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Sample records for layer epitaxial growth

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Defect Reduction in Epitaxial Growth Using Superlattice Buffer Layers

    Science.gov (United States)

    1988-07-01

    Katsuyama, Y. J. Yang and S. M. Bedair, Electron Dev. Lett., vol. 8, p. 240, 1987. 0 -15 -" Journal of (ryOstal (io iih 77 (108(,) ,xQ 9i4 S9 North-I...layer facilitat the csea of Gaosu 3 (5% in H2) + 500 sccm of H , and ed cross-sectional thickness measurements. trimethylgallium (TMG) + 500 sccm of H

  12. 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.

  13. Epitaxial growth of cadmium telluride films on silicon with a buffer silicon carbide layer

    Science.gov (United States)

    Antipov, V. V.; Kukushkin, S. A.; Osipov, A. V.

    2017-02-01

    An epitaxial 1-3-μm-thick cadmium telluride film has been grown on silicon with a buffer silicon carbide layer using the method of open thermal evaporation and condensation in vacuum for the first time. The optimum substrate temperature was 500°C at an evaporator temperature of 580°C, and the growth time was 4 s. In order to provide more qualitative growth of cadmium telluride, a high-quality 100-nm-thick buffer silicon carbide layer was previously synthesized on the silicon surface using the method of topochemical substitution of atoms. The ellipsometric, Raman, X-ray diffraction, and electron-diffraction analyses showed a high structural perfection of the CdTe layer in the absence of a polycrystalline phase.

  14. Growth of bismuth telluride thin film on Pt by electrochemical atomic layer epitaxy

    Institute of Scientific and Technical Information of China (English)

    ZHU Wen; YANG Jun-you; GAO Xian-hui; HOU Jie; ZHANG Tong-jun; CUI Kun

    2005-01-01

    An automated thin-layer flow cell electrodeposition system was developed for growing Bi2 Te3 thin film by ECALE. The dependence of the Bi and Te deposition potentials on Pt electrode was studied. In the first attempt,this reductive Te underpotential deposition (UPD)/reductive Bi UPD cycle was performed to 100 layers. A better linearity of the stripping charge with the number of cycles has been shown and confirmed a layer-by-layer growth mode, which is consistent with an epitaxial growth. The 4: 3 stoichiometric ratio of Bi to Te suggests that the incomplete charge transfer in HTeO2+ reduction excludes the possibility of Bi2 Te3 formation. X-ray photoelectron spectroscopy (XPS) analysis also reveals that the incomplete charge transfer in HTeO2+ occurs in Te direct deposition. The effective way of depositing Bi2 Te3 on Pt consists in oxidative Te UPD and reductive Bi UPD. The thin film deposited by this procedure was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). A polycrystalline characteristic was confirmed by XRD. The 2 : 3 stoichiometric ratio was confirmed by XPS. The SEM image indicates that the deposit looks like a series of buttons about 0.3 - 0.4 μm in diameter, which is corresponding with calculated thickness of the epitaxial film. This suggests that the particle growth appears to be linear with the number of cycles, as it is consistent with a layer by layer growth mode.

  15. 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.)

  16. 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

  17. Growth by atomic layer epitaxy and characterization of thin films of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Kopalko, K.; Lusakowska, E.; Paszkowicz, W.; Domagala, J.Z.; Szczerbakow, A.; Swiatek, K.; Dybko, K. [Institute of Physics, Polish Acad. of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Wojcik, A.; Godlewski, M. [Institute of Physics, Polish Acad. of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Dep. of Mathem. and Natural Sci. College of Science, Cardinal S. Wyszynski Univ., Warsaw (Poland); Godlewski, M.M. [Dept. of Physiology, Biochem., Pharmacology and Toxicology, Fac. of Veterinary Medicine, Warsaw Agriculture University, Warsaw (Poland)

    2005-02-01

    ABSTRACT Atomic layer epitaxy (ALE) was applied to grow thin films of monocrystalline and polycrystalline ZnO. Monocrystalline films were obtained only for GaN/Al{sub 2}O{sub 3} substrates, whereas use of sapphire, silicon or soda lime glass resulted in either 3D growth mode or in polycrystalline films showing preferential orientation along the c axis. Successful Mn doping of ZnO films is reported, when using organic Mn precursors. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Low-temperature growth of fully epitaxial CoFe/Ge/Fe3Si layers on Si for vertical-type semiconductor spintronic devices

    Science.gov (United States)

    Sakai, S.; Kawano, M.; Ikawa, M.; Sato, H.; Yamada, S.; Hamaya, K.

    2017-09-01

    We develop a low-temperature growth technique of epitaxial Ge layers on a body-centered-cubic ferromagnetic metal (bcc-FM), Fe3Si, by combining solid phase epitaxy (SPE) and molecular beam epitaxy (MBE). The insertion of an SPE-grown Ge layer enables two-dimensional epitaxial growth of Ge layers by MBE even at a growth temperature of ∼175 {}\\circ C. Thanks to the relatively flat surface of the Ge epilayers, we can obtain an epitaxial CoFe (bcc-FM) layer on top of the Ge layers, leading to the all-epitaxial CoFe/Ge/Fe3Si trilayer with a reasonable magnetization reversal process. We believe that the all-epitaxial CoFe/Ge/Fe3Si trilayer has great potential to be utilized as novel vertical-type Ge-channel spintronic devices.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Layer-Controlled Chemical Vapor Deposition Growth of MoS2 Vertical Heterostructures via van der Waals Epitaxy.

    Science.gov (United States)

    Samad, Leith; Bladow, Sage M; Ding, Qi; Zhuo, Junqiao; Jacobberger, Robert M; Arnold, Michael S; Jin, Song

    2016-07-26

    The fascinating semiconducting and optical properties of monolayer and few-layer transition metal dichalcogenides, as exemplified by MoS2, have made them promising candidates for optoelectronic applications. Controllable growth of heterostructures based on these layered materials is critical for their successful device applications. Here, we report a direct low temperature chemical vapor deposition (CVD) synthesis of MoS2 monolayer/multilayer vertical heterostructures with layer-controlled growth on a variety of layered materials (SnS2, TaS2, and graphene) via van der Waals epitaxy. Through precise control of the partial pressures of the MoCl5 and elemental sulfur precursors, reaction temperatures, and careful tracking of the ambient humidity, we have successfully and reproducibly grown MoS2 vertical heterostructures from 1 to 6 layers over a large area. The monolayer MoS2 heterostructure was verified using cross-sectional high resolution transmission electron microscopy (HRTEM) while Raman and photoluminescence spectroscopy confirmed the layer-controlled MoS2 growth and heterostructure electronic interactions. Raman, photoluminescence, and energy dispersive X-ray spectroscopy (EDS) mappings verified the uniform coverage of the MoS2 layers. This reaction provides an ideal method for the scalable layer-controlled growth of transition metal dichalcogenide heterostructures via van der Waals epitaxy for a variety of optoelectronic applications.

  6. 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.

  7. Epitaxial growth of zinc oxide by the method of atomic layer deposition on SiC/Si substrates

    Science.gov (United States)

    Kukushkin, S. A.; Osipov, A. V.; Romanychev, A. I.

    2016-07-01

    For the first time, zinc oxide epitaxial films on silicon were grown by the method of atomic layer deposition at a temperature T = 250°C. In order to avoid a chemical reaction between silicon and zinc oxide (at the growth temperature, the rate constant of the reaction is of the order of 1022), a high-quality silicon carbide buffer layer with a thickness of ~50 nm was preliminarily synthesized by the chemical substitution of atoms on the silicon surface. The zinc oxide films were grown on n- and p-type Si(100) wafers. The ellipsometric, Raman, electron diffraction, and trace element analyses showed that the ZnO films are epitaxial.

  8. Epitaxial Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Growth Mechanism, Controllability, and Scalability

    KAUST Repository

    Li, Henan

    2017-07-06

    Recently there have been many research breakthroughs in two-dimensional (2D) materials including graphene, boron nitride (h-BN), black phosphors (BPs), and transition-metal dichalcogenides (TMDCs). The unique electrical, optical, and thermal properties in 2D materials are associated with their strictly defined low dimensionalities. These materials provide a wide range of basic building blocks for next-generation electronics. The chemical vapor deposition (CVD) technique has shown great promise to generate high-quality TMDC layers with scalable size, controllable thickness, and excellent electronic properties suitable for both technological applications and fundamental sciences. The capability to precisely engineer 2D materials by chemical approaches has also given rise to fascinating new physics, which could lead to exciting new applications. In this Review, we introduce the latest development of TMDC synthesis by CVD approaches and provide further insight for the controllable and reliable synthesis of atomically thin TMDCs. Understanding of the vapor-phase growth mechanism of 2D TMDCs could benefit the formation of complicated heterostructures and novel artificial 2D lattices.

  9. Photo-irradiation effects on GaAs atomic layer epitaxial growth. GaAs no genshiso epitaxial seicho ni okeru hikari reiki koka

    Energy Technology Data Exchange (ETDEWEB)

    Mashita, M.; Kawakyu, Y.; Sasaki, M.; Ishikawa, H. (Toshiba Corp., Kawasaki (Japan). Research and Development Center)

    1990-08-10

    Single atomic layer epitaxy (ALE) aims at controlling a growing film at a precision of single molecular layer. In this article, it is reported that the growth temperature range of ALE was expanded by the vertical irradiation of KrF exima laser (248 nm) onto the substrate for the ALE growth of GaAs using the metalorganic chemical vapor deposition (MOCVD) method. Thanks for the results of the above experiment, it was demonstrated that the irradiation effect was not thermal, but photochemical. In addition, this article studies the possibility of adsorption layer irradiation and surface irradiation as the photo-irradiation mechanism, and points out that coexistence of both irradiation mechanisms can be considered and, in case of exima laser, strong possibility of direct irradiation of the adsorption layer because of its high power density. Hereinafter, by using both optical growth ALE and thermal growth ALE jointly, the degree of freedom of combination of hetero ALE increases and its application to various material systems becomes possible. 16 refs., 6 figs.

  10. Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum

    Science.gov (United States)

    Jokubavicius, Valdas; Sun, Jianwu; Liu, Xinyu; Yazdi, Gholamreza; Ivanov, Ivan. G.; Yakimova, Rositsa; Syväjärvi, Mikael

    2016-08-01

    We demonstrate growth of thick SiC layers (100-200 μm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10-5 mbar) at temperatures varying from 1700 to 1975 °C with growth rates up to 270 μm/h and 70 μm/h for 6H- and 4H-SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C-SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200 μm thick homoepitaxial 6H-SiC layer co-doped with nitrogen and boron in a range of 1018 cm-3 at a growth rate of about 270 μm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer.

  11. 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.

  12. Crystal Growth and Characterization of Epitaxial Layers of Laser and Nonlinear Optical Materials for Thin-Disk and Waveguide laser applications

    Energy Technology Data Exchange (ETDEWEB)

    W Bolanos; M Segura; J Cugat; J Carvajal; X Mateos; M Pujol; R Solé; F Díaz; M Aguiló; et. al.

    2011-12-31

    This paper summarizes the main results we obtained in our laboratories in relation with crystalline layers obtained by liquid phase epitaxial growth of lanthanide doped KLu(WO{sub 4}){sub 2} and Nb:RbTiOPO{sub 4} grown on KLu(WO{sub 4}){sub 2} and RbTiOPO{sub 4} substrates, respectively. Macroscopic defect free epitaxial layers were grown and characterized in terms of their compositional homogeneity, structural stress in the layer/substrate interface and laser and waveguiding performances.

  13. Effect of Buffer Layer on Epitaxial Growth of YSZ Deposited on Si Substrate by Slower Q-switched 266 nm YAG Laser

    Science.gov (United States)

    Kaneko, Satoru; Akiyama, Kensuke; Shimizu, Yoshitada; Ito, Takeshi; Yasaka, Shinji; Mitsuhashi, Masahiko; Ohya, Seishiro; Saito, Keisuke; Watanabe, Takayuki; Okamoto, Shoji; Funakubo, Hiroshi

    2004-04-01

    Yttria-stabilized zirconia (YSZ) was grown on Si(100) substrate by pulsed laser deposition (PLD). The laser used in this study was a 266 nm YAG laser with a second function generator modulating only the Q-switch while the primary generator modulated the flash lamp (slower Q-switch). Epitaxial growth was verified on YSZ film deposited without oxygen gas followed by primary deposition in oxygen atmosphere on Si substrate with a ˜0.4-nm-thin oxide layer. The crystallinity was strongly dependent on the thickness of the buffer layer deposited prior to the primary deposition of YSZ. The epitaxial growth was confirmed by φ scan, and ω scan (rocking curve) showed the full width at half maximum (FWHM) of 1.1 deg. The required oxygen pressure for epitaxial growth was quite high compared to that of excimer deposition.

  14. Monte Carlo simulation of epitaxial growth on a (111) layer with mismatch

    Science.gov (United States)

    Tan, S.; Ghazali, A.; Lévy, J.-C. S.

    1997-04-01

    A high-temperature deposition of adatoms on a substrate with or without lattice mismatch from -10% to +10%, followed by slow cooling to a given temperature, is simulated by means of a Monte Carlo algorithm with Lennard-Jones interatomic pair potentials. Stranski-Krastanov growth is always observed with a lateral island size controlled by the lattice mismatch, while the deposition mode acts strongly on the island slope. Complete healing of the island structure never occurs before the tenth layer. The interlayer distance undergoes oscillations as a function of the layer number. This is observed for a ±10% mismatch as well as for a -5% mismatch.

  15. Epitaxial growth of an antireflective, conductive, graded index ITO nanowire layer

    Directory of Open Access Journals (Sweden)

    Colm eO'Dwyer

    2013-10-01

    Full Text Available Nanoporous and nanostructured films, assemblies and arrangements are important from an applied point of view in microelectronics, photonics and optical materials. The ability to minimize reflection, control light output and use contrast and variation of the refractive index to modify photonic characteristics can provide routes to enhanced photonic crystal devices, omnidirectional reflectors, antireflection coatings and broadband absorbing materials. This work shows how multiscale branching of defect-free ITO NWs grown as a layer with a graded refractive index improves antireflection properties and shifts the transparency window into the near-infrared (NIR. The measurements confirm the structural quality and growth mechanism of the NW layer without any heterogeneous seeding for NW growth. Optical reflectance measurements confirm broadband antireflection down to <5% between 1.3-1.6 um which is tunable with the NW density. The work also outlines how the suppression of the Burstein-Moss shifts using refractive index variation allows transparency in a conductive NW layer into NIR range.

  16. Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition.

    Science.gov (United States)

    Lin, Edward L; Edmondson, Bryce I; Hu, Shen; Ekerdt, John G

    2016-07-26

    Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2×1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

  17. 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,

  18. Photoenhanced atomic layer epitaxy. Hikari reiki genshiso epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Mashita, M.; Kawakyu, Y. (Toshiba corp., Tokyo (Japan))

    1991-10-01

    The growth temperature range was greatly expanded of atomic layer epitaxy (ALE) expected as the growth process of ultra-thin stacks. Ga layers and As layers were formed one after the other on a GaAs substrate in the atmosphere of trimethylgallium (TMG) or AsH{sub 2} supplied alternately, by KrF excimer laser irradiation normal to the substrate. As a result, the growth temperature range was 460-540{degree}C nearly 10 times that of 500 {plus minus} several degrees centigrade in conventional thermal growth method. Based on the experimental result where light absorption of source molecules adsorbed on a substrate surface was larger than that under gaseous phase condition, new adsorbed layer enhancement model was proposed to explain above irradiation effect verifying it by experiments. As this photoenhancement technique is applied to other materials, possible fabrication of new crystal structures as a super lattice with ultra-thin stacks of single atomic layers is expected because of a larger freedom in material combination for hetero-ALE. 11 refs., 7 figs.

  19. 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.

  20. Van der Waals Epitaxial Growth of Atomic Layered HfS2 Crystals for Ultrasensitive Near-Infrared Phototransistors.

    Science.gov (United States)

    Fu, Lei; Wang, Feng; Wu, Bin; Wu, Nian; Huang, Wei; Wang, Hanlin; Jin, Chuanhong; Zhuang, Lin; He, Jun; Fu, Lei; Liu, Yunqi

    2017-08-01

    As a member of the group IVB transition metal dichalcogenides (TMDs) family, hafnium disulfide (HfS2 ) is recently predicted to exhibit higher carrier mobility and higher tunneling current density than group VIB (Mo and W) TMDs. However, the synthesis of high-quality HfS2 crystals, sparsely reported, has greatly hindered the development of this new field. Here, a facile strategy for controlled synthesis of high-quality atomic layered HfS2 crystals by van der Waals epitaxy is reported. Density functional theory calculations are applied to elucidate the systematic epitaxial growth process of the S-edge and Hf-edge. Impressively, the HfS2 back-gate field-effect transistors display a competitive mobility of 7.6 cm(2) V(-1) s(-1) and an ultrahigh on/off ratio exceeding 10(8) . Meanwhile, ultrasensitive near-infrared phototransistors based on the HfS2 crystals (indirect bandgap ≈1.45 eV) exhibit an ultrahigh responsivity exceeding 3.08 × 10(5) A W(-1) , which is 10(9) -fold higher than 9 × 10(-5) A W(-1) obtained from the multilayer MoS2 in near-infrared photodetection. Moreover, an ultrahigh photogain exceeding 4.72 × 10(5) and an ultrahigh detectivity exceeding 4.01 × 10(12) Jones, superior to the vast majority of the reported 2D-materials-based phototransistors, imply a great promise in TMD-based 2D electronic and optoelectronic applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Low temperature laser molecular beam epitaxy and characterization of AlGaN epitaxial layers

    Science.gov (United States)

    Tyagi, Prashant; Ch., Ramesh; Kushvaha, S. S.; Kumar, M. Senthil

    2017-05-01

    We have grown AlGaN (0001) epitaxial layers on sapphire (0001) by using laser molecular beam epitaxy (LMBE) technique. The growth was carried out using laser ablation of AlxGa1-x liquid metal alloy under r.f. nitrogen plasma ambient. Before epilayer growth, the sapphire nitradation was performed at 700 °C using r.f nitrogen plasma followed by AlGaN layer growth. The in-situ reflection high energy electron diffraction (RHEED) was employed to monitor the substrate nitridation and AlGaN epitaxial growth. High resolution x-ray diffraction showed wurtzite hexagonal growth of AlGaN layer along c-axis. An absorption bandgap of 3.97 eV is obtained for the grown AlGaN layer indicating an Al composition of more than 20 %. Using ellipsometry, a refractive index (n) value of about 2.19 is obtained in the visible region.

  2. The Growth of Gallium Nitride Films via the Innovative Technique of Atomic Layer Epitaxy

    Science.gov (United States)

    1989-06-01

    6 3.2 Aluminum Nitride and AIN/GaN Layered Structures ............ 8 3.3 Boron Nitride and BGaN Graded...of tearing in lower left region, indirectly indicating the presence of multiple layers of BGaN ............................... 14 12. Auger electron...electron spectroscopy sputtered depth profile of a BN/ BGaN /GaN/P-SiC film. Note peak in nitrogen trace as interface of BN is passed

  3. Epitaxial growth of thick 4H?SiC layers in a vertical radiant-heating reactor

    Science.gov (United States)

    Tsuchida, H.; Kamata, I.; Jikimoto, T.; Izumi, K.

    2002-04-01

    A vertical radiant-heating reactor has been developed for thick silicon carbide (SiC) epitaxial growth, in which the susceptor and substrates are heated by radiation from the hot wall. The benefit of the heating and sample-holding method is demonstrated by improvements in the curvature of crystal bending and FWHM of X-ray ω-rocking curves followed by epitaxial growth. The typical growth rate is 13-16 μm/h at 1530-1550°C at the susceptor top under reduced pressure as low as 50-70 mbar. Low background doping at low 10 13 cm -3 ( Nd- Na) was achieved, and some of the 4H-SiC epilayers exhibited a high resistivity. We also succeeded in growing a 4H-SiC epilayer over 240 μm-thick with minimal surface roughness. Little sign of impurities was observed by low-temperature photoluminescence (LTPL), and no impurities (Al, B, Ti, V and Cr) exceeding 1×10 14 cm -3 were found by secondary ion mass spectroscopy (SIMS) for a 150 μm-thick 4H-SiC epilayer. Thickness and doping uniformity along the gas flow of ˜5% and ˜11%, respectively, were obtained for 2-in substrates. Molten KOH etching analysis revealed that some of the micropipes were dissociated into closed core screw dislocations during epitaxial growth. The electrical performance of high-voltage devices was also demonstrated.

  4. Comparison of Epitaxial Growth Techniques for III-V Layer Structures

    Science.gov (United States)

    1992-05-22

    FOR Ill-V LAYER STRUCTURES DTIC byS ELECTE G. B. STRINGFELLOW MAY 2 819S2 A Prepared for Publication in the Proceedings of croissance de cristaux et de...overall process. This very area, that has retarded the development of OMVPE, now provides a significant advantage relative to other, competing...having miscibility gaps, as discussed in the last paper.[22] Another major factor retarding the development of OMVPE has been the inability to escape

  5. Effects of AlN nucleation layers on the growth of AlN films using high temperature hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Balaji, M. [Science et Ingenierie des Materiaux et des Procedes, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Heres (France); ACERDE, 452 rue des sources, 38920 Crolles (France); Crystal Growth Centre, Anna University-Chennai, Chennai 600025 (India); Claudel, A. [ACERDE, 452 rue des sources, 38920 Crolles (France); Fellmann, V. [Science et Ingenierie des Materiaux et des Procedes, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Heres (France); Gelard, I. [ACERDE, 452 rue des sources, 38920 Crolles (France); Blanquet, E., E-mail: elisabeth.blanquet@simap.grenoble-inp.fr [Science et Ingenierie des Materiaux et des Procedes, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Heres (France); Boichot, R. [Science et Ingenierie des Materiaux et des Procedes, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Heres (France); Pierret, A. [Departement de Mesures Physiques, ONERA, Chemin de la Huniere, 91761 Palaiseau Cedex (France); CEA-CNRS Group ' NanoPhysique et SemiConducteurs' , INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble, Cedex 9 (France); and others

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer Growth of AlN Nucleation layers and its effect on high temperature AlN films quality were investigated. Black-Right-Pointing-Pointer AlN nucleation layers stabilizes the epitaxial growth of AlN and improves the surface morphology of AlN films. Black-Right-Pointing-Pointer Increasing growth temperature of AlN NLs as well as AlN films improves the structural quality and limits the formation of cracks. - Abstract: AlN layers were grown on c-plane sapphire substrates with AlN nucleation layers (NLs) using high temperature hydride vapor phase epitaxy (HT-HVPE). Insertion of low temperature NLs, as those typically used in MOVPE process, prior to the high temperature AlN (HT-AlN) layers has been investigated. The NLs surface morphology was studied by atomic force microscopy (AFM) and NLs thickness was measured by X-ray reflectivity. Increasing nucleation layer deposition temperature from 650 to 850 Degree-Sign C has been found to promote the growth of c-oriented epitaxial HT-AlN layers instead of polycrystalline layers. The growth of polycrystalline layers has been related to the formation of dis-oriented crystallites. The density of such disoriented crystallites has been found to decrease while increasing NLs deposition temperature. The HT-AlN layers have been characterized by X-ray diffraction {theta} - 2{theta} scan and (0 0 0 2) rocking curve measurement, Raman and photoluminescence spectroscopies, AFM and field emission scanning electron microscopy. Increasing the growth temperature of HT-AlN layers from 1200 to 1400 Degree-Sign C using a NL grown at 850 Degree-Sign C improves the structural quality as well as the surface morphology. As a matter of fact, full-width at half-maximum (FWHM) of 0 0 0 2 reflections was improved from 1900 to 864 arcsec for 1200 Degree-Sign C and 1400 Degree-Sign C, respectively. Related RMS roughness also found to decrease from 10 to 5.6 nm.

  6. Aqueous phase synthesis of upconversion nanocrystals through layer-by-layer epitaxial growth for in vivo X-ray computed tomography

    KAUST Repository

    Li, Feifei

    2013-05-21

    Lanthanide-doped core-shell upconversion nanocrystals (UCNCs) have tremendous potential for applications in many fields, especially in bio-imaging and medical therapy. As core-shell UCNCs are mostly synthesized in organic solvents, tedious organic-aqueous phase transfer processes are usually needed for their use in bio-applications. Herein, we demonstrate the first example of one-step synthesis of highly luminescent core-shell UCNCs in the "aqueous" phase under mild conditions using innocuous reagents. A microwave-assisted approach allowed for layer-by-layer epitaxial growth of a hydrophilic NaGdF4 shell on NaYF4:Yb, Er cores. During this process, surface defects of the nanocrystals could be gradually passivated by the homogeneous shell deposition, resulting in obvious enhancement in the overall upconversion emission efficiency. In addition, the up-down conversion dual-mode luminescent NaYF4:Yb, Er@NaGdF4:Ce, Ln (Eu, Tb, Sm, Dy) nanocrystals were also synthesized to further validate the successful formