasma-assisted molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Zhang Dongyan; Zheng Xinhe; Li Xuefei; Wu Yuanyuan; Wang Jianfeng; Yang Hui

    2012-01-01

    High-quality In0.2Ga0.8N epilayers were grown on a GaN template at temperatures of 520 and 580 ℃ via plasma-assisted molecular beam epitaxy.The X-ray rocking curve full widths at half maximum (FWHM) of (10.2)reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature.When the growth temperature increases to 580 ℃,the FWHM of (00.2) reflections for these samples is very narrow and keeps similar,while significant improvement of(10.2) reflections with an FWHM value of 612 arcsec has been observed.This improved quality in InGaN layers grown at 580 ℃ is also reflected by the much larger size of the crystalline column from the AFM results,stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.

  2. Self-assembled GaInNAs/GaAsN quantum dot lasers: solid source molecular beam epitaxy growth and high-temperature operation

    Directory of Open Access Journals (Sweden)

    Yoon SF

    2006-01-01

    Full Text Available AbstractSelf-assembled GaInNAs quantum dots (QDs were grown on GaAs (001 substrate using solid-source molecular-beam epitaxy (SSMBE equipped with a radio-frequency nitrogen plasma source. The GaInNAs QD growth characteristics were extensively investigated using atomic-force microscopy (AFM, photoluminescence (PL, and transmission electron microscopy (TEM measurements. Self-assembled GaInNAs/GaAsN single layer QD lasers grown using SSMBE have been fabricated and characterized. The laser worked under continuous wave (CW operation at room temperature (RT with emission wavelength of 1175.86 nm. Temperature-dependent measurements have been carried out on the GaInNAs QD lasers. The lowest obtained threshold current density in this work is ∼1.05 kA/cm2from a GaInNAs QD laser (50 × 1,700 µm2 at 10 °C. High-temperature operation up to 65 °C was demonstrated from an unbonded GaInNAs QD laser (50 × 1,060 µm2, with high characteristic temperature of 79.4 K in the temperature range of 10–60 °C.

  3. Molecular beam epitaxy growth of GaN/AlGaN quantum cascade structure using droplet elimination by thermal annealing technique

    Energy Technology Data Exchange (ETDEWEB)

    Terashima, Wataru; Hirayama, Hideki [Terahertz Quantum Device Laboratory, RIKEN, 519-1399 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)

    2011-05-15

    We studied on the radio-frequency molecular beam epitaxial (RF-MBE) growth of GaN/AlGaN quantum cascade (QC) structure grown on a metal organic chemical vapor deposition (MOCVD)-GaN template by employing the droplet elimination by thermal annealing (DETA) technique, in order to realize the successful fabrication of a QC structure with a large number of periods and to increase the radiant intensity from terahertz-quantum cascade lasers (THz-QCL) sample. DETA is a technique in which the metal droplets that form on the surface are evaporated and eliminated by temporarily increasing the substrate temperature, utilizing the property whereby the equilibrium vapor pressures of the metal components (Ga, Al) are larger than those of the resulting nitrides (GaN, AlN). DETA is a useful method which not only makes it possible to increase the number of periods in the QC structure, but also to improve the surface and structural properties of the QC structure. We could successfully increase the radiant intensity from a THz-QCL sample by increasing the number of periods in the stacked QC structure by using the DETA technique. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Direct observation of strain in InAs quantum dots and cap layer during molecular beam epitaxial growth using in situ X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Shimomura, Kenichi; Ohshita, Yoshio; Kamiya, Itaru, E-mail: kamiya@toyota-ti.ac.jp [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Suzuki, Hidetoshi [Faculty of Engineering, University of Miyazaki, 1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192 (Japan); Sasaki, Takuo; Takahasi, Masamitu [Quantum Beam Science Center, Japan Atomic Energy Agency, Koto 1-1-1, Sayo-cho, Hyogo 679-5148 (Japan)

    2015-11-14

    Direct measurements on the growth of InAs quantum dots (QDs) and various cap layers during molecular beam epitaxy are performed by in situ X-ray diffraction (XRD). The evolution of strain induced both in the QDs and cap layers during capping is discussed based on the XRD intensity transients obtained at various lattice constants. Transients with different features are observed from those obtained during InGaAs and GaAs capping. The difference observed is attributed to In-Ga intermixing between the QDs and the cap layer under limited supply of In. Photoluminescence (PL) wavelength can be tuned by controlling the intermixing, which affects both the strain induced in the QDs and the barrier heights. The PL wavelength also varies with the cap layer thickness. A large redshift occurs by reducing the cap thickness. The in situ XRD observation reveals that this is a result of reduced strain. We demonstrate how such information about strain can be applied for designing and preparing novel device structures.

  5. Growth and characterization of molecular beam epitaxy-grown Bi{sub 2}Te{sub 3−x}Se{sub x} topological insulator alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tung, Y.; Chiang, Y. F.; Chong, C. W., E-mail: cheongwei2000@yahoo.com, E-mail: jcahuang@mail.ncku.edu.tw, E-mail: makalu@nsrrc.org.tw; Deng, Z. X.; Chen, Y. C. [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Huang, J. C. A., E-mail: cheongwei2000@yahoo.com, E-mail: jcahuang@mail.ncku.edu.tw, E-mail: makalu@nsrrc.org.tw [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Advanced Optoelectronic Technology Center (AOTC), National Cheng Kung University, Tainan 70101, Taiwan (China); Taiwan Consortium of Emergent Crystalline Materials (TCECM), Ministry of Science and Technology, Taipei 10622, Taiwan (China); Cheng, C.-M., E-mail: cheongwei2000@yahoo.com, E-mail: jcahuang@mail.ncku.edu.tw, E-mail: makalu@nsrrc.org.tw; Pi, T.-W.; Tsuei, K.-D. [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Li, Z.; Qiu, H. [School of Electronic Science and Applied Physics, HeFei University of Technology, Anhui (China)

    2016-02-07

    We report a systematic study on the structural and electronic properties of Bi{sub 2}Te{sub 3−x}Se{sub x} topological insulator alloy grown by molecular beam epitaxy (MBE). A mixing ratio of Bi{sub 2}Se{sub 3} to Bi{sub 2}Te{sub 3} was controlled by varying the Bi:Te:Se flux ratio. X-ray diffraction and Raman spectroscopy measurements indicate the high crystalline quality for the as-grown Bi{sub 2}Te{sub 3−x}Se{sub x} films. Substitution of Te by Se is also revealed from both analyses. The surfaces of the films exhibit terrace-like quintuple layers and their size of the characteristic triangular terraces decreases monotonically with increasing Se content. However, the triangular terrace structure gradually recovers as the Se content further increases. Most importantly, the angle-resolved photoemission spectroscopy results provide evidence of single-Dirac-cone like surface states in which Bi{sub 2}Te{sub 3−x}Se{sub x} with Se/Te-substitution leads to tunable surface states. Our results demonstrate that by fine-tuned MBE growth conditions, Bi{sub 2}Te{sub 3−x}Se{sub x} thin film alloys with tunable topological surface states can be obtained, providing an excellent platform for exploring the novel device applications based on this compound.

  6. Molecular beam epitaxy of GaAs nanowires and their sustainability for optoelectronic applications. Comparing Au- and self-assisted growth methods

    Energy Technology Data Exchange (ETDEWEB)

    Breuer, Steffen

    2011-09-28

    In this work the synthesis of GaAs nanowires by molecular beam epitaxy (MBE) using the vapour-liquid-solid (VLS) mechanism is investigated. A comparison between Au- and self-assisted VLS growth is at the centre of this thesis. While the Au-assisted method is established as a versatile tool for nanowire growth, the recently developed self-assisted variation results from the exchange of Au by Ga droplets and thus eliminates any possibility of Au incorporation. By both methods, we achieve nanowires with epitaxial alignment to the Si(111) substrates. Caused by differences during nanowire nucleation, a parasitic planar layer grows between the nanowires by the Au-assisted method, but can be avoided by the self-assisted method. Au-assisted nanowires grow predominantly in the metastable wurtzite crystal structure, while their self-assisted counterparts have the zincblende structure. All GaAs nanowires are fully relaxed and the strain arising from the lattice mismatch between GaAs and Si of 4.1 % is accommodated by misfit dislocations at the interface. Self-assisted GaAs nanowires are generally found to have vertical and non-polar side facets, while tilted and polar nanofacets were described for Au-assisted GaAs nanowires. We employ VLS nucleation theory to understand the effect of the droplet material on the lateral facets. Optoelectronic applications require long minority carrier lifetimes at room temperature. We fabricate GaAs/(Al,Ga)As core-shell nanowires and analyse them by transient photoluminescence (PL) spectroscopy. The results are 2.5 ns for the self-assisted nanowires as well as 9 ps for the Au-assisted nanowires. By temperature-dependent PL measurements we find a characteristic activation energy of 77 meV that is present only in the Au-assisted nanowires. We conclude that most likely Au is incorporated from the droplets into the GaAs nanowires and acts as a deep, non-radiative recombination centre.

  7. Growth of Y3Fe5O12/GaN layers by laser molecular-beam epitaxy and characterization of their structural and magnetic properties

    Science.gov (United States)

    Kaveev, A. K.; Bursian, V. E.; Gastev, S. V.; Krichevtsov, B. B.; Suturin, S. M.; Volkov, M. P.; Sokolov, N. S.

    2016-12-01

    Laser molecular-beam epitaxy has been employed to obtain layers of yttrium-iron garnet (YIG) Y3Fe5O12 on gallium nitride substrates. It was found that there exists a polycrystalline YIG phase without admixtures of other structural phases. A magnetic anisotropy of films of the "easy-magnetic plane" type was found. The gyromagnetic ratio and the demagnetizing field 4π M S were calculated.

  8. Lattice gas models and kinetic Monte Carlo simulations of epitaxial growth

    NARCIS (Netherlands)

    Biehl, Michael; Voigt, A

    2005-01-01

    A brief introduction is given to Kinetic Monte Carlo (KMC) simulations of epitaxial crystal growth. Molecular Beam Epitaxy (MBE) serves as the prototype example for growth far from equilibrium. However, many of the aspects discussed here would carry over to other techniques as well. A variety of app

  9. Growth optimisation of the GaN layers and GaN/AlGaN heterojunctions on bulk GaN substrates using plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Skierbiszewski, C.; Siekacz, M.; Feduniewicz, A.; Pastuszka, B.; Grzegory, I.; Leszczynski, M.; Porowski, S. [High Pressure Research Center, Polish Academy of Sciences, 01-142 Warsaw (Poland); Wasilewski, Z. [Institute for Microstructural Sciences, National Research Council, Ottawa (Canada)

    2004-01-01

    Influence of growth conditions in plasma assisted molecular beam epitaxy on quality of GaN layers and GaN/AlGaN heterojunctions is studied. The growth diagram for step-flow growth mode and different nitrogen flux is presented. The low defect density of bulk GaN substrates together with very low impurity background concentrations resulted in high electron mobility for GaN/AlGaN heterojunctions: 109,000 cm{sup 2}/Vs at 1.5 K, and 2500 cm{sup 2}/Vs at 295 K. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Epitaxy of an Al-Droplet-Free AlN Layer with Step-Flow Features by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    PAN Jian-Hai; WANG Xin-Qiang; CHEN Guang; LIU Shi-Tao; FENG Li; XU Fu-Jun; TANG Ning; SHEN Bo

    2011-01-01

    We investigate epitaxy of A1N layers on sapphire substrates by molecular beam epitaxy. It is found that an atomically Bat surface can be obtained under Al-rich conditions at growth temperature of 780°C. However, the growth window to obtain an Al-droplet-free surface is too narrow to be well-controlled. However, the growth window can be greatly broadened by increasing the growth temperature up to 950 "C, where an Al-droplet-free surface with a step-How feature is obtained due to the enhanced re-evaporization rate and migration ability of Al adatoms. The samples grown at the higher temperature also show a higher crystalline quality than those grown at lower temperatures.%@@ We investigate epitaxy of AlN layers on sapphire substrates by molecular beam epitaxy.It is found that an atomically fiat surface can be obtained under Al-rich conditions at growth temperature of 780℃.However, the growth window to obtain an Al-droplet-free surface is too narrow to be well-controlled.However, the growth window can be greatly broadened by increasing the growth temperature up to 950℃, where an Al-droplet-free surface with a step-flow feature is obtained due to the enhanced re-evaporization rate and migration ability of Al adatoms.The samples grown at the higher temperature also show a higher crystalline quality than those grown at lower temperatures.

  11. Endotaxial growth of CoSi2 within (111) oriented Si in a molecular beam epitaxy system

    Science.gov (United States)

    George, T.; Fathauer, R. W.

    1991-01-01

    A new mode of growth is reported in which buried metallic layers can be fabricated within a single-crystal semiconductor through preferential subsurface growth on previously-grown 'seed' regions. The deposition of Co at 800 C at a rate of 0.01 nm/s on (111) Si substrates containing buried CoSi2 columns 40-100 nm below the Si surface results in the growth and coalescence of these subsurface columns. The formation of a CoSi2 layer on the Si surface is suppressed by this growth mode. It is proposed that the high diffusion rate of Co at 800 C, coupled with the high growth rate of CoSi2 at the subsurface columns, is responsible for this preferred 'endotaxial' growth mode. This growth technique was used to produce a continuous buried single-crystal layer of CoSi2 under a single-crystal Si capping layer.

  12. Growth of InAs quantum dots on vicinal GaAs substrates by molecular beam epitaxy

    Science.gov (United States)

    Weir, Nicholas; Yao, Ruizhe; Lee, Chi-Sen; Guo, Wei

    2016-10-01

    Previous work shows the benefits of using vicinal substrates but there is currently a gap in the experimental studies of the effects under different MBE growth conditions. To fully realize controllable growth while using a vicinal substrate, we systematically explore and discuss the mechanism behind the dependence of the optical characteristics of MBE grown InAs QD ensembles with different growth parameters on a vicinal substrate. In addition, the potential improvement in optical quality with a vicinal substrate over an on-axis is demonstrated and an investigation into applying a two-step growth procedure on a vicinal substrate is conducted. Photoluminescence of the grown QD ensembles shows that increasing V/III ratio increased wavelength and decreased FWHM. Decreasing substrate temperature increased wavelength and FWHM. Utilizing the two-step growth method increased both wavelength and FWHM with increased interruption time.

  13. The effect of metal-rich growth conditions on the microstructure of Sc{sub x}Ga{sub 1-x}N films grown using molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, H.C.L.; Moram, M.A. [Department of Materials, Imperial College London (United Kingdom); Goff, L.E. [Department of Materials, Imperial College London (United Kingdom); Department of Physics, University of Cambridge (United Kingdom); Barradas, N.P. [CTN - Centro de Ciencias e Tecnologias Nucleares, Instituto Superior Tecnico, Universidade de Lisboa, Bobadela LRS (Portugal); Alves, E. [IPFN - Instituto de Plasmas e Fusao Nuclear, Lisboa (Portugal); Laboratorio de Aceleradores e Tecnologias de Radiacao, Instituto Superior Tecnico, Universidade de Lisboa, Bobadela LRS (Portugal); Pereira, S. [CICECO and Department of Physics, Universidade de Aveiro (Portugal); Beere, H.E.; Farrer, I.; Nicoll, C.A.; Ritchie, D.A. [Department of Physics, University of Cambridge (United Kingdom)

    2015-12-15

    Epitaxial Sc{sub x}Ga{sub 1-x}N films with 0 ≤ x ≤ 0.50 were grown using molecular beam epitaxy under metal-rich conditions. The Sc{sub x}Ga{sub 1-x}N growth rate increased with increasing Sc flux despite the use of metal-rich growth conditions, which is attributed to the catalytic decomposition of N{sub 2} induced by the presence of Sc. Microstructural analysis showed that phase-pure wurtzite Sc{sub x}Ga{sub 1-x}N was achieved up to x = 0.26, which is significantly higher than that previously reported for nitrogen-rich conditions, indicating that the use of metal-rich conditions can help to stabilise wurtzite phase Sc{sub x}Ga{sub 1-x}N. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Interfacial coarsening dynamics in epitaxial growth with slope selection

    Science.gov (United States)

    Moldovan; Golubovic

    2000-06-01

    We investigate interfacial dynamics of molecular-beam epitaxy (MBE) growth in the presence of instabilities inducing formation of pyramids. We introduce a kinetic scaling theory which provides an analytic understanding of the coarsening dynamics laws observed in numerous experiments and simulations of the MBE. We address MBE growth on crystalline surfaces with different symmetries in order to explain experimentally observed differences between the growth on (111) and (001) surfaces and understand the coarsening exponents measured on these surfaces. We supplement our kinetic scaling theory by numerical simulations which document that the edges of the pyramids, forming a network across the growing interface, are essential for qualitative understanding of the coarsening dynamics of molecular-beam epitaxy.

  15. Epitaxial growth of single crystal films

    Science.gov (United States)

    Lind, M. D.; Kroes, R. L.; Immorlica, A. A., Jr.

    1981-01-01

    An experiment in gallium arsenide liquid phase epitaxy (LPE) on a flight of the SPAR 6 is described. A general purpose LPE processor suitable for either SPAR or Space Transportation System flights was designed and built. The process was started before the launch, and only the final step, in which the epitaxial film is grown, was performed during the flight. The experiment achieved its objectives; epitaxial films of reasonably good quality and very nearly the thickness predicted for convection free diffusion limited growth were produced. The films were examined by conventional analytical techniques and compared with films grown in normal gravity.

  16. Graphitic carbon grown on fluorides by molecular beam epitaxy.

    Science.gov (United States)

    Jerng, Sahng-Kyoon; Lee, Jae Hong; Kim, Yong Seung; Chun, Seung-Hyun

    2013-01-03

    We study the growth mechanism of carbon molecules supplied by molecular beam epitaxy on fluoride substrates (MgF2, CaF2, and BaF2). All the carbon layers form graphitic carbon with different crystallinities depending on the cation. Especially, the growth on MgF2 results in the formation of nanocrystalline graphite (NCG). Such dependence on the cation is a new observation and calls for further systematic studies with other series of substrates. At the same growth temperature, the NCG on MgF2 has larger clusters than those on oxides. This is contrary to the general expectation because the bond strength of the carbon-fluorine bond is larger than that of the carbon-oxygen bond. Our results show that the growth of graphitic carbon does not simply depend on the chemical bonding between the carbon and the anion in the substrate.

  17. Infrared Rugates by Molecular Beam Epitaxy

    Science.gov (United States)

    Rona, M.

    1993-01-01

    Rugates are optical structures that have a sinusoidal index of refraction (harmonic gradient-index field). As their discrete high/ low index filter counterparts, they can be used as narrow rejection band filters. However, since rugates do not have abrupt interfaces, they tend to have a smaller absorption, hence deliver a higher in band reflectivity. The absence of sharp interfaces makes rugates even more desirable for high-energy narrow band reflectors. In this application, the lack of a sharp interface at the maximum internal standing wave electric field results in higher breakdown strengths. Our method involves fabricating rugates, with molecular beam epitaxy, on GaAs wafers as an Al(x)Ga(1-x)As single-crystal film.

  18. Growth and structure of epitaxial Ce0.8Sm0.2O1.9 by oxygen-plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Zhongqing [Nanjing Normal Univ. (China); Kuchibhatla, Satyanarayana V.N.T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Central Florida, Orlando, FL (United States); Engelhard, Mark H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shutthanandan, V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wang, Chong M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nachimuthu, Ponnusamy [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Marina, Olga A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saraf, Laxmikant V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thevuthasan, Suntharampillai [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Seal, Sudipta [Univ. of Central Florida, Orlando, FL (United States)

    2008-01-30

    The epitaxial growth of Ce0.8Sm0.2O1.9 films on sapphire (0001) substrate by oxygen-plasma-assisted MBE has been characterized using RHEED, XPS, XRD, AFM, HRTEM and RBS in order to determine their structure and compositions. The composition of the films was determined to be Ce: Sm: O of 0.8:0.2:1.9 by RBS. The film/substrate epitaxial relationship can be written as CeO2 (111)// α-Al2O3 (0001) and CeO2 [110]// α-Al2O3 . The Ce has only 4+ oxidation state in the films and Sm is fully oxidized in the films with formal oxidation of 3+. CeO2 (111) face is preferred orientation and the thin films are cubic phases.

  19. Reflection high energy electron diffraction studies on Si{sub x}Sn{sub y}Ge{sub 1−x−y} on Si(100) molecular beam epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, A.I., E-mail: nikif@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrentjeva 13, 630090 Novosibirsk (Russian Federation); Mashanov, V.I.; Timofeev, V.A.; Pchelyakov, O.P. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrentjeva 13, 630090 Novosibirsk (Russian Federation); Cheng, H.-H. [Center for Condensed Matter Sciences and Graduate Institute of Electronic Engineering, National Taiwan University, Taipei, 106, Taiwan, ROC (China)

    2014-04-30

    In situ reflection high energy electron diffraction was used to study the surface micromorphology of Si{sub x}Sn{sub y}Ge{sub 1−x−y} / Si(100) heterostructures obtained by molecular beam epitaxy. The obtained reflection high energy electron diffraction data allowed us to conclude that the epitaxial Si{sub x}Sn{sub y}Ge{sub 1−x−y} films are grown by the Stranski–Krastanov mechanism. It was established that Si{sub x}Sn{sub y}Ge{sub 1−x−y} and Ge{sub 1−z}Sn{sub z} wetting layer thicknesses depend on the substrate temperature. The observed surface superstructures changed during the wetting layer growth. - Highlights: • Stranski–Krastanov mechanism • Wetting layers depend on the temperature • Superstructures change.

  20. Molecular beam epitaxial growth of Bi2Te3 and Sb2Te3 topological insulators on GaAs (111 substrates: a potential route to fabricate topological insulator p-n junction

    Directory of Open Access Journals (Sweden)

    Zhaoquan Zeng

    2013-07-01

    Full Text Available 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.

  1. Selective epitaxial growth for YBCO thin films

    NARCIS (Netherlands)

    Damen, C.A.J.; Smilde, H.-J.H.; Blank, D.H.A.; Rogalla, H.

    1998-01-01

    A novel selective epitaxial growth (SEG) technique for (YBCO) thin films is presented. The method involves the deposition of a thin (about 10 nm) metal layer, in the desired pattern, on a substrate before the deposition of the superconducting thin film. During growth the metal reacts with the YBCO,

  2. Modelling, Design, Growth and Characterization of Strain Balanced Quantum Cascade Lasers (3-11mum), grown by Gas Source Molecular Beam Epitaxy

    Science.gov (United States)

    Bandyopadhyay, Neelanjan

    Quantum Cascade Laser (QCL) is a compact room temperature (RT) source of mid-infrared radiation, which can be used for spectroscopic detection of trace amount of chemicals. The mid-infrared spectral range between (3-11 microm), has a dense array of absorption lines of numerous molecules, due to the presence of fundamental vibrational modes. The goal of this thesis can be subdivided into two parts. Firstly, short wavelength QCLs, emitting below 4microm, perform poorly at RT, due to inter-valley Gamma --- L carrier scattering, carrier escape to the continuum, heat removal from the core region at high power density corresponding to short wavelength operation, and large interface scattering due to highly strained materials. Secondly, it is desirable to have a single QCL based source emitting between 6-10microm, which be used to detect multiple molecules having their peak absorptions far apart, inside this spectral range. However, gain bandwidth of a single core QCL is relatively small, so laser emission cannot be tuned over a wide spectral range. This thesis describes the working principle of a QCL based on superlattice transport, rate equations, scattering mechanism, and waveguide design. The choice of the material system for this work and the fundamentals of band structure engineering has been derived. Gas source molecular beam epitaxy - growth optimization and characterization is one of the most important features of this work, especially for short wavelength QCLs, and has been explained in depth. Different strategies for design of active region design of short wavelength QCL and heterogeneous broadband QCL has been explored. The major milestones, of this research was the world's first watt level continuous wave (CW), RT demonstration at 3.76 microm, which was followed by another milestone of the first CW, RT demonstration at 3.39microm and 3.55microm, and finally the elusive result of QCL emitting at CW, RT at a wavelength as short as lambda ~3microm, a record. In

  3. Effects of shutter transients in molecular beam epitaxy.

    Science.gov (United States)

    Gozu, Shin-Ichiro; Mozume, Teruo; Kuwatsuka, Haruhiko; Ishikawa, Hiroshi

    2012-11-12

    : We have studied the effects of shutter transients (STs) in molecular beam epitaxy (MBE). Two series of samples were grown by MBE and evaluated by X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements. The effects of STs were evaluated by growth rate (GR) analysis using a combination of growth time (GT) and thickness evaluated by XRD and XRR measurements. We revealed two opposite effects of STs: (1) overshoot of GR and (2) increase in GR with GT and subsequent saturation. Each effect was consistent with the previous studies; however, the previous studies showed no relationships between these two effects. By considering closing time of the shutter, the two opposite effects were well understood.

  4. Epitaxial growth of CZT(S,Se) on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Bojarczuk, Nestor A.; Gershon, Talia S.; Guha, Supratik; Shin, Byungha; Zhu, Yu

    2016-03-15

    Techniques for epitaxial growth of CZT(S,Se) materials on Si are provided. In one aspect, a method of forming an epitaxial kesterite material is provided which includes the steps of: selecting a Si substrate based on a crystallographic orientation of the Si substrate; forming an epitaxial oxide interlayer on the Si substrate to enhance wettability of the epitaxial kesterite material on the Si substrate, wherein the epitaxial oxide interlayer is formed from a material that is lattice-matched to Si; and forming the epitaxial kesterite material on a side of the epitaxial oxide interlayer opposite the Si substrate, wherein the epitaxial kesterite material includes Cu, Zn, Sn, and at least one of S and Se, and wherein a crystallographic orientation of the epitaxial kesterite material is based on the crystallographic orientation of the Si substrate. A method of forming an epitaxial kesterite-based photovoltaic device and an epitaxial kesterite-based device are also provided.

  5. Growth of Ge films by cluster beam deposition

    CERN Document Server

    Xu, J L; Feng, J Y

    2002-01-01

    Ge epitaxial layers with reasonable quality were grown on the Si(1 1 1) substrates by cluster beam deposition (CBD) process. The growth temperature plays a dominant role in the epitaxial growth of Ge films. The substrate temperature for epitaxial growth is about 500 deg. C, which is lower than the reported critical temperature of Ge epitaxial growth by MBE and CVD. A stress induced phase transition of Ge lattice from cubic to tetragonal is also observed in the CBD process, and the mechanism is discussed.

  6. Growth and characterization of lattice-matched InAlN/GaN Bragg reflectors grown by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM and Dpt. de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Luna, E.; Trampert, A. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2009-06-15

    We demonstrate six to ten period lattice-matched In{sub 0.18}Al{sub 0.82}N/GaN distributed Bragg reflectors with peak reflectivity centred around 400 nm, grown by molecular beam epitaxy. Thanks to the well-tuned ternary alloy composition crack-free layers have been obtained as confirmed by both optical and scanning electron microscopy. In addition, cross-sectional analysis by high resolution transmission electron microscopy reveals highly periodic structure with abrupt interfaces. When the number of DBRs periods increased from six to ten, peak reflectivity increased from 45% to 60%. This increase was found to be in reasonable agreement with theoretical simulations. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. InPBi single crystals grown by molecular beam epitaxy.

    Science.gov (United States)

    Wang, K; Gu, Y; Zhou, H F; Zhang, L Y; Kang, C Z; Wu, M J; Pan, W W; Lu, P F; Gong, Q; Wang, S M

    2014-06-26

    InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III-V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4-2.7 μm which can't be explained by the existing theory.

  8. Molecular beam epitaxy for high-efficiency nitride optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Heffernan, J.; Kauer, M.; Windle, J.; Hooper, S.E.; Bousquet, V.; Zellweger, C.; Barnes, J.M. [Sharp Laboratories of Europe, Edmund Halley Road, Oxford Science Park, Oxford OX4 4GB (United Kingdom)

    2006-06-15

    We review the significant progress made in the development of nitride laser diodes by molecular beam epitaxy (MBE). We report on our recent result of room temperature continuous-wave operation of InGaN quantum well laser diodes grown by MBE. Ridge waveguide lasers fabricated on freestanding GaN substrates have a continuous-wave threshold current of 125 mA, corresponding to a threshold current density of 5.7 kA cm{sup -2}. The lasers have a threshold voltage of 8.6 V and a lifetime of several minutes. We outline the further technical challenges associated with demonstrating lifetimes of several thousand hours and present an assessment of the potential of MBE as a growth method for commercial quality nitride optoelectronic devices. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Photoluminescence Characterization of Boron-doped Si Layers Grown by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    LI Cheng; LAI Hong-kai; CHEN Song-yan

    2005-01-01

    Photoluminescence spectra were used to characterize the boron-doped Si layers grown by molecular beam epitaxy using HBO2 as the doping source. The influence of boron doping concentration on the dislocation-related photoluminescence spectra of molecular beam epitaxy Si layers annealed at 900 ℃ was studied with different doping concentrations and growth temperature. The broad photoluminescence band(from 0.75 eV to 0.90 eV) including D1 and D2 bands was associated with high boron doping concentration in the samples, while D3 and D4 bands might be related to oxygen precipitates.

  10. Creating Ruddlesden-Popper phases by hybrid molecular beam epitaxy

    Science.gov (United States)

    Haislmaier, Ryan C.; Stone, Greg; Alem, Nasim; Engel-Herbert, Roman

    2016-07-01

    The synthesis of a 50 unit cell thick n = 4 Srn+1TinO3n+1 (Sr5Ti4O13) Ruddlesden-Popper (RP) phase film is demonstrated by sequentially depositing SrO and TiO2 layers in an alternating fashion using hybrid molecular beam epitaxy (MBE), where Ti was supplied using titanium tetraisopropoxide (TTIP). A detailed calibration procedure is outlined for determining the shuttering times to deposit SrO and TiO2 layers with precise monolayer doses using in-situ reflection high energy electron diffraction (RHEED) as feedback. Using optimized Sr and TTIP shuttering times, a fully automated growth of the n = 4 RP phase was carried out over a period of >4.5 h. Very stable RHEED intensity oscillations were observed over the entire growth period. The structural characterization by X-ray diffraction and high resolution transmission electron microscopy revealed that a constant periodicity of four SrTiO3 perovskite unit cell blocks separating the double SrO rocksalt layer was maintained throughout the entire film thickness with a very little amount of planar faults oriented perpendicular to the growth front direction. These results illustrate that hybrid MBE is capable of layer-by-layer growth with atomic level precision and excellent flux stability.

  11. Epitaxial growth of strained and unstrained GeSn alloys up to 25% Sn

    Energy Technology Data Exchange (ETDEWEB)

    Oehme, Michael, E-mail: oehme@iht.uni-stuttgart.de; Kostecki, Konrad; Schmid, Marc; Oliveira, Filipe; Kasper, Erich; Schulze, Jörg

    2014-04-30

    Strained and unstrained GeSn layers on Si substrates were grown with Sn contents up to 20% and 25%, respectively. All metastable layer structures were fabricated by means of an ultra-low temperature molecular beam epitaxy process. The useful thickness of the metastable layers for a range of Sn contents, growth temperatures and two different strain values (unstrained, compressive strained) is explored. The epitaxial breakdown thickness which limits the useful thickness range decreases exponentially with increasing growth temperature and Sn concentration. - Highlights: • GeSn epitaxy • GeSn layers with Sn contents up to 25% • Limited layer thickness.

  12. Growth and stability of rocksalt Zn1-xMgxO epilayers and ZnO/MgO superlattice on MgO (100) substrate by molecular beam epitaxy.

    Science.gov (United States)

    Lu, C-Y James; Tu, Y-T; Yan, T; Trampert, A; Chang, L; Ploog, K H

    2016-06-07

    Zn1-xMgxO films with x = 0.04-0.50 grown on MgO (100) substrates by molecular beam epitaxy retain the rocksalt (rs) crystal structure and grow epitaxially for x ≥ 0.17. In addition, the rs-ZnO epilayer is observed to be stable up to a thickness of 5 nm and also in a ZnO/MgO superlattice sample. However, a portion of the superlattice has transformed to wurtzite (wz)-structure islands in a self-accommodated manner during growth. The transformation is a combination of a Bain distortion, an in-plane rotation of 14.5°, and a Peierls distortion, resulting in an orientation relationship of (100)rs//(101̄0)wz and 〈011〉rs ∼//〈1̄21̄3〉wz. In such a manner, the volume expansion is only necessary along the growth direction and the in-plane strains can be minimized. A negative pressure generated during the transformation of ZnO stabilizes the MgO into a wurtzite structure.

  13. Applying CLIPS to control of molecular beam epitaxy processing

    Science.gov (United States)

    Rabeau, Arthur A.; Bensaoula, Abdelhak; Jamison, Keith D.; Horton, Charles; Ignatiev, Alex; Glover, John R.

    1990-01-01

    A key element of U.S. industrial competitiveness in the 1990's will be the exploitation of advanced technologies which involve low-volume, high-profit manufacturing. The demands of such manufacture limit participation to a few major entities in the U.S. and elsewhere, and offset the lower manufacturing costs of other countries which have, for example, captured much of the consumer electronics market. One such technology is thin-film epitaxy, a technology which encompasses several techniques such as Molecular Beam Epitaxy (MBE), Chemical Beam Epitaxy (CBE), and Vapor-Phase Epitaxy (VPE). Molecular Beam Epitaxy (MBE) is a technology for creating a variety of electronic and electro-optical materials. Compared to standard microelectronic production techniques (including gaseous diffusion, ion implantation, and chemical vapor deposition), MBE is much more exact, though much slower. Although newer than the standard technologies, MBE is the technology of choice for fabrication of ultraprecise materials for cutting-edge microelectronic devices and for research into the properties of new materials.

  14. Self-catalyzed growth of dilute nitride GaAs/GaAsSbN/GaAs core-shell nanowires by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kasanaboina, Pavan Kumar [Department of Electrical and Computer Engineering, North Carolina A& T State University, Greensboro, North Carolina 27411 (United States); Ahmad, Estiak [Nanoengineering, Joint School of Nanoscience and Nanoengineering, NCA& T State University, Greensboro, North Carolina 27401 (United States); Li, Jia; Iyer, Shanthi [Department of Electrical and Computer Engineering, North Carolina A& T State University, Greensboro, North Carolina 27411 (United States); Nanoengineering, Joint School of Nanoscience and Nanoengineering, NCA& T State University, Greensboro, North Carolina 27401 (United States); Reynolds, C. Lewis; Liu, Yang [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-09-07

    Bandgap tuning up to 1.3 μm in GaAsSb based nanowires by incorporation of dilute amount of N is reported. Highly vertical GaAs/GaAsSbN/GaAs core-shell configured nanowires were grown for different N contents on Si (111) substrates using plasma assisted molecular beam epitaxy. X-ray diffraction analysis revealed close lattice matching of GaAsSbN with GaAs. Micro-photoluminescence (μ-PL) revealed red shift as well as broadening of the spectra attesting to N incorporation in the nanowires. Replication of the 4K PL spectra for several different single nanowires compared to the corresponding nanowire array suggests good compositional homogeneity amongst the nanowires. A large red shift of the Raman spectrum and associated symmetric line shape in these nanowires have been attributed to phonon localization at point defects. Transmission electron microscopy reveals the dominance of stacking faults and twins in these nanowires. The lower strain present in these dilute nitride nanowires, as opposed to GaAsSb nanowires having the same PL emission wavelength, and the observation of room temperature PL demonstrate the advantage of the dilute nitride system offers in the nanowire configuration, providing a pathway for realizing nanoscale optoelectronic devices in the telecommunication wavelength region.

  15. Epitaxial growth of MgB2 films at ambient temperature

    Science.gov (United States)

    Shishido, Hiroaki; Yoshida, Takuya; Nakagami, Takatoshi; Ishida, Takekazu

    We grew crystalline MgB2 thin films using molecular beam epitaxy at a low substrate temperature of 110 °C under an ultrahigh vacuum of about 10-6 Pa. MgB2 thin films were deposited on the (001) surface of a 4H-SiC substrate with an epitaxial Mg buffer layer. The epitaxial growth was confirmed by X-ray diffraction measurements. MgB2 thin films show a sharp superconducting transition at 27.2 K, with a relatively narrow superconducting transition width ΔTc = 0.9 K. The growth temperature was lower than any in prior reports on superconducting MgB2 thin films. The presence of the epitaxial Mg buffer layer is crucial for reducing the epitaxial temperature.

  16. Molecular beam epitaxy growth of peak wavelength-controlled InGaAs/AlGaAs quantum wells for 4.3-μm mid-wavelength infrared detection.

    Science.gov (United States)

    Shi, Zhenwu; Wang, Lu; Zhen, Honglou; Wang, Wenxin; Chen, Hong

    2013-07-03

    InGaAs/AlGaAs multiple quantum wells used for 4.3 μm mid-wavelength infrared quantum well infrared detectors were grown by molecular beam epitaxy. In composition loss was observed and quantitatively studied by high-resolution X-ray diffraction technology. By this In composition loss effect, the energy band engineering on the photo-response wavelength is not easily achieved. A thin AlGaAs barrier grown at low temperature is used to suppress the In atom desorption, and this growth process was verified to be able to adjust the photo-response wavelength as designed by energy band engineering in the photocurrent spectrum.

  17. Epitaxial growth of cubic Gd2O3 thin films on Ge substrates

    Science.gov (United States)

    Molle, A.; Wiemer, C.; Bhuiyan, M. D. N. K.; Tallarida, G.; Fanciulli, M.

    2008-03-01

    Gd2O3 thin films were grown on Ge (001) substrates by molecular beam epitaxy. The epitaxial character of the film is demonstrated by electron diffraction during the growth. The structural characterization of the films shows that the Gd2O3 forms a bixbyite polymorph with a (110) out-of-plane orientation. The formation of bixbyite structured Gd2O3 is discussed in terms of the atomic arrangement of the oxide planes on the Ge(001) surface.

  18. Molecular beam epitaxy of three dimensional topological insulator Bi₂Se₃ thin films

    OpenAIRE

    Guo, Xin; 郭欣

    2013-01-01

    In this thesis, molecular-beam epitaxy (MBE) of three-dimensional (3D) topological insulator (TI) Bi_2 Se_3 thin films on different substrates is presented. The substrates experimented include InP(111)A, GaAs(111)A, InP(001) and GaAs(001). Multiple characterization techniques are employed to investigate the film’s structural, morphological and electrical properties. To facilitate growth of high quality epitaxial Bi_2 Se_3, thermal treatment of the substrate surfaceturnsout to be crucial for b...

  19. Site-controlled Ag nanocrystals grown by molecular beam epitaxy-Towards plasmonic integration technology

    OpenAIRE

    Urbańczyk, Adam; NöTZEL, R

    2012-01-01

    We demonstrate site-controlled growth of epitaxial Ag nanocrystals on patterned GaAs substrates by molecular beam epitaxy with high degree of long-range uniformity. The alignment is based on lithographically defined holes in which position controlled InAs quantum dots are grown. The Ag nanocrystals self-align preferentially on top of the InAs quantum dots. No such ordering is observed in the absence of InAs quantum dots, proving that the ordering is strain-driven. The presented technique faci...

  20. Molecular beam epitaxy growth and post-growth annealing of FeSe films on SrTiO3: a scanning tunneling microscopy study.

    Science.gov (United States)

    Li, Zhi; Peng, Jun-Ping; Zhang, Hui-Min; Zhang, Wen-Hao; Ding, Hao; Deng, Peng; Chang, Kai; Song, Can-Li; Ji, Shuai-Hua; Wang, Lili; He, Ke; Chen, Xi; Xue, Qi-Kun; Ma, Xu-Cun

    2014-07-02

    Low temperature scanning tunneling microscopy and spectroscopy are used to investigate the atomic and electronic structure evolution of FeSe films grown on SrTiO3 as a function of post-growth annealing. Single unit cell FeSe films are found to bond strongly with the underlying substrate, and become superconductive with diminishing chemical bond disorders at the interface via post-annealing. For thicker FeSe films, post-annealing removes excess Se in the films and leads to a transition from semiconductor into metallic behaviors. In double and multilayer films, strain-induced complex textures are observed and suggested to be the main cause for the absent superconductivity.

  1. InGaAsP-based uni-travelling carrier photodiode structure grown by solid source molecular beam epitaxy.

    Science.gov (United States)

    Natrella, Michele; Rouvalis, Efthymios; Liu, Chin-Pang; Liu, Huiyun; Renaud, Cyril C; Seeds, Alwyn J

    2012-08-13

    We report the first InGaAsP-based uni-travelling carrier photodiode structure grown by Solid Source Molecular Beam Epitaxy; the material contains layers of InGaAsP as thick as 300 nm and a 120 nm thick InGaAs absorber. Large area vertically illuminated test devices have been fabricated and characterised; the devices exhibited 0.1 A/W responsivity at 1550 nm, 12.5 GHz -3 dB bandwidth and -5.8 dBm output power at 10 GHz for a photocurrent of 4.8 mA. The use of Solid Source Molecular Beam Epitaxy enables the major issue associated with the unintentional diffusion of zinc in Metal Organic Vapour Phase Epitaxy to be overcome and gives the benefit of the superior control provided by MBE growth techniques without the costs and the risks of handling toxic gases of Gas Source Molecular Beam Epitaxy.

  2. Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination

    Science.gov (United States)

    Debiossac, M.; Atkinson, P.; Zugarramurdi, A.; Eddrief, M.; Finocchi, F.; Etgens, V. H.; Momeni, A.; Khemliche, H.; Borisov, A. G.; Roncin, P.

    2017-01-01

    Two aspects of the contribution of grazing incidence fast atom diffraction (GIFAD) to molecular beam epitaxy (MBE) are reviewed here: the ability of GIFAD to provide in-situ a precise description of the atomic-scale surface topology, and its ability to follow larger-scale changes in surface roughness during layer-by-layer growth. Recent experimental and theoretical results obtained for the He atom beam incident along the highly corrugated [ 1 1 bar 0 ] direction of the β2(2 × 4) reconstructed GaAs(001) surface are summarized. We also discuss the measurements and calculations for the beam incidence along the weakly corrugated [010] direction where a periodicity twice smaller than expected is observed. The combination of the experiment, quantum scattering matrix calculations, and semiclassical analysis allows structural characteristics of the surface to be revealed. For the in situ measurements of GIFAD during molecular beam epitaxy of GaAs on GaAs surface we analyze the change in elastic and inelastic contributions in the scattered beam, and the variation of the diffraction pattern in polar angle scattering. This analysis outlines the robustness, the simplicity and the richness of the GIFAD as a technique to monitor the layer-by-layer epitaxial growth.

  3. Epitaxial growth by monolayer restricted galvanic displacement

    Directory of Open Access Journals (Sweden)

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  4. Molecular beam epitaxy of GaN(0001) utilizing NH{sub 3} and/or NH{sup +}{sub {ital x}} ions: Growth kinetics and defect structure

    Energy Technology Data Exchange (ETDEWEB)

    Lee, N.; Powell, R.C.; Kim, Y.; Greene, J.E. [Materials Science Department, the Coordinated Science Laboratory, and the Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    1995-09-01

    Gas-source molecular beam epitaxy (GS-MBE), utilizing Ga and NH{sub 3}, and reactive-ion MBE (RIMBE), incorporating both thermal NH{sub 3} and low-energy NH{sup +}{sub {ital x}} ions, were used to grow single crystal GaN(0001) layers on Al{sub 2}O{sub 3}(0001) at temperatures {ital T}{sub {ital s}} between 700 and 850 {degree}C with deposition rates of 0.2--0.5 {mu}m h{sup {minus}1}. The RIMBE experiments were carried out with incident NH{sup +}{sub {ital x}}/Ga flux ratios {ital J}{sub NH{sup +}{sub {ital x}}}/{ital J}{sub Ga}=1.9--3.2 and NH{sup +}{sub {ital x}} acceleration energies {ital E}{sub NH{sup +}{sub {ital x}}}=45--90 eV. Plan-view and cross-sectional transmission electron microscopy analyses showed that the primary defects in the GS-MBE films were threading dislocations having either pure edge or mixed edge/screw characteristics with Burgers vectors {bar b}=1/3{l_angle}2{bar 1}{bar 1}0{r_angle}, basal-plane stacking faults with displacement vectors {bar R}=1/6{l_angle}02{bar 2}3{r_angle}, and prismatic stacking faults with {bar R}=1/2{l_angle}{bar 1}101{r_angle}. In the case of RIMBE films, no stacking faults or residual ion-induced defects were observed with {ital E}{sub NH{sup +}{sub {ital x}}}=45 eV and {ital T}{sub {ital s}}{ge}800 {degree}C. However, increasing {ital E}{sub NH{sup +}{sub {ital x}}} to {ge}60 eV at {ital T}{sub {ital s}}=800 {degree}C gave rise to the formation of residual ion-induced point-defect clusters observable by transmission electron microscopy (TEM). Increasing {ital T}{sub {ital s}} to 850 {degree}C with {ital E}{sub NH{sup +}{sub {ital x}}}{ge}60 eV resulted in the ion-induced defects aggregating to form interstitial basal and prismatic dislocation loops, whose number densities depended upon the ion flux, with Burgers vectors 1/2{l_angle}0001{r_angle} and 1/3{l_angle}2{bar 1}{bar 1}0{r_angle}, respectively. (Abstract Truncated)

  5. High-mobility BaSnO3 grown by oxide molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Santosh Raghavan

    2016-01-01

    Full Text Available High-mobility perovskite BaSnO3 films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO3 films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE approach, which supplies pre-oxidized SnOx. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO3. We demonstrate room temperature electron mobilities of 150 cm2 V−1 s−1 in films grown on PrScO3. The results open up a wide range of opportunities for future electronic devices.

  6. High-mobility BaSnO{sub 3} grown by oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Santosh; Schumann, Timo; Kim, Honggyu; Zhang, Jack Y.; Cain, Tyler A.; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-01-01

    High-mobility perovskite BaSnO{sub 3} films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO{sub 3} films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnO{sub x}. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO{sub 3}. We demonstrate room temperature electron mobilities of 150 cm{sup 2} V{sup −1} s{sup −1} in films grown on PrScO{sub 3}. The results open up a wide range of opportunities for future electronic devices.

  7. Shaping metal nanocrystals through epitaxial seeded growth

    Energy Technology Data Exchange (ETDEWEB)

    Habas, Susan E.; Lee, Hyunjoo; Radmilovic, Velimir; Somorjai,Gabor A.; Yang, Peidong

    2008-02-17

    Morphological control of nanocrystals has becomeincreasingly important, as many of their physical and chemical propertiesare highly shape-dependent. Nanocrystal shape control for both single andmultiple material systems, however, remains fairly empirical andchallenging. New methods need to be explored for the rational syntheticdesign of heterostructures with controlled morphology. Overgrowth of adifferent material on well-faceted seeds, for example, allows for the useof the defined seed morphology to control nucleation and growth of thesecondary structure. Here, we have used highly faceted cubic Pt seeds todirect the epitaxial overgrowth of a secondary metal. We demonstrate thisconcept with lattice matched Pd to produce conformal shape-controlledcore-shell particles, and then extend it to lattice mismatched Au to giveanisotropic growth. Seeding with faceted nanocrystals may havesignificant potential towards the development of shape-controlledheterostructures with defined interfaces.

  8. Properties of Ga1-xMnxN Epilayers Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Marcet, S.; Bellet, E.; Biquard, X.; Bougerol, C.; Cibert, J.; Ferrand, D.; Giraud, R.; Halley, D.; Kulatov, E.; Kuroda, S.; Mariette, H.; Titov, A.

    2005-06-01

    Wurtzite (Ga,Mn)N epilayers were grown by plasma-assisted molecular beam epitaxy. Mn incorporation strongly depends on growth conditions. Infrared optical absorption shows absorption bands related to neutral Mn acceptor A0 at 1.412 eV and 1.43 eV. Magnetic circular dichroism spectroscopyat the band gap edge, in agreement with magnetization data, exhibits temperature and magnetic field dependence revealing paramagnetic properties of Mn-doped GaN.

  9. High Performance Photocathodes based on Molecular Beam Epitaxy Deposition for Next Generation Photo Detectors and Light Sources

    CERN Document Server

    Xie, Junqi; Wagner, Robert

    2013-01-01

    The development of high-performance photocathodes is a key challenge for future accelerator and particle physics applications. In this paper photocathode growth through molecular beam epitaxy is introduced as a promising technique to obtain robust, highly efficient alkali-antimonide based photocathodes. Recent research shows that the quantum efficiency of photocathodes can be significantly enhanced through control of the photocathode crystallinity. Molecular beam epitaxy allows for cost-effective growth of large-area photocathodes with excellent control of the stoichiometry and crystallinity, making photocathodes with peak quantum efficiencies exceeding 35% routine.

  10. Ⅲ-V族三元化合物半导体材料分子束外延的生长热力学%Thermodynamic analysis of growth of ternary III-V semiconductor materials by molecular-beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    叶志成; 舒永春; 曹雪; 龚亮; 皮彪; 姚江宏; 邢晓东; 许京军

    2011-01-01

    Thermodynamic models for molecular-beam epitaxy (MBE) growth of ternary Ⅲ-V semiconductor materials are proposed. These models are in agreement with our experimental materials InGaP/GaAs and InGaAs/InP, and reported GaAsP/GaAs and InAsP/InP in thermodynamic growth. The lattice strain energy ΔG and thermal decomposition sensitive to growth temperature are demonstrated in the models simultaneously. ΔG is the function of the alloy composition, which is affected by flux ratio and growth temperature directly. The calculation results reveal that flux ratio and growth temperature mainly influence the growth process. Thermodynamic model of quaternary InGaAsP/GaAs semiconductor material is discussed also.%建立Ⅲ-V族三元化合物半导体材料的分子束外延生长热力学模型.该模型与实验材料InGaP/GaAs, InGaAs/InP 及已发表的GaAsP/GaAs, InAsP/InP 的数据吻合得很好.将晶格应变能ΔG及脱附对温度敏感这两个因素同时纳入热力学模型中,束流和生长温度直接影响合金组分,晶格应变能是合金组分的函数.热力学模型计算结果反映了束流和生长温度是生长过程中最主要的影响因素.讨论和分析了四元半导体材料InGaAsP/GaAs的热力学生长模型.

  11. Selective epitaxial growth of sub-micron structures of YBaCuO by substrate modification

    NARCIS (Netherlands)

    Blank, Dave H.A.; Damen, Cas A.J.; Kropman, Boike L.; Rogalla, Horst

    1994-01-01

    Sub-micron structures of high-Tc thin films have been realized with Selective Epitaxial Growth (SEG). Two different techniques to achieve SEG have been studied. First, narrow trenches down to 100 nm are etched into the substrate with a four-layer E-beam lithography technique. Second, amorphous metal

  12. GaAs Core/SrTiO3 Shell Nanowires Grown by Molecular Beam Epitaxy.

    Science.gov (United States)

    Guan, X; Becdelievre, J; Meunier, B; Benali, A; Saint-Girons, G; Bachelet, R; Regreny, P; Botella, C; Grenet, G; Blanchard, N P; Jaurand, X; Silly, M G; Sirotti, F; Chauvin, N; Gendry, M; Penuelas, J

    2016-04-13

    We have studied the growth of a SrTiO3 shell on self-catalyzed GaAs nanowires grown by vapor-liquid-solid assisted molecular beam epitaxy on Si(111) substrates. To control the growth of the SrTiO3 shell, the GaAs nanowires were protected using an arsenic capping/decapping procedure in order to prevent uncontrolled oxidation and/or contamination of the nanowire facets. Reflection high energy electron diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were performed to determine the structural, chemical, and morphological properties of the heterostructured nanowires. Using adapted oxide growth conditions, it is shown that most of the perovskite structure SrTiO3 shell appears to be oriented with respect to the GaAs lattice. These results are promising for achieving one-dimensional epitaxial semiconductor core/functional oxide shell nanostructures.

  13. Hexagonal Boron Nitride Tunnel Barriers Grown on Graphite by High Temperature Molecular Beam Epitaxy

    Science.gov (United States)

    Cho, Yong-Jin; Summerfield, Alex; Davies, Andrew; Cheng, Tin S.; Smith, Emily F.; Mellor, Christopher J.; Khlobystov, Andrei N.; Foxon, C. Thomas; Eaves, Laurence; Beton, Peter H.; Novikov, Sergei V.

    2016-01-01

    We demonstrate direct epitaxial growth of high-quality hexagonal boron nitride (hBN) layers on graphite using high-temperature plasma-assisted molecular beam epitaxy. Atomic force microscopy reveals mono- and few-layer island growth, while conducting atomic force microscopy shows that the grown hBN has a resistance which increases exponentially with the number of layers, and has electrical properties comparable to exfoliated hBN. X-ray photoelectron spectroscopy, Raman microscopy and spectroscopic ellipsometry measurements on hBN confirm the formation of sp2-bonded hBN and a band gap of 5.9 ± 0.1 eV with no chemical intermixing with graphite. We also observe hexagonal moiré patterns with a period of 15 nm, consistent with the alignment of the hBN lattice and the graphite substrate. PMID:27681943

  14. ZnS:N and ZnS:N,Ag grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Ichino, K.; Kotani, A.; Tanaka, H.; Kawai, T. [Department of Information and Electronics, Tottori University, 4-101 Koyama-minami, Tottori 680-8552 (Japan)

    2010-06-15

    The N-doping conditions have been investigated in the growth of ZnS:N by molecular beam epitaxy using RF plasma of N{sub 2} gas. As a result, high growth temperatures are found to be suitable for the effective incorporation and the activation of N acceptors. The capacitance versus voltage data of the ZnS:N layers grown at around 350 C exhibit p-type behavior, while the undoped layers show an n-type characteristic due to residual donors. ZnS:N,Ag epitaxial layers were also grown to investigate the effect of Ag-co-doping. It is shown that the p-type behavior of the N-doped layers is enhanced by the Ag-co-doping. This suggests the formation of Ag-related complex centers compensating residual donors (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Ge/GeSn heterostructures grown on Si (100) by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sadofyev, Yu. G., E-mail: sadofyev@hotmail.com; Martovitsky, V. P.; Bazalevsky, M. A.; Klekovkin, A. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Averyanov, D. V.; Vasil’evskii, I. S. [National Research Nuclear University MEPhI (Russian Federation)

    2015-01-15

    The growth of GeSn layers by molecular-beam epitaxy on Si (100) wafers coated with a germanium buffer layer is investigated. The properties of the fabricated structures are controlled by reflection high-energy electron diffraction, atomic-force microscopy, X-ray diffractometry, Rutherford backscattering, and Raman scattering. It is shown that GeSn layers with thicknesses up to 0.5 μm and Sn molar fractions up to 0.073 manifest no sign of plastic relaxation upon epitaxy. The lattice constant of the GeSn layers within the growth plane is precisely the same as that of Ge. The effect of rapid thermal annealing on the conversion of metastable elastically strained GeSn layers into a plastically relaxed state is examined. Ge/GeSn quantum wells with Sn molar fraction up to 0.11 are obtained.

  16. Growth of high purity semiconductor epitaxial layers by liquid phase epitaxy and their characterization

    Indian Academy of Sciences (India)

    S Dhar

    2005-07-01

    This paper briefly describes our work and the results on the growth of several III–V epitaxial semiconductor materials in high purity form by liquid phase epitaxy (LPE) technique. Various possible sources of impurities in such growth are listed and step-by-step procedures adopted to reduce them are discussed in particular reference to the growth of GaAs layers. The technique of growing very high purity layers by treating the melt with erbium is described for the growth of InGaAs and GaSb layers.

  17. Control of ion content and nitrogen species using a mixed chemistry plasma for GaN grown at extremely high growth rates >9 μm/h by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Gunning, Brendan P.; Clinton, Evan A.; Merola, Joseph J.; Doolittle, W. Alan, E-mail: alan.doolittle@ece.gatech.edu [Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Bresnahan, Rich C. [Veeco Instruments, St. Paul, Minnesota 55127 (United States)

    2015-10-21

    Utilizing a modified nitrogen plasma source, plasma assisted molecular beam epitaxy (PAMBE) has been used to achieve higher growth rates in GaN. A higher conductance aperture plate, combined with higher nitrogen flow and added pumping capacity, resulted in dramatically increased growth rates up to 8.4 μm/h using 34 sccm of N{sub 2} while still maintaining acceptably low operating pressure. It was further discovered that argon could be added to the plasma gas to enhance growth rates up to 9.8 μm/h, which was achieved using 20 sccm of N{sub 2} and 7.7 sccm Ar flows at 600 W radio frequency power, for which the standard deviation of thickness was just 2% over a full 2 in. diameter wafer. A remote Langmuir style probe employing the flux gauge was used to indirectly measure the relative ion content in the plasma. The use of argon dilution at low plasma pressures resulted in a dramatic reduction of the plasma ion current by more than half, while high plasma pressures suppressed ion content regardless of plasma gas chemistry. Moreover, different trends are apparent for the molecular and atomic nitrogen species generated by varying pressure and nitrogen composition in the plasma. Argon dilution resulted in nearly an order of magnitude achievable growth rate range from 1 μm/h to nearly 10 μm/h. Even for films grown at more than 6 μm/h, the surface morphology remained smooth showing clear atomic steps with root mean square roughness less than 1 nm. Due to the low vapor pressure of Si, Ge was explored as an alternative n-type dopant for high growth rate applications. Electron concentrations from 2.2 × 10{sup 16} to 3.8 × 10{sup 19} cm{sup −3} were achieved in GaN using Ge doping, and unintentionally doped GaN films exhibited low background electron concentrations of just 1–2 × 10{sup 15} cm{sup −3}. The highest growth rates resulted in macroscopic surface features due to Ga cell spitting, which is an engineering challenge still to be

  18. Growth and characterization of Hg1–CdTe epitaxial films by isothermal vapour phase epitaxy (ISOVPE)

    Indian Academy of Sciences (India)

    Manju Malhotra; Madhukar Gautam; J K Radhakrishnan; Vinod Kapoor; Sudeep Verma; Upendra Kumar; Anand Kumar; Garima Gupta; Anshu Goyal; S Sitharaman

    2005-04-01

    Growth of Hg1–CdTe epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication have been successfully solved. The epitaxial films have been electrically characterized by using the Hall effect and capacitance–voltage (–) measurements.

  19. Epitaxial Growth of Rhenium with Sputtering

    Science.gov (United States)

    2016-05-06

    match (a = 2.76 Å) to the oxygen sublattice (a = 2.77 Å) of α-Al2O3 (0001) [2]. Re also has a reasonably high superconducting critical temperature...to copyright. Keywords: Epitaxy, Rhenium, Sputtering 1. Introduction Epitaxial superconducting films of refractory metals are a promising new...than the RF sputtered films. These differences are most likely due to the fact that RF sputtering has more of an etching effect on the sample

  20. Growth Interruption Effect on the Fabrication of GaAs Concentric Multiple Rings by Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Fedorov A

    2010-01-01

    Full Text Available Abstract We present the molecular beam epitaxy fabrication and optical properties of complex GaAs nanostructures by droplet epitaxy: concentric triple quantum rings. A significant difference was found between the volumes of the original droplets and the final GaAs structures. By means of atomic force microscopy and photoluminescence spectroscopy, we found that a thin GaAs quantum well-like layer is developed all over the substrate during the growth interruption times, caused by the migration of Ga in a low As background.

  1. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    Energy Technology Data Exchange (ETDEWEB)

    Krockenberger, Y.

    2006-07-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  2. Molecular beam epitaxy of cubic III-nitrides on GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    As, D.J.; Schikora, D.; Lischka, K. [Dept. of Physics, Univ. of Paderborn, Paderborn (Germany)

    2003-07-01

    Molecular beam epitaxy has successfully been used to grow crystalline layers of group III-nitrides (GaN, AlN and InN) with cubic (zinc-blende) structure on GaAs substrates. In this article, we discuss these efforts that, despite inherent difficulties due to the metastability of the c-III nitrides, led to substantial improvements of the structural, electrical and optical quality of these wide gap semiconductors. We review experimental work concerned with the epitaxy of c-GaN and the control of the growth process in-situ, the important issue of p- and n-type doping of c-GaN and investigations of the structural and optical properties of c-InGaN and c-AlGaN. (orig.)

  3. Cleaning chemistry of InSb(100) molecular beam epitaxy substrates

    Science.gov (United States)

    Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

    1983-01-01

    InSb has been used as a substrate for molecular beam epitaxy. For good epitaxial growth, a substrate surface which is smooth and clean on an atomic scale is required. Chemical cleaning procedures provide an oxide film to passivate the surface. This film is then desorbed by in situ heating. The material forming the film should, therefore, have a high vapor pressure at some temperature less than the substrate melting temperature. A chloride film appears to satisfy the latter requirement. The present investigation is, therefore, concerned with the formation of a chloride film rather than an oxide film. Carbon contamination has been found to cause problems in chemical cleaning procedures. The level of carbon contamination found in the case of chloride film formation, is therefore compared with the corresponding level observed in procedures using oxide films. It appears that a chloride film grown in connection with a short exposure time to a Cl2 plasma is preferable to other passivation films studied.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bhargava, Nupur; Coppinger, Matthew; Prakash Gupta, Jay; Kolodzey, James [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)

    2013-07-22

    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.

  5. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Zuo, Jianmin; Braun, Paul V., E-mail: pbraun@illinois.edu [Department of Materials Science and Engineering, 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); Sardela, Mauro [Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, Royal Institute of Technology (KTH), Electrum 229, 164 40 Kista (Sweden)

    2015-12-14

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  6. Raman investigation of GaP–Si interfaces grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Bondi, A.; Cornet, C.; Boyer, S.; Nguyen Thanh, T.; Létoublon, A.; Pedesseau, L.; Durand, O. [Université Européenne de Bretagne, INSA, FOTON, UMR CNRS 6082, 20 Avenue des Buttes de Coësmes, F-35708 Rennes (France); Moreac, A. [Institut de Physique de Rennes, UMR-CNRS n°6251, Université Rennes1, Campus de Beaulieu — 35042 Rennes cedex (France); Ponchet, A. [CEMES, UPR CNRS 8011, F-31055 Toulouse (France); Le Corre, A. [Université Européenne de Bretagne, INSA, FOTON, UMR CNRS 6082, 20 Avenue des Buttes de Coësmes, F-35708 Rennes (France); Even, J., E-mail: jacky.even@insa.rennes.fr [Université Européenne de Bretagne, INSA, FOTON, UMR CNRS 6082, 20 Avenue des Buttes de Coësmes, F-35708 Rennes (France)

    2013-08-31

    Raman spectroscopy was used to investigate the residual strain in thin GaP layers deposited on Si substrates by molecular beam epitaxy. Different growth conditions were used to obtain a clean GaP–Si interface, including migration enhanced epitaxy. The strain induced Raman shifts of the longitudinal and the transverse optical GaP lattice modes were analyzed. The effects of crystalline defects are discussed, supported by high resolution transmission electron microscopy and X-ray scattering studies. Finally, Raman Spectroscopy reveals the presence of disorder (or surface)-activated optical phonons. This result is discussed in the light of surface morphology analyses. - Highlights: ► GaP thin layers grown by molecular beam epitaxy on Si substrates. ► Strain-induced Raman shifts of the optical GaP modes are analyzed. ► Simulation of optical GaP modes by density functional perturbation theory. ► Comparison with X-ray diffraction and electron and scanning probe microscopy data.

  7. Epitaxial growth with pulsed deposition: Submonolayer scaling and Villain instability

    DEFF Research Database (Denmark)

    Hinnemann, Berit; Hinrichsen, H.; Wolf, D.E.

    2003-01-01

    It has been observed experimentally that under certain conditions, pulsed laser deposition (PLD) produces smoother surfaces than ordinary molecular beam epitaxy (MBE). So far, the mechanism leading to the improved quality of surfaces in PLD is not yet fully understood. In the present work, we...

  8. A portable molecular beam epitaxy system for in situ x-ray investigations at synchrotron beamlines.

    Science.gov (United States)

    Slobodskyy, T; Schroth, P; Grigoriev, D; Minkevich, A A; Hu, D Z; Schaadt, D M; Baumbach, T

    2012-10-01

    A portable synchrotron molecular beam epitaxy (MBE) system is designed and applied for in situ investigations. The growth chamber is equipped with all the standard MBE components such as effusion cells with shutters, main shutter, cooling shroud, manipulator, reflection high energy electron diffraction setup, and pressure gauges. The characteristic feature of the system is the beryllium windows which are used for in situ x-ray measurements. An UHV sample transfer case allows in vacuo transfer of samples prepared elsewhere. We describe the system design and demonstrate its performance by investigating the annealing process of buried InGaAs self-organized quantum dots.

  9. Existence and regularity of weak solutions to a model for coarsening in molecular beam epitaxy

    CERN Document Server

    Zhang, Jun

    2011-01-01

    Taking into account the occurrence of a zero of the surface diffusion current and the requirement of the Ehrlich-Schwoebel effect, Siegert et al \\cite{Siegert94} formulate a model of Langevin type that describes the growth of pyramidlike structures on a surface under conditions of molecular beam epitaxy, and that the slope of these pyramids is selected by the crystalline symmetries of the growing film. In this article, the existence and uniqueness of weak solution to an initial boundary value problem for this model is proved, in the case that the noise is neglected. The regularity of the weak solution to models, with/without slope selection, is also investigated.

  10. Investigation of InN layers grown by molecular beam epitaxy on GaN templates

    Energy Technology Data Exchange (ETDEWEB)

    Vilalta-Clemente, A.; Mutta, G.R.; Chauvat, M.P.; Morales, M.; Doualan, J.L.; Ruterana, P. [CIMAP UMR 6252 CNRS-ENSICAEN-CEA-UCBN, Caen (France); Grandal, J.; Sanchez-Garcia, M.A.; Calle, F. [ISOM y Department de Ingenieria Electronica, E.T.S.I. Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria (Spain); Valcheva, E.; Kirilov, K. [Faculty of Physics, Sofia University (Bulgaria)

    2010-05-15

    An investigation of InN layers grown on GaN templates by molecular beam epitaxy (MBE) has been carried out by X-ray diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). A good correlation is noticed between their crystalline quality and optical properties. The best samples exhibit a PL emission between 0.6 and 0.7 eV. The surface structure was quite different from one sample to the other, pointing out to a critical role of the growth conditions, which probably need to be tightly optimized for a good reproducibility. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Silicon sheet with molecular beam epitaxy for high efficiency solar cells

    Science.gov (United States)

    Allen, F. G.

    1983-01-01

    The capabilities of the new technique of Molecular Beam Epitaxy (MBE) are applied to the growth of high efficiency silicon solar cells. Because MBE can provide well controlled doping profiles of any desired arbitrary design, including doping profiles of such complexity as built-in surface fields or tandem junction cells, it would appear to be the ideal method for development of high efficiency solar cells. It was proposed that UCLA grow and characterize silicon films and p-n junctions of MBE to determine whether the high crystal quality needed for solar cells could be achieved.

  12. High electron mobility of modulation doped GaAs after growing InP by solid source molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    SHU Yong-chun; PI Biao; LIN Yao-wang; XING Xiao-dong; YAO Jiang-hong; WANG Zhan-guo; XU Jing-jun

    2005-01-01

    Modulation-doped AlGaAs/GaAs structures were grown on GaAs(100) substrate by solid source molecular beam epitaxy (SSMBE) system. The factors which influence the electron mobility were investigated. After growing InP based materials, growth conditions were deteriorated, but by an appropriate method and using reasonaand growth conditions have been studied and optimized via Hall measurements. For a typical sample, 2.0 K electron served.

  13. Emission control of InGaN nanocolumns grown by molecular-beam epitaxy on Si(111) substrates

    OpenAIRE

    Albert, S; Bengoechea-Encabo, A.; Lefebvre, P.; Sanchez-Garcia, M. A.; Calleja, E.; Jahn, U.; Trampert, A

    2011-01-01

    International audience; This work studies the effect of the growth temperature on the morphology and emission characteristics of self-assembled InGaN nanocolumns grown by plasma assisted molecular beam epitaxy. Morphology changes are assessed by scanning electron microscopy, while emission is measured by photoluminescence. Within the growth temperature range of 750 to 650°C, an increase in In incorporation for decreasing temperature is observed. This effect allows tailoring the InGaN nanocolu...

  14. Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T; Lopez-Esteban, S; Pecharroman, C; Esteban-Cubillo, A; Moya, J S [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz 3, 28049, Cantoblanco, Madrid (Spain); Diaz, L A; Torrecillas, R [Nanomaterials and Nanotechnology Research Center (CINN), Consejo Superior de Investigaciones CientIficas (CSIC), C/ Francisco Pintado Fe 26, 33011, Oviedo, Asturias (Spain); Gremillard, L [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)], E-mail: jsmoya@icmm.csic.es

    2008-05-28

    Isolated tungsten nanoparticles ({alpha}-W and {beta}-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of {<=}20 nm for a low tungsten content (of {<=}1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (22-bar 0){sub Al2O3} parallel (121){sub W} and (311){sub MgAl2O4} parallel (110){sub W}.

  15. Organic/inorganic epitaxy : commensurate epitaxial growth of truxenone on Cu (111)

    OpenAIRE

    Ramadan, Alexandra J.; Nielsen, C. B.; Holliday, Sarah; Jones, T. S.; McCulloch, Iain; Rochford, L. A. (Luke A.)

    2016-01-01

    The growth of monolayers of truxenone on Cu (111) is investigated using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Two distinct molecular packing motifs are observed that exist individually at low and high coverage, and coexist at intermediate states. In each case a commensurate epitaxial relationship between the molecular surface mesh and the substrate is observed.\\ud \\ud

  16. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H.; Freeland, J. W.; Hong, Hawoong, E-mail: hhong@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Tung, I. C. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Chang, S.-H.; Bhattacharya, A.; Fong, D. D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2016-01-15

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  17. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J. H. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Tung, I. C. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA; Chang, S. -H. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Bhattacharya, A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Fong, D. D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; Freeland, J. W. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA; Hong, Hawoong [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  18. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy.

    Science.gov (United States)

    Lee, J H; Tung, I C; Chang, S-H; Bhattacharya, A; Fong, D D; Freeland, J W; Hong, Hawoong

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  19. Stabilizing CrO by epitaxial growth

    NARCIS (Netherlands)

    Rogojanu, Oana Corina; Sawatzky, G.A; Tjeng, L.H

    2002-01-01

    This thesis describes the efforts to stabilize chromium monoxide (CrO) as a thin epitaxial film on various substrates. The most stable and common oxidation phase for chromium is in chromium sesquioxide (Cr2O3). CrO does not exist as a bulk material in nature, therefore we have to grow it in a artifi

  20. Influence of substrate orientation on the structural quality of GaAs nanowires in molecular beam epitaxy.

    Science.gov (United States)

    Zhang, Zhi; Shi, Sui-Xing; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-01-26

    In this study, the effect of substrate orientation on the structural quality of Au-catalyzed epitaxial GaAs nanowires grown by a molecular beam epitaxy reactor has been investigated. It was found that the substrate orientations can be used to manipulate the nanowire catalyst composition and the catalyst surface energy and, therefore, to alter the structural quality of GaAs nanowires grown on different substrates. Defect-free wurtzite-structured GaAs nanowires grown on the GaAs (110) substrate have been achieved under our growth conditions.

  1. Composition control of quinary GaInNAsSb alloy grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Miyashita, Naoya; Ahsan, Nazmul; Okada, Yoshitaka [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Islam, Muhammad Monirul [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

    2013-11-15

    In order to precisely control the composition of quinary GaInNAsSb alloy, we investigated the incorporation behavior of constituent atoms during atomic hydrogen-assisted molecular beam epitaxial growth. The nitrogen (N) composition, in comparison of GaNAs and GaNAsSb, increased by the supply of antimony (Sb). However, addition of indium (In) decreases the N composition during Sb mediated growth of GaInNAsSb, which enables obtaining the same N composition when an adequate In composition is chosen. It was revealed that Sb incorporation was increased when (i) In composition decreased, (ii) Sb flux increased, (iii) growth temperature decreased, and (iv) growth rate increased. These results are thought to be related to the effect of competitive role among strain, coverage, desorption, and segregation. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Formation of GeSn alloy on Si(100) by low-temperature molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Talochkin, A. B., E-mail: tal@isp.nsc.ru [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)

    2014-12-29

    GeSn alloys grown on Si(100) by the low-temperature (100 °C) molecular beam epitaxy are studied using scanning tunneling microscopy and Raman spectroscopy. It is found that the effect of Sn as a surfactant modifies substantially the low-temperature growth mechanism of Ge on Si. Instead of the formation of small Ge islands surrounded by amorphous Ge, in the presence of Sn, the growth of pure Ge islands appears via the Stranski-Krastanov growth mode, and a partially relaxed Ge{sub 1−x}Sn{sub x} alloy layer with the high Sn-fraction up to 40 at. % is formed in the area between them. It is shown that the observed growth mode induced by high surface mobility of Sn and the large strain of the pseudomorphic state of Ge to Si ensures the minimum elastic-strain energy of the structure.

  3. Photoluminescence of ingaas/inp grown by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Harmand Jean Christophe

    2004-01-01

    Full Text Available Photoluminescence (PL measurements due to temperature and excitation power were carried out in as function of sample containing a In0,53Ga0,47. As layer, grown by Molecular Beam Epitaxy on an InP substrate. The origins of the several luminescence processes observed at low temperature were determined by studying their different behaviors with increasing temperature and excitation power and by comparing the results with the data found in the literature. The following transitions have been identified: one transition involving localized excitons and two transitions involving acceptor impurities. A review of the main works published in the literature related to the optical transitions observed at low temperature in InGaAs/InP is also presented.

  4. Nitrides optoelectronic devices grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kauer, M.; Bousquet, V.; Hooper, S.E.; Barnes, J.M.; Windle, J.; Tan, W.S.; Heffernan, J. [Sharp Laboratories of Europe, Edmund Halley Road, Oxford Science Park, Oxford OX4 4GB (United Kingdom)

    2007-01-15

    We report on the characteristics of our recent room temperature continuous-wave InGaN quantum well laser diodes grown by by molecular beam epitaxy (MBE). Uncoated ridge waveguide lasers fabricated on freestanding GaN substrates have a continuous-wave (cw) threshold current of 110 mA, corresponding to a threshold current density of 5.5 kA cm{sup -2}. We report on our steps taken to reduce threshold voltage to 7 V. Lasers with uncoated facets have a maximum cw output power of 14 mW and a cw characteristic temperature T{sub 0} of 123 K. Cw laser lifetime vs. power dissipation data is presented, with a maximum lifetime of 2.6 hours for the best laser. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    Directory of Open Access Journals (Sweden)

    K. Jeganathan

    2014-09-01

    Full Text Available We investigate the role of growth temperature on the optimization of lattice-matched In0.17Al0.83N/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 × 1013 cm−2 with the sheet resistance of ∼450 Ω/□ at room temperature as due to the manifestation of spontaneous polarization charge differences between InAlN and GaN layers.

  6. Epitaxial few-layer graphene: towards single crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Hibino, H; Kageshima, H; Nagase, M, E-mail: hibino@will.brl.ntt.co.j [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan)

    2010-09-22

    We review our research towards single-crystal growth of epitaxial few-layer graphene (FLG) on SiC substrates. We have established a method for evaluating the number of graphene layers microscopically using low-energy electron microscopy. Scanning probe microscopy in air is also useful for estimating the number-of-layers distribution in epitaxial FLG. The number-of-layers dependence of the work function and C1s binding energy is determined using photoelectron emission microscopy. We investigate the growth processes of epitaxial FLG on the basis of the microscopic observations of surface morphology and graphene distribution. To gain insights into the growth mechanism, we calculate the SiC surface structures with various C coverages using a first-principles scheme. Uniform bilayer graphene a few micrometres in size is obtained by annealing in UHV.

  7. The competing oxide and sub-oxide formation in metal-oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, Patrick; Bierwagen, Oliver [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

    2015-02-23

    The hetero-epitaxial growth of the n-type semiconducting oxides β-Ga{sub 2}O{sub 3}, In{sub 2}O{sub 3}, and SnO{sub 2} on c- and r-plane sapphire was performed by plasma-assisted molecular beam epitaxy. The growth-rate and desorbing flux from the substrate were measured in-situ under various oxygen to metal ratios by laser reflectometry and quadrupole mass spectrometry, respectively. These measurements clarified the role of volatile sub-oxide formation (Ga{sub 2}O, In{sub 2}O, and SnO) during growth, the sub-oxide stoichiometry, and the efficiency of oxide formation for the three oxides. As a result, the formation of the sub-oxides decreased the growth-rate under metal-rich growth conditions and resulted in etching of the oxide film by supplying only metal flux. The flux ratio for the exclusive formation of the sub-oxide (e.g., the p-type semiconductor SnO) was determined, and the efficiency of oxide formation was found to be the highest for SnO{sub 2}, somewhat lower for In{sub 2}O{sub 3}, and the lowest for Ga{sub 2}O{sub 3}. Our findings can be generalized to further oxides that possess related sub-oxides.

  8. A Study of GaAsSb Nanowires by Molecular Beam Epitaxy for Near IR Applications

    Science.gov (United States)

    2015-09-18

    NWs. Chen et al. [24] reported an InSb NW- based IR photodetector grown by Au catalyst-assisted molecular beam epitaxy (MBE). Recently, GaSb NWs were...these, Be is the commonly used p-type dopant in molecular beam epitaxy as it has a high diffusion coefficient4 and less memory effects5. Additionally...flux. Be is the commonly used p-type dopant in molecular beam epitaxy as it has a high diffusion coefficient [1] and less memory effects [2

  9. Growth, Antimony Incorporation Behaviour and Beryllium Doping of GaAs1-ySby Grown on GaAs by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    GAO Han-Chao; WANG Wen-Xin; JIANG Zhong-Wei; LIU Jian; YANG Cheng-Liang; WU Dian-Zhong; ZHOU Jun-Ming; CHEN Hong

    2008-01-01

    @@ A series of GaAs1-ySby epilayers are grown on GaAs substrates under different growth conditions, Different antimony compositions of samples with beryllium doping are obtained.A non-equilibrium thermodynamics model is used to calibrate and fit the Sb composition.Activation energy of 0.37eV for the dissociation process of Sb4 molecules is obtained.Carrier mobility and concentration of samples are influenced by the Sb composition.Quasi-qualitative analysis of mobility is used to explain the relations among Sb composition, carrier mobility and concentration.High resolution x-ray diffraction (HRXRD) rocking curves and Hall effects measurements are used to determine the crystal quality, carrier mobility and concentration.

  10. High-efficiency AlGaInP solar cells grown by molecular beam epitaxy

    Science.gov (United States)

    Faucher, J.; Sun, Y.; Jung, D.; Martin, D.; Masuda, T.; Lee, M. L.

    2016-10-01

    AlGaInP is an ideal material for ultra-high efficiency, lattice-matched multi-junction solar cells grown by molecular beam epitaxy (MBE) because it can be grown lattice-matched to GaAs with a wide 1.9-2.2 eV bandgap. Despite this potential, AlGaInP grown by molecular beam epitaxy (MBE) has yet to be fully explored, with the initial 2.0 eV devices suffering from poor performance due to low minority carrier diffusion lengths in both the emitter and base regions of the solar cell. In this work, we show that implementing an AlGaInP graded layer to introduce a drift field near the front surface of the device enabled greatly improved internal quantum efficiency (IQE) across all wavelengths. In addition, optimizing growth conditions and post-growth annealing improved the long-wavelength IQE and the open-circuit voltage of the cells, corresponding to a 3× increase in diffusion length in the base. Taken together, this work demonstrates greatly improved IQE, attaining peak values of 95%, combined with an uncoated AM1.5G efficiency of 10.9%, double that of previously reported MBE-grown devices.

  11. Reduction in the crystal defect density of Zn Se layers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lopez L, M.; Perez C, A.; Luyo A, J.; Melendez L, M.; Tamura, M. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del instituto politecnico Nacional, A.P. 14-740, 07000 Mexico D.F. (Mexico); Mendez G, V.H.; Vidal, M.A. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2000-07-01

    We present a study of the molecular beam epitaxial (MBE) grown of Zn Se layers on Ga-As and Si substrates. For the growth on GaAs substrates we investigated the effects of introducing buffer layers of Al{sub x}Ga{sub 1-x} As and In{sub x}Ga{sub 1-x} As with x = 0.01. Moreover, an analysis by secondary ion mass spectroscopy revealed that the use of AlGaAs buffer layers effectively suppress the Ga segregation onto the Zn Se layers surface. On the other hand, for the growth of Zn Se on Si substrates, we achieved a significant improvement in the crystal quality of Zn Se by irradiating the Si substrates with plasma of nitrogen prior to the growth. (Author)

  12. Synthesis of atomically thin hexagonal boron nitride films on nickel foils by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Nakhaie, S.; Wofford, J. M.; Schumann, T.; Jahn, U.; Ramsteiner, M.; Hanke, M.; Lopes, J. M. J., E-mail: lopes@pdi-berlin.de; Riechert, H. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2015-05-25

    Hexagonal boron nitride (h-BN) is a layered two-dimensional material with properties that make it promising as a dielectric in various applications. We report the growth of h-BN films on Ni foils from elemental B and N using molecular beam epitaxy. The presence of crystalline h-BN over the entire substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used to examine the morphology and continuity of the synthesized films. A scanning electron microscopy study of films obtained using shorter depositions offers insight into the nucleation and growth behavior of h-BN on the Ni substrate. The morphology of h-BN was found to evolve from dendritic, star-shaped islands to larger, smooth triangular ones with increasing growth temperature.

  13. Si Incorporation in InP Nanowires Grown by Au-Assisted Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Lorenzo Rigutti

    2009-01-01

    Full Text Available We report on the growth, structural characterization, and conductivity studies of Si-doped InP nanowires grown by Au-assisted molecular beam epitaxy. It is shown that Si doping reduces the mean diffusion length of adatoms on the lateral nanowire surface and consequently reduces the nanowire growth rate and promotes lateral growth. A resistivity as low as 5.1±0.3×10−5 Ω⋅cm is measured for highly doped nanowires. Two dopant incorporation mechanisms are discussed: incorporation via catalyst particle and direct incorporation on the nanowire sidewalls. The first mechanism is shown to be less efficient than the second one, resulting in inhomogeneous radial dopant distribution.

  14. Synthesis of long group IV semiconductor nanowires by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Patriarche Gilles

    2011-01-01

    Full Text Available Abstract We report the growth of Si and Ge nanowires (NWs on a Si(111 surface by molecular beam epitaxy. While Si NWs grow perpendicular to the surface, two types of growth axes are found for the Ge NWs. Structural studies of both types of NWs performed with electron microscopies reveal a marked difference between the roughnesses of their respective sidewalls. As the investigation of their length dependence on their diameter indicates that the growth of the NWs predominantly proceeds through the diffusion of adatoms from the substrate up along the sidewalls, difference in the sidewall roughness qualitatively explains the length variation measured between both types of NWs. The formation of atomically flat {111} sidewalls on the <110>-oriented Ge NWs accounts for a larger diffusion length.

  15. HfSe2 thin films: 2D transition metal dichalcogenides grown by molecular beam epitaxy.

    Science.gov (United States)

    Yue, Ruoyu; Barton, Adam T; Zhu, Hui; Azcatl, Angelica; Pena, Luis F; Wang, Jian; Peng, Xin; Lu, Ning; Cheng, Lanxia; Addou, Rafik; McDonnell, Stephen; Colombo, Luigi; Hsu, Julia W P; Kim, Jiyoung; Kim, Moon J; Wallace, Robert M; Hinkle, Christopher L

    2015-01-27

    In this work, we demonstrate the growth of HfSe2 thin films using molecular beam epitaxy. The relaxed growth criteria have allowed us to demonstrate layered, crystalline growth without misfit dislocations on other 2D substrates such as highly ordered pyrolytic graphite and MoS2. The HfSe2 thin films exhibit an atomically sharp interface with the substrates used, followed by flat, 2D layers with octahedral (1T) coordination. The resulting HfSe2 is slightly n-type with an indirect band gap of ∼ 1.1 eV and a measured energy band alignment significantly different from recent DFT calculations. These results demonstrate the feasibility and significant potential of fabricating 2D material based heterostructures with tunable band alignments for a variety of nanoelectronic and optoelectronic applications.

  16. Monte carlo simulation of epitaxial growth of gainassb films

    OpenAIRE

    Morales, Jheison Alejandro; Ríos-Olaya, Manuel Eduardo; Tirado Mejia, Liliana

    2014-01-01

    Material engineering finds an important support on simulation methods. The study of semiconductors growth techniques through simulation allows the determination of the influence of some growth parameters on the film properties. Experimentally, the variations of these parameters are difficult due to the high experimental demands and expenses. In this work we present the numerical simulation of the epitaxial growth of GaInAsSb by three methods. Devices based on this semiconductor material are t...

  17. Ion beam assisted film growth

    CERN Document Server

    Itoh, T

    2012-01-01

    This volume provides up to date information on the experimental, theoretical and technological aspects of film growth assisted by ion beams.Ion beam assisted film growth is one of the most effective techniques in aiding the growth of high-quality thin solid films in a controlled way. Moreover, ion beams play a dominant role in the reduction of the growth temperature of thin films of high melting point materials. In this way, ion beams make a considerable and complex contribution to film growth. The volume will be essential reading for scientists, engineers and students working in thi

  18. AlN interlayer to improve the epitaxial growth of SmN on GaN (0001)

    Science.gov (United States)

    Vézian, S.; Damilano, B.; Natali, F.; Khalfioui, M. Al; Massies, J.

    2016-09-01

    An in situ study of the epitaxial growth of SmN thin films on Ga-polar GaN (0001) templates by molecular beam epitaxy is reported. Using X-ray photoelectron spectroscopy we found that Ga segregates at the surface during the first stages of growth. We showed that the problem related to Ga surface segregation can be simply suppressed by growing a few monolayers of AlN before starting the SmN growth. This results in a significant improvement of the crystallinity of SmN thin films assessed by X-ray diffraction.

  19. Study of electrical properties of single GaN nanowires grown by molecular beam epitaxy

    Science.gov (United States)

    Mozharov, A. M.; Komissarenko, F. E.; Vasiliev, A. A.; Bolshakov, A. D.; Moiseev, E. I.; Mukhin, M. S.; Cirlin, G. E.; Mukhin, I. S.

    2016-08-01

    Electrical properties of single GaN nanowires grown by means of molecular beam epitaxy with N-plasma source were studied. Ohmic contacts connected to single n-type GaN wires were produced by the combination of electron beam lithography, metal vacuum evaporation and rapid thermal annealing technique. The optimal annealing temperature to produce ohmic contacts implemented in the form of Ti/Al/Ti/Au stack has been determined. By means of 2-terminal measurement wiring diagram the conductivity of single NW has been obtained for NWs with different growth parameters. The method of MESFET measurement circuit layout of single GaN nanowires (NWs) has been developed. In accordance with performed numerical calculation, free carriers' concentration and mobility of single NWs could be independently estimated using MESFET structure.

  20. Metallic impurities in gallium nitride grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    McHugo, S.A.; Krueger, J.; Kisielowski, C. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Transition metals are often encountered in trace amounts in semiconductors. They have been extensively studied in most elemental and compound systems, since they form deep donor and/or acceptor levels which usually degrade the electronic and optical material properties. Only very little is known about transition metals in recent III-V semiconducting materials, such as GaN, AlN and InN. These few studies have been done exclusively on Metal-Organic Chemical Vapor Deposition (MOCVD) or Hybrid Vapor Phase Epitaxy HVPE-grown GaN. Preliminary x-ray fluorescence studies at the Advanced Light Source, beamline 10.3.1, Lawrence Berkeley National Laboratory have revealed that GaN materials grown by Molecular Beam Epitaxy (MBE) have Fe, Ni and Cr as the dominant transition metal contaminants. This finding is commensurate with the extremely high concentrations of hydrogen, carbon and oxygen (up to 10{sup 20} cm{sup {minus}3}) measured by Secondary Ion Mass Spectroscopy (SIMS). Preliminary work using the mapping capabilities of the x-ray fluorescence microprobe revealed the metal impurities were inhomogeneously distributed over the film. Future work of this collaboration will be to find a correlation between the existence of transition metals in MBE films, as revealed by x-ray fluorescence, and Photoluminescence (PL) spectra taken in the infrared region. Also, the authors will make use of the 1 {mu}m spatial resolution of x-ray microprobe to locate the contaminants in relation to structural defects in the GaN films. Because of the large strain caused by the lattice mismatch between the GaN films and the substrates, the films grow in a columnar order with high densities of grain boundaries and dislocations. These structural defects offer preferential sites for metal precipitation or agglomeration which could degrade the optical properties of this material more so than if the impurities were left dissolved in the GaN.

  1. Influence of Growth Parameters of Frequency-Radio Plasma Nitrogen Source on Extending Emission Wavelengths from 1.31 μm to 1.55 μm GaInNAs/GaAs Quantum Wells Grown by Molecular-Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    WU Dong-Hai; WU Rong-Han; NIU Zhi-Chuan; ZHANG Shi-Yong; NI Hai-Qiao; HE Zhen-Hong; ZHAO Huan; PENG Hong-Ling; YANG Xiao-Hong; HAN Qin

    2006-01-01

    @@ High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3 μm to 1.5 μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N2 flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31 μm.

  2. Radical-source molecular beam epitaxy of ZnO-based heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sadofiev, Sergey

    2009-10-27

    This work focuses on the development of the novel growth approaches for the fabrication of Group II-oxide materials in the form of epitaxial films and heterostructures. It is shown that molecular-beam epitaxial growth far from thermal equilibrium allows one to overcome the standard solubility limit and to alloy ZnO with MgO or CdO in strict wurtzite phase up to mole fractions of several 10 %. In this way, a band-gap range from 2.2 to 4.4 eV can be covered. A clear layer-by-layer growth mode controlled by oscillations in reflection high-energy electron diffraction makes it possible to fabricate atomically smooth heterointerfaces and well-defined quantum well structures exhibiting prominent band-gap related light emission in the whole composition range. On appropriately designed structures, laser action from the ultraviolet down to green wavelengths and up to room temperature is achieved. The properties and potential of the ''state-of-the-art'' materials are discussed in relation to the advantages for their applications in various optoelectronic devices. (orig.)

  3. Epitaxial Properties of Co-Doped ZnO Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    CAO Qiang; DENG Jiang-Xia; LIU Guo-Lei; CHEN Yan-Xue; YAN Shi-Shen

    2007-01-01

    High quality Co-doped ZnO thin films are grown on single crystalline Al2O3(0001) and ZnO(0001) substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450 ℃. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction (RHEED) and ex-situ high resolution x-ray diffraction (HRXRD). The epitaxial thin films are single crystal at film thickness smaller than 500nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co2+ substituting Zn2+ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures TC above room temperature.

  4. Molecular beam epitaxy of c-plane wurtzite GaN on nitridized a-plane {beta}-Ga{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Villora, Encarnacion G. E-mail: villora.garcia@nims.go.jp; Shimamura, Kiyoshi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Aoki, Kazuo [Koha Co., Ltd., 2-6-8 Kouyama, Nerima-ku, Tokyo 176-0022 (Japan); Kitamura, Kenji [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2006-04-03

    Epitaxial growth of GaN on {beta}-Ga{sub 2}O{sub 3} single crystal substrates by the molecular beam epitaxy technique is demonstrated for the first time. Standard and in-plane X-ray diffraction evidence the growth of c-plane wurtzite GaN on a-plane {beta}-Ga{sub 2}O{sub 3}, the epitaxial relationship being <0 1 0>{sub Ga{sub 2}}{sub O{sub 3}}-parallel <1 1 2-bar 0>{sub GaN} and <0 0 1>{sub Ga{sub 2}}{sub O{sub 3}}-parallel <1-bar 1 0 0>{sub GaN}. Epitaxial growth without any buffer layer is achieved after an effective surface nitridation under NH{sub 3} gas.

  5. Interfaces in InAs/GaSb Superlattices Grown by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    GUO Jie; SUN Wei-Guo; PENG Zhen-Yu; ZHOU Zhi-Qiang; XU Ying-Qiang; NIU Zhi-Chuan

    2009-01-01

    @@ Short period InAs(4ML)/GaSb(SML) superlattices (SLs) with InSb- and mixed-like (or Ga1-xInxAs1-ySby-like) interfaces (IFs) are grown by molecular-beam epitaxy (MBE) on (001) GaSh substrates at optimized growth temperature. Raman scattering reveals that two kinds of IFs can be formed by controlling shutter sequences. X-ray diffraction (XRD) and atomic force microscopy (AFM) demonstrate that SLs with mixed-like IFs are more sensitive to growth temperature than that with InSb-like IFs. The photoluminescence (PL) spectra of SLs with mixed-like IFs show a stronger intensity and narrower line width than with InSb-like IFs. It is concluded that InAs/GaSb SLs with mixed-like IFs have better crystalline and optical properties.

  6. Self-organized dots of GaN:Mn grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, S.; Marcet, S. [CEA-CNRS Group ' ' Nanophysique et Semiconducteurs' ' , Laboratoire de Spectrometrie Physique, Universite Joseph Fourier, Grenoble I and CEA/DRFMC/SP2M, 17 avenue des Martyrs, 38054 Grenoble, Cedex 9 (France); Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Halley, D.; Ferrand, D.; Mariette, H. [CEA-CNRS Group ' ' Nanophysique et Semiconducteurs' ' , Laboratoire de Spectrometrie Physique, Universite Joseph Fourier, Grenoble I and CEA/DRFMC/SP2M, 17 avenue des Martyrs, 38054 Grenoble, Cedex 9 (France); Cibert, J. [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble (France); Yamamoto, S.; Sakai, T.; Ohshima, T.; Itoh, H. [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gumma 370-1292 (Japan)

    2006-07-01

    Self-organized dots of Mn-doped GaN were grown on AlN by plasma-assisted molecular beam epitaxy. The growth was performed in the nitrogen-rich growth regime with the addition of small amount of Mn flux. The in-situ surface observation using reflection high energy electron diffraction (RHEED) and the ex-situ examination using atomic force microscope (AFM) revealed that the dot formation was observed only in the case where the amount of Mn flux was small. The estimate of Mn composition using particle induced X-ray emission (PIXE) experiment showed that the Mn composition in the dots layer was much higher than in thick (Ga,Mn)N layers grown with the same amount of Mn flux. The maximum Mn composition for the high-density dot formation was about x=0.01. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Concentration transient analysis of antimony surface segregation during Si(100) molecular beam epitaxy

    Science.gov (United States)

    Markert, L. C.; Greene, J. E.; Ni, W.-X.; Hansson, G. V.; Sundgren, J.-E.

    1991-01-01

    Antimony surface segregation during Si(100) molecular beam epitaxy (MBE) was investigated at temperatures T(sub s) = 515 - 800 C using concentration transient analysis (CTA). The dopant surface coverage Theta, bulk fraction gamma, and incorporation probability sigma during MBE were determined from secondary-ion mass spectrometry depth profiles of modulation-doped films. Programmed T(sub s) changes during growth were used to trap the surface-segregated dopant overlayer, producing concentration spikes whose integrated area corresponds to Theta. Thermal antimony doping by coevaporation was found to result in segregation strongly dependent on T(sub s) with Theta(sub Sb) values up to 0.9 monolayers (ML): in films doped with Sb(+) ions accelerated by 100 V, Theta(sub Sb) was less than or equal to 4 x 10(exp -3) ML. Surface segregation of coevaporated antimony was kinematically limited for the film growth conditions in these experiments.

  8. Surfactant-assisted epitaxial growth and magnetism of Fe films on Cu(111)

    Energy Technology Data Exchange (ETDEWEB)

    Nino, M A; Camarero, J; Miguel, J J de; Miranda, R [Departamento de Fisica de la Materia Condensada and Instituto de Ciencia de Materiales ' Nicolas Cabrera' , Universidad Autonoma de Madrid, Cantoblanco, 28049-Madrid (Spain); Gomez, L [Facultad de Ciencias Exactas, IngenierIa y Agrimensura, Instituto de Fisica Rosario, 2000-Rosario (Argentina); Ferron, J [Instituto de Desarrollo Tecnologico para la Industria Quimica (CONICET-UNL), Departamento de Materiales, Facultad de IngenierIa Quimica, UNL, 3000 Santa Fe (Argentina)

    2008-07-02

    The magnetic properties of thin epitaxial layers of Fe grown on Cu(111) depend sensitively on the films' structure and morphology. A combination of experiments and numerical simulations reveals that the use of a surfactant monolayer (ML) of Pb during molecular beam epitaxy (MBE) growth at room temperature reduces the amount of interdiffusion at the Cu-Fe interface, retards the fcc-to-bcc transformation by about 2 ML and substantially increases the films' coercivity. The origin of all these alterations to the magnetic behavior can be traced back to the structural modifications provoked by the surfactant during the early growth stages. These results open the way for the controlled fabrication of custom-designed materials with specific magnetic characteristics.

  9. High quality YBCO superconductive thin films fabricated by laser molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    CHEN; Fan

    2001-01-01

    [1]Hirata,K.,Yamamoto,K.,Iijinma,J.et al.,Tunneling measurements on superconductor/insulator/superconductor junctions using single-crystal YBa2Cu3O7-x thin films,Appl.Phys.Lett.,1990,56(7):683-685.[2]Kingston,J.J.,Wellstood,F.C.,Lerch,P.et al.,Multilayer YBa2Cu3Ox-SrTiO3-YBa2Cu3Ox films for insulating crossovers,Appl.Phys.Lett.,1990,56(2):189-191.[3]Grundler,D.,Krumme,J.P.,David,B.et al.,YBa2Cu3O7 ramp-type junctions and superconducting quantum interference devices with an ultra thin barrier of NdGaO3,Appl.Phys.Lett.,1994,65(14):1841-1843.[4]Yang Guozhen,Lu Huibin,Chen Zhenghao et al.,Laser molecular beam epitaxy system and its key technologies,Science in China (in Chinese),Ser.A,1998,28(3):260-265.[5]Wang Ning,Lu Huibin,Chen,W.Z.et al.,Morphology and microstructure of BaTiO3/SrTiO3 superlattices grown on SrTiO3 by laser molecular-beam epitaxy,Appl.Phys.Lett.,1999,75(22):3464-3466.[6]Chen Li-Chyng,Particulates generated by pulsed laser ablation,in Pulsed Laser Deposition of Thin Films (eds.Chrisey,D.B.,Hulber,G.K.),New York:John Wiley & Sons,Inc.,1994,167-198.[7]Wang,H.S.,Dietsche,W.,Eissler,D.et al.,Molecular beam epitaxial growth and structure properties of DyBa2Cu3O7-y,J.Crys.Growth,1993,126:565-577.[8]Kita,R.,Hase,T.,Itti,R.et al.,Synthesis of CuO films using mass-separated,low-energy O+ ion beams,Appl.Phys.Lett.,1992,60(21):2684-2685.[9]Lu Huibin,Zhou Yueliang,Yang Guozhen et al.,Active gas source for thin film preparation,Chinese Patent (in Chinese),1996,No.ZL 96219046.2.[10]Wang Jing,Chen Fan,Zhao Tong et al.,Fabrication of high stable DC-SQUIDS with L-MBE YBCO thin films,Chinese Journal of Low Temperature Physics (in Chinese),1999,21(1):13-16.

  10. Epitaxial Fe3Si films on GaAs(100) substrates by means of electron beam evaporation

    Science.gov (United States)

    Thomas, J.; Schumann, J.; Vinzelberg, H.; Arushanov, E.; Engelhard, R.; Schmidt, O. G.; Gemming, T.

    2009-06-01

    This paper presents results on the preparation, structural, electrical and magnetic properties of Fe3Si films as a representative for a Heusler alloy-like compound which are known as half-metallic materials with ferromagnetic behaviour. The films have been prepared by means of ultra-high vacuum (UHV) electron beam evaporation with the aim of achieving epitaxial growth on GaAs(100) substrates. The main focus of this work is the structural characterization of the Fe3Si films grown on GaAs by means of high resolution transmission electron microscopy (TEM) to confirm the epitaxial growth. For Fe3Si with a composition in the vicinity of stoichiometry an almost lattice-matched growth on GaAs(001) has been observed characterized by a high crystalline quality and a good interface perfection. Besides the studies on cross-sectional samples by TEM data from reflection high energy electron diffraction (RHEED) and x-ray diffraction (XRD) were also included into the discussion. The electrical and magnetic parameters of the films studied are found to be in good agreement with data reported for the best Fe3Si molecular beam epitaxy (MBE) layers. As evidenced by x-ray diffraction, transmission electron microscopy, resistivity and magnetic measurements, we find an optimum growth temperature of 280-350 °C to obtain ferromagnetic layers with high crystal and interface perfection as well as a high degree of atomic ordering.

  11. Emission control of InGaN nanocolumns grown by molecular-beam epitaxy on Si(111) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Lefebvre, P. [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Universite Montpellier 2, F-34095 Montpellier, Cedex 5 (France); Jahn, U.; Trampert, A. [Paul-Drude-Institut fuer Festkoeperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2011-09-26

    This work studies the effect of the growth temperature on the morphology and emission characteristics of self-assembled InGaN nanocolumns grown by plasma assisted molecular beam epitaxy. Morphology changes are assessed by scanning electron microscopy, while emission is measured by photoluminescence. Within the growth temperature range of 750 to 650 deg. C, an increase in In incorporation for decreasing temperature is observed. This effect allows tailoring the InGaN nanocolumns emission line shape by using temperature gradients during growth. Depending on the gradient rate, span, and sign, broad emission line shapes are obtained, covering the yellow to green range, even yielding white emission.

  12. Epitaxial growth and electrical characterization of germanium

    Energy Technology Data Exchange (ETDEWEB)

    Bosi, M.; Attolini, G.; Ferrari, C.; Frigeri, C.; Calicchio, M.; Gombia, E. [IMEM-CNR, Parma (Italy); Asar, T.; Boyali, E.; Aydemir, U.; Ozcelik, S.; Kasap, M. [Physics Department of Arts and Science Faculty, Gazi University, Ankara (Turkey)

    2011-08-15

    Ge homojunctions were deposited by means of Metal Organic Vapour Phase Epitaxy (MOVPE) on Ge substrates at 550 C and 675 C, using AsH{sub 3} as n-type dopant. Ge{sub n}/Ge{sub p}, GaAs{sub n}/InGaP{sub n}/Ge{sub n}/Ge{sub p} and Ge{sub n}/Ge{sub p}/Ge{sub p} structures were prepared and studied, where n and p identify the layer or substrate doping. Vertical mesa junctions were obtained on the above structures by using conventional photolithographic and evaporation techniques. The junctions were characterized by I-V measurements under dark and illumination conditions and by EBIC technique. It has been observed that the samples grown at lower temperature showed better rectifying I-V characteristics and light conversion efficiency while EBIC results may suggest that a high As diffusion is present in the samples grown at higher temperature. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Meng; Zhao, Yuning; Yan, Xiaodong; Li, Guowang; Verma, Jai; Fay, Patrick [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Nomoto, Kazuki; Zhu, Mingda; Hu, Zongyang; Protasenko, Vladimir; Song, Bo; Xing, Huili Grace; Jena, Debdeep, E-mail: djena@cornell.edu [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Departments of ECE and MSE, Cornell University, Ithaca, New York 14853 (United States); Bader, Samuel [Departments of ECE and MSE, Cornell University, Ithaca, New York 14853 (United States)

    2015-12-07

    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm{sup 2} is obtained with reverse bias voltage up to −20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm{sup 2} is achieved, with a breakdown voltage corresponding to a peak electric field of ∼3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low.

  14. Thin film phase diagram of iron nitrides grown by molecular beam epitaxy

    Science.gov (United States)

    Gölden, D.; Hildebrandt, E.; Alff, L.

    2017-01-01

    A low-temperature thin film phase diagram of the iron nitride system is established for the case of thin films grown by molecular beam epitaxy and nitrided by a nitrogen radical source. A fine-tuning of the nitridation conditions allows for growth of α ‧ -Fe8Nx with increasing c / a -ratio and magnetic anisotropy with increasing x until almost phase pure α ‧ -Fe8N1 thin films are obtained. A further increase of nitrogen content below the phase decomposition temperature of α ‧ -Fe8N (180 °C) leads to a mixture of several phases that is also affected by the choice of substrate material and symmetry. At higher temperatures (350 °C), phase pure γ ‧ -Fe4N is the most stable phase.

  15. Controlling crystal phases in GaAs nanowires grown by Au-assisted molecular beam epitaxy.

    Science.gov (United States)

    Dheeraj, D L; Munshi, A M; Scheffler, M; van Helvoort, A T J; Weman, H; Fimland, B O

    2013-01-11

    Control of the crystal phases of GaAs nanowires (NWs) is essential to eliminate the formation of stacking faults which deteriorate the optical and electronic properties of the NWs. In addition, the ability to control the crystal phase of NWs provides an opportunity to engineer the band gap without changing the crystal material. We show that the crystal phase of GaAs NWs grown on GaAs(111)B substrates by molecular beam epitaxy using the Au-assisted vapor-liquid-solid growth mechanism can be tuned between wurtzite (WZ) and zinc blende (ZB) by changing the V/III flux ratio. As an example we demonstrate the realization of WZ GaAs NWs with a ZB GaAs insert that has been grown without changing the substrate temperature.

  16. Performance and degradation characteristics of blue-violet laser diodes grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tan, W.S.; Kauer, M.; Hooper, S.E.; Smeeton, T.M.; Bousquet, V.; Rossetti, M.; Heffernan, J. [Sharp Laboratories of Europe Ltd., Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB (United Kingdom); Xiu, H.; Humphreys, C.J. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom)

    2009-06-15

    This paper reports the state of the art performance for blue-violet laser diodes (LD) grown by molecular beam epitaxy. Improvements in device design and growth have resulted in a threshold current density of 3.6 kA/cm{sup 2}, which translates into improved cw lifetime of up to 42 hours. Reducing the internal loss resulted in a high cw slope efficiency of 1.08 W/A and a maximum cw output power of 145 mW. To obtain a better understanding of the LD failure mechanism, degraded LDs were analysed using surface mapping techniques such as photoluminescence and electroluminescence on a micrometric scale, which allows the identification of failure regions. These measurements revealed increased nonradiative recombination in localized regions and increased current injection non-uniformities as possible mechanisms for LD performance degradation after aging. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-12-15

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

  18. Epitaxial growth of aligned GaN nanowires and nanobridges

    OpenAIRE

    2007-01-01

    Homo-epitaxialy grown aligned GaN nanowires were prepared on crystalline GaN mesas. The GaN nanowires showed preferential growth along the 〈100〉 direction (m-axis direction). By using selectively positioned and crystallographically well defined GaN epitaxial lateral overgrowth (ELO) mesas as substrate, we obtained horizontally aligned GaN nanowires, in comb-like arrays and hexagonal network interconnecting the ELO mesas. Preliminary testing of the nanomechanical behavior of horizontal nanowir...

  19. Large array of single, site-controlled InAs quantum dots fabricated by UV-nanoimprint lithography and molecular beam epitaxy.

    Science.gov (United States)

    Schramm, A; Tommila, J; Strelow, C; Hakkarainen, T V; Tukiainen, A; Dumitrescu, M; Mews, A; Kipp, T; Guina, M

    2012-05-04

    We present the growth of single, site-controlled InAs quantum dots on GaAs templates using UV-nanoimprint lithography and molecular beam epitaxy. A large quantum dot array with a period of 1.5 µm was achieved. Single quantum dots were studied by steady-state and time-resolved micro-photoluminescence experiments. We obtained single exciton emission with a linewidth of 45 µeV. In time-resolved experiments, we observed decay times of about 670 ps. Our results underline the potential of nanoimprint lithography and molecular beam epitaxy to create large-scale, single quantum dot arrays.

  20. Big-data reflection high energy electron diffraction analysis for understanding epitaxial film growth processes.

    Science.gov (United States)

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

    2014-10-28

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED images, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the data set are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of a RHEED image sequence. This approach is illustrated for growth of La(x)Ca(1-x)MnO(3) films grown on etched (001) SrTiO(3) substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the asymmetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  1. Big-Data RHEED analysis for understanding epitaxial film growth processes

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-28

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in-situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED image, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the dataset are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of RHEED image sequence. This approach is illustrated for growth of LaxCa1-xMnO3 films grown on etched (001) SrTiO3 substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the assymetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  2. Epitaxial growth and electronic properties of mixed valence YbAl3 thin films

    Science.gov (United States)

    Chatterjee, Shouvik; Sung, Suk Hyun; Baek, David J.; Kourkoutis, Lena F.; Schlom, Darrell G.; Shen, Kyle M.

    2016-07-01

    We report the growth of thin films of the mixed valence compound YbAl3 on MgO using molecular-beam epitaxy. Employing an aluminum buffer layer, epitaxial (001) films can be grown with sub-nm surface roughness. Using x-ray diffraction, in situ low-energy electron diffraction, and aberration-corrected scanning transmission electron microscopy, we establish that the films are ordered in the bulk as well as at the surface. Our films show a coherence temperature of 37 K, comparable to that reported for bulk single crystals. Photoelectron spectroscopy reveals contributions from both f13 and f12 final states establishing that YbAl3 is a mixed valence compound and shows the presence of a Kondo Resonance peak near the Fermi-level.

  3. Structural and optical properties of self-catalytic GaAs:Mn nanowires grown by molecular beam epitaxy on silicon substrates

    DEFF Research Database (Denmark)

    Gas, Katarzyna; Sadowski, Janusz; Kasama, Takeshi;

    2013-01-01

    Mn-doped GaAs nanowires were grown in the self-catalytic growth mode on the oxidized Si(100) surface by molecular beam epitaxy and characterized by scanning and transmission electron microscopy, Raman scattering, photoluminescence, cathodoluminescence, and electron transport measurements...

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

    2014-05-07

    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 Δ1 minority spin state towards the Fermi level.

  5. Strain-Engineered Graphene Grown on Hexagonal Boron Nitride by Molecular Beam Epitaxy.

    Science.gov (United States)

    Summerfield, Alex; Davies, Andrew; Cheng, Tin S; Korolkov, Vladimir V; Cho, YongJin; Mellor, Christopher J; Foxon, C Thomas; Khlobystov, Andrei N; Watanabe, Kenji; Taniguchi, Takashi; Eaves, Laurence; Novikov, Sergei V; Beton, Peter H

    2016-03-01

    Graphene grown by high temperature molecular beam epitaxy on hexagonal boron nitride (hBN) forms continuous domains with dimensions of order 20 μm, and exhibits moiré patterns with large periodicities, up to ~30 nm, indicating that the layers are highly strained. Topological defects in the moiré patterns are observed and attributed to the relaxation of graphene islands which nucleate at different sites and subsequently coalesce. In addition, cracks are formed leading to strain relaxation, highly anisotropic strain fields, and abrupt boundaries between regions with different moiré periods. These cracks can also be formed by modification of the layers with a local probe resulting in the contraction and physical displacement of graphene layers. The Raman spectra of regions with a large moiré period reveal split and shifted G and 2D peaks confirming the presence of strain. Our work demonstrates a new approach to the growth of epitaxial graphene and a means of generating and modifying strain in graphene.

  6. Direct Measurements of Island Growth and Step-Edge Barriers in Colloidal Epitaxy

    KAUST Repository

    Ganapathy, R.

    2010-01-21

    Epitaxial growth, a bottom-up self-assembly process for creating surface nano- and microstructures, has been extensively studied in the context of atoms. This process, however, is also a promising route to self-assembly of nanometer- and micrometer-scale particles into microstructures that have numerous technological applications. To determine whether atomic epitaxial growth laws are applicable to the epitaxy of larger particles with attractive interactions, we investigated the nucleation and growth dynamics of colloidal crystal films with single-particle resolution. We show quantitatively that colloidal epitaxy obeys the same two-dimensional island nucleation and growth laws that govern atomic epitaxy. However, we found that in colloidal epitaxy, step-edge and corner barriers that are responsible for film morphology have a diffusive origin. This diffusive mechanism suggests new routes toward controlling film morphology during epitaxy.

  7. Epitaxy physical principles and technical implementation

    CERN Document Server

    Herman, Marian A; Sitter, Helmut

    2004-01-01

    Epitaxy provides readers with a comprehensive treatment of the modern models and modifications of epitaxy, together with the relevant experimental and technological framework. This advanced textbook describes all important aspects of the epitaxial growth processes of solid films on crystalline substrates, including a section on heteroepitaxy. It covers and discusses in details the most important epitaxial growth techniques, which are currently widely used in basic research as well as in manufacturing processes of devices, namely solid-phase epitaxy, liquid-phase epitaxy, vapor-phase epitaxy, including metal-organic vapor-phase epitaxy and molecular-beam epitaxy. Epitaxy’s coverage of science and texhnology thin-film is intended to fill the need for a comprehensive reference and text examining the variety of problems related to the physical foundations and technical implementation of epitaxial crystallization. It is intended for undergraduate students, PhD students, research scientists, lecturers and practic...

  8. Epitaxial growth of cubic Gd{sub 2}O{sub 3} thin films on Ge substrates

    Energy Technology Data Exchange (ETDEWEB)

    Molle, A; Wiemer, C; Bhuiyan, M D N K; Tallarida, G; Fanciulli, M [CNR-INFM, Laboratorio Nazionale MDM, via C. Olivetti 2, I-20041 Agrate Brianza (Italy)], E-mail: alessandro.molle@mdm.infm.it

    2008-03-15

    Gd{sub 2}O{sub 3} thin films were grown on Ge (001) substrates by molecular beam epitaxy. The epitaxial character of the film is demonstrated by electron diffraction during the growth. The structural characterization of the films shows that the Gd{sub 2}O{sub 3} forms a bixbyite polymorph with a (110) out-of-plane orientation. The formation of bixbyite structured Gd{sub 2}O{sub 3} is discussed in terms of the atomic arrangement of the oxide planes on the Ge(001) surface.

  9. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy.

    Science.gov (United States)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R

    2014-04-01

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  10. Facility for low-temperature spin-polarized-scanning tunneling microscopy studies of magnetic/spintronic materials prepared in situ by nitride molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wenzhi; Foley, Andrew; Alam, Khan; Wang, Kangkang; Liu, Yinghao; Chen, Tianjiao; Pak, Jeongihm; Smith, Arthur R., E-mail: smitha2@ohio.edu [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States)

    2014-04-15

    Based on the interest in, as well as exciting outlook for, nitride semiconductor based structures with regard to electronic, optoelectronic, and spintronic applications, it is compelling to investigate these systems using the powerful technique of spin-polarized scanning tunneling microscopy (STM), a technique capable of achieving magnetic resolution down to the atomic scale. However, the delicate surfaces of these materials are easily corrupted by in-air transfers, making it unfeasible to study them in stand-alone ultra-high vacuum STM facilities. Therefore, we have carried out the development of a hybrid system including a nitrogen plasma assisted molecular beam epitaxy/pulsed laser epitaxy facility for sample growth combined with a low-temperature, spin-polarized scanning tunneling microscope system. The custom-designed molecular beam epitaxy growth system supports up to eight sources, including up to seven effusion cells plus a radio frequency nitrogen plasma source, for epitaxially growing a variety of materials, such as nitride semiconductors, magnetic materials, and their hetero-structures, and also incorporating in situ reflection high energy electron diffraction. The growth system also enables integration of pulsed laser epitaxy. The STM unit has a modular design, consisting of an upper body and a lower body. The upper body contains the coarse approach mechanism and the scanner unit, while the lower body accepts molecular beam epitaxy grown samples using compression springs and sample skis. The design of the system employs two stages of vibration isolation as well as a layer of acoustic noise isolation in order to reduce noise during STM measurements. This isolation allows the system to effectively acquire STM data in a typical lab space, which during its construction had no special and highly costly elements included, (such as isolated slabs) which would lower the environmental noise. The design further enables tip exchange and tip coating without

  11. Crystal nucleation and near-epitaxial growth in nacre

    CERN Document Server

    Olson, Ian C; Tamura, Nobumichi; Kunz, Martin; Gilbert, Pupa U P A

    2013-01-01

    Nacre, the iridescent inner lining of many mollusk shells, interests materials scientists because of its unique brick-and-mortar periodic structure at the sub-micron scale and its remarkable resistance to fracture. However, it remains unclear how nacre forms. Here we present 20-nm, 2{\\deg}-resolution Polarization-dependent Imaging Contrast (PIC) images of shells from 15 species, mapping nacre tablets and their orientation patterns, showing where crystals nucleate and how they grow in nacre. In all shells we found stacks of co-oriented aragonite (CaCO3) tablets arranged into vertical columns or staggered diagonally. Only near the nacre-prismatic boundary are disordered crystals nucleated, as spherulitic aragonite. Overgrowing nacre tablet crystals are most frequently co-oriented with the underlying spherulitic aragonite or with another tablet, connected by mineral bridges. Therefore aragonite crystal growth in nacre is epitaxial or near-epitaxial, with abrupt or gradual changes in orientation, with c-axes with...

  12. Growth instability due to lattice-induced topological currents in limited-mobility epitaxial growth models.

    Science.gov (United States)

    Kanjanaput, Wittawat; Limkumnerd, Surachate; Chatraphorn, Patcha

    2010-10-01

    The energetically driven Ehrlich-Schwoebel barrier had been generally accepted as the primary cause of the growth instability in the form of quasiregular moundlike structures observed on the surface of thin film grown via molecular-beam epitaxy (MBE) technique. Recently the second mechanism of mound formation was proposed in terms of a topologically induced flux of particles originating from the line tension of the step edges which form the contour lines around a mound. Through large-scale simulations of MBE growth on a variety of crystalline lattice planes using limited-mobility, solid-on-solid models introduced by Wolf-Villain and Das Sarma-Tamborenea in 2+1 dimensions, we show that there exists a topological uphill particle current with strong dependence on specific lattice crystalline structure. Without any energetically induced barriers, our simulations produce spectacular mounds very similar, in some cases, to what have been observed in many recent MBE experiments. On a lattice where these currents cease to exist, the surface appears to be scale invariant, statistically rough as predicted by the conventional continuum growth equation.

  13. Growth of c-plane ZnO on γ-LiAlO{sub 2} (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yan, T. [Department of Materials and Optoelectronic Science/Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC (China); Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002 (China); Lu, C.-Y.J. [Department of Materials and Optoelectronic Science/Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC (China); Schuber, R. [Institute of Applied Physics/DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology, DE-76131 Karlsruhe (Germany); Chang, L., E-mail: lwchang@mail.nsysu.edu.tw [Department of Materials and Optoelectronic Science/Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC (China); Schaadt, D.M. [Institute of Applied Physics/DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology, DE-76131 Karlsruhe (Germany); Institute of Energy Research and Phyiscal Technologies, Clausthal Technical University, Am Stollen 19B, D-38640 Goslar (Germany); Chou, M.M.C.; Ploog, K.H. [Department of Materials and Optoelectronic Science/Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC (China); Chiang, C.-M. [Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC (China)

    2015-10-01

    Highlights: • ZnO epilayers were grown on LiAlO{sub 2} (1 0 0) substrate with a GaN buffer layer by MBE. • A high Zn/O flux ratio is beneficial for reducing the density of screw dislocations. • Reciprocal space maps demonstrate that the misfit strain in ZnO has been relaxed. • No interfacial layer is formed at ZnO/GaN interface using a Zn pre-exposure strategy. - Abstract: C-plane ZnO epilayers were grown on LiAlO{sub 2} (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy. Both the X-ray rocking curves and the transmission electron microscopy analyses indicate that the ZnO epilayers exhibit a lower threading dislocation density (∼1 × 10{sup 10} cm{sup −2}) as compared to those grown on LiAlO{sub 2} substrate without the buffer layer. A high Zn/O flux ratio is beneficial for reducing the density of screw-type dislocations. Reciprocal space maps demonstrate that the misfit strain has been relaxed. No interfacial layer is formed at the ZnO/GaN interface by using a Zn pre-exposure strategy. The ZnO epilayers exhibit a strong near band edge emission at 3.28 eV at room temperature with a negligible green band emission.

  14. Tuning the effective band gap and finding the optimal growth condition of InN thin films on GaN/sapphire substrates by plasma assisted molecular beam epitaxy technique

    Science.gov (United States)

    Ghosh, Kankat; Rathore, Jaswant Singh; Laha, Apurba

    2017-01-01

    InN thin films are grown on GaN/sapphire substrates with varying the nitrogen plasma power in plasma assisted molecular beam epitaxy (PA-MBE) system. In order to evaluate the effect of nitrogen plasma power on the different properties of the InN films, several characterization viz. x-ray diffraction, atomic force microscopy, photoluminescence measurement, infra-red spectroscopy and Hall measurement were performed. Two interesting phenomena observed from the measurements are described in this paper. Firstly, it is found from both the photoluminescence and infrared spectroscopy that only by varying the nitrogen plasma power (thus the III/V ratio), one can fine tune the optical absorption edge, i.e., the effective band gap of InN from ∼0.72 eV to ∼ 0.77 eV. Secondly, it is inferred that the film grown with stoichiometric condition (III/V ∼ 1) exhibits the best structural and electrical properties.

  15. Growth of epitaxial CdTe/CdS heterostructures for single crystal thin film solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Kessler, K.; Tiwari, A.N.; Blunier, S.; Zogg, H. [Swiss Federal Inst. of Tech., Zuerich (Switzerland). Arbeitsgemeinschaft fuer Industrielle Forschung

    1994-12-31

    Epitaxial CdTe/CdS heterostructures have been grown by molecular beam epitaxy onto BaF{sub 2} covered Si (111) substrates. An epitaxial BaF{sub 2} buffer is used for compatibility reasons, and because of easier dissolution during the lift-off processing. Epitaxy of cubic CdS (111) layers on BaF{sub 2}/Si (111) is achieved; electron channeling patterns exhibit a three-fold symmetry which is a characteristic for cubic crystal structures. The growth kinetics and structural properties of epitaxial CdS and CdTe/CdS have been studied with reflection high energy electron diffraction, Rutherford backscattering spectrometry and X-ray diffraction rocking curve measurements.the full width at half maximum of the (222) CdS and (333) CdTe X-ray peaks are {approximately} 1,150 arc sec for 2.7 and 3.4 {micro}m thick CdS and CdTe layers, respectively. To fabricate CdTe/CdS single crystal thin film solar cells, a lift-off process has been developed to remove the epitaxial layers from the Si substrates.

  16. Identifying potential BO2 oxide polymorphs for epitaxial growth candidates.

    Science.gov (United States)

    Mehta, Prateek; Salvador, Paul A; Kitchin, John R

    2014-03-12

    Transition metal dioxides (BO2) exhibit a number of polymorphic structures with distinct properties, but the isolation of different polymorphs for a given composition is carried out using trial and error experimentation. We present computational studies of the relative stabilities and equations of state for six polymorphs (anatase, brookite, rutile, columbite, pyrite, and fluorite) of five different BO2 dioxides (B = Ti, V, Ru, Ir, and Sn). These properties were computed in a consistent fashion using several exchange correlation functionals within the density functional theory formalism, and the effects of the different functionals are discussed relative to their impact on predictive synthesis. We compare the computational results to prior observations of high-pressure synthesis and epitaxial film growth and then use this discussion to predict new accessible polymorphs in the context of epitaxial stabilization using isostructural substrates. For example, the relative stabilities of the columbite polymorph for VO2 and RuO2 are similar to those of TiO2 and SnO2, the latter two of which have been previously stabilized as epitaxial films.

  17. Growth and characterization of III-N ternary thin films by plasma assisted atomic layer epitaxy at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Nepal, Neeraj; Anderson, Virginia R.; Hite, Jennifer K.; Eddy, Charles R.

    2015-08-31

    We report the growth and characterization of III-nitride ternary thin films (Al{sub x}Ga{sub 1−x}N, In{sub x}Al{sub 1−x}N and In{sub x}Ga{sub 1−x}N) at ≤ 500 °C by plasma assisted atomic layer epitaxy (PA-ALE) over a wide stoichiometric range including the range where phase separation has been an issue for films grown by molecular beam epitaxy and metal organic chemical vapor deposition. The composition of these ternaries was intentionally varied through alterations in the cycle ratios of the III-nitride binary layers (AlN, GaN, and InN). By this digital alloy growth method, we are able to grow III-nitride ternaries by PA-ALE over nearly the entire stoichiometry range including in the spinodal decomposition region (x = 15–85%). These early efforts suggest great promise of PA-ALE at low temperatures for addressing miscibility gap challenges encountered with conventional growth methods and realizing high performance optoelectronic and electronic devices involving ternary/binary heterojunctions, which are not currently possible. - Highlights: • III-N ternaries grown at ≤ 500 °C by plasma assisted atomic layer epitaxyGrowth of InGaN and AlInN in the spinodal decomposition region (15–85%) • Epitaxial, smooth and uniform III-N film growth at low temperatures.

  18. Self-catalyzed GaAsP nanowires grown on silicon substrates by solid-source molecular beam epitaxy.

    Science.gov (United States)

    Zhang, Yunyan; Aagesen, Martin; Holm, Jeppe V; Jørgensen, Henrik I; Wu, Jiang; Liu, Huiyun

    2013-08-14

    We realize the growth of self-catalyzed GaAsP nanowires (NWs) on silicon (111) substrates using solid-source molecular beam epitaxy. By optimizing the V/III and P/As flux ratios, as well as the Ga flux, high-crystal-quality GaAsP NWs have been demonstrated with almost pure zinc-blende phase. Comparing the growth of GaAsP NWs with that of the conventional GaAs NWs indicates that the incorporation of P has significant effects on catalyst nucleation energy, and hence the nanowire morphology and crystal quality. In addition, the incorporation ratio of P/As between vapor-liquid-solid NW growth and the vapor-solid thin film growth has been compared, and the difference between these two growth modes is explained through growth kinetics. The vapor-solid epitaxial growth of radial GaAsP shell on core GaAsP NWs is further demonstrated with room-temperature emission at ~710 nm. These results give valuable new information into the NW nucleation mechanisms and open up new perspectives for integrating III-V nanowire photovoltaics and visible light emitters on a silicon platform by using self-catalyzed GaAsP core-shell nanowires.

  19. Molecular beam epitaxy of InN dots on nitrided sapphire

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-04-20

    A series of self-assembled InN dots are grown by radio frequency (RF) plasma-assisted molecular beam epitaxy (MBE) directly on nitrided sapphire. Initial nitridation of the sapphire substrates at 900 C results in the formation of a rough AlN surface layer, which acts as a very thin buffer layer and facilitates the nucleation of the InN dots according to the Stranski-Krastanow growth mode, with a wetting layer of {approx}0.9 nm. Atomic force microscopy (AFM) reveals that well-confined InN nanoislands with the greatest height/width at half-height ratio of 0.64 can be grown at 460 C. Lower substrate temperatures result in a reduced aspect ratio due to a lower diffusion rate of the In adatoms, whereas the thermal decomposition of InN truncates the growth at T>500 C. The densities of separated dots vary between 1.0 x 10{sup 10} cm{sup -2} and 2.5 x 10{sup 10} cm{sup -2} depending on the growth time. Optical response of the InN dots under laser excitation is studied with apertureless near-field scanning optical microscopy and photoluminescence spectroscopy, although no photoluminescence is observed from these samples. In view of the desirable implementation of InN nanostructures into photonic devices, the results indicate that nitrided sapphire is a suitable substrate for growing self-assembled InN nanodots.

  20. InAsP/InGaAsP Strained Microstructures Grown by Gas Source Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    CHEN Yi-Qiao; CHEN Jian-Xin; ZHANG Yong-Gang; LI Ai-Zhen; K. Frbjdh; B. Stotz

    2000-01-01

    Device quality InAsP/InGaAsP strained multiquantum-well (MQW) structures are successfully grown by using gas source molecular beam epitaxy method. The grown MQW and InGaAsP quanternary alloy are characterized by using x-ray diffraction, room temperature photoluminescence measurements, confirming that optimum growth condition and high quality material have been obtained for device application. The grown laser structures are processed into ridge waveguide lasers. A threshold current as low as 16mA at 250C for 300μm long device has been obtained. Temperature-dependent light-current measurement shows a characteristic temperature of75K.

  1. Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy on semipolar GaN (2021) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sawicka, M.; Grzanka, S.; Skierbiszewski, C. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw (Poland); Cheze, C. [TopGaN Sp. z o.o., Sokolowska 29/37, 01-142 Warsaw (Poland); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Turski, H.; Muziol, G.; Krysko, M.; Grzanka, E.; Sochacki, T. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); Hauswald, C.; Brandt, O. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Siekacz, M. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Kucharski, R. [Ammono S.A., Czerwonego Krzyza 2/31, 00-377 Warsaw (Poland); Remmele, T.; Albrecht, M. [Leibniz Institute for Crystal Growth, Max-Born Strasse 2, Berlin 12489 (Germany)

    2013-03-18

    Multi-quantum well (MQW) structures and light emitting diodes (LEDs) were grown on semipolar (2021) and polar (0001) GaN substrates by plasma-assisted molecular beam epitaxy. The In incorporation efficiency was found to be significantly lower for the semipolar plane as compared to the polar one. The semipolar MQWs exhibit a smooth surface morphology, abrupt interfaces, and a high photoluminescence intensity. The electroluminescence of semipolar (2021) and polar (0001) LEDs fabricated in the same growth run peaks at 387 and 462 nm, respectively. Semipolar LEDs with additional (Al,Ga)N cladding layers exhibit a higher optical output power but simultaneously a higher turn-on voltage.

  2. Synthesis of as-grown superconducting MgB_2 thin films by molecular beam epitaxy in UHV conditions

    OpenAIRE

    Harada, Y.; Udsuka, M.; Nakanishi, Y.; Yoshizawa, M.

    2004-01-01

    As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001), MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method with novel co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c determined by resistivity measurement w...

  3. Structural and magnetic properties of magnetoelectric oxide heterostructures deposited by molecular beam epitaxy

    Science.gov (United States)

    Sterbinsky, George Evan

    There is considerable interest in incorporating magnetic materials into electronic devices to achieve new functions such as nonvolatile memories. Electric field control of magnetism is of much interest for new low power electronic devices because it eliminates the need to apply magnetic fields. One approach to achieving electrical control of magnetism is to exploit magnetoelastic effects in composites of ferromagnetic and ferroelectric materials. Application of an electric field to the composite will induce a strain through the piezo-electric effect, and the strain will alter the magnetization of the ferromagnetic constituent through the magnetoelastic effect. In this work, we examine the relationships between growth, strain, and magnetic properties of epitaxial ferrimagnetic Fe3O4 (magnetite) and ferroelectric BaTiO3 thin film heterostructures. We find that altering the strain state of a magnetite layer deposited on a BaTiO3 substrate has a profound effect on its magnetization. Here, we demonstrate the interaction between strain and magnetization is mediated by magnetic anisotropy and the magnetic domains structure of the films. Epitaxial magnetite films were deposited on MgO, BaTiO3, and SrTiO3 substrates by molecular beam epitaxy between temperatures of 573 and 723 K. Examination of the morphologies of Fe3O 4 films indicates that island growth is favored. Films exhibit in-plane magnetic isotropy and reduced saturation magnetizations with respect to the bulk material, as demonstrated by superconducting quantum interference device magnetometry. Magnetic hysteresis measurements suggest that these differences originate from antiphase boundary defects within the films. The strain in magnetite films deposited on BaTiO3 single crystal substrates was measured by x-ray diffraction. Measurements reveal a dependence of magnetization (M) on strain (epsilon) with discontinuities in magnetization versus temperature curves resulting from changes in the domain structure of the

  4. Imaging pulsed laser deposition growth of homo-epitaxial SrTiO3 by low-energy electron microscopy

    Science.gov (United States)

    van der Torren, A. J. H.; van der Molen, S. J.; Aarts, J.

    2016-12-01

    By combining low-energy electron microscopy with in situ pulsed laser deposition we have developed a new technique for film growth analysis, making use of both diffraction and real-space information. Working at the growth temperature, we can use: the intensity and profile variations of the specular beam to follow the coverage in a layer-by-layer fashion; real-space microscopy to follow e.g. atomic steps at the surface; and electron reflectivity to probe the unoccupied band structure of the grown material. Here, we demonstrate our methodology for homo-epitaxial growth of SrTiO3. Interestingly, the same combination of techniques will also be applicable to hetero-epitaxial oxide growth, largely extending the scope of research possibilities.

  5. Scanning Tunneling Microscopy Studies of Topological Insulators Grown by Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Xue Qikun

    2012-03-01

    Full Text Available We summarize our recent scanning tunneling microscopy (STM study of topological insulator thin films grown by molecular beam epitaxy (MBE, which includes the observation of electron standing waves on topological insulator surface and the Landau quantization of topological surface states. The work has provided valuable information to the understanding of intriguing properties of topological insulators, as predicted by theory.

  6. Origin of Spontaneous Core-Shell AIGaAs Nanowires Grown by Molecular Beam Epitaxy

    DEFF Research Database (Denmark)

    Dubrovskii, V. G.; Shtrom, I. V.; Reznik, R. R.;

    2016-01-01

    Based on the high-angle annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy studies, we unravel the origin of spontaneous core shell AlGaAs nanowires grown by gold-assisted molecular beam epitaxy. Our AlGaAs nanowires have a cylindrical core...

  7. Electron beam pumped III-V nitride vertical cavity surface emitting lasers grown by molecular beam epitaxy

    Science.gov (United States)

    Ng, Hock Min

    The design and fabrication by molecular beam epitaxy of a prototype vertical cavity laser based on the III-V nitrides were investigated in this work. The bottom mirror of the laser consists of distributed Bragg reflectors (DBRs) based on quarterwave AlN (or AlxGa1-xN) and GaN layers. Such DBRs were designed for maximum reflectivity in the spectral region from 390--600 nm. The epitaxial growth of these two binaries on each other revealed that while AlN grows on GaN in a two-dimensional mode (Frank-van der Merwe mode), GaN grows on AlN in a three-dimensional mode (Stranski-Krastanov mode). In spite of that, DBRs with peak reflectance up to 99% and bandwidths of 45nm were fabricated. The measured reflectance spectra were compared with simulations using the transmission matrix method. The mechanical stability of these DBR structures due to non-uniform distribution of strain arising from lattice or thermal mismatch of the various components were also addressed. The active region of the laser consists of InGaN/GaN multiple quantum wells (MQWs). The existence of up to the third order diffraction peaks in the x-ray diffraction spectra suggests that the interfaces between InGaN and GaN are sharp with little interdiffusion at the growth temperature. The photoluminescence and cathodoluminescence spectra were analyzed to determine the optical quality of the MQWs. The best MQWs were shown to have a single emission peak at 397nm with full width half maximum (FWHM) of 11nm. Cathodoluminescence studies showed that there are spatially localized areas of intense light emission. The complete device was formed on (0001) sapphire substrates using the previously described DBRs as bottom mirrors and the MQWs as the active region. The top mirror of the device consists of metallic silver. The device was pumped by an electron beam from the top mirror side and the light output was collected from the sapphire side. Measurements at 100K showed narrowing of the linewidth with increasing pump

  8. Isotype InGaN/GaN heterobarrier diodes by ammonia molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Fireman, Micha N.; Browne, David A.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2016-02-07

    The design of isotype InGaN/GaN heterobarrier diode structures grown by ammonia molecular beam epitaxy is presented. On the (0001) Ga-polar plane, a structure consisting of a surface n{sup +} GaN contact layer, followed by a thin InGaN layer, followed by a thick unintentionally doped (UID) GaN layer, and atop a buried n{sup +} GaN contact layer induces a large conduction band barrier via a depleted UID GaN layer. Suppression of reverse and subthreshold current in such isotype barrier devices under applied bias depends on the quality of this composite layer polarization. Sample series were grown under fixed InGaN growth conditions that varied either the UID GaN NH{sub 3} flow rate or the UID GaN thickness, and under fixed UID GaN growth conditions that varied InGaN growth conditions. Decreases in subthreshold current and reverse bias current were measured for thicker UID GaN layers and increasing InGaN growth rates. Temperature-dependent analysis indicated that although extracted barrier heights were lower than those predicted by 1D Schrödinger Poisson simulations (0.9 eV–1.4 eV for In compositions from 10% to 15%), optimized growth conditions increased the extracted barrier height from ∼11% to nearly 85% of the simulated values. Potential subthreshold mechanisms are discussed, along with those growth factors which might affect their prevalence.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-01

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

  10. Misfit dislocation free InAs/GaSb core-shell nanowires grown by molecular beam epitaxy.

    Science.gov (United States)

    Rieger, T; Grützmacher, D; Lepsa, M I

    2015-01-07

    In this report, we present the growth and structural analyses of broken gap InAs/GaSb core-shell nanowires by molecular beam epitaxy using an Au-free approach. Depending on the shell growth temperature, two distinct growth regimes for the GaSb shells are identified resulting in conformal or tapered shells. Morphological analyses reveal a dodecagonal nanowire cross-section after GaSb shell growth. Detailed transmission electron microscope investigations from different zone axes confirm that the small lattice mismatch of 0.6% allows the deposition of 40 nm thick GaSb shells free of misfit dislocations. Additionally, an abrupt interface from InAs to GaSb is found. These nanowires are suitable for future devices such as TFETs.

  11. Structural and Electrical Properties of MoTe2 and MoSe2 Grown by Molecular Beam Epitaxy.

    Science.gov (United States)

    Roy, Anupam; Movva, Hema C P; Satpati, Biswarup; Kim, Kyounghwan; Dey, Rik; Rai, Amritesh; Pramanik, Tanmoy; Guchhait, Samaresh; Tutuc, Emanuel; Banerjee, Sanjay K

    2016-03-23

    We demonstrate the growth of thin films of molybdenum ditelluride and molybdenum diselenide on sapphire substrates by molecular beam epitaxy. In situ structural and chemical analyses reveal stoichiometric layered film growth with atomically smooth surface morphologies. Film growth along the (001) direction is confirmed by X-ray diffraction, and the crystalline nature of growth in the 2H phase is evident from Raman spectroscopy. Transmission electron microscopy is used to confirm the layered film structure and hexagonal arrangement of surface atoms. Temperature-dependent electrical measurements show an insulating behavior that agrees well with a two-dimensional variable-range hopping model, suggesting that transport in these films is dominated by localized charge-carrier states.

  12. Surface optical phonons in GaAs nanowires grown by Ga-assisted chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    García Núñez, C., E-mail: carlos.garcia@uam.es; Braña, A. F.; Pau, J. L.; Ghita, D.; García, B. J. [Grupo de Electrónica y Semiconductores, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Madrid (Spain); Shen, G.; Wilbert, D. S.; Kim, S. M.; Kung, P. [Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487 (United States)

    2014-01-21

    Surface optical (SO) phonons were studied by Raman spectroscopy in GaAs nanowires (NWs) grown by Ga-assisted chemical beam epitaxy on oxidized Si(111) substrates. NW diameters and lengths ranging between 40 and 65 nm and between 0.3 and 1.3 μm, respectively, were observed under different growth conditions. The analysis of the Raman peak shape associated to either longitudinal or surface optical modes gave important information about the crystal quality of grown NWs. Phonon confinement model was used to calculate the density of defects as a function of the NW diameter resulting in values between 0.02 and 0.03 defects/nm, indicating the high uniformity obtained on NWs cross section size during growth. SO mode shows frequency downshifting as NW diameter decreases, this shift being sensitive to NW sidewall oxidation. The wavevector necessary to activate SO phonon was used to estimate the NW facet roughness responsible for SO shift.

  13. Diffusion of Pt in molecular beam epitaxy grown ZnSe

    Science.gov (United States)

    Slotte, J.; Salonen, R.; Ahlgren, T.; Räisänen, J.; Rauhala, E.; Uusimaa, P.

    1998-05-01

    Diffusion of platinum in zinc selenide has been studied by the use of the 4He and 12C ion backscattering techniques. The samples were thin films grown by molecular beam epitaxy on GaAs (100) epitaxial layers followed by evaporation of platinum and annealing in the temperature range 500-800 °C. The diffusion coefficients were determined by the fitting of a concentration independent solution of the diffusion equation to the experimental depth profiles. The activation energy and the pre-exponential factor of the diffusion process were found to be 1.7 eV and 6.4×10-6 cm2/s, respectively.

  14. Molecular beam epitaxy of GeTe-Sb{sub 2}Te{sub 3} phase change materials studied by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Shayduk, Roman

    2010-05-20

    The integration of phase change materials into semiconductor heterostructures may lead to the development of a new generation of high density non-volatile phase change memories. Epitaxial phase change materials allow to study the detailed structural changes during the phase transition and to determine the scaling limits of the memory. This work is dedicated to the epitaxial growth of Ge-Sb-Te phase change alloys on GaSb(001). We deposit Ge-Sb-Te (GST) films on GaSb(001) substrates by means of molecular beam epitaxy (MBE). The film orientation and lattice constant evolution is determined in real time during growth using grazing incidence X-ray diffraction (GID). The nucleation stage of the growth is studied in situ using reflection high energy electron diffraction (RHEED). Four growth regimes of GST on GaSb(001) were observed: amorphous, polycrystalline, incubated epitaxial and direct epitaxial. Amorphous film grows for substrate temperatures below 100 C. For substrate temperatures in the range 100-160 C, the film grows in polycrystalline form. Incubated epitaxial growth is observed at temperatures from 180 to 210 C. This growth regime is characterized by an initial 0.6nm thick amorphous layer formation, which crystallizes epitaxially as the film thickness increases. The determined lattice constant of the films is 6.01 A, very close to that of the metastable GST phase. The films predominantly possess an epitaxial cube-on-cube relationship. At higher temperatures the films grow epitaxially, however the growth rate is rapidly decreasing with temperature. At temperatures above 270 C the growth rate is zero. The composition of the grown films is close to 2:2:5 for Ge, Sb and Te, respectively. The determined crystal structure of the films is face centered cubic (FCC) with a rhombohedral distortion. The analysis of X-ray peak widths gives a value for the rhombohedral angle of 89.56 . We observe two types of reflections in reciprocal space indicating two FCC sublattices in

  15. Epitaxial growth of silicon nanowires using an aluminium catalyst.

    Science.gov (United States)

    Wang, Yewu; Schmidt, Volker; Senz, Stephan; Gösele, Ulrich

    2006-12-01

    Silicon nanowires have been identified as important components for future electronic and sensor nanodevices. So far gold has dominated as the catalyst for growing Si nanowires via the vapour-liquid-solid (VLS) mechanism. Unfortunately, gold traps electrons and holes in Si and poses a serious contamination problem for Si complementary metal oxide semiconductor (CMOS) processing. Although there are some reports on the use of non-gold catalysts for Si nanowire growth, either the growth requires high temperatures and/or the catalysts are not compatible with CMOS requirements. From a technological standpoint, a much more attractive catalyst material would be aluminium, as it is a standard metal in Si process lines. Here we report for the first time the epitaxial growth of Al-catalysed Si nanowires and suggest that growth proceeds via a vapour-solid-solid (VSS) rather than a VLS mechanism. It is also found that the tapering of the nanowires can be strongly reduced by lowering the growth temperature.

  16. GaAs-based long-wavelength InAs bilayer quantum dots grown by molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Zhu Yan; Li Mifeng; He Jifang; Yu Ying; Ni Haiqiao; Xu Yingqiang; Wang Juan; He Zhenhong; Niu Zhichuan

    2011-01-01

    Molecular beam epitaxy growth ofa bilayer stacked InAs/GaAs quantum dot structure on a pure GaAs matrix has been systemically investigated.The influence of growth temperature and the InAs deposition of both layers on the optical properties and morphologies of the bilayer quantum dot (BQD) structures is discussed.By optimizing the growth parameters,InAs BQD emission at 1.436μm at room temperature with a narrower FWHM of 27 meV was demonstrated.The density of QDs in the second layer is around 9 × 109 to 1.4 × 1010 cm-2.The BQD structure provides a useful way to extend the emission wavelength of GaAs-based material for quantum functional devices.

  17. Molecular beam epitaxy of GaN{sub 1-x}Bi{sub x} alloys with high bismuth content

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, S.V.; Kent, A.J.; Foxon, C.T. [School of Physics and Astronomy, University of Nottingham (United Kingdom); Yu, K.M.; Liliental-Weber, Z.; Walukiewicz, W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Levander, A.X.; Tseng, A.; Dubon, O.D.; Wu, J. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Department of Materials Science and Engineering, University of California, Berkeley, CA (United States); Dos Reis, R. [Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Instituto de Fisica, UFRGS, Porto Alegre (Brazil); Denlinger, J. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Luckert, F.; Edwards, P.R.; Martin, R.W. [Department of Physics, SUPA, University of Strathclyde, Glasgow (United Kingdom)

    2012-03-15

    We have analysed bismuth incorporation into GaN layers using plasma-assisted molecular beam epitaxy (PA-MBE) at extremely low growth temperatures of less than {proportional_to}100 C under both Ga-rich and N-rich growth conditions. The formation of amorphous GaN{sub 1-x}Bi{sub x} alloys is promoted by growth under Ga-rich conditions. The amorphous matrix has a short-range order resembling random crystalline GaN{sub 1-x}Bi{sub x} alloys. We have observed the formation of small crystalline clusters embedded into amorphous GaN{sub 1-x}Bi{sub x} alloys. Despite the fact that the films are pseudo-amorphous we observe a well defined optical absorption edges that rapidly shift to very low energy of {proportional_to}1 eV. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Real time spectroscopic ellipsometry investigation of homoepitaxial GaN grown by plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tong-Ho; Choi, Soojeong; Wu, Pae; Brown, April [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Losurdo, Maria; Giangregorio, Maria M.; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy); Moto, Akihiro [Innovation Core SEI, Inc., 3235 Kifer Road, Santa Clara, CA 95051 (United States)

    2006-06-15

    The growth of GaN by plasma assisted molecular beam epitaxy on GaN template substrates (GaN on sapphire) is investigated with in-situ multi-channel spectroscopic ellipsometry. Growth is performed under various Ga/N flux ratios at growth temperatures in the range 710-780 C. The thermal roughening of the GaN template caused by decomposition of the surface is investigated through the temporal variation of the GaN pseudodielectric function over the temperature range of 650 C to 850 C. The structural, morphological, and optical properties are also discussed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Formation of strained interfaces in AlSb/InAs multilayers grown by molecular beam epitaxy for quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Nicolaï, J.; Warot-Fonrose, B.; Gatel, C., E-mail: christophe.gatel@cemes.fr; Ponchet, A. [CEMES CNRS-UPR 8011, Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse (France); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); Teissier, R.; Baranov, A. N. [IES CNRS-UMR 5214, 34095 Montpellier (France); Magen, C. [Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA)—ARAID and Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018 Zaragoza (Spain)

    2015-07-21

    Structural and chemical properties of InAs/AlSb interfaces have been studied by transmission electron microscopy. InAs/AlSb multilayers were grown by molecular beam epitaxy with different growth sequences at interfaces. The out-of-plane strain, determined using high resolution microscopy and geometrical phase analysis, has been related to the chemical composition of the interfaces analyzed by high angle annular dark field imaging. Considering the local strain and chemistry, we estimated the interface composition and discussed the mechanisms of interface formation for the different growth sequences. In particular, we found that the formation of the tensile AlAs-type interface is spontaneously favored due to its high thermal stability compared to the InSb-type interface. We also showed that the interface composition could be tuned using an appropriate growth sequence.

  20. Epitaxial crystallization and nucleation during MeV-ion beam processing of amorphous GaAs surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Bachmann, T. [Jena Univ. (Germany). Inst. fuer Festkoerperphysik; Glaser, E. [Jena Univ. (Germany). Inst. fuer Festkoerperphysik; Schulz, R. [Jena Univ. (Germany). Inst. fuer Festkoerperphysik; Kaiser, U. [Jena Univ. (Germany). Inst. fuer Festkoerperphysik; Safran, G. [Research Institute for Technical Physics, P.O. Box 76, H-1325 Budapest (Hungary)

    1996-06-01

    <100> -GaAs wafers were preamorphized in a thin surface layer using 50 keV {sup 14}N{sup +}-ions. Ion beam induced epitaxial crystallization (IBIEC) and interfacial amorphization (IBIIA) were studied as a function of the target temperature using MeV Ar{sup +}- or Kr{sup +}-ions. Backscattering experiments and electron microscopy show that the IBIEC process is stopped above a critical irradiation temperature due to enhanced ion beam induced nucleation and growth of crystallites. At a fixed dose an optimum irradiation temperature for IBIEC was found, at which the recrystallized layer thickness has a maximum and crystallite formation is negligible. This offers the possibility to crystallize much larger layer thicknesses than {approx}65 nm which stands for the maximum value reported up to now. (orig.).

  1. Multiferroic fluoride BaCoF4 Thin Films Grown Via Molecular Beam Epitaxy

    Science.gov (United States)

    Borisov, Pavel; Johnson, Trent; García-Castro, Camilo; Kc, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo; Lederman, David

    Multiferroic materials exhibit exciting physics related to the simultaneous presence of multiple long-range orders, in many cases consisting of antiferromagnetic (AF) and ferroelectric (FE) orderings. In order to provide a new, promising route for fluoride-based multiferroic material engineering, we grew multiferroic fluoride BaCoF4 in thin film form on Al2O3 (0001) substrates by molecular beam epitaxy. The films grow with the orthorhombic b-axis out-of-plane and with three in-plane structural twin domains along the polar c-axis directions. The FE ordering in thin films was verified by FE remanent hysteresis loops measurements at T = 14 K and by room temperature piezoresponse force microscopy (PFM). An AF behavior was found below Neel temperature TN ~ 80 K, which is in agreement with the bulk properties. At lower temperatures two additional magnetic phase transitions at 19 K and 41 K were found. First-principles calculations demonstrated that the growth strain applied to the bulk BaCoF4 indeed favors two canted spin orders, along the b- and a-axes, respectively, in addition to the main AF spin order along the c-axis. Supported by FAME (Contract 2013-MA-2382), WV Research Challenge Grant (HEPC.dsr.12.29), and DMREF-NSF 1434897.

  2. Thermal Stability of Annealed Germanium-Tin Alloys Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Bhargava, Nupur; Gupta, Jay Prakash; Faleev, Nikolai; Wielunski, Leszek; Kolodzey, James

    2017-01-01

    The thermal stability of undoped and boron-doped germanium tin (Ge1-x Sn x ) alloys grown by molecular beam epitaxy with varying composition and layer thickness was investigated. The alloys were annealed in forming gas at various temperatures up to 800°C for 1 min using rapid thermal processing, and were characterized using high-resolution x-ray diffraction and Rutherford backscattering spectrometry. It was found that the Ge1-x Sn x alloys were stable to well above the growth temperature, but the stability decreased with increasing thickness, Sn content, and doping. Ge1-x Sn x alloys with low Sn composition (x ˜ 0.025) were stable up to 700°C, and for a given Sn composition, the undoped alloys were more thermally stable than the doped alloys. As the thickness of the Ge0.975Sn0.025 alloys increased to about 950 nm, the temperature of thermal stability dropped to 500°C. As the Sn composition of the 90 nm-Ge1-x Sn x alloys increased up to x = 0.08, the temperature of thermal stability dropped to 300°C. At higher annealing temperatures, the Ge1-x Sn x alloy degraded with lower crystal quality, and a gradient in the Sn composition appeared, which may be due to Sn diffusion or segregation.

  3. Structural and electrical properties of large area epitaxial VO2 films grown by electron beam evaporation

    Science.gov (United States)

    Théry, V.; Boulle, A.; Crunteanu, A.; Orlianges, J. C.; Beaumont, A.; Mayet, R.; Mennai, A.; Cosset, F.; Bessaudou, A.; Fabert, M.

    2017-02-01

    Large area (up to 4 squared inches) epitaxial VO2 films, with a uniform thickness and exhibiting an abrupt metal-insulator transition with a resistivity ratio as high as 2.85 × 10 4 , have been grown on (001)-oriented sapphire substrates by electron beam evaporation. The lattice distortions (mosaicity) and the level of strain in the films have been assessed by X-ray diffraction. It is demonstrated that the films grow in a domain-matching mode where the distortions are confined close to the interface which allows growth of high-quality materials despite the high film-substrate lattice mismatch. It is further shown that a post-deposition high-temperature oxygen annealing step is crucial to ensure the correct film stoichiometry and provide the best structural and electrical properties. Alternatively, it is possible to obtain high quality films with a RF discharge during deposition, which hence do not require the additional annealing step. Such films exhibit similar electrical properties and only slightly degraded structural properties.

  4. InGaN violet laser diodes grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Heffernan, J.; Kauer, M.; Hooper, S.E.; Bousquet, V.; Johnson, K. [Sharp Laboratories of Europe Ltd, Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB (United Kingdom)

    2004-09-01

    We report on the first InGaN quantum well laser diodes grown by molecular beam epitaxy (MBE). Devices were grown by gas-source MBE using ammonia as a source of nitrogen and elemental group III sources. The devices were grown on commercially available GaN template substrates. The lasers consist of a separate confinement heterostructure including an active region consisting of three In{sub 0.1}Ga{sub 0.9}N quantum wells with a nominal thickness of 2 nm. P-type doping of GaN and AlGaN cladding regions was obtained without the use of post-growth thermal annealing. The lasers were fabricated into a ridge-stripe geometry with ridge width of 5 {mu}m and length of 500-1500 {mu}m. Electron cyclotron resonance (ECR) dry-etching was used to fabricate the laser facets. Under pulsed current injection conditions, the lasers exhibit a room temperature threshold current density of 22 kA cm{sup -2} emitting at 400 nm. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Formation of Ge-Sn nanodots on Si(100 surfaces by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Yu Ing-Song

    2011-01-01

    Full Text Available Abstract The surface morphology of Ge0.96Sn0.04/Si(100 heterostructures grown at temperatures from 250 to 450°C by atomic force microscopy (AFM and scanning tunnel microscopy (STM ex situ has been studied. The statistical data for the density of Ge0.96Sn0.04 nanodots (ND depending on their lateral size have been obtained. Maximum density of ND (6 × 1011 cm-2 with the average lateral size of 7 nm can be obtained at 250°C. Relying on the reflection of high energy electron diffraction, AFM, and STM, it is concluded that molecular beam growth of Ge1-xSnx heterostructures with the small concentrations of Sn in the range of substrate temperatures from 250 to 450°C follows the Stranski-Krastanow mechanism. Based on the technique of recording diffractometry of high energy electrons during the process of epitaxy, the wetting layer thickness of Ge0.96Sn0.04 films is found to depend on the temperature of the substrate.

  6. Molecular beam epitaxy grown GeSn p-i-n photodetectors integrated on Si

    Energy Technology Data Exchange (ETDEWEB)

    Werner, J., E-mail: werner@iht.uni-stuttgart.de; Oehme, M.; Schirmer, A.; Kasper, E.; Schulze, J.

    2012-02-01

    GeSn p-i-n photodetectors with a low Sn mole fraction made by molecular beam epitaxy on Si substrates show higher optical responsivities for wavelength {lambda} > 1400 nm compared with p-i-n photodetectors made from pure Ge. The Sn incorporation in Ge is done by a low temperature growth step in order to minimize Sn segregation. The Sn incorporation and the alloy content are investigated by {mu}-Raman spectroscopy and calibrated Secondary Ion Mass Spectrometry. The photodetectors are manufactured with sharp doping transitions and are realized as double mesa structures with diameters from 1.5 {mu}m up to 80 {mu}m. The optical measurements are carried out with a broadband super continuum laser from {lambda} = 1200 nm up to {lambda} = 1700 nm. At a wavelength of {lambda} = 1550 nm the optical responsivity of these vertical GeSn diodes is 0.1 A/W. In comparison with a pure Ge detector of the same geometrical dimensions the optical responsivity is increased by factor of three as a result of Sn caused band gap reduction.

  7. Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

    Science.gov (United States)

    Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

    1988-01-01

    Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

  8. Superconducting thin films of As-free pnictide LaPd{sub 1-x}Sb{sub 2} grown by reactive molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Retzlaff, Reiner; Buckow, Alexander; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany)

    2013-07-01

    We use reactive molecular beam epitaxy as synthesis technique for the search of arsenic free pnictide superconductors. Epitaxial thin films of LaPd{sub 1-x}Sb{sub 2} were grown on (100) MgO substrates from elemental sources by simultaneous evaporation of high purity La, Pd and Sb metals by e-gun. LaPd{sub 1-x}Sb{sub 2} belongs to a novel class of pnictide superconductors with a peculiar pnictide square net layer. Previously, we have reported epitaxial growth of isostructural Bi based compounds. The substitution of Bi by Sb leads to thin films with metallic behavior and room temperature resistivity of about 85 μΩ cm. The highest observed transition temperature T{sub c} inLaPd{sub 1-x}Sb{sub 2} is 3.1 K and does not depend on x. We discuss strategies to increase T{sub c} in this pnictide subfamily.

  9. Ge-on-Si: Single-Crystal Selective Epitaxial Growth in a CVD Reactor

    NARCIS (Netherlands)

    Sammak, A.; De Boer, W.B.; Nanver, L.K.

    2012-01-01

    A standard Si/SiGe ASM CVD reactor that was recently modified for merging GaAs and Si epitaxial growth in one system is utilized to achieve intrinsic and doped epitaxial Ge-on-Si with low threading dislocation and defect densities. For this purpose, the system is equipped with 2% diluted GeH4 as the

  10. Growth-Rate Induced Epitaxial Orientation of CeO2 on Al2O3(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Gao, Fei; Jiang, Weilin; Shutthanandan, V.; Engelhard, Mark H.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2009-05-19

    High-quality ceria (CeO2) films were grown on sapphire (Al2O3) (0001) substrates using oxygen plasma-assisted molecular beam epitaxy. The epitaxial orientation of the ceria films has been found to be (100) and (111) at low (< 8 Å/min) and higher growth rates (up to ~30 Å/min), respectively. Evidence shows that CeO2 (100) film grows as three-dimensional islands, while CeO2 (111) proceeds with layered growth. Three in-plane domains at 30° to each other are observed in the CeO2 (100), which is attributed to the close match of the oxygen sub-lattices in the film and substrate that has a three-fold symmetry. Molecular dynamic simulations have further confirmed that the CeO2 film retains (100) orientation on the Al2O3 (0001) substrate.

  11. Studies of arsenic incorporation and P-type doping in epitaxial mercury cadmium telluride thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Zandian, Majid

    Doped layer semiconductor structures provide possibilities for novel electronic devices. Growth of Hg1-xCdxTe by molecular beam epitaxy (MBE) allows precise control over the doping profile and position of heterojunctions as well as structural properties of this ternary alloy. Even though n-type doping using indium is well established, little is known about p-type doping in this material system by MBE. Several elements such as Ag, Au, Sb, Bi and P have been previously used, however high diffusion coefficient and amphoteric behavior of these atoms in HgCdTe has restricted their use in heterojunction devices where control over doping profiles and concentrations is needed. We investigated arsenic incorporation efficiency as a function of As 4 flux and growth temperature. The sticking coefficient of As is substantially higher at lower growth temperature compared to growth at 190°C. For samples grown at 170°C, the etch pit density (EPD) is higher compared to p-type As doped samples grown at 190°C. Higher EPD is associated with columnar twin defects observed in transmission electron microscopy (TEM) studies of low growth temperature samples. Growth at low temperature of 170°C causes Hg rich condition promoting twin formation. Therefore, growth of p-type layers doped with As at low temperatures require optimization of II/VI flux ratio to eliminate columnar twin defects. It is possible to incorporate As at normal MBE growth temperature of 190°C but very high flux of As has to used to overcome low sticking coefficient of As at these temperatures. We proposed a mechanism for the activation of As involving Hg vacancies (VHg··) where Te is moved to a Hg vacancy, leaving behind a Te vacancy, which is then filled by an As atom. The Te that is now on a Hg site (i.e., Te antisite) migrates to the surface and leaves the crystal.

  12. Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy.

    Science.gov (United States)

    Lin, Shih-Wei; Wu, Yue-Han; Chang, Li; Liang, Chi-Te; Lin, Sheng-Di

    2015-01-01

    We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy. This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy. The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

  13. Mn2Au: body-centered-tetragonal bimetallic antiferromagnets grown by molecular beam epitaxy.

    Science.gov (United States)

    Wu, Han-Chun; Liao, Zhi-Min; Sofin, R G Sumesh; Feng, Gen; Ma, Xiu-Mei; Shick, Alexander B; Mryasov, Oleg N; Shvets, Igor V

    2012-12-11

    Mn(2)Au, a layered bimetal, is successfully grown using molecular beam epitaxy (MBE). The experiments and theoretical calculations presented suggest that Mn(2)Au film is antiferromagnetic with a very low critical temperature. The antiferromagnetic nature is demonstrated by measuring the exchange-bias effect of Mn(2)Au/Fe bilayers. This study establishes a primary basis for further research of this new antiferromagnet in spin-electronic device applications.

  14. GaSb film growth by liquid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cruz, M.L.; Martinez-Juarez, J.; Lopez-Salazar, P. [CIDS-ICUAP, BUAP, Av. 14 Sur y San Claudio, C.U. Edif.103C, Col. Sn Manuel, C.P. 72570, Puebla, Pue. (Mexico); Diaz, G.J. [Centro de Investigacion y Estudios Avanzados, IPN, Av. IPN 2508, Col. Sn. Pedro Zacatenco, C.P. 07360, D.F. (Mexico)

    2010-04-15

    Doped GaSb (Gallium Antimonide) films on p-GaSb substrates have been obtained by means of a low-cost and fast-growth method: the liquid phase epitaxy (LPE) technique. The growth temperature was 400 C, and the growth time was varied between1 and 5 min. Characterization of the films was performed by means of high resolution X-ray Diffraction, low temperature-photoluminescence and current-voltage curve measurements. The X-ray diffraction pattern confirms a zincblende-type crystal structure with a high-thin peak centred at 30.36 . The PL spectra at 27 K allowed to confirm the band-gap energy to be 0.8 eV and the I-V curves presented a PN junction behavior which corresponds to the obtained structured. Metal contacts of Au-Zn and Au-Ge were placed to perform electrical characterization (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Modeling and Optimization for Epitaxial Growth: Transport and Growth Studies

    Science.gov (United States)

    1999-01-01

    Epsilon-1 microprocessor and controlled automatically in–situ. For example, PID controllers and MFCs regulate the thermocouple temperatures and inlet flow...thermocouples are regulated by PID controllers . The set-up of the reactor apparatus may partially explain the smaller variation in actual growth rates. Recall

  16. Homo-epitaxial diamond film growth on ion implanted diamond substrates

    Energy Technology Data Exchange (ETDEWEB)

    Weiser, P.S.; Prawer, S.; Nugent, K.W.; Bettiol, A.A.; Kostidis, L.I.; Jamieson, D.N. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    The nucleation of CVD diamond is a complicated process, governed by many interrelated parameters. In the present work we attempt to elucidate the effect of strain on the growth of a homo-epitaxial CVD diamond. We have employed laterally confined high dose (MeV) Helium ion implantation to produce surface swelling of the substrate. The strain is enhanced by the lateral confinement of the implanted region to squares of 100 x 100 {mu}m{sup 2}. After ion implantation, micro-Raman spectroscopy was employed to map the surface strain. The substrates were then inserted into a CVD reactor and a CVD diamond film was grown upon them. Since the strained regions were laterally confined, it was then possible to monitor the effect of strain on diamond nucleation. The substrates were also analysed using Rutherford Backscattering Spectroscopy (RBS), Proton induced X-ray Emission (PIXE) and Ion Beam induced Luminescence (IBIL). 7 refs., 5 figs.

  17. Compositional variations in In(0.5)Ga(0.5)N nanorods grown by molecular beam epitaxy.

    Science.gov (United States)

    Cherns, D; Webster, R F; Novikov, S V; Foxon, C T; Fischer, A M; Ponce, F A; Haigh, S J

    2014-05-30

    The composition of InxGa1 - xN nanorods grown by molecular beam epitaxy with nominal x = 0.5 has been mapped by electron microscopy using Z-contrast imaging and x-ray microanalysis. This shows a coherent and highly strained core-shell structure with a near-atomically sharp boundary between a Ga-rich shell (x ∼ 0.3) and an In-rich core (x ∼ 0.7), which itself has In- and Ga-rich platelets alternating along the growth axis. It is proposed that the shell and core regions are lateral and vertical growth sectors, with the core structure determined by spinodal decomposition.

  18. Elemental boron-doped p(+)-SiGe layers grown by molecular beam epitaxy for infrared detector applications

    Science.gov (United States)

    Lin, T. L.; George, T.; Jones, E. W.; Ksendzov, A.; Huberman, M. L.

    1992-01-01

    SiGe/Si heterojunction internal photoemission (HIP) detectors have been fabricated utilizing molecular beam epitaxy of p(+)-SiGe layers on p(-)-Si substrates. Elemental boron from a high-temperature effusion cell was used as the dopant source during MBE growth, and high doping concentrations have been achieved. Strong infrared absorption, mainly by free-carrier absorption, was observed for the degenerately doped SiGe layers. The use of elemental boron as the dopant source allows a low MBE growth temperature, resulting in improved crystalline quality and smooth surface morphology of the Si(0.7)Ge(0.3) layers. Nearly ideal thermionic emission dark current characteristics have been obtained. Photoresponse of the HIP detectors in the long-wavelength infrared regime has been demonstrated.

  19. Low Microwave Surface Resistance in NdBa2Cu3O7-d Films Grown by Molecular Beam Epitaxy

    OpenAIRE

    2004-01-01

    We report the growth of NdBa2Cu3O7-d films on (100) MgO substrate by Molecular Beam Epitaxy (MBE). Large area NdBa2Cu3O7-d films with homogeneous superconducting properties were grown by precise control of stoichiometry and the optimisation of growth parameters. The stoichiometric ratio of Nd:Ba:Cu close to 1:2:3 yields films with TC of 94 K and JC values above 3.5 MA/cm2 at 77 K on bare MgO substrate. The NdBa2Cu3O7-d films grown under optimised conditions had excellent in-plane texture and ...

  20. Ge doping of β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Ahmadi, Elaheh; Koksaldi, Onur S.; Kaun, Stephen W.; Oshima, Yuichi; Short, Dane B.; Mishra, Umesh K.; Speck, James S.

    2017-04-01

    The Ge doping of β-Ga2O3(010) films was investigated using plasma-assisted molecular beam epitaxy as the growth method. The dependences of the amount of Ge incorporated on the substrate temperature, Ge-cell temperature, and growth regime were studied by secondary ion mass spectrometry. The electron concentration and mobility were investigated using Van der Pauw Hall patterns. Hall measurement confirmed that Ge acts as an n-dopant in β-Ga2O3(010) films. These results were compared with similar films doped by Sn. The Hall data showed an improved electron mobility for the same electron concentration when Ge is used instead of Sn as the dopant.

  1. Epitaxial growth and characterization of InN nanorods and compact layers on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Garcia, M.A.; Grandal, J.; Calleja, E. [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Lazic, S.; Calleja, J.M. [Dpt. Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Trampert, A. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    This work reports on the morphology and optical properties of wurtzite InN layers grown by plasma assisted molecular beam epitaxy (PA-MBE) on Si(111) substrates. The layer morphology can be controlled by the effective indium to nitrogen molecular flux ratio, from N-rich conditions that lead to InN nanorods, to stoichiometric conditions leading to compact InN layers. The nanorods deliver a much higher intensity of the photoluminescence emission than compact layers, with a full width at half maximum down to 34 meV, indicative of a high crystal quality. Raman and X-ray measurements on the InN nanorods and compact layers confirm the practical full relaxation of both types of materials. TEM measurements reveal a perfect epitaxial alignment of Si substrate-AlN buffer and InN epilayer with clean AlN-InN interfaces when growth conditions are optimized. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Liquid phase epitaxial growth of bismuth based superconductors

    Science.gov (United States)

    Takemoto, J.; Miyashita, S.; Inoue, T.; Komatsu, H.

    1996-05-01

    The liquid phase epitaxial growth of superconducting films of Bi 2Sr 2CaCu 2O y (2212 phase) and Bi 2Sr 2CuO z (2201 phase) were carried out on three types of substrates; SrTiO 3, LaAlO 3 and NdGaO 3. Twinning structures of the 2212 phase were observed in the films grown on the SrTiO 3 (100) and LaAlO 3 (100) substrates which belong to the cubic crystal system, while nearly twin-free structures were obtained when the film was grown on the NdGaO 3 (001) substrate (orthorhombic system). Atomic force microscopy revealed a 2201 phase film with a reasonably flat area (several μm 2) grown on the LaAlO 3 (100) substrate. It was observed that the 2212 phase nucleated on the substrate following the Volmer-Weber type mechanism (three-dimensional island growth mode). The enlarging processes of the island layers were discussed.

  3. Growth of GaN epitaxial films on polycrystalline diamond by metal-organic vapor phase epitaxy

    Science.gov (United States)

    Jiang, Quanzhong; Allsopp, Duncan W. E.; Bowen, Chris R.

    2017-04-01

    Heat extraction is often essential in ensuring efficient performance of semiconductor devices and requires minimising the thermal resistance between the functional semiconductor layers and any heat sink. This paper reports the epitaxial growth of N-polar GaN films on polycrystalline diamond substrates of high thermal conductivity with metal-organic vapor phase epitaxy, by using a Si x C layer formed during deposition of polycrystalline diamond on a silicon substrate. The Si x C layer acts to provide the necessary structure ordering information for the formation of a single crystal GaN film at the wafer scale. It is shown that a three-dimensional island (3D) growth process removes hexagonal defects that are induced by the non-single crystal nature of the Si x C layer. It is also shown that intensive 3D growth and the introduction of a convex curvature of the substrate can be deployed to reduce tensile stress in the GaN epitaxy to enable the growth of a crack-free layer up to a thickness of 1.1µm. The twist and tilt can be as low as 0.65° and 0.39° respectively, values broadly comparable with GaN grown on Si substrates with a similar structure.

  4. GaN Bulk Growth and Epitaxy from Ca-Ga-N Solutions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovations proposed here are Ka-band (38 GHz) group III-nitride power FETs and the dislocation density reducing epitaxial growth methods (LPE) needed for their...

  5. GaN Bulk Growth and Epitaxy from Ca-Ga-N Solutions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR proposal addresses the liquid phase epitaxy (LPE) of gallium nitride (GaN) films using nitrogen-enriched metal solutions. Growth of GaN from solutions...

  6. Improvement of GaAsSb alloys on InP grown by molecular beam epitaxy with substrate tilting

    Science.gov (United States)

    Chou, C. Y.; Torfi, A.; Wang, W. I.

    2013-10-01

    GaAsSb alloys lattice-matched to InP substrate have been used in various electronic and optoelectronic applications due to their highly desirable band alignment for high-speed double heterojunction bipolar transistors. There is however an issue with GaAsSb alloys, composed approximately of 50% As and 50% Sb, lattice-matched to an InP substrate; it exhibits a miscibility gap, which is a significant problem for crystal growth. This paper addresses the effect of substrate tilting on the material properties of GaAsSb alloys closely lattice-matched to InP substrates by molecular beam epitaxy (MBE). InP(100) substrates tilted 0°off-(on-axis), 2°off-, 3°off-, and 4°off-axis were used for MBE growth, then the material qualities of GaAsSb epitaxial layers were compared using various techniques, including high resolution X-ray diffraction, photoluminescence (PL), Raman scattering, and transmission-line measurements (TLM). Substrate tilting improved the GaAsSb alloys with crystalline quality, shown by a narrower x-ray linewidth and enhanced optical quality as evidenced by a strong PL peak. The results of TLM show that the lowest sheet resistance was achieved at a 2° off-axis tilt. The results are expected to be applicable in devices that incorporate GaAsSb in the active layer grown by MBE.

  7. An aberration-corrected STEM study of structural defects in epitaxial GaN thin films grown by ion beam assisted MBE.

    Science.gov (United States)

    Poppitz, David; Lotnyk, Andriy; Gerlach, Jürgen W; Lenzner, Jörg; Grundmann, Marius; Rauschenbach, Bernd

    2015-06-01

    Ion-beam assisted molecular-beam epitaxy was used for direct growth of epitaxial GaN thin films on super-polished 6H-SiC(0001) substrates. The GaN films with different film thicknesses were studied using reflection high energy electron diffraction, X-ray diffraction, cathodoluminescence and primarily aberration-corrected scanning transmission electron microscopy techniques. Special attention was devoted to the microstructural characterization of GaN thin films and the GaN-SiC interface on the atomic scale. The results show a variety of defect types in the GaN thin films and at the GaN-SiC interface. A high crystalline quality of the produced hexagonal GaN thin films was demonstrated. The gained results are discussed.

  8. Fabrication of atomically smooth SrRuO3 thin films by laser molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    High-quality SrRuO3 (SRO) thin films and SrTiO3/SRO bilayer were grown epitaxially on SrTiO3 (STO)(001) substrates by laser molecular beam epitaxy. The results of in situ observation of reflection high-energy electron diffraction and ex situ X-ray diffraction θ -2θ scan indicate that the SRO thin films have good crystallinity. The measurements of atomic force microscopy and scan tunneling microscopy reveal that the surface of the SRO thin film is atomically smooth. The resistivity of the SRO thin film is 300 μΩ·cm at room temperature. Furthermore, the transmission electron microscopy study shows that the interfaces of STO/SRO and SRO/STO are very clear and no interfacial reaction layer was observed. The experimental results show that the SRO thin film is an excellent electrode material for devices based on perovskite oxide materials.

  9. Epitaxial niobium dioxide thin films by reactive-biased target ion beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuhan, E-mail: yw9ep@virginia.edu; Kittiwatanakul, Salinporn; Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Comes, Ryan B. [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Wolf, Stuart A. [Department of Materials Science and Engineering and Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2015-03-15

    Epitaxial NbO{sub 2} thin films were synthesized on Al{sub 2}O{sub 3} (0001) substrates via reactive bias target ion beam deposition. X-ray diffraction and Raman spectra were used to confirm the tetragonal phase of pure NbO{sub 2}. Through XPS, it was found that there was a ∼1.3 nm thick Nb{sub 2}O{sub 5} layer on the surface and the bulk of the thin film was NbO{sub 2}. The epitaxial relationship between the NbO{sub 2} film and the substrate was determined. Electrical transport measurement was measured up to 400 K, and the conduction mechanism was discussed.

  10. Epitaxial growth of thermally stable cobalt films on Au(111)

    Science.gov (United States)

    Haag, N.; Laux, M.; Stöckl, J.; Kollamana, J.; Seidel, J.; Großmann, N.; Fetzer, R.; Kelly, L. L.; Wei, Z.; Stadtmüller, B.; Cinchetti, M.; Aeschlimann, M.

    2016-10-01

    Ferromagnetic thin films play a fundamental role in spintronic applications as a source for spin polarized carriers and in fundamental studies as ferromagnetic substrates. However, it is challenging to produce such metallic films with high structural quality and chemical purity on single crystalline substrates since the diffusion barrier across the metal-metal interface is usually smaller than the thermal activation energy necessary for smooth surface morphologies. Here, we introduce epitaxial thin Co films grown on an Au(111) single crystal surface as a thermally stable ferromagnetic thin film. Our structural investigations reveal an identical growth of thin Co/Au(111) films compared to Co bulk single crystals with large monoatomic Co terraces with an average width of 500 Å, formed after thermal annealing at 575 K. Combining our results from photoemission and Auger electron spectroscopy, we provide evidence that no significant diffusion of Au into the near surface region of the Co film takes place for this temperature and that no Au capping layer is formed on top of Co films. Furthermore, we show that the electronic valence band is dominated by a strong spectral contribution from a Co 3d band and a Co derived surface resonance in the minority band. Both states lead to an overall negative spin polarization at the Fermi energy.

  11. Molecular beam epitaxy and properties of GaAsBi/GaAs quantum wells grown by molecular beam epitaxy: effect of thermal annealing.

    Science.gov (United States)

    Makhloufi, Hajer; Boonpeng, Poonyasiri; Mazzucato, Simone; Nicolai, Julien; Arnoult, Alexandre; Hungria, Teresa; Lacoste, Guy; Gatel, Christophe; Ponchet, Anne; Carrère, Hélène; Marie, Xavier; Fontaine, Chantal

    2014-03-17

    We have grown GaAsBi quantum wells by molecular beam epitaxy. We have studied the properties of a 7% Bi GaAsBi quantum well and their variation with thermal annealing. High-resolution X-ray diffraction, secondary ion mass spectrometry, and transmission electron microscopy have been employed to get some insight into its structural properties. Stationary and time-resolved photoluminescence shows that the quantum well emission, peaking at 1.23 μm at room temperature, can be improved by a rapid annealing at 650°C, while the use of a higher annealing temperature leads to emission degradation and blue-shifting due to the activation of non-radiative centers and bismuth diffusion from the quantum well.

  12. Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

    Energy Technology Data Exchange (ETDEWEB)

    Madni, I.; Umana-Membreno, G. A.; Lei, W.; Gu, R.; Antoszewski, J.; Faraone, L. [School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Crawley, Western Australia 6009 (Australia)

    2015-11-02

    The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg{sub 1−x}Cd{sub x}Te (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3} without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 10{sup 4} cm{sup 2}/V s to 7 × 10{sup 3} cm{sup 2}/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3}. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.

  13. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  14. Cleaning chemistry of GaAs(100) and InSb(100) substrates for molecular beam epitaxy

    Science.gov (United States)

    Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

    1983-01-01

    Ploog (1980) and Bachrach and Krusor (1981) have pointed out the importance of substrate preparation and surface cleaning for obtaining high quality films with the aid of molecular beam epitaxial growth techniques. In the present investigation, high resolution X-ray photoemission (XPS) is used to determine the oxide removal mechanism for GaAs(100) substrates which have undergone a standardized cleaning procedure. Other objectives of the investigation are related to a comparison of different cleaning procedures in order to minimize carbon contamination, the extension of these cleaning techniques to other III-V compound semiconductors such as InSb, and the evaluation of the sensitivity of the compositional results to electron-induced damage effects.

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

    Science.gov (United States)

    Taioli, Simone; Garberoglio, Giovanni; Simonucci, Stefano; a Beccara, Silvio; Aversa, Lucrezia; Nardi, Marco; Verucchi, Roberto; Iannotta, Salvatore; Dapor, Maurizio; Alfè, Dario

    2013-01-28

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

  16. Correlation between Defect Concentration and Carrier Lifetime of GaAs Grown by Molecular Beam Epitaxy at Different Temperatures

    Science.gov (United States)

    Lin, Gong-Ru; Liu, Tze-An; Pan, Ci-Ling

    2001-11-01

    A pump-probe study of GaAs grown by molecular beam epitaxy at low temperatures (LT-GaAs) is performed. Ultrashort carrier lifetimes of the as-grown LT-GaAs increase from Schokley-Read-Hall model. The decreasing trend in the amplitudes of continuous-wave and transient reflectivities (Δ R/R) as a function of the growth temperature for the LT-GaAs is explained as an induced absorption caused by dense arsenic antisite defects. The sign of the transient Δ R/R reversed for LT-GaAs grown at 200°C. This is tentatively attributed to the band gap renormalization effect.

  17. Synthesis of as-grown superconducting MgB{sub 2} thin films by molecular beam epitaxy in UHV conditions

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y.; Uduka, M.; Nakanishi, Y.; Yoshimoto, N.; Yoshizawa, M

    2004-10-01

    As-grown superconducting MgB{sub 2} thin films have been grown on SrTiO{sub 3}(0 0 1), MgO(0 0 1), and Al{sub 2}O{sub 3}(0 0 0 1) substrates by a molecular beam epitaxy (MBE) method with novel co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The RHEED patterns indicate three-dimensional growth for MgB{sub 2}. The highest T{sub c} determined by resistivity measurement was about 36 K in these samples. And a clear Meissner effect below T{sub c} was observed using magnetic susceptibility measurement. We will discuss the influence of B buffer layer on the structural and physical properties.

  18. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  19. Advanced Si IR detectors using molecular beam epitaxy

    Science.gov (United States)

    Lin, T. L.; Jones, E. W.; George, T.; Ksendzov, A.; Huberman, M. L.

    1991-01-01

    SiGe/Si heterojunction internal photoemission (HIP) long wavelength infrared (LWIR) detectors have been fabricated by MBE. The SiGe/Si HIP detector offers a tailorable spectral response in the long wavelength infrared regime by varying the SiGe/Si heterojunction barrier. Degenerately doped p(+) SiGe layers were grown using elemental boron, as the dopant source allows a low growth temperature. Good crystalline quality was achieved for boron-doped SiGe due to the reduced growth temperature. The dark current density of the boron-doped HIP detectors was found to be thermionic emission limited. HIP detectors with a 0.066 eV were fabricated and characterized using activation energy analysis, corresponding to a 18 micron cutoff wavelength. Photoresponse of the detectors at wavelengths ranging from 2 to 12 microns has been characterized with corresponding quantum efficiencies of 5 - 0.1 percent.

  20. Growth and magnetic properties of ultrathin epitaxial FeO films and Fe/FeO bilayers on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kozioł-Rachwał, A., E-mail: akoziol@agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Ślęzak, T. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Nozaki, T.; Yuasa, S. [National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Korecki, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland); Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland)

    2016-01-25

    Ultrathin FeO(001) films were grown via molecular beam epitaxy on MgO(001) using reactive deposition of Fe. The growth conditions were adjusted toward stabilization of the wüstite phase, the existence of which was confirmed by means of conversion electron Mössbauer spectroscopy. It was shown how the metallic Fe overlayer modified the chemical state and the magnetic properties of the FeO oxide. Finally, we observed the exchange bias for an epitaxial Fe/FeO bilayer grown on MgO(001)

  1. Optical and Structural Properties of Microcrystalline GaN on an Amorphous Substrate Prepared by a Combination of Molecular Beam Epitaxy and Metal-Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Min, Jung-Wook; Hwang, Hyeong-Yong; Kang, Eun-Kyu; Park, Kwangwook; Kim, Ci-Hyun; Lee, Dong-Seon; Jho, Young-Dahl; Bae, Si-Young; Lee, Yong-Tak

    2016-05-01

    Microscale platelet-shaped GaN grains were grown on amorphous substrates by a combined epitaxial growth method of molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). First, MBE GaN was grown on an amorphous substrate as a pre-orienting layer and its structural properties were investigated. Second, MOCVD grown GaN samples using the different growth techniques of planar and selective area growth (SAG) were comparatively investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). In MOCVD planar GaN, strong bound exciton peaks dominated despite the high density of the threading dislocations (TDs). In MOCVD SAG GaN, on the other hand, TDs were clearly reduced with bending, but basal stacking fault (BSF) PL peaks were observed at 3.42 eV. The combined epitaxial method not only provides a deep understanding of the growth behavior but also suggests an alternative approach for the growth of GaN on amorphous substances.

  2. Arrayed van der Waals Vertical Heterostructures Based on 2D GaSe Grown by Molecular Beam Epitaxy.

    Science.gov (United States)

    Yuan, Xiang; Tang, Lei; Liu, Shanshan; Wang, Peng; Chen, Zhigang; Zhang, Cheng; Liu, Yanwen; Wang, Weiyi; Zou, Yichao; Liu, Cong; Guo, Nan; Zou, Jin; Zhou, Peng; Hu, Weida; Xiu, Faxian

    2015-05-13

    Vertically stacking two-dimensional (2D) materials can enable the design of novel electronic and optoelectronic devices and realize complex functionality. However, the fabrication of such artificial heterostructures on a wafer scale with an atomically sharp interface poses an unprecedented challenge. Here, we demonstrate a convenient and controllable approach for the production of wafer-scale 2D GaSe thin films by molecular beam epitaxy. In situ reflection high-energy electron diffraction oscillations and Raman spectroscopy reveal a layer-by-layer van der Waals epitaxial growth mode. Highly efficient photodetector arrays were fabricated, based on few-layer GaSe on Si. These photodiodes show steady rectifying characteristics and a high external quantum efficiency of 23.6%. The resultant photoresponse is super-fast and robust, with a response time of 60 μs. Importantly, the device shows no sign of degradation after 1 million cycles of operation. We also carried out numerical simulations to understand the underlying device working principles. Our study establishes a new approach to produce controllable, robust, and large-area 2D heterostructures and presents a crucial step for further practical applications.

  3. Optical sites in Eu- and Mg-codoped GaN grown by NH3-source molecular beam epitaxy

    Science.gov (United States)

    Sekiguchi, Hiroto; Sakai, Masaru; Kamada, Takuho; Tateishi, Hiroki; Syouji, Atsushi; Wakahara, Akihiro

    2016-10-01

    Mg codoping can improve the luminescence properties of Eu-doped GaN. However, the enhanced optical sites differ depending on the fabrication method. In this study, the optical sites in Eu- and Mg-codoped GaN [GaN:(Eu, Mg)] grown by NH3-source molecular beam epitaxy (MBE) were evaluated. The optical properties of an Eu-Mg-related site grown by NH3-MBE were highly stable against thermal annealing. Although the luminescence at sites A (622.3 and 633.8 nm) and B (621.9 and 622.8 nm) was dominant under indirect excitation of Eu ions through GaN, four different optical site groups in addition to sites A and B were observed under resonant excitation. These optical sites are inconsistent with the Eu-Mg-related sites reportedly observed in GaN:(Eu, Mg) fabricated by organometallic vapor phase epitaxy, indicating that the optical site constitution strongly depends on the growth method. Furthermore, site A, with a high cross section, contributed to as much as 22% of the total photoluminescence (PL) integrated intensity for GaN:(Eu, Mg) grown by NH3-MBE, which resulted in a high PL intensity.

  4. Fabrication of GeSn-multiple quantum wells by overgrowth of Sn on Ge by using molecular beam epitaxy

    Science.gov (United States)

    Oliveira, F.; Fischer, I. A.; Benedetti, A.; Zaumseil, P.; Cerqueira, M. F.; Vasilevskiy, M. I.; Stefanov, S.; Chiussi, S.; Schulze, J.

    2015-12-01

    We report on the fabrication and structural characterization of epitaxially grown ultra-thin layers of Sn on Ge virtual substrates (Si buffer layer overgrown by a 50 nm thick Ge epilayer followed by an annealing step). Samples with 1 to 5 monolayers of Sn on Ge virtual substrates were grown using solid source molecular beam epitaxy and characterized by atomic force microscopy. We determined the critical thickness at which the transition from two-dimensional to three-dimensional growth occurs. This transition is due to the large lattice mismatch between Ge and Sn (≈14.7%). By depositing Ge on top of Sn layers, which have thicknesses at or just below the critical thickness, we were able to fabricate ultra-narrow GeSn multi-quantum-well structures that are fully embedded in Ge. We report results on samples with one and ten GeSn wells separated by 5 and 10 nm thick Ge spacer layers that were characterized by high resolution transmission electron microscopy and X-ray diffraction. We discuss the structure and material intermixing observed in the samples.

  5. Fabrication of GeSn-multiple quantum wells by overgrowth of Sn on Ge by using molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, F. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Fischer, I. A.; Schulze, J. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Benedetti, A. [CACTI, Univ. de Vigo, Campus Universitario Lagoas Marcosende 15, Vigo (Spain); Zaumseil, P. [IHP GmbH, Innovations for High Performance Microelectronics, Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Cerqueira, M. F.; Vasilevskiy, M. I. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Stefanov, S.; Chiussi, S. [Dpto. Fisica Aplicada, Univ. de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2015-12-28

    We report on the fabrication and structural characterization of epitaxially grown ultra-thin layers of Sn on Ge virtual substrates (Si buffer layer overgrown by a 50 nm thick Ge epilayer followed by an annealing step). Samples with 1 to 5 monolayers of Sn on Ge virtual substrates were grown using solid source molecular beam epitaxy and characterized by atomic force microscopy. We determined the critical thickness at which the transition from two-dimensional to three-dimensional growth occurs. This transition is due to the large lattice mismatch between Ge and Sn (≈14.7%). By depositing Ge on top of Sn layers, which have thicknesses at or just below the critical thickness, we were able to fabricate ultra-narrow GeSn multi-quantum-well structures that are fully embedded in Ge. We report results on samples with one and ten GeSn wells separated by 5 and 10 nm thick Ge spacer layers that were characterized by high resolution transmission electron microscopy and X-ray diffraction. We discuss the structure and material intermixing observed in the samples.

  6. Ge-on-Si: Single-Crystal Selective Epitaxial Growth in a CVD Reactor

    OpenAIRE

    Sammak, A.; De Boer, W.B.; Nanver, L. K.

    2012-01-01

    A standard Si/SiGe ASM CVD reactor that was recently modified for merging GaAs and Si epitaxial growth in one system is utilized to achieve intrinsic and doped epitaxial Ge-on-Si with low threading dislocation and defect densities. For this purpose, the system is equipped with 2% diluted GeH4 as the main precursor gas for Ge deposition; and 0.7% diluted AsH3 and B2H6 precursor gases as well as a TriMethylGallium (TMGa) bubbler system for As, B and Ga doping of epitaxial Ge, respectively. The ...

  7. Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Schou, Jørgen;

    2011-01-01

    Epitaxial growth of Ce0.8Gd0.2O2(CGO) films on (001) TiO2-terminated SrTiO3 substrates by pulsed laser deposition was investigated using in situ reflective high energy electron diffraction. The initial film growth shows a Stransky–Krastanov growth mode. However, this three-dimensional island...

  8. Development of gallium nitride-based ultraviolet and visible light-emitting diodes using hydride vapor-phase epitaxy and molecular beam epitaxy

    Science.gov (United States)

    Cabalu, Jasper Sicat

    Much of the work done on ultraviolet (UV) and visible III-Nitrides-based light emitting diodes (LEDs) involves growth by metal-organic chemical vapor deposition (MOCVD). In this dissertation, the growth, development, and fabrication of III-Nitrides-based UV and visible LEDs with very high photon conversion and extraction efficiencies using hydride vapor-phase epitaxy (HVPE) and radio frequency (rf) plasma-assisted molecular beam epitaxy (PAMBE) is presented. High-power electrically-pumped UV-LEDs based on GaN/AlGaN multiple quantum wells (MQWs) emitting at 340 nm and 350 nm have been fabricated in a flip-chip configuration and evaluated. Under pulsed operation, UV-LEDs emitting at 340 nm have output powers that saturate, due to device heating, at approximately 3 mW. Devices emitting at 350 nm show DC operation output powers as high as 4.5 mW under 200 mA drive current. These results were found to be equivalent with those of UV-LEDs produced by the MOCVD and HVPE methods. The concept of using textured MQWs on UV-LED structures was tested by optical pumping of GaN/AlGaN MQWs grown on textured GaN templates. Results show highly enhanced (>700 times) blue-shifted photoluminescence (PL) at 360 nm compared to similarly produced MQWs on smooth GaN templates whose PL emission is red-shifted. These results are attributed partly to enhancement in light extraction efficiency (LEE) and partly to enhancement in internal quantum efficiency (IQE). The origin of the increase in IQE is partly due to reduction of the quantum-confined Stark effect (QCSE) on QW-planes not perpendicular to the polarization direction and partly due to charge redistribution in the QWs caused by the polarization component parallel to the planes of the QWs. Similar studies have been done for visible LEDs using InGaN/GaN MQWs. Growth of LED structures on textured GaN templates employing textured MQW-active regions resulted in the production of dichromatic (430 nm and 530 nm) phosphorless white LEDs with

  9. Molecular Beam Epitaxy-Grown InGaN Nanowires and Nanomushrooms for Solid State Lighting

    KAUST Repository

    Gasim, Anwar A.

    2012-05-01

    InGaN is a promising semiconductor for solid state lighting thanks to its bandgap which spans the entire visible regime of the electromagnetic spectrum. InGaN is grown heteroepitaxially due to the absence of a native substrate; however, this results in a strained film and a high dislocation density—two effects that have been associated with efficiency droop, which is the disastrous drop in efficiency of a light-emitting diode (LED) as the input current increases. Heteroepitaxially grown nanowires have recently attracted great interest due to their property of eliminating the detrimental effects of the lattice mismatch and the corollary efficiency droop. In this study, InGaN nanowires were grown on a low-cost Si (111) substrate via molecular beam epitaxy. Unique nanostructures, taking the form of mushrooms, have been observed in localized regions on the samples. These nanomushrooms consist of a nanowire body with a wide cap on top. Photoluminescence characterization revealed that the nanowires emit violet-blue, whilst the nanomushrooms emit a broad yellow-orange-red luminescence. The simultaneous emission from the nanowires and nanomushrooms forms white light. Structural characterization of a single nanomushroom via transmission electron microscopy revealed a simultaneous increase in indium and decrease in gallium at the interface between the body and the cap. Furthermore, the cap itself was found to be indium-rich, confirming it as the source of the longer wavelength yellow-orange-red luminescence. It is believed that the nanomushroom cap formed as a consequence of the saturation of growth on the c-plane of the nanowire. It is proposed that the formation of an indium droplet on the tip of the nanowire saturated growth on the c-plane, forcing the indium and gallium adatoms to incorporate on the sidewall m-planes instead, but only at the nanowire tip. This resulted in the formation of a mushroom-like cap on the tip. How and why the indium droplets formed is not

  10. Epitaxy of Semiconductors Introduction to Physical Principles

    CERN Document Server

    Pohl, Udo W

    2013-01-01

    Introduction to Epitaxy provides the essential information for a comprehensive upper-level graduate course treating the crystalline growth of semiconductor heterostructures. Heteroepitaxy represents the basis of advanced electronic and optoelectronic devices today and is considered one of the top fields in materials research. The book covers the structural and electronic properties of strained epitaxial layers, the thermodynamics and kinetics of layer growth, and the description of the major growth techniques metalorganic vapor phase epitaxy, molecular beam epitaxy and liquid phase epitaxy. Cubic semiconductors, strain relaxation by misfit dislocations, strain and confinement effects on electronic states, surface structures and processes during nucleation and growth are treated in detail. The Introduction to Epitaxy requires only little knowledge on solid-state physics. Students of natural sciences, materials science and electrical engineering as well as their lecturers benefit from elementary introductions t...

  11. Growth and magnetic properties of epitaxial Fe4N films on insulators possessing lattice spacing close to Si(001) plane

    Science.gov (United States)

    Ito, Keita; Higashikozono, Soma; Takata, Fumiya; Gushi, Toshiki; Toko, Kaoru; Suemasu, Takashi

    2016-12-01

    We grew ferromagnetic Fe4N films by molecular beam epitaxy on MgO(001), MgAl2O4(MAO)(001), SrTiO3(STO)(001), and CaF2(001) substrates, possessing the lattice spacing close to Si(001) plane. Highly oriented epitaxial growth was confirmed for the Fe4N films on the MgO, MAO, and STO by reflection high-energy electron diffraction and x-ray diffractions. The degree of orientation of the Fe4N film on the STO was the best among these samples. This was attributed to the smallest lattice mismatch of -2.8% between Fe4N(001) and STO(001). On the other hand, crystallinity of the Fe4N film on the CaF2(001) substrate was poor due to a very large lattice mismatch of -30% between Fe4N(001) and CaF2(001) arising from the unexpected epitaxial relationship as Fe4N(001)[100] || CaF2(001)[100]. The saturation magnetization of the Fe4N films was approximately 1200 emu/cm3 at room temperature for all the samples, and the magnetization easy axis was in-plane Fe4N[100]. We consider that STO is the suitable buffer layer for the growth of Fe4N on Si(001), hence to realize the Si-based spintronics devices using highly spin-polarized Fe4N.

  12. Epitaxial Growth of High-Quality Silicon Films on Double-Layer Porous Silicon

    Institute of Scientific and Technical Information of China (English)

    黄宜平; 竺士炀; 李爱珍; 王瑾; 黄靖云; 叶志镇

    2001-01-01

    The epitaxial growth of a high-quality silicon layer on double-layer porous silicon by ultra-high vacuum/chemical vapour deposition has been reported. The two-step anodization process results in a double-layer porous silicon structure with a different porosity. This double-layer porous silicon structure and an extended low-temperature annealing in a vacuum system was found to be helpful in subsequent silicon epitaxial growth. X-ray diffraction,cross-sectional transmission electron microscopy and spreading resistance testing were used in this work to study the properties of epitaxial silicon layers grown on the double-layer porous silicon. The results show that the epitaxial silicon layer is of good crystallinity and the same orientation with the silicon substrate and the porous silicon layer.

  13. Epitaxial growth of magnetic ZnCuO thin films by pulsed laser deposition

    Science.gov (United States)

    Kim, Dong Hun; Kim, Tae Cheol; Lee, Seung Han; Jung, Hyun Kyu; Jeong, Jaeeun; Han, Seung Ho

    2017-02-01

    The crystal structure and magnetic properties of epitaxial ZnO thin films doped with 5 at% Cu on SrTiO3 (001) and (111) substrates were investigated. In the case of films deposited in oxygen, unique crystallographic growth directions on different substrates were observed, while a metallic phase was detected in films grown under vacuum. The Cu-doped ZnO thin films deposited on the SrTiO3 (111) substrates, with hexagonal structures, showed a single epitaxial relationship with the substrates, whereas those deposited on the SrTiO3 (001) substrates showed a double epitaxial growth mode. The epitaxial ZnCuO thin films deposited on the SrTiO3 (111) substrates under high vacuum exhibited a ferromagnetic signal at room temperature.

  14. Step-Flow Growth on Vicinal GaAs Surfaces by Migration-Enhanced Epitaxy

    Science.gov (United States)

    Yamaguchi, Hiroshi; Horikoshi, Yoshiji

    1989-08-01

    The mechanism of step-flow growth on vicinal GaAs substrates during migration-enhanced epitaxy are studied using the reflection high-energy electron diffraction technique. Results show that the low As pressure during migration-enhanced epitaxy growth accelerates step-flow growth. In addition, it is also shown that monolayer terraces composed of surface Ga atoms are formed from step edges during the Ga deposition process. A GaAs/AlAs tilted superlattice is established using this growth technique. X-ray diffraction measurement and transmission electron microscopy observations show that the fabricated structure has periodic composition modulation along the axis tilted from the substrate azimuth.

  15. Crystallographic dependence of photocatalytic activity of WO3 thin films prepared by molecular beam epitaxy.

    Science.gov (United States)

    Li, Guoqiang; Varga, Tamas; Yan, Pengfei; Wang, Zhiguo; Wang, Chongmin; Chambers, Scott A; Du, Yingge

    2015-06-21

    We investigated the impact of crystallographic orientation on the photocatalytic activity of single crystalline WO3 thin films prepared by molecular beam epitaxy on the photodegradation of rhodamine B (RhB). A clear effect is observed, with (111) being the most reactive surface, followed by (110) and (001). Photoreactivity is directly correlated with the surface free energy determined by density functional theory calculations. The RhB photodegradation mechanism is found to involve hydroxyl radicals in solution formed from photo-generated holes and differs from previous studies performed on nanoparticles and composites.

  16. In situ photoelectron spectroscopy of molecular-beam-epitaxy grown surfaces

    CERN Document Server

    Oshima, M; Okabayashi, J; Ono, K

    2003-01-01

    Two in situ high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) systems combined with a molecular beam epitaxy (MBE) chamber for III-V compound semiconductors and a laser MBE chamber for strongly correlated oxide films, respectively, have been designed and fabricated to analyze intrinsic and surface/interface electronic structures of these unique materials. The importance of the in situ SRPES has been demonstrated by the results of 1) Si surface nanostructures, 2) GaAs surfaces/interfaces and nanostructures, 3) MnAs magnetic nanostructures, and 4) strongly-correlated La sub 1 sub - sub x Sr sub x MnO sub 3 surfaces/interfaces and superstructures.

  17. Perspective: Extremely fine tuning of doping enabled by combinatorial molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, J.; Božović, I. [Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

    2015-06-01

    Chemical doping provides an effective method to control the electric properties of complex oxides. However, the state-of-art accuracy in controlling doping is limited to about 1%. This hampers elucidation of the precise doping dependences of physical properties and phenomena of interest, such as quantum phase transitions. Using the combinatorial molecular beam epitaxy, we improve the accuracy in tuning the doping level by two orders of magnitude. We illustrate this novel method by two examples: a systematic investigation of the doping dependence of interface superconductivity, and a study of the competing ground states in the vicinity of the insulator-to-superconductor transition.

  18. Perspective: Extremely fine tuning of doping enabled by combinatorial molecular-beam epitaxy

    Directory of Open Access Journals (Sweden)

    J. Wu

    2015-06-01

    Full Text Available Chemical doping provides an effective method to control the electric properties of complex oxides. However, the state-of-art accuracy in controlling doping is limited to about 1%. This hampers elucidation of the precise doping dependences of physical properties and phenomena of interest, such as quantum phase transitions. Using the combinatorial molecular beam epitaxy, we improve the accuracy in tuning the doping level by two orders of magnitude. We illustrate this novel method by two examples: a systematic investigation of the doping dependence of interface superconductivity, and a study of the competing ground states in the vicinity of the insulator-to-superconductor transition.

  19. Near-bandgap optical properties of pseudomorphic GeSn alloys grown by molecular beam epitaxy

    Science.gov (United States)

    D'Costa, Vijay Richard; Wang, Wei; Yeo, Yee-Chia

    2016-08-01

    We investigated the compositional dependence of the near-bandgap dielectric function and the E0 critical point in pseudomorphic Ge1-xSnx alloys grown on Ge (100) substrate by molecular beam epitaxy. The complex dielectric functions were obtained using spectroscopic ellipsometry from 0.5 to 4.5 eV at room temperature. Analogous to the E1 and E1+Δ1 transitions, a model consisting of the compositional dependence of relaxed alloys along with the strain contribution predicted by the deformation potential theory fully accounts for the observed compositional dependence in pseudomorphic alloys.

  20. Control growth of silicon nanocolumns' epitaxy on silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chong, Su Kong, E-mail: sukong1985@yahoo.com.my [University of Malaya, Low Dimensional Materials Research Centre, Department of Physics (Malaysia); Dee, Chang Fu [Universiti Kebangsaan Malaysia (UKM), Institute of Microengineering and Nanoelectronics (IMEN) (Malaysia); Yahya, Noorhana [Universiti Teknologi PETRONAS, Faculty of Science and Information Technology (Malaysia); Rahman, Saadah Abdul [University of Malaya, Low Dimensional Materials Research Centre, Department of Physics (Malaysia)

    2013-04-15

    The epitaxial growth of Si nanocolumns on Si nanowires was studied using hot-wire chemical vapor deposition. A single-crystalline and surface oxide-free Si nanowire core (core radius {approx}21 {+-} 5 nm) induced by indium crystal seed was used as a substance for the vapor phase epitaxial growth. The growth process is initiated by sidewall facets, which then nucleate upon certain thickness to form Si islands and further grow to form nanocolumns. The Si nanocolumns with diameter of 10-20 nm and aspect ratio up to 10 can be epitaxially grown on the surface of nanowires. The results showed that the radial growth rate of the Si nanocolumns remains constant with the increase of deposition time. Meanwhile, the radial growth rates are controllable by manipulating the hydrogen to silane gas flow rate ratio. The optical antireflection properties of the Si nanocolumns' decorated SiNW arrays are discussed in the text.

  1. Epitaxial Growth of Metastable hcp-Ni and hcp-NiFe Thin Films on Au(100)fcc Single-Crystal Underlayers and Their Structure Characterization

    Science.gov (United States)

    Ohtake, Mitsuru; Sato, Yoichi; Higuchi, Jumpei; Tanaka, Takahiro; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-10-01

    Metastable hcp-Ni and hcp-NiFe epitaxial thin films are prepared on Au(100)fcc single-crystal underlayers by molecular beam epitaxy. The epitaxial growth and the transformation from metastable hcp to more stable fcc phase are studied by in-situ reflection high-energy electron diffraction. In an early stage of film growth, hcp(1120) crystal is stabilized through hetero-epitaxial growth. The epitaxial orientation relationship between the film and the underlayer is determined to be hcp(1120)[0001], hcp(1120)[1100] ∥ Au(100)[001]fcc. With increasing the film thickness, the hcp structure starts to transform into fcc structure. High-resolution transmission electron microscopy shows that the film consists of a mixture of hcp and fcc crystals and that a large number of stacking faults exist parallel to the close-packed plane. The results suggest that the hcp structure starts to transform from these stacking faults into fcc structure in the lateral direction by atomic displacement parallel to the hcp(0001) close-packed plane. The crystallographic orientation relationships between the hcp and transformed fcc crystals are determined to be fcc(110)[111], fcc(110)[111] ∥ hcp(1120)[0001] and fcc(110)[112], fcc(110)[112] ∥ hcp(1120)[1100].

  2. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Wan-Jian [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Department of Physics & Astronomy, and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606 (United States); Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Wei, Su-Huai, E-mail: Suhuai.Wei@nrel.gov [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Yan, Yanfa [Department of Physics & Astronomy, and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606 (United States)

    2015-10-05

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  3. Electron-Beam Detection of Bits Reversibly Recorded on Epitaxial InSe/GaSe/Si Phase-Change Diodes

    Science.gov (United States)

    Chaiken, Alison; Gibson, Gary A.; Chen, John; Yeh, Bao S.; Jasinski, J. B.; Liliental‑Weber, Z.; Nauka, K.; Yang, C. C.; Lindig, D. D.; Subramanian, S.

    2006-04-01

    We demonstrate a data read-back scheme based on electron-beam induced current in a data storage device that utilizes thermal recording onto a phase-change medium. The phase-change medium is part of a heterojunction diode whose local charge-collection efficiency depends on the crystalline or amorphous state of a bit. Current gains up to 65 at 2 keV electron beam energy have been demonstrated using InSe/GaSe/Si epitaxial diodes. Fifteen write-erase cycles are obtained without loss of signal contrast by using a protective cap layer and short write pulses. 100 write-erase cycles have been achieved with some loss of contrast. Erasure times for the bits are longer than in similar polycrystalline In-Se media films. Possible reasons for the long erasure times are discussed in terms of a nucleation- or growth-dominated recrystallization. Prospects for extension to smaller bit sizes using electron-beam writing are considered.

  4. Laser Molecular Beam Epitaxy of Multilayer Heterostructure SrNb0.05 Ti0.95O3/La0.9Sr0.1MnO3 in 10000 Unit-Cell Layers

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan-Hong; HE Meng; TIAN Huan-Fang; ZHAO Kun; L(U) Hui-Bin; JIN Kui-Juan; LI Jian-Qi; YANG Guo-Zhen

    2008-01-01

    Ten thousands of unit-cell multilayer heterosturctures, [SrNb0.05 Ti0.95 O3/La0.9Sr0.1MnO3]3 (SNTO/LSMO),have been epitaxial grown on SrTiO3 (001) substrates by laser molecular beam epitaxy. The monitor of insitu reflection high-energy electron diffraction demonstrates that the heterosturctures are layer-by-layer epitaxial growth. Atomic force microscope observation indicates that the surface of the heterosturcture is atomically smooth. The measurements of cross-sectional low magnification and high-resolution transmission electron microscopy as well as the corresponding selected area electron diffraction reveal that the interfaces are of perfect orientation, and the epitaxial crystalline structure shows the orientation relation of SNTO(001)//LSMO(001),and SNTO[100]//LSMO[100].

  5. Phase transformation of molecular beam epitaxy-grown nanometer-thick Gd₂O₃ and Y₂O₃ on GaN.

    Science.gov (United States)

    Chang, Wen-Hsin; Wu, Shao-Yun; Lee, Chih-Hsun; Lai, Te-Yang; Lee, Yi-Jun; Chang, Pen; Hsu, Chia-Hung; Huang, Tsung-Shiew; Kwo, J Raynien; Hong, Minghwei

    2013-02-01

    High quality nanometer-thick Gd₂O₃ and Y₂O₃ (rare-earth oxide, R₂O₃) films have been epitaxially grown on GaN (0001) substrate by molecular beam epitaxy (MBE). The R₂O₃ epi-layers exhibit remarkable thermal stability at 1100 °C, uniformity, and highly structural perfection. Structural investigation was carried out by in situ reflection high energy electron diffraction (RHEED) and ex-situ X-ray diffraction (XRD) with synchrotron radiation. In the initial stage of epitaxial growth, the R₂O₃ layers have a hexagonal phase with the epitaxial relationship of R₂O₃ (0001)(H)(H)//GaN(0001)(H)(H). With the increase in R₂O₃ film thickness, the structure of the R₂O₃ films changes from single domain hexagonal phase to monoclinic phase with six different rotational domains, following the R₂O₃ (201)(M)[020](M)//GaN(0001)(H)(H) orientational relationship. The structural details and fingerprints of hexagonal and monoclinic phase Gd₂O₃ films have also been examined by using electron energy loss spectroscopy (EELS). Approximate 3-4 nm is the critical thickness for the structural phase transition depending on the composing rare earth element.

  6. Improved thermodynamic analysis of gas reactions for compound semiconductor growth by vapor-phase epitaxy

    Science.gov (United States)

    Inatomi, Yuya; Kangawa, Yoshihiro; Kakimoto, Koichi; Koukitu, Akinori

    2017-03-01

    An improved thermodynamic analysis method for vapor-phase epitaxy is proposed. In the conventional method, the mass-balance constraint equations are expressed in terms of variations in partial pressure. Although the conventional method is appropriate for gas–solid reactions occurring near the growth surface, it is not suitable for gas reactions that involve changes in the number of gas molecules. We reconsider the constraint equations in order to predict the effect of gas reactions on semiconductor growth processes. To demonstrate the feasibility of the improved method, the growth process of group-III nitrides by metalorganic vapor-phase epitaxy has been investigated.

  7. Selective growth of GaAs by organometallic vapor phase epitaxy at atmospheric pressure

    Science.gov (United States)

    Azoulay, R.; Dugrand, L.

    1991-01-01

    Complete selective epitaxy of GaAs by organometallic vapor phase epitaxy at atmospheric pressure was achieved by using TMG, AsH3, and AsCl3 as starting gases. Selectivity was observed at growth temperatures ranging from 650 to 750 °C. The blocking of polycrystal deposition on the mask, Si3N4, or W, is attributed to the adsorption of HCl on the mask, thus preventing the nucleation of GaAs. On the openings, the growth rate may be adjusted by controlling the TMG/AsCl3 ratio. When TMG/AsCl3<1, no growth occurs, but etching is observed.

  8. Effect of thickness on the microstructure of GaN films on Al203 (0001) by laser molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Liu Ying-Ying; Zhu Jun; Luo Wen-Bo; Hao Lan-Zhong; Zhang Ying; Li Yan-Rong

    2011-01-01

    Heteroepitaxia1l GaN films are grown on sapphire (0001) substrates using laser molecular beam epitaxy.The growth processes are in-situ monitored by reflection high energy electron diffraction.It is revealed that the growth mode of GaN transformed from three-dimensional (3D) island mode to two-dimensional (2D) layer-by-layer mode with the increase of thickness.This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns.Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm.The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode.The 110-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes.The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films.

  9. Kinetic limitation of chemical ordering in Bi2Te3-x Se x layers grown by molecular beam epitaxy.

    Science.gov (United States)

    Schreyeck, S; Brunner, K; Kirchner, A; Bass, U; Grauer, S; Schumacher, C; Gould, C; Karczewski, G; Geurts, J; Molenkamp, L W

    2016-04-13

    We study the chemical ordering in Bi2Te3-x Se x grown by molecular beam epitaxy on Si substrates. We produce films in the full composition range from x = 0 to 3, and determine their material properties using energy dispersive x-ray spectroscopy, x-ray diffraction and Raman spectroscopy. By fitting the parameters of a kinetic growth model to these results, we obtain a consistent description of growth at a microscopic level. Our main finding is that despite the incorporation of Se in the central layer being much more probable than that of Te, the formation of a fully ordered Te-Bi-Se-Bi-Te layer is prevented by kinetic of the growth process. Indeed, the Se concentration in the central layer of Bi2Te2Se1 reaches a maximum of only ≈ 75% even under ideal growth conditions. A second finding of our work is that the intensity ratio of the 0 0 12 and 0 0 6 x-ray reflections serves as an experimentally accessible quantitative measure of the degree of ordering in these films.

  10. Hybrid ZnO/GaN distributed Bragg reflectors grown by plasma-assisted molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    David Adolph

    2016-08-01

    Full Text Available We demonstrate crack-free ZnO/GaN distributed Bragg reflectors (DBRs grown by hybrid plasma-assisted molecular beam epitaxy using the same growth chamber for continuous growth of both ZnO and GaN without exposure to air. This is the first time these ZnO/GaN DBRs have been demonstrated. The Bragg reflectors consisted up to 20 periods as shown with cross-sectional transmission electron microscopy. The maximum achieved reflectance was 77% with a 32 nm wide stopband centered at 500 nm. Growth along both (0001 and (000 1 ̄ directions was investigated. Low-temperature growth as well as two-step low/high-temperature deposition was carried out where the latter method improved the DBR reflectance. Samples grown along the (0001 direction yielded a better surface morphology as revealed by scanning electron microscopy and atomic force microscopy. Reciprocal space maps showed that ZnO(000 1 ̄ /GaN reflectors are relaxed whereas the ZnO(0001/GaN DBRs are strained. The ability to n-type dope ZnO and GaN makes the ZnO(0001/GaN DBRs interesting for various optoelectronic cavity structures.

  11. Growth and characterization of epitaxial aluminum layers on gallium-arsenide substrates for superconducting quantum bits

    Science.gov (United States)

    Tournet, J.; Gosselink, D.; Miao, G.-X.; Jaikissoon, M.; Langenberg, D.; McConkey, T. G.; Mariantoni, M.; Wasilewski, Z. R.

    2016-06-01

    The quest for a universal quantum computer has renewed interest in the growth of superconducting materials on semiconductor substrates. High-quality superconducting thin films will make it possible to improve the coherence time of superconducting quantum bits (qubits), i.e., to extend the time a qubit can store the amplitude and phase of a quantum state. The electrical losses in superconducting qubits highly depend on the quality of the metal layers the qubits are made from. Here, we report on the epitaxy of single-crystal Al (011) layers on GaAs (001) substrates. Layers with 110 nm thickness were deposited by means of molecular beam epitaxy at low temperature and monitored by in situ reflection high-energy electron diffraction performed simultaneously at four azimuths. The single-crystal nature of the layers was confirmed by ex situ high-resolution x-ray diffraction. Differential interference contrast and atomic force microscopy analysis of the sample’s surface revealed a featureless surface with root mean square roughness of 0.55 nm. A detailed in situ study allowed us to gain insight into the nucleation mechanisms of Al layers on GaAs, highlighting the importance of GaAs surface reconstruction in determining the final Al layer crystallographic orientation and quality. A highly uniform and stable GaAs (001)-(2× 4) reconstruction reproducibly led to a pure Al (011) phase, while an arsenic-rich GaAs (001)-(4× 4) reconstruction yielded polycrystalline films with an Al (111) dominant orientation. The near-atomic smoothness and single-crystal character of Al films on GaAs, in combination with the ability to trench GaAs substrates, could set a new standard for the fabrication of superconducting qubits.

  12. Growth of superconducting SmFeAs(O, F) epitaxial films by F diffusion

    Science.gov (United States)

    Takeda, S.; Ueda, S.; Takano, S.; Yamamoto, A.; Naito, M.

    2012-03-01

    We report on our growth of superconducting SmFeAs(O, F) films by F diffusion. In our process, F-free SmFeAsO films were grown by molecular beam epitaxy (MBE) first, and subsequently F was introduced to the films via F diffusion from an overlayer of SmF3. We compared the growth conditions and also the properties of resultant films for CaF2 and LaAlO3 substrates. The best films on CaF2 exhibited a high transition temperature, {T}_{{c}}^{{on}}~({T}_{{c}}^{{end}})=57.8 K (56.4 K) at the highest, which may exceed the highest Tc ever reported for bulk samples. Furthermore, the films on CaF2 also showed high critical current density over 1 MA cm-2 in self-field at 5 K. On the other hand, the {T}_{{c}}^{{on}}~({T}_{{c}}^{{end}}) of the film on LaAlO3 was 50.3 K (49.3 K). The deteriorated superconducting properties on LaAlO3 appear to be due to oxygen diffusion from LaAlO3 to films.

  13. Large-area selective CVD epitaxial growth of Ge on Si substrates

    NARCIS (Netherlands)

    Sammak, A.; De Boer, W.; Nanver, L.K.

    2011-01-01

    Selective epitaxial growth of crystalline Ge on Si in a standard ASM Epsilon 2000 CVD reactor is investigated for the fabrication of Ge p+n diodes. At the deposition temperature of 700˚C, most of the lattice mismatch-defects are trapped within first 300nm of Ge growth and good quality single crystal

  14. Epitaxial Growth of Graphene on 6H-SiC (0001) by Thermal Annealing

    Institute of Scientific and Technical Information of China (English)

    TANG Jun; LIU Zhong-Liang; KANG Chao-Yang; PAN Hai-Bin; WEI Shi-Qiang; XU Peng-Shou; GAO Yu-Qiang; XU Xian-Gang

    2009-01-01

    An epitaxial graphene (EG) layer is successfully grown on a Si-terminated 6H-SiC (0001) substrate by the method of thermal annealing in an ultrahigh vacuum molecular beam epitaxy chamber.The structure and morphology of the EG sample are characterized by reflection high energy diffraction (RHEED),Raman spectroscopy and atomic force microscopy (AFM).Graphene diffraction streaks can be seen in RHEED.The G and 2D peaks of graphene are clearly observed in the Raman spectrum.The AFM results show that the graphene nominal thickness is about 4-10 layers.

  15. Epitaxial growth of ZnSe and ZnSe/CdSe nanowires on ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Bellet-Amalric, E.; Bounouar, S.; Kheng, K. [CEA-CNRS-UJF Group, Nanophysique et Semiconducteurs, CEA Grenoble, INAC, 17 rue des Martyrs, 38 054 Grenoble (France); Elouneg-Jamroz, M.; Bougerol, C.; Hertog, M. den; Genuist, Y.; Poizat, J.P.; Andre, R.; Tatarenko, S. [CEA-CNRS-UJF Group, Nanophysique et Semiconducteurs, Institut Neel, BP 166, 38 042 Grenoble (France)

    2010-06-15

    We report the molecular beam epitaxy (MBE) growth of ZnSe nanowires (NWs) on a ZnSe(100) epilayer assisted by gold catalyst. Gold dewetting assists in the formation of nanotrenches along the [0-1-1] direction in the ZnSe buffer layer. Nucleation of the gold catalyst in the trenches leads to the growth of NWs preferentially in directions orthogonal to the trenches. The wires adopt mostly the wurtzite type structure and grow along the c-axis. CdSe quantum dots were inserted in the ZnSe NWs. The CdSe insertions systematically adopt a cubic zinc-blende arrangement with a[111] growth axis, as confirmed by transmission electron microscopy. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Epitaxial growth of amorphous Ge films deposited on single-crystal Ge

    OpenAIRE

    M. G. Grimaldi; Mäenpää, M. (Markus); Paine, B. M.; Nicolet, M-A.; Lau, S. S.; Tseng, W. F.

    1981-01-01

    The epitaxial growth of amorphous Ge films deposited onto 110 Ge substrate is demonstrated. Substrate cleaning prior to deposition involves only conventional chemical procedures. The growth appears to be a strong function of the interface cleanliness. Two different growth mechanisms are observed: (a) a direct transition from amorphous to single-crystalline layer and (b) the growth involving the transition of amorphous to polycrystals to single crystal.

  17. Demonstration of isotype GaN/AlN/GaN heterobarrier diodes by NH{sub 3}-molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Fireman, Micha N.; Browne, David A.; Mazumder, Baishakhi; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2015-05-18

    The results of vertical transport through nitride heterobarrier structures grown by ammonia molecular beam epitaxy are presented. Structures are designed with binary layers to avoid the effects of random alloy fluctuations in ternary nitride barriers. The unintentional incorporation of Ga in the AlN growth is investigated by atom probe tomography and is shown to be strongly dependent on both the NH{sub 3} flowrate and substrate temperature growth parameters. Once nominally pure AlN layer growth conditions are achieved, structures consisting of unintentionally doped (UID) GaN spacer layers adjacent to a nominally pure AlN are grown between two layers of n+ GaN, from which isotype diodes are fabricated. Varying the design parameters of AlN layer thickness, UID spacer layer thickness, and threading dislocation density show marked effects on the vertical transport characteristics of these structures. The lack of significant temperature dependence, coupled with Fowler-Nordheim and/or Milliken-Lauritsen analysis, point to a prevalently tunneling field emission mechanism through the AlN barrier. Once flatband conditions in the UID layer are achieved, electrons leave the barrier with significant energy. This transport mechanism is of great interest for applications in hot electron structures.

  18. Nucleation phenomena during molecular beam epitaxy of GaN observed by line-of-sight quadrupole mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Koblmueller, G.; Averbeck, R.; Riechert, H. [Infineon Technologies AG, Corporate Research Photonics, Otto-Hahn-Ring 6, 81739 Munich (Germany); Pongratz, P. [Vienna University of Technology, Institute of Solid State Physics, Wiedner Hauptstrasse 8-10, 1040 Vienna (Austria)

    2002-12-16

    We investigate nucleation and growth phenomena during molecular beam epitaxy of GaN on sapphire, 6H-SiC and GaN templates using in situ line-of-sight quadrupole mass spectrometry. Moreover, this method allows the quantitative study of nucleation phenomena by monitoring desorption processes. Heteroepitaxial growth of GaN on sapphire and 6H-SiC faces a high energy barrier to nucleation giving rise to a substantial Ga desorption during the initial phase of nucleation. The amount of initial Ga desorption in heteroepitaxy is independent of the chosen substrate material and is as high as 8 {+-} 1.5 nm equivalent GaN thickness. Once critical-sized islands have nucleated they grow three-dimensional (3D) leading to a quadratic increase of the GaN coverage and finally to a steady growth rate after coalescence, as also determined by Rutherford backscattering and atomic force microscopy. In contrast, homoepitaxy on Ga- and N-face GaN templates is distinguished by immediate nucleation. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  19. Synthesis of semimetal A{sub 3}Bi (A = Na, K) thin films by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Jing, E-mail: wenj07@126.com [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China); Guo, Hua [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China); Yan, Chen-Hui [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, Zhen-Yu; Chang, Kai; Deng, Peng; Zhang, Teng [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China); Zhang, Zhi-Dong [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Ji, Shuai-Hua [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China); Wang, Li-Li; He, Ke; Ma, Xu-Cun [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Chen, Xi; Xue, Qi-Kun [State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 (China)

    2015-02-01

    Highlights: • First realization of MBE growth of Na{sub 3}Bi on Si(1 1 1)-7 × 7. • The lattice of Na{sub 3}Bi is rotated 30 degree to substrate. • ARPES reveals multi-linear cone structure near Fermi surface. • K{sub 3}Bi was successfully grown on Na{sub 3}Bi/Si(1 1 1)–7 × 7. - Abstract: Three-dimensional (3D) Dirac cones are predicted to reside in semimetals A{sub 3}Bi (A = Na, K). By using molecular beam epitaxy (MBE) and scanning tunneling microscopy (STM), we have successfully established the growth conditions for Na{sub 3}Bi thin films on Si(1 1 1)-7 × 7, and determined that the lattice of Na{sub 3}Bi is rotated by 30 degree with respect to that of Si(1 1 1)-7 × 7. The Na{sub 3}Bi/Si(1 1 1)-7 × 7 thin film was further used as the substrate for the growth of K{sub 3}Bi. The 3D Dirac-cone-like electronic band structures of Na{sub 3}Bi and K{sub 3}Bi have been clearly revealed by angle resolved photoelectron spectroscopy (ARPES)

  20. Growth and characterisation of epitaxially ordered zinc aluminate domains on c-sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Grabowska, J.; Rajendra Kumar, R.T. [School of Physical Sciences/National Centre for Plasma Science and Technology, Dublin City University (Ireland); McGlynn, E. [School of Physical Sciences/National Centre for Plasma Science and Technology, Dublin City University (Ireland)], E-mail: enda.mcglynn@dcu.ie; Nanda, K.K. [School of Physical Sciences/National Centre for Plasma Science and Technology, Dublin City University (Ireland); Newcomb, S.B. [Glebe Scientific Ltd., Newport, Co. Tipperary (Ireland); McNally, P.J.; O' Reilly, L. [School of Electronic Engineering/Research Institute for Networks and Communications Engineering, Dublin City University (Ireland); Mosnier, J.-P.; Henry, M.O. [School of Physical Sciences/National Centre for Plasma Science and Technology, Dublin City University (Ireland)

    2008-02-29

    Epitaxially ordered zinc aluminate domains with sub-micron dimensions are formed on bare c-sapphire substrates using a vapour phase method (with vapour generated by carbothermal reduction of ZnO) at various temperatures and growth durations. A zinc aluminate (ZnAl{sub 2}O{sub 4}) layer is formed by reaction of the source materials (Zn and O) with the substrate. We observe crystallites with a well-defined epitaxial relationship on the sapphire substrate in addition to polycrystalline material. The epitaxially oriented deposit displays the form of characteristically twinned (singly or multiply) grains of sub-micron dimensions with three variants, consistent with the c-sapphire substrate symmetry. Scanning electron microscopy and transmission electron microscopy studies show that the formation of these grains is associated with the presence of extended defects in the sapphire substrate. Epitaxially ordered grains formed at higher temperatures show a change in the nature of the twin boundaries and epitaxial relations as a function of growth time, attributed to the effects of annealing during growth.

  1. The Utility of Droplet Elimination by Thermal Annealing Technique for Fabrication of GaN/AlGaN Terahertz Quantum Cascade Structure by Radio Frequency Molecular Beam Epitaxy

    Science.gov (United States)

    Terashima, Wataru; Hirayama, Hideki

    2010-12-01

    We investigated the utility of a droplet elimination by thermal annealing (DETA) technique during the radio-frequency molecular beam epitaxy growth of a quantum cascade laser (QCL) structure. DETA is a method in which droplets deposited on the surface are eliminated by temporarily increasing the substrate temperature. DETA is a useful method which makes it possible not only to increase the number of periods in the QC structure, but also to improve the surface and structural properties of the QC structure. We could successfully increase the radiant intensity from a QCL sample by increasing the number of periods in the stacked QC structure with the DETA method.

  2. Molecular beam epitaxy of free-standing bulk wurtzite AlxGa1-xN layers using a highly efficient RF plasma source

    OpenAIRE

    2016-01-01

    Recent developments with group III nitrides suggest AlxGa1-xN based LEDs can be new alternative commer-cially viable deep ultra-violet light sources. Due to a sig-nificant difference in the lattice parameters of GaN and AlN, AlxGa1-xN substrates would be preferable to either GaN or AlN for ultraviolet device applications. We have studied the growth of free-standing wurtzite AlxGa1-xN bulk crystals by plasma-assisted molecular beam epitaxy (PA-MBE) using a novel RF plasma source. Thick wurtz-i...

  3. Analysis of Mg content of Zn1-xMgxO film grown on sapphire substrates by plasma-assisted molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    YAN Fengping; JIAN Shuisheng; K. Ogata; K. Koike; S. Sasa; M. Inoue; M. Yano

    2004-01-01

    The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP)and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.

  4. X-rays diffraction on a new chromium oxide single-crystal thin film prepared by molecular beam epitaxy

    NARCIS (Netherlands)

    Du, X. S.; Hak, S.; Hibma, T.; Rogojanu, O. C.; Struth, B.

    2006-01-01

    Chromium oxide films were prepared on MgO substrates by molecular beam epitaxy. The crystalline structure of the films was characterized by X-ray diffraction (XRD) with conventional as well as synchrotron X-ray sources. The theta-2 theta spectra showed that the film was a new chromium oxide epitaxia

  5. Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy.

    Science.gov (United States)

    Wu, Han-Chun; Mauit, Ozhet; Coileáin, Cormac Ó; Syrlybekov, Askar; Khalid, Abbas; Mouti, Anas; Abid, Mourad; Zhang, Hong-Zhou; Abid, Mohamed; Shvets, Igor V

    2014-11-12

    Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics.

  6. Formation of Ga droplets on patterned GaAs (100) by molecular beam epitaxy.

    Science.gov (United States)

    Li, Ming-Yu; Hirono, Yusuke; Koukourinkova, Sabina D; Sui, Mao; Song, Sangmin; Kim, Eun-Soo; Lee, Jihoon; Salamo, Gregory J

    2012-10-03

    In this paper, the formation of Ga droplets on photo-lithographically patterned GaAs (100) and the control of the size and density of Ga droplets by droplet epitaxy using molecular beam epitaxy are demonstrated. In extension of our previous result from the journal Physical Status Solidi A, volume 209 in 2012, the sharp contrast of the size and density of Ga droplets is clearly observed by high-resolution scanning electron microscope, atomic force microscope, and energy dispersive X-ray spectrometry. Also, additional monolayer (ML) coverage is added to strength the result. The density of droplets is an order of magnitude higher on the trench area (etched area), while the size of droplets is much larger on the strip top area (un-etched area). A systematic variation of ML coverage results in an establishment of the control of size and density of Ga droplets. The cross-sectional line profile analysis and root mean square roughness analysis show that the trench area (etched area) is approximately six times rougher. The atomic surface roughness is suggested to be the main cause of the sharp contrast of the size and density of Ga droplets and is discussed in terms of surface diffusion.

  7. Graphene films grown on sapphire substrates via solid source molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Tang Jun; Kang Chao-Yang; Li Li-Min; Liu Zhong-Liang; Yan Wen-Sheng; Wei Shi-Qiang; Xu Peng-Shou

    2012-01-01

    A method for growing graphene on a sapphire substrate by depositing an SiC buffer layer and then annealing at high temperature in solid source molecular beam epitaxy(SSMBE)equipment was presented.The structural and electronic properties of the samples were characterized by reflection high energy diffraction(RHEED),X-ray diffractionφ scans,Raman spectroscopy,and near edge X-ray absorption fine structure(NEXAFS)spectroscopy.The results of the RHEED and φ scan,as well as the Raman spectra,showed that an epitaxial hexagonal α-SiC layer was grown on the sapphire substrate.The results of the Raman and NEXAFS spectra revealed that the graphene films with the AB Bernal stacking structure were formed on the sapphire substrate after annealing.The layer number of the graphene was between four and five,and the thickness of the unreacted SiC layer was about 1-1.5 mm.

  8. Chirality-dependent vapor-phase epitaxial growth and termination of single-wall carbon nanotubes.

    Science.gov (United States)

    Liu, Bilu; Liu, Jia; Tu, Xiaomin; Zhang, Jialu; Zheng, Ming; Zhou, Chongwu

    2013-09-11

    Structurally uniform and chirality-pure single-wall carbon nanotubes are highly desired for both fundamental study and many of their technological applications, such as electronics, optoelectronics, and biomedical imaging. Considerable efforts have been invested in the synthesis of nanotubes with defined chiralities by tuning the growth recipes but the approach has only limited success. Recently, we have shown that chirality-pure short nanotubes can be used as seeds for vapor-phase epitaxial cloning growth, opening up a new route toward chirality-controlled carbon nanotube synthesis. Nevertheless, the yield of vapor-phase epitaxial growth is rather limited at the present stage, due in large part to the lack of mechanistic understanding of the process. Here we report chirality-dependent growth kinetics and termination mechanism for the vapor-phase epitaxial growth of seven single-chirality nanotubes of (9, 1), (6, 5), (8, 3), (7, 6), (10, 2), (6, 6), and (7, 7), covering near zigzag, medium chiral angle, and near armchair semiconductors, as well as armchair metallic nanotubes. Our results reveal that the growth rates of nanotubes increase with their chiral angles while the active lifetimes of the growth hold opposite trend. Consequently, the chirality distribution of a nanotube ensemble is jointly determined by both growth rates and lifetimes. These results correlate nanotube structures and properties with their growth behaviors and deepen our understanding of chirality-controlled growth of nanotubes.

  9. Emittance growth from electron beam modulation

    Energy Technology Data Exchange (ETDEWEB)

    Blaskiewicz, M.

    2009-12-01

    In linac ring colliders like MeRHIC and eRHIC a modulation of the electron bunch can lead to a modulation of the beam beam tune shift and steering errors. These modulations can lead to emittance growth. This note presents simple formulas to estimate these effects which generalize some previous results.

  10. Photoluminescence properties of MgxZn1-xO films grown by molecular beam epitaxy

    Science.gov (United States)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Chou, W. C.; Shen, J. L.

    2017-02-01

    The optical properties of MgxZn1-xO films with x=0.03, 0.06, 0.08, and 0.11 grown by molecular beam epitaxy (MBE) have been studied by temperature-dependent photoluminescence (PL) measurement. It is presented that the full-width at half-maximum (FWHM) of the 12 K PL spectrum of MgZnO films increases with increasing Mg concentration and would deviate significantly from the simulation curve of Schubert model with higher Mg contents. The abnormal broader PL FWHM is inferred from larger compositional fluctuation by incorporating higher Mg contents, which results in larger effect of excitonic localization to induce more significant S-shaped behavior of the PL peak energy with temperature dependence. Additionally, the degree of localization increases as the linear proportion of the PL FWHM, indicating that the excitonic behavior in MgZnO films belong to the strong localization effect.

  11. High quality YBCO superconductive thin films fabricated by laser molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    High quality YBa2Cu3O6+x (YBCO) superconductive thin films have been fabricated on the SrTiO3(100) substrate using laser molecular beam epitaxy (laser-MBE).The active oxygen source was used,which made the necessary ambient oxygen pressure be 2-3 orders lower than that in pulsed laser deposition (PLD).Tc0 is 85-87 K,and Jc~1.0×106 A/cm2.Atomic force microscopy (AFM) measurements show that no obvious particulates can be observed and the root mean square roughness is 7.8 nm.High stability DC superconducting quantum interference devices (DC-SQUID) was fabricated using this YBCO thin film.

  12. Investigation of Localized States in GaAsSb Epilayers Grown by Molecular Beam Epitaxy.

    Science.gov (United States)

    Gao, Xian; Wei, Zhipeng; Zhao, Fenghuan; Yang, Yahui; Chen, Rui; Fang, Xuan; Tang, Jilong; Fang, Dan; Wang, Dengkui; Li, Ruixue; Ge, Xiaotian; Ma, Xiaohui; Wang, Xiaohua

    2016-07-06

    We report the carrier dynamics in GaAsSb ternary alloy grown by molecular beam epitaxy through comprehensive spectroscopic characterization over a wide temperature range. A detailed analysis of the experimental data reveals a complex carrier relaxation process involving both localized and delocalized states. At low temperature, the localized degree shows linear relationship with the increase of Sb component. The existence of localized states is also confirmed by the temperature dependence of peak position and band width of the emission. At temperature higher than 60 K, emissions related to localized states are quenched while the band to band transition dominates the whole spectrum. This study indicates that the localized states are related to the Sb component in the GaAsSb alloy, while it leads to the poor crystal quality of the material, and the application of GaAsSb alloy would be limited by this deterioration.

  13. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Federico Baiutti

    2014-05-01

    Full Text Available In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2−xSrxNiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control.

  14. Molecular-Beam Epitaxially Grown MgB2 Thin Films and Superconducting Tunnel Junctions

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Laloë

    2011-01-01

    Full Text Available Since the discovery of its superconducting properties in 2001, magnesium diboride has generated terrific scientific and engineering research interest around the world. With a of 39 K and two superconducting gaps, MgB2 has great promise from the fundamental point of view, as well as immediate applications. Several techniques for thin film deposition and heterojunction formation have been established, each with its own advantages and drawbacks. Here, we will present a brief overview of research based on MgB2 thin films grown by molecular beam epitaxy coevaporation of Mg and B. The films are smooth and highly crystalline, and the technique allows for virtually any heterostructure to be formed, including all-MgB2 tunnel junctions. Such devices have been characterized, with both quasiparticle and Josephson tunneling reported. MgB2 remains a material of great potential for a multitude of further characterization and exploration research projects and applications.

  15. Photoluminescence studies of ZnO nanorods grown by plasma-assisted molecular beam epitaxy.

    Science.gov (United States)

    Kim, Min Su; Nam, Giwoong; Leem, Jae-Young

    2013-05-01

    Metal catalyst-free ZnO nanorods were grown on PS with buffer layers grown at 450 degrees C by plasma-assisted molecular beam epitaxy. Room temperature and temperature-dependent photoluminescence were carried out to investigate the optical properties of the ZnO nanorods with the average diameter of 120 nm and length of 300 nm. Three emission peaks, free excition, neutral-donor exciton, and free electron-to-neutral acceptor, were observed at 10 K. Huang-Rhys factor S of the ZnO nanorods was 0.978, which is much higher than that of ZnO thin films. The values of Varshni's empirical equation fitting parameters were alpha = 4 x 10(-3) eV/K, beta = 4.1 x 10(4) K, and E9(0) = 3.388 eV and the activation energy was about 96 meV.

  16. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy.

    Science.gov (United States)

    Baiutti, Federico; Christiani, Georg; Logvenov, Gennady

    2014-01-01

    In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2- x Sr x NiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control.

  17. AlN Nanowall Structures Grown on Si (111) Substrate by Molecular Beam Epitaxy.

    Science.gov (United States)

    Tamura, Yosuke; Hane, Kazuhiro

    2015-12-01

    AlN nanowall structures were grown on Si (111) substrate using molecular beam epitaxy at substrate temperature of 700 °C with N/Al flux ratios ranging from 50 to 660. A few types of other AlN nanostructures were also grown under the nitrogen-rich conditions. The AlN nanowalls were ranged typically 60-120 nm in width and from 190 to 470 nm in length by changing N/Al flux ratio. The AlN nanowall structures grown along the c-plane consisted of AlN (0002) crystal with full-width at half maximum of the rocking curve about 5000 arcsec.

  18. Structural and optical characterizations of InPBi thin films grown by molecular beam epitaxy.

    Science.gov (United States)

    Gu, Yi; Wang, Kai; Zhou, Haifei; Li, Yaoyao; Cao, Chunfang; Zhang, Liyao; Zhang, Yonggang; Gong, Qian; Wang, Shumin

    2014-01-13

    InPBi thin films have been grown on InP by gas source molecular beam epitaxy. A maximum Bi composition of 2.4% is determined by Rutherford backscattering spectrometry. X-ray diffraction measurements show good structural quality for Bi composition up to 1.4% and a partially relaxed structure for higher Bi contents. The bandgap was measured by optical absorption, and the bandgap reduction caused by the Bi incorporation was estimated to be about 56 meV/Bi%. Strong and broad photoluminescence signals were observed at room temperature for samples with xBi < 2.4%. The PL peak position varies from 1.4 to 1.9 μm, far below the measured InPBi bandgap.

  19. Effects of hydrogen during molecular beam epitaxy of GaN

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Y.; Feenstra, R.M. [Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2005-05-01

    We study the effect of introducing hydrogen gas through the RF plasma source during plasma-assisted molecular beam epitaxy of GaN(0001). The well-known smooth-to-rough transition that occurs for this surface as a function of decreasing Ga flux in the absence of H is found to persist even with H present. But, the critical Ga flux for this transition is increased by the presence of H, and for sufficiently high H pressure a new 2 x 2 surface structure that is believed to be H-terminated is observed. Under Ga-rich conditions, the presence of hydrogen is found to induce step bunching on the surface, from which we argue that H selectively bonds to surface step and/or kink sites. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Deep levels in Ga-doped ZnSe grown by molecular-beam epitaxy

    Science.gov (United States)

    Venkatesan, S.; Pierret, R. F.; Qiu, J.; Kobayashi, M.; Gunshor, R. L.; Kolodziejski, L. A.

    1989-10-01

    Results of a deep-level transient spectroscopy study of Ga-doped ZnSe thin films grown by molecular-beam epitaxy are presented. Two prominent deep levels were observed in all the samples investigated. The concentration of the trap detected at 0.34 eV below the conduction-band edge was essentially independent of the doping concentration and is attributed to native defects arising from Se vacancies in the ZnSe films. The second level with an activation energy of 0.26 eV shows a very strong doping dependence and is tentatively identified as arising from dopant-site (gallium-on-zinc-site) defects complexed with selenium vacancies. Preliminary results also indicate that planar doping of ZnSe significantly reduces the concentration of the Ga-vacancy complex.

  1. Infrared electroluminescence from GeSn heterojunction diodes grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-06-24

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

  2. Infrared photoresponse of GeSn/n-Ge heterojunctions grown by molecular beam epitaxy.

    Science.gov (United States)

    Kim, Sangcheol; Bhargava, Nupur; Gupta, Jay; Coppinger, Matthew; Kolodzey, James

    2014-05-05

    Heterojunction devices of Ge(1-x)Sn(x) / n-Ge were grown by solid source molecular beam epitaxy (MBE), and the mid-infrared (IR) photocurrent response was measured. With increasing Sn composition from 4% to 12%, the photocurrent spectra became red-shifted, suggesting that the bandgap of Ge(1-x)Sn(x) alloys was lowered compared to pure Ge. At a temperature of 100 K, the wavelengths of peak photocurrent were shifted from 1.42 µm for pure Ge (0% Sn) to 2.0 µm for 12% Sn. The bias dependence of the device response showed that the optimum reverse bias was > 0.5 volts for saturated photocurrent. The responsivity of the Ge(1-x)Sn(x) devices was estimated to be 0.17 A/W for 4% Sn. These results suggest that Ge(1-x)Sn(x) photodetectors may have practical applications in the near/mid IR wavelength regime.

  3. Double acceptor in p-type GaAsN grown by chemical beam epitaxy

    Science.gov (United States)

    Elleuch, Omar; Wang, Li; Lee, Kan-Hua; Ikeda, Kazuma; Kojima, Nobuaki; Ohshita, Yoshio; Yamaguchi, Masafumi

    2015-12-01

    The properties of the acceptor states in GaAsN grown by chemical beam epitaxy (CBE) are studied by analyzing their charges based on the Poole-Frenkel model. Deep level transient spectroscopy (DLTS) shows two acceptor levels at 0.11 and 0.19 eV above the valence band maximum. The emission rates of carriers from these states are enhanced with increasing the electric field during the DLTS measurement, which indicates that the energies required for the emission are decreased. By analyzing this field-enhanced emission process, the polarizabilities of the levels at 0.11 and 0.19 eV are found to be -1 (±0.1) and -2 (±0.1), respectively. In addition, these states have almost the same concentration. Therefore, we conclude that they originate from the same defect, acting as a double acceptor in GaAsN film grown by CBE.

  4. Study on Long Wavelength Multi-layer InAs QDs Growth by Molecular Beam Epitaxy%分子束外延生长长波长多层InAs量子点

    Institute of Scientific and Technical Information of China (English)

    刘学东; 刘羽; 尤明慧; 刘国军

    2014-01-01

    采用应变InGaAs覆盖层可以实现GaAs基量子点1.3μm,但是1.55μm GaAs基量子点的制备难度要大得多,需要高In含量的覆盖层和较大的量子点。但是高In量子点容易引起快速降解的非辐射复合中心,影响QD材料的晶体和光学特性。较为系统的研究了长波长多层InAs量子点的MBE生长,优化了生长条件,获得了波长约为1568nm的多层InAs量子点材料。%Compared to the development of 1.3 mm GaAs based quantum dots (QDs),the shift to 1.55 mm poses sig-nificant challenges. Following the introduction of a strained InGaAs cap layer to reach 1.3 mm, pushing the technology to 1.55 mm devices would logically merely require even higher indium content QD capping layers and larger QDs. However,concentration in the QDs and the surrounding matrix very readily induces non-radiative recombination centres which rapidly degrade the crystal and optical quality of the QDs. In this paper had systematic studied on the MBE growth InAs QDs , optimization of the growth conditions , and1568nm long-wavelength InAs QDs material were obtained.

  5. Ultrafast carrier dynamics and the role of grain boundaries in polycrystalline silicon thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Titova, Lyubov V.; Cocker, Tyler L.; Xu, Sijia; Baribeau, Jean-Marc; Wu, Xiaohua; Lockwood, David J.; Hegmann, Frank A.

    2016-10-01

    We have used time-resolved terahertz spectroscopy to study microscopic photoconductivity and ultrafast photoexcited carrier dynamics in thin, pure, non-hydrogenated silicon films grown by molecular beam epitaxy on quartz substrates at temperatures ranging from 335 °C to 572 °C. By controlling the growth temperature, thin silicon films ranging from completely amorphous to polycrystalline with minimal amorphous phase can be achieved. Film morphology, in turn, determines its photoconductive properties: in the amorphous phase, carriers are trapped in bandtail states on sub-picosecond time scales, while the carriers excited in crystalline grains remain free for tens of picoseconds. We also find that in polycrystalline silicon the photoexcited carrier mobility is carrier-density-dependent, with higher carrier densities mitigating the effects of grain boundaries on inter-grain transport. In a film grown at the highest temperature of 572 °C, the morphology changes along the growth direction from polycrystalline with needles of single crystals in the bulk of the film to small crystallites interspersed with amorphous silicon at the top of the film. Depth profiling using different excitation wavelengths shows corresponding differences in the photoconductivity: the photoexcited carrier lifetime and mobility are higher in the first 100-150 nm from the substrate, suggesting that thinner, low-temperature grown polycrystalline silicon films are preferable for photovoltaic applications.

  6. InN nanorods prepared with CrN nanoislands by plasma-assisted molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Young Sheng-Joue

    2011-01-01

    Full Text Available Abstract The authors report the influence of CrN nanoisland inserted on growth of baseball-bat InN nanorods by plasma-assisted molecular beam epitaxy under In-rich conditions. By inserting CrN nanoislands between AlN nucleation layer and the Si (111 substrate, it was found that we could reduce strain form Si by inserting CrN nanoisland, FWHM of the x-ray rocking curve measured from InN nanorods from 3,299 reduced to 2,115 arcsec. It is due to the larger strain from lattice miss-match of the film-like InN structure; however, the strain from lattice miss-match was obvious reduced owing to CrN nanoisland inserted. The TEM images confirmed the CrN structures and In droplets dissociation from InN, by these results, we can speculate the growth mechanism of baseball-bat-like InN nanorods.

  7. Distribution of carriers in gradient-doping transmission-mode GaAs photocathodes grown by molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Jun; Chang Ben-Kang; Yang Zhi; Niu Jun; Zou Ji-Jun

    2009-01-01

    The gradient-doping structure is first applied to prepare the transmission-mode OaAs photocathode and the integral sensitivity of the sealed image tube achieves 1420μA/lm. This paper studies the inner carrier concentration distribution of the gradient-doping transmission-mode GaAs photocathode after molecular beam epitaxy (MBE) growth using the electrochemical capacitance-voltage profiling. The results show that an ideal gradient-doping structure can be obtained by using MBE growth. The total band-bending energy in the gradient-doping GaAs active-layer with doping concentration ranging from 1×10~(19) cm~(-3) to 1×10~(18) cm~(-3) is calculated to be 46.3 meV, which helps to improve the photoexcited electrons movement toward surface for the thin epilayer. In addition, by analysis of the band offsets, it is found that the worse carrier concentration discrepancy between GaAs and GaAlAs causes a lower back interface electron potential barrier which decreases the amount of high-energy photoelectrons and affects the short-wave response.

  8. Molecular beam epitaxy and characterization of thin Bi2Se3 films on Al2O3 (110)

    Science.gov (United States)

    Tabor, Phillip; Keenan, Cameron; Urazhdin, Sergei; Lederman, David

    2011-07-01

    The structural and electronic properties of thin Bi2Se3 films grown on Al2O3 (110) by molecular beam epitaxy are investigated. The epitaxial films grow in the Frank-van der Merwe mode and are c-axis oriented. They exhibit the highest crystallinity, the lowest carrier concentration, and optimal stoichiometry at a substrate temperature of 200 °C determined by the balance between surface kinetics and desorption of Se. The crystallinity of the films improves with increasing Se/Bi flux ratio. Our results enable studies of thin topological insulator films on inert, non-conducting substrates that allow optical access to both film surfaces.

  9. Epitaxial Growth of Germanium on Silicon for Light Emitters

    Directory of Open Access Journals (Sweden)

    Chengzhao Chen

    2012-01-01

    Full Text Available This paper describes the role of Ge as an enabler for light emitters on a Si platform. In spite of the large lattice mismatch of ~4.2% between Ge and Si, high-quality Ge layers can be epitaxially grown on Si by ultrahigh-vacuum chemical vapor deposition. Applications of the Ge layers to near-infrared light emitters with various structures are reviewed, including the tensile-strained Ge epilayer, the Ge epilayer with a delta-doping SiGe layer, and the Ge/SiGe multiple quantum wells on Si. The fundamentals of photoluminescence physics in the different Ge structures are discussed briefly.

  10. Growth and characterization of AlGaN/GaN/AlGaN double-heterojunction high-electron-mobility transistors on 100-mm Si(111) using ammonia-molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Ravikiran, L.; Radhakrishnan, K., E-mail: ERADHA@ntu.edu.sg; Yiding, Lin; Ng, G. I. [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Dharmarasu, N.; Agrawal, M.; Arulkumaran, S.; Vicknesh, S. [Temasek Laboratories@NTU, Nanyang Technological University, Singapore 637553 (Singapore)

    2015-01-14

    To improve the confinement of two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures, AlGaN/GaN/AlGaN double heterojunction HEMT (DH-HEMT) heterostructures were grown using ammonia-MBE on 100-mm Si substrate. Prior to the growth, single heterojunction HEMT (SH-HEMT) and DH-HEMT heterostructures were simulated using Poisson-Schrödinger equations. From simulations, an AlGaN buffer with “Al” mole fraction of 10% in the DH-HEMT was identified to result in both higher 2DEG concentration (∼10{sup 13 }cm{sup −2}) and improved 2DEG confinement in the channel. Hence, this composition was considered for the growth of the buffer in the DH-HEMT heterostructure. Hall measurements showed a room temperature 2DEG mobility of 1510 cm{sup 2}/V.s and a sheet carrier concentration (n{sub s}) of 0.97 × 10{sup 13 }cm{sup −2} for the DH-HEMT structure, while they are 1310 cm{sup 2}/V.s and 1.09 × 10{sup 13 }cm{sup −2}, respectively, for the SH-HEMT. Capacitance-voltage measurements confirmed the improvement in the confinement of 2DEG in the DH-HEMT heterostructure, which helped in the enhancement of its room temperature mobility. DH-HEMT showed 3 times higher buffer break-down voltage compared to SH-HEMT, while both devices showed almost similar drain current density. Small signal RF measurements on the DH-HEMT showed a unity current-gain cut-off frequency (f{sub T}) and maximum oscillation frequency (f{sub max}) of 22 and 25 GHz, respectively. Thus, overall, DH-HEMT heterostructure was found to be advantageous due to its higher buffer break-down voltages compared to SH-HEMT heterostructure.

  11. Control of the lateral growth morphology in GaAs Droplet Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Somaschini, C; Bietti, S; Sanguinetti, S; Koguchi, N [LNESS and Dipartimento di Scienza dei Materiali dell' Universita di Milano-Bicocca, via Cozzi 53, 20125 Milano (Italy); Fedorov, A, E-mail: stefano.sanguinetti@mater.unimib.i [CNISM, LNESS and Dipartimento di Fisica del Politecnico di Milano, via Anzani 42, 22100 Como (Italy)

    2010-09-01

    We present the detailed fabrication method of two different GaAs nanostructures with cylindrical symmetry by the Droplet Epitaxy technique. Concentric Multiple Rings or Coupled Rings/Disks are successfully obtained, exploiting the lateral growth around the Ga droplets, through a fine control of the crystallization dynamics.

  12. Epitaxial Growth of a Methoxy-Functionalized Quaterphenylene on Alkali Halide Surfaces

    DEFF Research Database (Denmark)

    Balzer, Frank; Sun, Rong; Parisi, Jürgen

    2015-01-01

    The epitaxial growth of the methoxy functionalized para-quaterphenylene (MOP4) on the (001) faces of the alkali halides NaCl and KCl and on glass is investigated by a combination of lowenergy electron diffraction (LEED), polarized light microscopy (PLM), atomic force microscopy (AFM), and X...

  13. New synthesis method for the growth of epitaxial graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yu, X.Z. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Laboratory of Condensed Matter Spectroscopy and Opto-Electronic Physics, Department of Physics, Shanghai Jiao Tong University, 1954 Hua Shan Road, Shanghai 200030 (China); Hwang, C.G.; Jozwiak, C.M.; Koehl, A. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Schmid, A.K. [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94709 (United States); Lanzara, A., E-mail: ALanzara@lbl.gov [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Department of Physics, University of California, Berkeley, CA 94720 (United States)

    2011-04-15

    Highlights: {yields} We report a new straightforward method for the synthesis of micrometer scale graphene sheets. {yields} The process is based on a face to face mehtod in which two SiC substrates are placed one on top of the other and are heated simultaneously, leading to highly homogeneous samples. {yields} The number of graphene layers is determined by the annealing temperature. - Abstract: As a viable candidate for an all-carbon post-CMOS electronics revolution, epitaxial graphene has attracted significant attention. To realize its application potential, reliable methods for fabricating large-area single-crystalline graphene domains are required. A new way to synthesize high quality epitaxial graphene, namely 'face-to-face' method, has been reported in this paper. The structure and morphologies of the samples are characterized by low-energy electron diffraction, atomic force microscopy, angle-resolved photoemission spectroscopy and Raman spectroscopy. The grown samples show better quality and larger length scales than samples grown through conventional thermal desorption. Moreover, the graphene thickness can be easily controlled by changing annealing temperature.

  14. Double epitaxy as a paradigm for templated growth of highly ordered three-dimensional mesophase crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Yongsoon; Tao, Jinhui; Arey, Bruce W.; Wang, Chongmin; Exarhos, Gregory J.; De Yoreo, James J.; Sushko, Maria L.; Liu, Jun

    2016-08-30

    Molecular templating and self-assembly are fundamental mechanisms for controlling the morphology of biominerals, while in synthetic two-dimensional layered materials similar levels of control over materials structure can be achieved through the epitaxial relationship with the substrate. In this study these two concepts are combined to provide an approach for the nucleation and growth of three-dimensional ordered mesophases on solid surfaces. A combined experimental and theoretical study revealed how atomic ordering of the substrate controls the structure of surfactant template and the orientation and morphology of the epitaxially grown inorganic material. Such dual epitaxial relationship between the substrate, surfactant template and inorganic mesophase gives rise to a highly ordered porous mesophase with a well-defined cubic lattice of pores. The level of control over material’s three-dimensional architecture achieved in this one-step synthesis is reminiscent to that in biomineralization.

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

    Science.gov (United States)

    Wang, Qi; Stradins, Paul; Teplin, Charles; Branz, Howard M.

    2009-10-13

    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.

  16. Thick orientation-patterned growth of GaP on wafer-fused GaAs templates by hydride vapor phase epitaxy for frequency conversion

    Science.gov (United States)

    Vangala, Shivashankar; Kimani, Martin; Peterson, Rita; Stites, Ron; Snure, Michael; Tassev, Vladimir

    2016-10-01

    Quasi-phase-matched (QPM) GaP layers up to 300 μm thick have been produced by low-pressure hydride vapor phase epitaxy (LP-HVPE) overgrowth on orientation-patterned GaAs (OPGaAs) templates fabricated using a wafer-fusion bonding technique. The growth on the OPGaAs templates resulted in up to 200 μm thick vertically propagating domains, with a total GaP thickness of 300 μm. The successful thick growth on OPGaAs templates is the first step towards solving the material problems associated with unreliable material quality of commercially available GaP wafers and making the whole process of designing QPM frequency conversion devices molecular beam epitaxy free and more cost-effective.

  17. Growth mechanisms for Si epitaxy on O atomic layers: Impact of O-content and surface structure

    Science.gov (United States)

    Jayachandran, Suseendran; Billen, Arne; Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Moussa, Alain; Caymax, Matty; Bender, Hugo; Vandervorst, Wilfried; Heyns, Marc; Delabie, Annelies

    2016-10-01

    The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O3) or oxygen (O2) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH4) at 500 °C. After O3 exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH4 reactants, allowing more time for surface diffusion. After O2 exposure, the O atoms are present in the form of SiOx clusters. Regions of hydrogen-terminated Si remain present between the SiOx clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

  18. Laser Induced Chemical Vapor Phase Epitaxial Growth of III-V semiconductor Films

    Science.gov (United States)

    1991-05-14

    temperatures for the preparation and crystal growth of semiconductors . During the first phase of this program at Southern Methodist University, the epitaxial...approach to the preparation of device-quality 4 semiconductor films of controlled electrical and stru -.tural propierties . The excitation of reaction...temperatures for the preparation and crystal growth of semiconductors . The vapors of essentially all metalorganic compounds and group V hydrides are colorless

  19. Epitaxial growth of Ge-Sb-Te based phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Perumal, Karthick

    2013-07-30

    Ge-Sb-Te based phase change materials are considered as a prime candidate for optical and electrical data storage applications. With the application of an optical or electrical pulse, they can be reversibly switched between amorphous and crystalline state, thereby exhibiting large optical and electrical contrast between the two phases, which are then stored as information in the form of binary digits. Single crystalline growth is interesting from both the academic and industrial perspective, as ordered Ge-Sb-Te based metamaterials are known to exhibit switching at reduced energies. The present study deals with the epitaxial growth and analysis of Ge-Sb-Te based thin films. The first part of the thesis deals with the epitaxial growth of GeTe. Thin films of GeTe were grown on highly mismatched Si(111) and (001) substrates. On both the substrate orientations the film grows along [111] direction with an amorphous-to-crystalline transition observed during the initial stages of growth. The amorphous-to-crystalline transition was studied in-vivo using azimuthal reflection high-energy electron diffraction scans and grazing incidence X-ray diffraction. In the second part of the thesis epitaxy and characterization of Sb{sub 2}Te{sub 3} thin films are presented. The third part of the thesis deals with the epitaxy of ternary Ge-Sb-Te alloys. The composition of the films are shown to be highly dependent on growth temperatures and vary along the pseudobinary line from Sb{sub 2}Te{sub 3} to GeTe with increase in growth temperatures. A line-of-sight quadrupole mass spectrometer was used to reliably control the GeSbTe growth temperature. Growth was performed at different Ge, Sb, Te fluxes to study the compositional variation of the films. Incommensurate peaks are observed along the [111] direction by X-ray diffraction. The possibility of superstructural vacancy ordering along the [111] direction is discussed.

  20. Topography and structure of ultrathin topological insulator Sb2Te3 films on Si(111) grown by means of molecular beam epitaxy

    Science.gov (United States)

    Lanius, M.; Kampmeier, J.; Kölling, S.; Mussler, G.; Koenraad, P. M.; Grützmacher, D.

    2016-11-01

    We have studied the growth process of the topological insulator (TI) Sb2 Te3 on Si(111) by scanning tunneling microscopy. High quality thin films from more than 22 nm down to 1 nm in thickness have been deposited by molecular beam epitaxy. To determine the thickness and domain formation of the films, x-ray reflectivity and x-ray diffraction were utilized. In comparison to previous studies of the TI Bi2 Te3 , the growth mechanism of Sb2 Te3 shows a similar transition from nucleation and growth in Sb-Te and Te-Te bilayers, respectively, to mound formation for thicker films. Atom probe tomography measurements reveal a intermixed interface between Sb2 Te3 and Si(111) substrate. These findings can explain the high density of defects and domains.

  1. GaN layers with different polarities prepared by radio frequency molecular beam epitaxy and characterized by Raman scattering

    Institute of Scientific and Technical Information of China (English)

    Zhong Fei; Li Xin-Hua; Qiu Kai; Yin Zhi-Jun; Ji Chang-Jian; Cao Xian-Cun; Han Qi-Feng; Chen Jia-Rong; Wang Yu-Qi

    2007-01-01

    GaN layers with different polarities have been prepared by radio-frequency molecular beam epitaxy (RF-MBE) and characterized by Raman scattering. Polarity control are realized by controlling Al/N flux ratio during high temperature AlN buffer growth. The Raman results illustrate that the N-polarity GaN films have frequency shifts at A1(LO) mode because of their high carrier density; the forbidden A1 (TO) mode occurs for mixed-polarity GaN films due to the destroyed translation symmetry by inversion domain boundaries (IDBS); Raman spectra for Ga-polarity GaN films show that they have neither frequency shifts mode nor forbidden mode. These results indicate that Ga-polarity GaN films have a better quality, and they are in good agreement with the results obtained from the room temperature Hall mobility. The best values of Ga-polarity GaN films are 1042 cm2/Vs with a carrier density of 1.0×1017 cm-3.

  2. Molecular beam epitaxy of CdTe and HgCdTe on large-area Si(100)

    Science.gov (United States)

    Sporken, R.; Lange, M. D.; Faurie, Jean-Pierre

    1991-09-01

    The current status of molecular beam epitaxy (MBE) of CdTe and HgCdTe on Si(100) is reviewed. CdTe and HgCdTe grow in the (111)B orientation on Si(100); monocrystalline films with two domains are obtained on most nominal Si(100) substrates, single domain films are grown on misoriented substrates and on nominal Si(100) preheated to 900-950 degree(s)C. Double-crystal x-ray rocking curves (DCRCs) with full-width at half-maximum (FWHM) as low as 110 arcsec are reported for HgCdTe on silicon; these layers are n-type, and electron mobilities higher than 5 X 104 cm2V-2s-1 are measured at 23 K for x equals 0.26. Excellent thickness and composition uniformity is obtained: standard deviation of the CdTe thickness 0.4% of the average thickness on 2-in. and 2.3% on 5-in., standard deviation of the Cd concentration in the HgCdTe layers 0.6% of the average concentration on 3-in. and 2.4% on 5-in. First results regarding growth of CdTe on patterned Si substrates are also reported.

  3. Threading and misfit-dislocation motion in molecular-beam epitaxy-grown HgCdTe epilayers

    Science.gov (United States)

    Carmody, M.; Lee, D.; Zandian, M.; Phillips, J.; Arias, J.

    2003-07-01

    Lattice mismatch between the substrate and the absorber layer in single-color HgCdTe infrared (IR) detectors and between band 1 and band 2 in two-color detectors results in the formation of crosshatch lines on the surface and an array of misfit dislocations at the epi-interfaces. Threading dislocations originating in the substrate can also bend into the interface plane and result in misfit dislocations because of the lattice mismatch. The existence of dislocations threading through the junction region of HgCdTe IR-photovoltaic detectors can greatly affect device performance. High-quality CdZnTe substrates and controlled molecular-beam epitaxy (MBE) growth of HgCdTe can result in very low threading-dislocation densities as measured by the etch-pit density (EPD ˜ 104cm-2). However, dislocation gettering to regions of high stress (such as etched holes, voids, and implanted-junction regions) at elevated-processing temperatures can result in a high density of dislocations in the junction region that can greatly reduce detector performance. We have performed experiments to determine if the dislocations that getter to these regions of high stress are misfit dislocations at the substrate/absorber interface that have a threading component extending to the upper surface of the epilayer, or if the dislocations originate at the cap/absorber interface as misfit dislocations. The preceding mechanisms for dislocation motion are discussed in detail, and the possible diode-performance consequences are explored.

  4. Tailoring of polar and nonpolar ZnO planes on MgO (001) substrates through molecular beam epitaxy.

    Science.gov (United States)

    Zhou, Hua; Wang, Hui-Qiong; Liao, Xia-Xia; Zhang, Yufeng; Zheng, Jin-Cheng; Wang, Jia-Ou; Muhemmed, Emin; Qian, Hai-Jie; Ibrahim, Kurash; Chen, Xiaohang; Zhan, Huahan; Kang, Junyong

    2012-03-09

    Polar and nonpolar ZnO thin films were deposited on MgO (001) substrates under different deposition parameters using oxygen plasma-assisted molecular beam epitaxy (MBE). The orientations of ZnO thin films were investigated by in situ reflection high-energy electron diffraction and ex situ X-ray diffraction (XRD). The film roughness measured by atomic force microscopy evolved as a function of substrate temperature and was correlated with the grain sizes determined by XRD. Synchrotron-based X-ray absorption spectroscopy (XAS) was performed to study the conduction band structures of the ZnO films. The fine structures of the XAS spectra, which were consistent with the results of density functional theory calculation, indicated that the polar and nonpolar ZnO films had different electronic structures. Our work suggests that it is possible to vary ZnO film structures from polar to nonpolar using the MBE growth technique and hence tailoring the electronic structures of the ZnO films.PACS: 81; 81.05.Dz; 81.15.Hi.

  5. Effects of AIN nucleation layer thickness on crystal quality of AIN grown by plasma-assisted molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Ren Fan; Hao Zhi-Biao; Hu Jian-Nan; Zhang Chen; Luo Yi

    2010-01-01

    In this paper,the effects of thickness of AIN nucleation layer grown at high temperature on AIN epi-layer crystalline quality are investigated.Crack-free AIN samples with various nucleation thicknesses are grown on sapphire substrates by plasma-assisted molecular beam epitaxy.The AIN crystalline quality is analysed by transmission electron microscope and x-ray diffraction(XRD)rocking curves in both(002)and(102)planes.The surface profiles of nucleation layer with different thicknesses after in-situ annealing are also analysed by atomic force microscope.A critical nucleation thickness for realising high quality AIN films is found.When the nucleation thickness is above a certain value,the(102)XRD full width at half maximum(FWHM)of AIN bulk increases with nucleation thickness increasing,whereas the(002)XRD FWHM shows an opposite trend.These phenomena can be attributed to the characteristics of nucleation islands and the evolution of crystal grains during AIN main layer growth.

  6. Flux pinning properties of MgB{sub 2} thin films on Ti buffered substrate prepared by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Yonekura, K., E-mail: kenji@st.cs.kumamoto-u.ac.j [Department of Computer Science and Electrical Engineering, Kumamoto University, 2-39-1, Kurokami, Kumamoto 860-8555 (Japan); Kugo, A.; Fujiyoshi, T.; Sueyoshi, T. [Department of Computer Science and Electrical Engineering, Kumamoto University, 2-39-1, Kurokami, Kumamoto 860-8555 (Japan); Harada, Y. [JST Satellite Iwate, 3-35-2, Iiokashinden Morioka, Iwate 020-0852 (Japan); Yoshizawa, M.; Ikeda, T. [Department of Materials Science and Engineering, Iwate University, 4-3-5, Ueda, Morioka, Iwate 020-8551 (Japan); Awaji, S.; Watanabe, K. [Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2010-11-01

    Transport properties of the MgB{sub 2} thin films on Si, MgO and ZnO substrates with Ti buffer layer prepared by molecular beam epitaxy were investigated to clarify effects of the substrates and the Ti buffer layer on flux pinning. The critical current density J{sub c} of each sample shows different dependence on magnetic fields parallel to c-axis. However, the scaling analysis of the macroscopic pinning force for all the measured samples implies that the grain boundaries work as the dominant pinning centers for B//c. The pinning parameter for MgB{sub 2}/Ti/Si estimated from the electric field E vs. the current density J characteristics shows the highest value among all the measured samples. This result is attributed to the high density of grain boundaries caused by the effect of both the Ti buffer and Si substrate in the growth process. Therefore, the selection of substrates and buffer layer strongly affects the flux pining properties of MgB{sub 2} thin films and plays an important role in the determination of performance for superconducting devices and wires.

  7. Growth mechanisms for Si epitaxy on O atomic layers: Impact of O-content and surface structure

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Billen, Arne [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Moussa, Alain; Caymax, Matty; Bender, Hugo [Imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Heyns, Marc [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Delabie, Annelies [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium)

    2016-10-30

    Highlights: • O{sub 3} or O{sub 2} exposures on H-Si(100) result in O ALs with different surface structures. • Si-EPI on O AL using O{sub 3} process is by direct epitaxial growth mechanism. • Si-EPI on O AL using O{sub 2} process is by epitaxial lateral overgrowth mechanism. • Distortions by O AL, SiH{sub 4} flux rate and Si thickness has an impact on Si-EPI quality. - Abstract: The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O{sub 3}) or oxygen (O{sub 2}) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH{sub 4}) at 500 °C. After O{sub 3} exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH{sub 4} reactants, allowing more time for surface diffusion. After O{sub 2} exposure, the O atoms are present in the form of SiO{sub x} clusters. Regions of hydrogen-terminated Si remain present between the SiO{sub x} clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

  8. Optical properties and structural investigations of (11-22)-oriented GaN/Al{sub 0.5}Ga{sub 0.5}N quantum wells grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Rosales, Daniel; Gil, Bernard; Bretagnon, Thierry [CNRS, Laboratoire Charles Coulomb, UMR 5221, F-34095 Montpellier (France); Université de Montpellier, Laboratoire Charles Coulomb, UMR 5221, F-34095 Montpellier (France); Brault, Julien; Vennéguès, Philippe; Nemoz, Maud; Mierry, Philippe de; Damilano, Benjamin; Massies, Jean [CNRS Centre de Recherche sur l' Hétéro-Epitaxie et ses Applications, 06560 Valbonne (France); Bigenwald, Pierre [Institut Pascal, Campus des Cézeaux, 24 avenue des Landais, 63171 Aubière Cedex (France)

    2015-07-14

    We have grown (11-22)-oriented GaN/Al{sub 0.5}Ga{sub 0.5}N quantum wells (QWs) using molecular beam epitaxy on GaN (11-22)-oriented templates grown by metal-organic vapor phase epitaxy on m-plane oriented sapphire substrates. The performance of epitaxial growth of GaN/Al{sub 0.5}Ga{sub 0.5}N heterostructures on the semi-polar orientation (11-22) in terms of surface roughness and structural properties, i.e., strain relaxation mechanisms is discussed. In addition, high resolution transmission electron microscopy reveals very smooth QW interfaces. The photoluminescence of such samples are strictly originating from radiative recombination of free excitons for temperatures above 100 K. At high temperature, the population of localized excitons, moderately trapped (5 meV) at low temperature, is negligible.

  9. Polarity Effects of Substrate Surface in Epitaxial ZnO Film Growth

    Science.gov (United States)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.; McCarty, P.

    1999-01-01

    Epitaxial ZnO films were grown on the two polar surfaces (0-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films are also deposited on the (000 I) Al203 substrates. It is found that the two polar surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which are strongly inference the epitaxial film growth. The morphology and structure of epitaxial films on the ZnO substrates are different from the film on the Al203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite Surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth using reactive sputtering deposition.

  10. Unintentional gallium incorporation in InGaN layers during epitaxial growth

    Science.gov (United States)

    Zhou, Kun; Ren, Huaijin; Ikeda, Masao; Liu, Jianping; Ma, Yi; Gao, Songxin; Tang, Chun; Li, Deyao; Zhang, Liquan; Yang, Hui

    2017-01-01

    Unintentional gallium incorporation was observed and investigated in the epitaxial growth of InGaN by metalorganic vapor phase epitaxy. InGaN was grown without intentional gallium precursor and the gallium incorporation rate was found not dependent on TEGa source but was significantly influenced by temperature and TMIn source flow. The source of the unintentional gallium incorporation is confirmed to be from the flow distributor of the reactor. The incorporation mechanism was analyzed to be the diffusion of resultant of transmetalation reaction between TMIn or its decomposed products (for example DMIn) and residual gallium. Due to the unintentional gallium incorporation, the growth rate and indium content of InGaN layer are determined by indium source, gallium source and the growth temperature.

  11. Scaling in film growth by pulsed laser deposition and modulated beam deposition.

    Science.gov (United States)

    Lee, Sang Bub

    2011-04-01

    The scalings in film growth by pulsed laser deposition (PLD) and modulated beam deposition (MBD) were investigated by Monte Carlo simulations. In PLD, an atomic pulse beam with a period t(0) were deposited instantaneously on a substrate, whereas in MBD, adatoms were deposited during a short time interval t(1) (0≤t(1)≤t(0)) within each period. If t(1)=0, MBD will be identical to PLD and, if t(1)=t(0), MBD will become usual molecular beam epitaxy (MBE). Specifically, logarithmic scaling was investigated for the nucleation density reported for PLD, and the scaling of island density was studied regarding the growth for 0MBE growth was observed as t(1) increased. The phase diagram was also presented.

  12. A Kinetic Model for GaAs Growth by Hydride Vapor Phase Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, Kevin L.; Simon, John; Jain, Nikhil; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Precise control of the growth of III-V materials by hydride vapor phase epitaxy (HVPE) is complicated by the fact that the growth rate depends on the concentrations of nearly all inputs to the reactor and also the reaction temperature. This behavior is in contrast to metalorganic vapor phase epitaxy (MOVPE), which in common practice operates in a mass transport limited regime where growth rate and alloy composition are controlled almost exclusively by flow of the Group III precursor. In HVPE, the growth rate and alloy compositions are very sensitive to temperature and reactant concentrations, which are strong functions of the reactor geometry. HVPE growth, particularly the growth of large area materials and devices, will benefit from the development of a growth model that can eventually be coupled with a computational fluid dynamics (CFD) model of a specific reactor geometry. In this work, we develop a growth rate law using a Langmuir-Hinshelwood (L-H) analysis, fitting unknown parameters to growth rate data from the literature that captures the relevant kinetic and thermodynamic phenomena of the HVPE process. We compare the L-H rate law to growth rate data from our custom HVPE reactor, and develop quantitative insight into reactor performance, demonstrating the utility of the growth model.

  13. Low Temperature Epitaxial Growth of Semiconductors Using Synchrotron Radiation as a Light Source

    Institute of Scientific and Technical Information of China (English)

    Qixin GUO; Mitsuhiro NISHIO; Hiroshi OGAWA

    2000-01-01

    Results of our recent experiments relating to the synchrotron radiation (SR) excited growth of Ⅱ-V compounds using metalorganic sources are described. We discuss mainly the growth characteristics of films in addition to the characterization of the deposited films. ZnTe epitaxial layer without carbon and oxygen contamination is attainable even at room temperature using SR as a light source. The quantum yield for forming ZnTe molecules was estimated to be higher than 3%. Through these experiments, we propose that the SR-excited growth is a powerful technique for a novel low temperature growth of compounds.

  14. Growth of epitaxial {gamma}-Al{sub 2}O{sub 3} films on rigid single-crystal ceramic substrates and flexible, single-crystal-like metallic substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Junsoo, E-mail: jshin@ornl.go [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Goyal, Amit [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Wee, Sung-Hun [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States)

    2009-08-03

    Epitaxial {gamma}-Al{sub 2}O{sub 3} thin films were grown on diverse substrates using pulsed laser deposition. The high quality of epitaxial growth and cubic structure of {gamma}-Al{sub 2}O{sub 3} films was confirmed by X-ray diffraction. SrTiO{sub 3} and MgO single crystal substrates were used to optimize the growth conditions for epitaxial {gamma}-Al{sub 2}O{sub 3} film. Under the optimized conditions, epitaxial {gamma}-Al{sub 2}O{sub 3} thin films were grown on flexible, single-crystal-like, metallic templates. These included untextured Hastelloy substrates with a biaxially textured MgO layer deposited using ion-beam-assisted-deposition and biaxially textured Ni-W metallic tapes with epitaxially grown and a biaxially textured, MgO buffer layer. These biaxially textured, {gamma}-Al{sub 2}O{sub 3} films on flexible, single-crystal-like substrates are promising for subsequent epitaxial growth of various complex oxide films used for electrical, magnetic and electronic device applications.

  15. Epitaxial growth of III-V nitrides and phase separation and ordering in indium gallium nitride alloys

    Science.gov (United States)

    Doppalapudi, Dharanipal

    The family of III-V nitrides are wide band-gap semiconductors with a broad range of opto-electronic applications in LEDs, laser diodes, UV detectors as well as high temperature/high frequency devices. Due to the lack of good quality native substrates, GaN is grown on foreign substrates that have a lattice and thermal mismatch with GaN. This results in a material with a high density of defects, which in turn adversely affects the opto-electronic properties of the epilayer. In this study, GaN films were epitaxially grown on various substrates (C-plane sapphire, A-plane sapphire, SiC and ZnO) by molecular beam epitaxy. Additionally, GaN homoepitaxy onto laterally overgrown thick GaN substrates was investigated. It was demonstrated that the polarity of the GaN film plays a major role in determining the properties of the films. The growth parameters were optimized to eliminate inversion domain boundaries, which result in domains of opposite polarity in the GaN lattice. For growth on A-plane sapphire, it was found that substrate nitridation and low temperature buffer deposition are critical in order to obtain good epitaxial growth, in spite of the relatively small mismatch between the film and substrate. A crystallographic model was developed to explain this observation. By optimizing growth parameters, GaN films with excellent structural, transport, optical and device properties were grown. The second part of this research involves growth of ternary alloys and superlattice structures, which are essential in the fabrication of many devices. It was found that the InN-GaN pseudo-binary system is not homogeneous over the entire composition range. Due to the mismatch between the tetrahedral radii of GaN and InN, InGaN alloys exhibited phase separation and long-range atomic ordering. Investigations of InxGa1-xN films grown over a wide range of compositions by XRD and TEM showed that the predominant strain relieving mechanism was phase separation in films with x > 0.2, and

  16. Copper ion implanted aluminum nitride dilute magnetic semiconductors (DMS) prepared by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Shah, A., E-mail: attaullah77@yahoo.com [National Institute of Lasers and Optronics (NILOP), PO Nilore, Islamabad (Pakistan); DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Ahmad, Jamil [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Ahmad, Ishaq [Experimental Physics Lab, National Center for Physics (NCP), Islamabad (Pakistan); Mehmood, Mazhar [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan); Mahmood, Arshad [National Institute of Lasers and Optronics (NILOP), PO Nilore, Islamabad (Pakistan); Rasheed, Muhammad Asim [DMME, Pakistan Institute of Engineering and Applied Science (PIEAS), PO Nilore, Islamabad (Pakistan)

    2014-10-30

    Highlights: • AlN:Cu dilute magnetic semiconductors were successfully prepared by molecular beam epitaxy followed by Cu{sup +} implantation. • Room temperature ferromagnetism was observed after annealing the samples at appropriate temperature. • XRD and Raman spectrometry excluded the possibility of formation of any secondary phases. • By doping intrinsically nonmagnetic dopants (Cu), it has been proved experimentally that their precipitates do not contribute to ferromagnetism. • The reason for ferromagnetism in Cu-doped AlN as observed was explained on the basis of p–d hybridization mechanism (Wu et al.). - Abstract: Diluted magnetic semiconductor (DMS) AlN:Cu films were fabricated by implanting Cu{sup +} ions into AlN thin films at various ion fluxes. AlN films were deposited on c-plane sapphire by molecular beam epitaxy followed by Cu{sup +} ion implantation. The structural and magnetic characterization of the samples was performed through Rutherford backscattering and channeling spectrometry (RBS/C), X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometer (VSM) and SQUID. Incorporation of copper into the AlN lattice was confirmed by RBS, while XRD revealed that no new phase was formed as a result of ion implantation. RBS also indicated formation of defects as a result of implantation process and the depth and degree of damage increased with an increase in ion fluence. Raman spectra showed only E{sub 2} (high) and A{sub 1} (LO) modes of wurtzite AlN crystal structure and confirmed that no secondary phases were formed. It was found that both Raman modes shift with Cu{sup +} fluences, indicating that Cu ion may go to interstitial or substitutional sites resulting in distortion or damage of lattice. Although as implanted samples showed no magnetization, annealing of the samples resulted in appearance of room temperature ferromagnetism. The saturation magnetization increased with both the annealing temperature as well as with ion

  17. Anisotropy of superconductivity of as-grown MgB$_2$ thin films by molecular beam epitaxy

    OpenAIRE

    Harada, Y.; Udsuka, M.; Nakanishi, Y.; Yoshizawa, M.

    2004-01-01

    Superconducting thin films of magnesium diboride (MgB$_2$) were prepared on MgO (001) substrate by a molecular beam epitaxy (MBE) method with the co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, XPS, resistivity and magnetization measurements.All films demonstrated superconductivity without use of any post-annealing process.The highest {\\it T}$_{c,onset}$ determined by resistivity measurement...

  18. Investigation of CuGaSe2/CuInSe2 double heterojunction interfaces grown by molecular beam epitaxy

    OpenAIRE

    Sathiabama Thiru; Masaki Asakawa; Kazuki Honda; Atsushi Kawaharazuka; Atsushi Tackeuchi; Toshiki Makimoto; Yoshiji Horikoshi

    2015-01-01

    In-situ reflection high-energy electron diffraction (RHEED) observation and X-ray diffraction measurements were performed on heterojunction interfaces of CuGaSe2/CnInSe2/CuGaSe2 grown on GaAs (001) using migration-enhanced epitaxy. The streaky RHEED pattern and persistent RHEED intensity oscillations caused by the alternate deposition of migration-enhanced epitaxy sequence are observed and the growths of smooth surfaces are confirmed. RHEED observation results also confirmed constituent mater...

  19. Epitaxial growth of a methoxy-functionalized quaterphenylene on alkali halide surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Balzer, F., E-mail: fbalzer@mci.sdu.dk [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Sun, R. [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Parisi, J. [University of Oldenburg, Energy and Semiconductor Research Laboratory, Institute of Physics, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg (Germany); Rubahn, H.-G. [University of Southern Denmark, Mads Clausen Institute, Alsion 2, DK-6400 Sønderborg (Denmark); Lützen, A. [University of Bonn, Kekulé Institute of Organic Chemistry and Biochemistry, Gerhard-Domagk-Str. 1, D-53121 Bonn (Germany); Schiek, M. [University of Oldenburg, Energy and Semiconductor Research Laboratory, Institute of Physics, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg (Germany)

    2015-12-31

    The epitaxial growth of the methoxy functionalized para-quaterphenylene (MOP4) on the (001) faces of the alkali halides NaCl and KCl and on glass is investigated by a combination of low energy electron diffraction (LEED), polarized light microscopy (PLM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Both domains from upright molecules as well as fiber-like crystallites from lying molecules form. Neither a wetting layer from lying molecules nor widespread epitaxial fiber growth on the substrates is detected. Our results focus on the upright standing molecules, which condense into a thin film phase with an enlarged layer spacing compared to the bulk phase. - Highlights: • Growth of a methoxy-functionalized para-phenylene on dielectric surfaces is investigated. • Low-energy electron diffraction and X-ray diffraction techniques are employed for structural characterization. • Epitaxial growth of upright molecules only is documented. • Polarized optical microscopy together with atomic force microscopy complements the findings.

  20. Morphology and electronic properties of metal organic molecular beam epitaxy grown ZnO on hydrogen passivated 6H-SiC(0001)a)

    Science.gov (United States)

    Andres, Stefan; Pettenkofer, Christian; Speck, Florian; Seyller, Thomas

    2008-05-01

    Thin ZnO films were grown on hydrogen passivated 6H-SiC(0001) substrates by metal organic molecular beam epitaxy. The initial growth as well as the electronic properties of the growing interface were monitored by low electron diffraction and photoelectron spectroscopy (PES). From the PES intensities of the substrate and ZnO film a layered Frank-van-der-Merwe-like growth mode could be observed within the first 10nm. The ZnO films grow preferentially in (0001) direction and show a pronounced facetting in the {101¯2} direction. The experimentally determined band alignment reveals band offsets of ΔEVBM≈1.6eV and ΔECBM≈1.2eV between the valence and conduction bands, respectively. With growing ZnO thickness a band bending of about -0.51eV is observed in the SiC substrate.

  1. Evaluation of HgCdTe on GaAs Grown by Molecular Beam Epitaxy for High-Operating-Temperature Infrared Detector Applications

    Science.gov (United States)

    Wenisch, J.; Schirmacher, W.; Wollrab, R.; Eich, D.; Hanna, S.; Breiter, R.; Lutz, H.; Figgemeier, H.

    2015-09-01

    Molecular beam epitaxy (MBE) growth of HgCdTe (MCT) on alternative substrates enables production of both cheaper and more versatile (third-generation) infrared (IR) detectors. After rapid progress in the development of MBE-grown MCT on GaAs in recent years, the question of whether the considerable benefits of this material system are also applicable to high-operating-temperature (HOT) applications demands attention. In this paper, we present a mid-wavelength-IR 640 × 512 pixel, 15- μm-pitch focal-plane array with operability of 99.71% at operating temperature of 120 K and low dark current density. In the second part of the paper, MBE growth of short-wavelength IR material with Cd fraction of up to 0.8 is investigated as the basis for future evaluation of the material for low-light-level imaging HOT applications.

  2. Large-scale epitaxial growth kinetics of graphene: A kinetic Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Huijun; Hou, Zhonghuai, E-mail: hzhlj@ustc.edu.cn [Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at Microscales, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-08-28

    Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be C{sub 1}-attachment for concave growth-front segments and C{sub 5}-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.

  3. A Minimal Model for Large-scale Epitaxial Growth Kinetics of Graphene

    CERN Document Server

    Jiang, Huijun

    2015-01-01

    Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be $C_{1}$-attachment for concave growth front segments and $C_{5}$-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.

  4. Effect of as Passivation on Vapor-Phase Epitaxial Growth of Ge on (211)Si as a Buffer Layer for CdTe Epitaxy

    Science.gov (United States)

    2011-04-07

    time periods of (a) 5 min and (b) 10 min. It can be seen that Ge grows layer-by- layer, resulting in a very thin Ge film . Fig. 4. SEM image of Ge...REPORT Effect Of As Passivation On Vapor-Phase Epitaxial Growth of Ge on (211)Si As A Buffer Layer For CdTe Epitaxy 14. ABSTRACT 16. SECURITY...The films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cross-sectional 1. REPORT DATE (DD-MM-YYYY) 4

  5. High-reflectivity GaAs-AlGaAs mirrors: Sensitivity analysis with respect to epitaxial growth parameters

    Science.gov (United States)

    Baets, R.; Demeester, P.; Lagasse, P. E.

    1987-07-01

    High-reflectivity multilayer structures, consisting of a periodic stack of quarter-wavelength GaAs and AlGaAs layers, have been investigated concerning their optical behavior with respect to various deficiencies in the epitaxial growth process. Theoretical curves are compared with experimental ones from structures grown by metalorganic chemical vapor deposition. These layer structures are also shown to be useful in the characterization of thickness uniformity of an epitaxial growth process.

  6. Temperature stabilized effusion cell evaporation source for thin film deposition and molecular-beam epitaxy

    Science.gov (United States)

    Tiedje, H. F.; Brodie, D. E.

    2000-05-01

    A simple effusion cell evaporation source for thin film deposition and molecular-beam epitaxy is described. The source consists of a crucible with a thermocouple temperature sensor heated by a resistive crucible heater. Radiation heat transfer from the crucible to the thermocouple produces a consistent and reproducible thermocouple temperature for a given crucible temperature, without direct contact between the thermocouple and the crucible. The thermocouple temperature is somewhat less than the actual crucible temperature because of heat flow from the thermocouple junction along the thermocouple lead wires. In a typical case, the thermocouple temperature is 1007 °C while the crucible is at 1083 °C. The crucible temperature stability is estimated from the measured sensitivity of the evaporation rate of indium to temperature, and the observed variations in the evaporation rate for a fixed thermocouple temperature. The crucible temperature peak-to-peak variation over a one hour period is 1.2 °C. Machined molybdenum crucibles were used in the indium and copper sources for depositing CuInSe2 thin films for solar cells.

  7. Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy

    Science.gov (United States)

    Zaunbrecher, Katherine N.; Kuciauskas, Darius; Swartz, Craig H.; Dippo, Pat; Edirisooriya, Madhavie; Ogedengbe, Olanrewaju S.; Sohal, Sandeep; Hancock, Bobby L.; LeBlanc, Elizabeth G.; Jayathilaka, Pathiraja A. R. D.; Barnes, Teresa M.; Myers, Thomas H.

    2016-08-01

    Heterostructures with CdTe and CdTe1-xSex (x ˜ 0.01) absorbers between two wider-band-gap Cd1-xMgxTe barriers (x ˜ 0.25-0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have a zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ˜6 μm, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 μs with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 μs.

  8. Polarized infrared reflectance study of free standing cubic GaN grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.C., E-mail: saicheonglee86@yahoo.com [Nano-Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ng, S.S.; Hassan, H. Abu; Hassan, Z.; Zainal, N. [Nano-Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia); Novikov, S.V.; Foxon, C.T.; Kent, A.J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2014-07-01

    Optical properties of free standing cubic gallium nitride grown by molecular beam epitaxy system are investigated by a polarized infrared (IR) reflectance technique. A strong reststrahlen band, which reveals the bulk-like optical phonon frequencies, is observed. Meanwhile, continuous oscillation fringes, which indicate the sample consists of two homogeneous layers with different dielectric constants, are observed in the non-reststrahlen region. By obtaining the first derivative of polarized IR reflectance spectra measured at higher angles of incidence, extra phonon resonances are identified at the edges of the reststrahlen band. The observations are verified with the theoretical results simulated based on a multi-oscillator model. - Highlights: • First time experimental studies of IR optical phonons in bulk like, cubic GaN layer. • Detection of extra phonon modes of cubic GaN by polarized IR reflectance technique. • Revelation of IR multiphonon modes of cubic GaN by first derivative numerical method. • Observation of multiphonon modes requires very high angle of incidence. • Resonance splitting effect induced by third phonon mode is a qualitative indicator.

  9. Effects of magnesium contents in ZnMgO ternary alloys grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Sheng-Yao, E-mail: shenghu2729@yahoo.com [Department of Digital Technology Design, Tungfang Design Institute, Hunei, Kaohsiung 82941, Taiwan (China); Chou, Wu-Ching [Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Weng, Yu-Hsiang [Department of Electrical Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China)

    2015-07-05

    Highlights: • ZnMgO alloys with different Mg contents have been produced by MBE. • Optical and structural properties have been measured and investigated. • Stress is tensile and is increased as the increasing of Mg contents. • The asymmetric behavior of the Raman mode was influenced due to the Mg contents. - Abstract: Ternary alloys of ZnMgO samples with different magnesium contents have been grown by molecular beam epitaxy on the sapphire substrates. Room temperature photoluminescence energy of ZnMgO shifted as high as 3.677 eV by increasing Mg contents corresponding to the higher Urbach average localization energy which indicates more randomness in the alloys with higher Mg contents. XRD results are also verified that the c-axis length decreases as the increasing Mg contents linking to the increased tensile stress produced by the Mg atoms. Raman spectra analyzed by the spatial correlation model to describe that the linewidth Γ is decreased but the correlation length L is increased as the increasing of Mg contents.

  10. Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zaunbrecher, Katherine N. [Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA; National Renewable Energy Laboratory, Golden, Colorado 80401, USA; Kuciauskas, Darius [National Renewable Energy Laboratory, Golden, Colorado 80401, USA; Swartz, Craig H. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Dippo, Pat [National Renewable Energy Laboratory, Golden, Colorado 80401, USA; Edirisooriya, Madhavie [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Ogedengbe, Olanrewaju S. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Sohal, Sandeep [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Hancock, Bobby L. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; LeBlanc, Elizabeth G. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Jayathilaka, Pathiraja A. R. D. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA; Barnes, Teresa M. [National Renewable Energy Laboratory, Golden, Colorado 80401, USA; Myers, Thomas H. [Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA

    2016-08-29

    Heterostructures with CdTe and CdTe 1-xSex (x ~ 0.01) absorbers between two wider-band-gap Cd1-xMgxTe barriers (x ~ 0.25-0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have a zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ~6 um, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 us with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 us.

  11. Enhancement of minority carrier lifetime of GaInP with lateral composition modulation structure grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Park, K. W.; Ravindran, Sooraj; Kang, S. J.; Hwang, H. Y.; Jho, Y. D. [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Park, C. Y. [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Jo, Y. R.; Kim, B. J. [School of Material Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Lee, Y. T., E-mail: ytlee@gist.ac.kr [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

    2014-07-28

    We report the enhancement of the minority carrier lifetime of GaInP with a lateral composition modulated (LCM) structure grown using molecular beam epitaxy (MBE). The structural and optical properties of the grown samples are studied by transmission electron microscopy and photoluminescence, which reveal the formation of vertically aligned bright and dark slabs corresponding to Ga-rich and In-rich GaInP regions, respectively, with good crystal quality. With the decrease of V/III ratio during LCM GaInP growth, it is seen that the band gap of LCM GaInP is reduced, while the PL intensity remains high and is comparable to that of bulk GaInP. We also investigate the minority carrier lifetime of LCM structures made with different flux ratios. It is found that the minority carrier lifetime of LCM GaInP is ∼37 times larger than that of bulk GaInP material, due to the spatial separation of electrons and holes by In-rich and Ga-rich regions of the LCM GaInP, respectively. We further demonstrate that the minority carrier lifetime of the grown LCM GaInP structures can easily be tuned by simply adjusting the V/III flux ratio during MBE growth, providing a simple yet powerful technique to tailor the electrical and optical properties at will. The exceptionally high carrier lifetime and the reduced band gap of LCM GaInP make them a highly attractive candidate for forming the top cell of multi-junction solar cells and can enhance their efficiency, and also make them suitable for other optoelectronics devices, such as photodetectors, where longer carrier lifetime is beneficial.

  12. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    Science.gov (United States)

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-10-01

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

  14. Microstructural Properties of Single Crystalline PbTe Thin Films Grown on BaF2(111) by Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    SI Jian-Xiao; WU Hui-Zhen; XU Tian-Ning; CAO Chun-Fang; HUANG Zhan-Chao

    2005-01-01

    @@ Single crystal PbTe thin films have been grown on BaF2 (111) by using solid source molecular beam epitaxy.The studies of evolution of the surface morphology with the increasing growth temperature from 375 to 525℃by AFM show that PbTe epilayers exhibit smooth surface morphologies with atomic layer scale roughness and are crack free. It is found that for PbTe grown at 475℃, the morphology is dominated by triangles and the rms roughness is 3.987nm. Compared to the rms roughnesses of 0.432nm and 0.759nm for the samples grown at 375 and 525℃ respectively, the surface of the PbTe layer grown at 475℃ is much rougher. This roughening transition is due to the interaction between the elastic relaxation and the plastic relaxation during the strain relaxation process. In contrast to the result of the morphology that the PbTe epitaxial layer grown at 375℃ has most smooth surface, as observed from the line width of x-ray diffraction curves at higher growth temperature improves the crystal quality of the single-crystalline PbTe layer.

  15. Strain-relaxation in NH{sub 3}-source molecular beam epitaxy of AlN epilayers on GaN epitaxial templates

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, T.; Onuma, T.; Chichibu, S.F. [Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); NICP, ERATO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan); Sugawara, M.; Uchinuma, Y. [Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); Kaeding, J.F.; Sharma, R. [Department of Materials Engineering, University of California, Santa Barbara, CA 93106 (United States); Nakamura, S. [NICP, ERATO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan); Department of Materials Engineering, University of California, Santa Barbara, CA 93106 (United States)

    2006-05-15

    Temporal evolution of surface morphology in AlN epilayers grown by NH{sub 3}-source molecular beam epitaxy on the GaN/(0001) Al{sub 2}O{sub 3} epitaxial templates was correlated with changes in the degree of the residual strain and the layer thickness. They began to crack for the thickness as thin as 10 nm. However, atomic-layer step-and-terrace surface structures were maintained for the thickness up to 32 nm. Tensile biaxial stress decreased with further increase in the thickness due to the lattice relaxation, which caused surface roughening. An 1580-nm-thick, nearly strain-compensated AlN epilayer, of which threading dislocation density was reduced down to 6 x 10{sup 9} cm{sup -2}, exhibited excitonic photoluminescence peaks at 6.002 and 6.023 eV at 9 K and a near-band-edge peak at 5.872 eV at 293 K. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Interface engineering in epitaxial growth of layered oxides via a conducting layer insertion

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Yu; Meng, Dechao; Wang, Jianlin [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui (China); Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, Anhui (China); Ma, Chao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui (China); Zhai, Xiaofang, E-mail: xfzhai@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, Anhui (China); Huang, Haoliang; Fu, Zhengping; Peng, Ranran [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui (China); Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, Anhui (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, Anhui (China); Brown, Gail J. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433-7707 (United States); and others

    2015-07-06

    There is a long-standing challenge in the fabrication of layered oxide epitaxial films due to their thermodynamic phase-instability and the large stacking layer number. Recently, the demand for high-quality thin films is strongly pushed by their promising room-temperature multiferroic properties. Here, we find that by inserting a conducting and lattice matched LaNiO{sub 3} buffer layer, high quality m = 5 Bi{sub 6}FeCoTi{sub 3}O{sub 18} epitaxial films can be fabricated using the laser molecular beam epitaxy, in which the atomic-scale sharp interface between the film and the metallic buffer layer explains the enhanced quality. The magnetic and ferroelectric properties of the high quality Bi{sub 6}FeCoTi{sub 3}O{sub 18} films are studied. This study demonstrates that insertion of the conducting layer is a powerful method in achieving high quality layered oxide thin films, which opens the door to further understand the underline physics and to develop new devices.

  17. Epitaxial Growth of Permalloy Thin Films on MgO Single-Crystal Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Matsubara, Katsuki; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2011-07-06

    Permalloy (Py: Ni - 20 at. % Fe) thin films were prepared on MgO single-crystal substrates of (100), (110), and (111) orientations by molecular beam epitaxy. Py crystals consisting of fcc(100) and hcp(112-bar 0) orientations epitaxially nucleate on MgO(100) substrates. With increasing the substrate temperature, the volume ratio of fcc(100) to hcp(112-bar 0) crystal increases. The metastable hcp(112-bar 0) structure transforms into more stable fcc(110) structure with increasing the film thickness. Py(110){sub fcc} single-crystal films are obtained on MgO(110) substrates, whereas Py films epitaxially grow on MgO(111) substrates with two types of fcc(111) variants whose orientations are rotated around the film normal by 180 deg. each other. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of these fcc-Py films agree within {+-}0.4% with the values of bulk fcc-Py crystal, suggesting that the strains in the films are very small. High-resolution transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the films around the Py/MgO(100) and the Py/MgO(110) interfaces to reduce the lattice mismatches. The magnetic properties are considered to be reflecting the magnetocrystalline anisotropies of bulk fcc-Py and/or metastable hcp-Py crystals and the shape anisotropy caused by the surface undulations.

  18. Interfacial stability of CoSi2/Si structures grown by molecular beam epitaxy

    Science.gov (United States)

    George, T.; Fathauer, R. W.

    1992-01-01

    The stability of CoSi2/Si interfaces was examined in this study using columnar silicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were codeposited using MBE at 800 C and the resulting columnar silicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800 C results in the growth of the buried silicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The column sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer. In the second set of experiments, annealing of a 250 nm-thick buried columnar layer at 1000 C under a 100 nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.

  19. Increase in the diffusion length of minority carriers in Al{sub x}Ga{sub 1–x}N alloys ({sub x} = 0–0.1) fabricated by ammonia molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Malin, T. V., E-mail: mal-tv@mail.ru; Gilinsky, A. M.; Mansurov, V. G.; Protasov, D. Yu.; Kozhuhov, A. S. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Yakimov, E. B. [Russian Academy of Sciences, Institute of Microelectronics Technology and High Purity Materials (Russian Federation); Zhuravlev, K. S. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2015-10-15

    The room-temperature diffusion length of minority carriers in n-Al{sub 0.1}Ga{sub 0.9}N layers grown by ammonia molecular beam epitaxy on sapphire (0001) substrates used in structures for ultraviolet photodetectors is studied. Measurements were performed using the spectral dependence of the photocurrent recorded in a built-in p–n junction for thin samples and using the induced electron-current procedure for films up to 2 µm thick. The results show that the hole diffusion length in n-AlGaN films is 120–150 nm, which is larger than in GaN films grown under similar growth conditions by a factor of 3–4. This result can be associated with the larger lateral sizes characteristic of hexagonal columns in AlGaN layers grown by molecular beam epitaxy. No increase in the hole diffusion length is observed for thicker films.

  20. Cubic-to-monoclinic phase transition during the epitaxial growth of crystalline Gd2O3 films on Ge(001) substrates

    Science.gov (United States)

    Molle, Alessandro; Wiemer, Claudia; Bhuiyan, Md. Nurul Kabir; Tallarida, Grazia; Fanciulli, Marco; Pavia, Giuseppe

    2007-05-01

    Thin crystalline films of Gd2O3 are grown on an atomically flat Ge(001) surface by molecular beam epitaxy and are characterized in situ by reflection high energy electron diffraction and x-ray photoelectron spectroscopy, and ex situ by x-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy. The first stage of the growth corresponds to a cubic (110) structure, with two equiprobable, 90° rotated, in-plane domains. Increasing the thickness of the films, a phase transition from cubic (110) to monoclinic (100) oriented crystallites is observed which keeps the in-plane domain rotation, as evidenced by XRD and AFM.

  1. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals

    Science.gov (United States)

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-01

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni

  2. Laser Induced Chemical Vapor Epitaxial Growth of Gallium Arsenide Films.

    Science.gov (United States)

    1988-05-23

    heteroepitaxial growth of GaAs. The important process parameters are: the substrate surface cleanliness , substrate temperature, composition and flow rate of the...hydrogen was used as the diluent and win.dw purging gas [9]. The important process parameters are: the substrate surface cleanliness , substrate temperature

  3. Epitaxial Growth of Hard Ferrimagnetic Mn3Ge Film on Rhodium Buffer Layer

    Directory of Open Access Journals (Sweden)

    Atsushi Sugihara

    2015-06-01

    Full Text Available Mn\\(_3\\Ge has a tetragonal Heusler-like D0\\(_{22}\\ crystal structure, exhibiting a large uniaxial magnetic anisotropy and small saturation magnetization due to its ferrimagnetic spin structure; thus, it is a hard ferrimagnet. In this report, epitaxial growth of a Mn\\(_3\\Ge film on a Rh buffer layer was investigated for comparison with that of a film on a Cr buffer layer in terms of the lattice mismatch between Mn\\(_3\\Ge and the buffer layer. The film grown on Rh had much better crystalline quality than that grown on Cr, which can be attributed to the small lattice mismatch. Epitaxial films of Mn\\(_3\\Ge on Rh show somewhat small coercivity (\\(H_{\\rm c}\\ = 12.6 kOe and a large perpendicular magnetic anisotropy (\\(K_{\\rm u}\\ = 11.6 Merg/cm\\(^3\\, comparable to that of the film grown on Cr.

  4. Epitaxial growth of largely mismatched crystals on H-terminated Si(111) surfaces.

    Science.gov (United States)

    Asaoka, Hidehito

    2010-12-01

    A strontium or strontium oxide epitaxial layer was grown using a monoatomic buffer layer of hydrogen on silicon, in spite of a huge lattice mismatch. The onset of the initial growth stage of strontium crystals occur with only one atomic layer deposition. To investigate the growth mechanism in the highly mismatched system, combination analysis using neutron reflection, reflection high-energy electron diffraction, x-ray photoelectron spectra, and stress measurements is employed. The interface structure has opened up a new way to fabricate novel heterostructures, consisting of various kinds of one-, two- or three-dimensional materials for future silicon-based technology.

  5. Structural properties of SrO thin films grown by molecular beam epitaxy on LaAlO3 substrates

    Science.gov (United States)

    Maksimov, O.; Heydemann, V. D.; Fisher, P.; Skowronski, M.; Salvador, P. A.

    2006-12-01

    SrO films were grown on LaAlO3 substrates by molecular beam epitaxy and characterized using reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD). The evolution of the RHEED pattern is discussed as a function of film thickness. 500Å thick SrO films were relaxed and exhibited RHEED patterns indicative of an atomically smooth surface having uniform terrace heights. Films had the epitaxial relationship (001)SrO‖(001)LaAlO3; [010]SrO‖[110]LaAlO3. This 45° in-plane rotation minimizes mismatch and leads to films of high crystalline quality, as verified by Kikuchi lines in the RHEED patterns and narrow rocking curves of the (002) XRD peak.

  6. Dielectric and Structural Properties of SrTiO_3 Thin Films Grown by Laser Molecular Beam Epitaxy

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Dielectric and Structural Properties of SrTiO_3 Thin Films Grown by Laser Molecular Beam Epitaxy[1]Hao J H,Gao J,Wang Z,et al.Interface structure and phase of epitaxial SrTi O3(110)thin fil ms grown directly on silicon[J].Appl Phys Lett,2005,87:131908. [2]Hao J H,Gao J,Wang HK.SrTi O3(110)thin fil ms grown directly on different oriented silicon substrates[J].Appl Phys A,2005,81:1233. [3]Aki mov I A,Sirenko A A,Clark A M,et al.Electric-field-induced soft-mode hardening in SrTi O3fil ms[J].Phys Rev Lett...

  7. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y.; Hsu, C.-H.

    2016-08-01

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  8. Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2010-07-15

    Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  9. Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

    Science.gov (United States)

    Nakamura, Daisuke; Suzumura, Akitoshi; Shigetoh, Keisuke

    2015-02-01

    Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50-200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10-50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysis also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs.

  10. Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Daisuke; Suzumura, Akitoshi; Shigetoh, Keisuke [Toyota Central R and D Labs., Inc., Nagakute, Aichi 480-1192 (Japan)

    2015-02-23

    Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50–200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10–50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysis also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs.

  11. Scanning Tunneling Microscopy and Spectroscopy of Air Exposure Effects on Molecular Beam Epitaxy Grown WSe2 Monolayers and Bilayers.

    Science.gov (United States)

    Park, Jun Hong; Vishwanath, Suresh; Liu, Xinyu; Zhou, Huawei; Eichfeld, Sarah M; Fullerton-Shirey, Susan K; Robinson, Joshua A; Feenstra, Randall M; Furdyna, Jacek; Jena, Debdeep; Xing, Huili Grace; Kummel, Andrew C

    2016-04-26

    The effect of air exposure on 2H-WSe2/HOPG is determined via scanning tunneling microscopy (STM). WSe2 was grown by molecular beam epitaxy on highly oriented pyrolytic graphite (HOPG), and afterward, a Se adlayer was deposited in situ on WSe2/HOPG to prevent unintentional oxidation during transferring from the growth chamber to the STM chamber. After annealing at 773 K to remove the Se adlayer, STM images show that WSe2 layers nucleate at both step edges and terraces of the HOPG. Exposure to air for 1 week and 9 weeks caused air-induced adsorbates to be deposited on the WSe2 surface; however, the band gap of the terraces remained unaffected and nearly identical to those on decapped WSe2. The air-induced adsorbates can be removed by annealing at 523 K. In contrast to WSe2 terraces, air exposure caused the edges of the WSe2 to oxidize and form protrusions, resulting in a larger band gap in the scanning tunneling spectra compared to the terraces of air-exposed WSe2 monolayers. The preferential oxidation at the WSe2 edges compared to the terraces is likely the result of dangling edge bonds. In the absence of air exposure, the dangling edge bonds had a smaller band gap compared to the terraces and a shift of about 0.73 eV in the Fermi level toward the valence band. However, after air exposure, the band gap of the oxidized WSe2 edges became about 1.08 eV larger than that of the WSe2 terraces, resulting in the electronic passivation of the WSe2.

  12. Non-Epitaxial Thin-Film Indium Phosphide Photovoltaics: Growth, Devices, and Cost Analysis

    Science.gov (United States)

    Zheng, Maxwell S.

    In recent years, the photovoltaic market has grown significantly as module prices have continued to come down. Continued growth of the field requires higher efficiency modules at lower manufacturing costs. In particular, higher efficiencies reduce the area needed for a given power output, thus reducing the downstream balance of systems costs that scale with area such as mounting frames, installation, and soft costs. Cells and modules made from III-V materials have the highest demonstrated efficiencies to date but are not yet at the cost level of other thin film technologies, which has limited their large-scale deployment. There is a need for new materials growth, processing and fabrication techniques to address this major shortcoming of III-V semiconductors. Chapters 2 and 3 explore growth of InP on non-epitaxial Mo substrates by MOCVD and CSS, respectively. The results from these studies demonstrate that InP optoelectronic quality is maintained even by growth on non-epitaxial metal substrates. Structural characterization by SEM and XRD show stoichiometric InP can be grown in complete thin films on Mo. Photoluminescence measurements show peak energies and widths to be similar to those of reference wafers of similar doping concentrations. In chapter 4 the TF-VLS growth technique is introduced and cells fabricated from InP produced by this technique are characterized. The TF-VLS method results in lateral grain sizes of >500 mum and exhibits superior optoelectronic quality. First generation devices using a n-TiO2 window layer along with p-type TF-VLS grown InP have reached ˜12.1% power conversion efficiency under 1 sun illumination with VOC of 692 mV, JSC of 26.9 mA/cm2, and FF of 65%. The cells are fabricated using all non-epitaxial processing. Optical measurements show the InP in these cells have the potential to support a higher VOC of ˜795 mV, which can be achieved by improved device design. Chapter 5 describes a cost analysis of a manufacturing process using an

  13. Molecular beam epitaxy of large-area SnSe2 with monolayer thickness fluctuation

    Science.gov (United States)

    Park, Young Woon; Jerng, Sahng-Kyoon; Jeon, Jae Ho; Roy, Sanjib Baran; Akbar, Kamran; Kim, Jeong; Sim, Yumin; Seong, Maeng-Je; Kim, Jung Hwa; Lee, Zonghoon; Kim, Minju; Yi, Yeonjin; Kim, Jinwoo; Noh, Do Young; Chun, Seung-Hyun

    2017-03-01

    The interest in layered materials is largely based on the expectation that they will be beneficial for a variety of applications, from low-power-consuming, wearable electronics to energy harvesting. However, the properties of layered materials are highly dependent on thickness, and the difficulty of controlling thickness over a large area has been a bottleneck for commercial applications. Here, we report layer-by-layer growth of SnSe2, a layered semiconducting material, via van der Waals epitaxy. The films were fabricated on insulating mica substrates with substrate temperatures in the range of 210 °C-370 °C. The surface consists of a mixture of N and (N ± 1) layers, showing that the thickness of the film can be defined with monolayer accuracy (±0.6 nm). High-resolution transmission electron microscopy reveals a polycrystalline film with a grain size of ˜100 nm and clear Moiré patterns from overlapped grains with similar thickness. We also report field effect mobility values of 3.7 cm2 V-1 s-1 and 6.7 cm2 V-1 s-1 for 11 and 22 nm thick SnSe2, respectively. SnSe2 films with customizable thickness can provide valuable platforms for industry and academic researchers to fully exploit the potential of layered materials.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-24

    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.

  15. Molecular beam epitaxy of thin HfTe2 semimetal films

    Science.gov (United States)

    Aminalragia-Giamini, S.; Marquez-Velasco, J.; Tsipas, P.; Tsoutsou, D.; Renaud, G.; Dimoulas, A.

    2017-03-01

    Epitaxial thin films of 1T-HfTe2 semimetal are grown by MBE on AlN(0001) substrates. The measured in-plane lattice parameter indicates an unstrained film which is also azimuthally aligned with the AlN substrate, albeit with an in-plane mosaic spread, as it would be expected for van der Waals epitaxy. Angle resolved photoemission spectroscopy combined with first principles electronic band structure calculations show steep linearly dispersing conduction and valence bands which cross near the Brillouin zone center, providing evidence that HfTe2/AlN is an epitaxial topological Dirac semimetal.

  16. Atom probe tomography characterisation of a laser diode structure grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Samantha E.; Humphreys, Colin J.; Oliver, Rachel A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Smeeton, Tim M.; Hooper, Stewart E.; Heffernan, Jonathan [Sharp Laboratories of Europe Limited, Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB (United Kingdom); Saxey, David W.; Smith, George D. W. [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom)

    2012-03-01

    Atom probe tomography (APT) has been used to achieve three-dimensional characterization of a III-nitride laser diode (LD) structure grown by molecular beam epitaxy (MBE). Four APT data sets have been obtained, with fields of view up to 400 nm in depth and 120 nm in diameter. These data sets contain material from the InGaN quantum well (QW) active region, as well as the surrounding p- and n-doped waveguide and cladding layers, enabling comprehensive study of the structure and composition of the LD structure. Two regions of the same sample, with different average indium contents (18% and 16%) in the QW region, were studied. The APT data are shown to provide easy access to the p-type dopant levels, and the composition of a thin AlGaN barrier layer. Next, the distribution of indium within the InGaN QW was analyzed, to assess any possible inhomogeneity of the distribution of indium (''indium clustering''). No evidence for a statistically significant deviation from a random distribution was found, indicating that these MBE-grown InGaN QWs do not require indium clusters for carrier localization. However, the APT data show steps in the QW interfaces, leading to well-width fluctuations, which may act to localize carriers. Additionally, the unexpected presence of a small amount (x = 0.005) of indium in a layer grown intentionally as GaN was revealed. Finally, the same statistical method applied to the QW was used to show that the indium distribution within a thick InGaN waveguide layer in the n-doped region did not show any deviation from randomness.

  17. Nanoelectronic devices--resonant tunnelling diodes grown on InP substrates by molecular beam epitaxy with peak to valley current ratio of 17 at room temperature

    Institute of Scientific and Technical Information of China (English)

    Zhang Yang; Zeng Yi-Ping; Ma Long; Wang Bao-Qiang; Zhu Zhan-Ping; Wang Liang-Chen; Yang Fu-Hua

    2006-01-01

    This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm2 has been obtained for diodes with AlAs barriers of ten monolayers, and an In0.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.

  18. Magnetically Hard Fe3Se4 Embedded in Bi2Se3 Topological Insulator Thin Films Grown by Molecular Beam Epitaxy.

    Science.gov (United States)

    Vasconcelos, Hugo Menezes do Nascimento; Eddrief, Mahmoud; Zheng, Yunlin; Demaille, Dominique; Hidki, Sarah; Fonda, Emiliano; Novikova, Anastasiia; Fujii, Jun; Torelli, Piero; Salles, Benjamin Rache; Vobornik, Ivana; Panaccione, Giancarlo; de Oliveira, Adilson Jesus Aparecido; Marangolo, Massimiliano; Vidal, Franck

    2016-01-26

    We investigated the structural, magnetic, and electronic properties of Bi2Se3 epilayers containing Fe grown on GaAs(111) by molecular beam epitaxy. It is shown that, in the window of growth parameters leading to Bi2Se3 epilayers with optimized quality, Fe atom clustering leads to the formation of FexSey inclusions. These objects have platelet shape and are embedded within Bi2Se3. Monoclinic Fe3Se4 is identified as the main secondary phase through detailed structural measurements. Due to the presence of the hard ferrimagnetic Fe3Se4 inclusions, the system exhibits a very large coercive field at low temperature and room temperature magnetic ordering. Despite this composite structure and the proximity of a magnetic phase, the surface electronic structure of Bi2Se3 is preserved, as shown by the persistence of a gapless Dirac cone at Γ.

  19. Photoluminescence and photocurrent from InP nanowires with InAsP quantum dots grown on Si by molecular beam epitaxy.

    Science.gov (United States)

    Kuyanov, P; LaPierre, R R

    2015-08-07

    InP nanowires with InAsP quantum dots (QDs) were grown by molecular beam epitaxy on a Si (111) substrates. The structure of the InAsP QDs were studied using transmission electron microscopy, allowing the development of a model where QD growth occurs by group V desorption from the surrounding substrate surface. Micro-photoluminescence was performed at 10 K showing emission at 1.47-1.49 eV from the InP wurtzite structure, and various emission peaks between 0.93 and 1.33 eV attributed to the QDs. The emission was tuned by the QD composition. The effectiveness of an AlInP passivation shell was demonstrated via an improvement in the photoluminescence intensity. Spectrally-resolved photocurrent measurements at room temperature demonstrated infrared response due to absorption within the QDs. The absorption red-shifted with increasing As composition of the QD.

  20. X-ray photoelectron spectroscopic study of the oxide removal mechanism of GaAs /100/ molecular beam epitaxial substrates in in situ heating

    Science.gov (United States)

    Vasquez, R. P.; Lewis, B. F.; Grunthaner, F. J.

    1983-01-01

    A standard cleaning procedure for GaAs (100) molecular beam epitaxial (MBE) substrates is a chemical treatment with a solution of H2SO4/H2O2/H2O, followed by in situ heating prior to MBE growth. X-ray photoelectron spectroscopic (XPS) studies of the surface following the chemical treatment show that the oxidized As is primarily As(+ 5). Upon heating to low temperatures (less than (350 C) the As(+ 5) oxidizes the substrate to form Ga2O3 and elemental As, and the As(+ 5) is reduced to As(+ 3) in the process. At higher temperatures (500 C), the As(+ 3) and elemental As desorb, while the Ga(+ 3) begins desorbing at about 600 C.

  1. Influence of AlN Buffer Thickness on GaN Grown on Si(111) by Gas Source Molecular Beam Epitaxy with Ammonia

    Institute of Scientific and Technical Information of China (English)

    LIN Guo-Qiang; ZENG Yi-Ping; WANG Xiao-Liang; LIU Hong-Xin

    2008-01-01

    Hexagonal GaN is grown on a Si(111) substrate with AlN as a buffer layer by gas source molecular beam epitaxy(GSMBE) with ammonia. The thickness of AlN buffer is changed from 9 to 72nm. When the thickness of AlN buffer is 36nm, the surface morphology and crystal quality of GaN is optimal. The in-situ reflection high energy electron diffraction (RHEED) reveals that the transition to a two-dimensional growth mode of AlN is the key to the quality of GaN. However, the thickness of AlN buffer is not so critical to the residual in-plane tensile stress in GaN grown on Si(111) by GSMBE for AlN thickness between 9 to 72nm.

  2. Interfacial structure of molecular beam epitaxial grown cubic-GaN films on GaAs(001) probed by x-ray gazing-angle specular reflection

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    We report on a study of interfacial structure of GaN films grown on GaAs(001) substrates by plasma-assisted molecular beam epitaxy using x-ray grazing-angle specular reflection.We show that interfacial layers with electron densities differing from those of GaN and GaAs were formed upon deposition of GaN.It is also found that the interfacial structure of our systems depends strongly on the course of the initial layer deposition.The phase purity of the GaN films was examined by x-ray reciprocal space mapping.A simple kinetic growth model suggested by our results has been presented.

  3. Low threshold 1.55 {mu}m wavelength InAsP/InGaAsP strained multiquantum well laser diode grown by chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Carlin, J.F.; Syrbu, A.V.; Berseth, C.A.; Behrend, J.; Rudra, A.; Kapon, E. [Institut de Micro- et Optoelectronique, Departement de Physique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    1997-07-01

    By using chemical beam epitaxy at growth temperatures as low as 460{endash}480{degree}C, we have overcome strain relaxation problems that prevented so far the successful use of InAsP quantum wells in 1.55 {mu}m lasers. Five quantum well InAsP/InGaAsP horizontal cavity lasers showed 88{percent} internal efficiency, 1.6cm{sup {minus}1} losses per well, and 33A/cm{sup 2} transparency current density per well, which equal or even surpass the best published characteristics for 1.55 {mu}m wavelength lasers based on any material system. Moreover, up to 17 quantum wells were integrated in a strain-balanced laser, which showed equally good characteristics. {copyright} {ital 1997 American Institute of Physics.}

  4. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Du, Y., E-mail: yingge.du@pnnl.gov, E-mail: scott.chambers@pnnl.gov; Liyu, A. V. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Droubay, T. C.; Chambers, S. A., E-mail: yingge.du@pnnl.gov, E-mail: scott.chambers@pnnl.gov [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Li, G. [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2014-04-21

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-24

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

  6. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    Science.gov (United States)

    Du, Y.; Droubay, T. C.; Liyu, A. V.; Li, G.; Chambers, S. A.

    2014-04-01

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

  7. Epitaxial growth of crystalline polyaniline on reduced graphene oxide.

    Science.gov (United States)

    Majumdar, Dipanwita; Baskey, Moni; Saha, Shyamal K

    2011-08-17

    Due to its unique electronic properties, graphene has already been identified as a promising material for future carbon based electronics. To develop graphene technology, the fabrication of a high quality P-N junction is a great challenge. Here, we describe a general technique to grow single crystalline polyaniline (PANI) films on graphene sheets using in situ polymerization via the oxidation-reduction of aniline monomer and graphene oxide, respectively, to fabricate a high quality P-N junction, which shows diode-like behavior with a remarkably low turn-on voltage (60 mV) and high rectification ratio (1880:1) up to a voltage of 0.2 V. The origin of these superior electronic properties is the preferential growth of a highly crystalline PANI film as well as lattice matching between the d-values [∼2.48 Å] of graphene and {120} planes of PANI.

  8. Characterization and density control of GaN nanodots on Si (111) by droplet epitaxy using plasma-assisted molecular beam epitaxy.

    Science.gov (United States)

    Yu, Ing-Song; Chang, Chun-Pu; Yang, Chung-Pei; Lin, Chun-Ting; Ma, Yuan-Ron; Chen, Chun-Chi

    2014-01-01

    In this report, self-organized GaN nanodots have been grown on Si (111) by droplet epitaxy method, and their density can be controlled from 1.1 × 10(10) to 1.1 × 10(11) cm(-2) by various growth parameters, such as substrate temperatures for Ga droplet formation, the pre-nitridation treatment of Si substrate, the nitridation duration for GaN crystallization, and in situ annealing after GaN formation. Based on the characterization of in situ RHEED, we can observe the surface condition of Si and the formation of GaN nanodots on Si. The surface nitridaiton treatment at 600°C provides a-SiNx layer which makes higher density of GaN nanodots. Crystal GaN nanodots can be observed by the HRTEM. The surface composition of GaN nanodots can be analyzed by SPEM and μ-XPS with a synchrotron x-ray source. We can find GaN nanodots form by droplet epitaxy and then in situ annealing make higher-degree nitridation of GaN nanodots.

  9. Layer-by-layer epitaxial growth of a Bi sub 2 Sr sub 2 CuO sub 6 thin film on a Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, T.; Kawai, T.; Kitahama, K.; Kawai, S. (The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567, Japan (JP)); Shigaki, I.; Kawate, Y. (Superconducting Cryogenic Technology Center, Kobe Steel, Ltd., Takatsukadai 1-chome, Nishi-ku, Kobe 651-22, (Japan))

    1991-05-06

    The epitaxial growth of a Bi{sub 2}Sr{sub 2}CuO{sub 6} (2201) thin film on a Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (2212) single crystal has been performed using computer-controlled laser molecular beam epitaxy. The surface of the 2212 single crystal used as the substrate is smooth and invariant under the growth condition at 640 {degree}C in NO{sub 2} pressure of 1{times}10{sup {minus}5} mbar. The growth process of the 2201 film has been observed by {ital in} {ital situ} reflection high-energy electron diffraction (RHEED), and the layer-by-layer growth of the 2201 phase is confirmed by the oscillation of RHEED intensities. During the growth, a modulated surface structure which is characteristic of the Bi cuprate crystals is always present.

  10. Epitaxial growth of metals on (100) SrTiO{sub 3}: the influence of lattice mismatch and reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, T.; Polli, A.D.; Richter, G.; Stanzick, H. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

    2001-07-01

    The model system Me/(100) SrTiO{sub 3} (Me: Pd, Pt, Cu, Ni, Cr, Mo, Nb, and Al) was used to show that there exists a simple correlation between the formation of particular epitaxial orientations, the lattice mismatch between metal and SrTiO{sub 3}, and the oxygen affinity of the metal. The growth of the metal films on the (100) SrTiO{sub 3} surface was studied by reflection high-energy electron diffraction. Most metals (Pd, Pt, Ni, Nb and Al) grew with the following epitaxial orientation relationship on the SrTiO{sub 3}: (100) SrTiO{sub 3} parallel (100) Me, [001] SrTiO{sub 3} parallel [001] Me. A second epitaxial orientation relationship was detected for Cr and Mo: (100) SrTiO{sub 3} parallel (100) Cr, Mo, [001] SrTiO{sub 3} parallel [011] Cr, Mo. For Mo, this orientation was detected only at very high growth temperatures. For each of the epitaxial orientation relationships, the substrate and film planes of four fold symmetry were parallel. Besides the second epitaxial orientation relationship, a third epitaxial orientation relationship was detected for Mo at growth temperatures below 900 K: (100) SrTiO{sub 3} parallel (110) Mo, [001] SrTiO{sub 3} parallel [001] Mo. In contrast to all other metals under investigation, Cu grew with a (111) fiber texture on the (100) SrTiO{sub 3} surface. The appearance of the first two epitaxial orientation relationships can be interpreted with a simple relationship between the metals' oxygen affinities and the lattice mismatches with SrTiO{sub 3}. This relationship can be used for other metals to predict epitaxy on the (100) SrTiO{sub 3} surface. (orig.)

  11. Supercritical supersaturations and ultrafast cooling of the growth solution in liquid-phase epitaxy of semiconductors

    Science.gov (United States)

    Abramov, A. V.; Deryagin, N. G.; Tret'yakov, D. N.

    1996-04-01

    A method for accomplishing ultrafast cooling is proposed which makes possible supercritical supersaturations of the growth solution in liquid-phase epitaxy. Growth boat designs providing cooling rates as high as 0268-1242/11/4/025/img1 are considered. The temperatures of contact, 0268-1242/11/4/025/img2, of a GaAs substrate with a Ga-based solution and of a Si substrate with a Sn-based growth solution, calculated for various substrate 0268-1242/11/4/025/img3 and solution temperatures 0268-1242/11/4/025/img4, are in good agreement with experimental values. The maximum attainable supercooling is markedly increased to as high as 0268-1242/11/4/025/img5 for the Ga - As system, when the growth solution is subjected to ultrafast cooling. The prospects of using the method for fabricating heterostructures with a large lattice mismatch are discussed.

  12. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  13. Peculiarly strong room-temperature ferromagnetism from low Mn-doping in ZnO grown by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Zheng Zuo

    2013-03-01

    Full Text Available Strong room-temperature ferromagnetism is demonstrated in single crystalline Mn-doped ZnO thin films grown by molecular beam epitaxy. Very low Mn doping concentration is investigated, and the measured magnetic moment is much larger than what is expected for an isolated ion based on Hund's rules. The ferromagnetic behavior evolves with Mn concentration. Both magnetic anisotropy and anomalous Hall effect confirm the intrinsic nature of ferromagnetism. While the Mn dopant plays a crucial role, another entity in the system is needed to explain the observed large magnetic moments.

  14. Integration of carbon nanotubes with semiconductor technology: fabrication of hybrid devices by III–V molecular beam epitaxy

    DEFF Research Database (Denmark)

    Stobbe, Søren; Lindelof, P. E.; Nygård, J.

    2006-01-01

    on incorporation of singlewall nanotubes in III–V semiconductor heterostructures grown by molecular beam epitaxy (MBE). We demonstrate that singlewall carbon nanotubes can be overgrown using MBE; electrical contacts to the nanotubes are obtained by GaMnAs grown at 250 °C. The resulting devices can exhibit field......We review a number of essential issues regarding the integration of carbon nanotubes in semiconductor devices for electronics: material compatibility, electrical contacts, functionalities, circuit architectures and reliability. In the second part of the paper, we present our own recent results...

  15. Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001 surface: nucleation, morphology, and CMOS compatibility

    Directory of Open Access Journals (Sweden)

    Yuryev Vladimir

    2011-01-01

    Full Text Available Abstract Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001 surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C and high (≳600°C temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001 surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001 quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.

  16. Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si(001) surface: nucleation, morphology, and CMOS compatibility.

    Science.gov (United States)

    Yuryev, Vladimir A; Arapkina, Larisa V

    2011-09-05

    Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (≲600°C) and high (≳600°C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.

  17. DFT study for the anisotropic epitaxial growth of a-face ZnO(1120)

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, A.; Oda, Y.; Fujiwara, K. [Department of Applied Mathematics and Physics, Tottori University, Koyama, Tottori (Japan)

    2008-07-01

    The anisotropy of the epitaxial growth of a-face ZnO(1120) is investigated using the density functional theory. The potential energy surface for Zn adatom and O adatom on the a-face ZnO(1120) surface is calculated. The calculated results show us that the anisotropy of Zn adatom and O adatom is very large. The kinetic Monte Carlo simulation shows us that the such large anistropic migration barrier energy is the origin of the stripe structure. It is consistent with the experimentally observed anisotropic stripes on this surface. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Characterization and growth of epitaxial layers of Gs exhibiting high resistivity for ionic implantation

    Science.gov (United States)

    1979-01-01

    Either classical or low temperature epitaxial growth techniques can be used to control the deposition of buffer layers of GaAs on semiconducting substrates and to obtain the resistivity and purity desired. Techniques developed to study, as a function of thickness, the evolution of mobilities by photoHall, and the spectroscopy of shallow and deep centers by cathodoluminescence and current transients reveal one very pure layer of medium resistivity and high mobility, and another "dead layer" of elevated resistivity far from the surface. The highly resistive layer remains pure over several microns, which appears interesting for implantation.

  19. Transport, Growth Mechanisms, and Material Quality in GaN Epitaxial Lateral Overgrowth

    Energy Technology Data Exchange (ETDEWEB)

    Baca, Albert G.; Bartram, M.E.; Coltrin, M.E.; Crawford, M.H.; Han, J.; Missert, N.; Willan, C.C.

    1999-01-11

    Growth kinetics, mechanisms, and material quality in GaN epitaxial lateral over-growth (ELO) were examined using a single mask of systematically varied patterns. A 2-D gas phase reaction/diffusion model describes how transport of the Ga precursor to the growth surface enhances the lateral rate in the early stages of growth. In agreement with SEM studies of truncated growth runs, the model also predicts the dramatic decrease in the lateral rate that occurs as GaN over-growth reduces the exposed area of the mask. At the point of convergence, a step-flow coalescence mechanism is observed to fill in the area between lateral growth-fronts. This alternative growth mode in which a secondary growth of GaN is nucleated along a single convergence line, may be responsible for producing smooth films observed to have uniform cathodoluminescence (CL) when using 1{micro}m nucleation zones. Although emission is comprised of both UV ({approximately}365nm) and yellow ({approximately}550nm) components, the spectra suggest these films have reduced concentrations of threading dislocations normally associated with non-radiative recombination centers and defects known to accompany growth-front convergence lines.

  20. Epitaxial Growth of Aligned and Continuous Carbon Nanofibers from Carbon Nanotubes.

    Science.gov (United States)

    Lin, Xiaoyang; Zhao, Wei; Zhou, Wenbin; Liu, Peng; Luo, Shu; Wei, Haoming; Yang, Guangzhi; Yang, Junhe; Cui, Jie; Yu, Richeng; Zhang, Lina; Wang, Jiaping; Li, Qunqing; Zhou, Weiya; Zhao, Weisheng; Fan, Shoushan; Jiang, Kaili

    2017-02-28

    Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, "additive synthesis" of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an "annual ring" cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∼4-fold increased tensile strength and ∼10-fold increased Young's modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers.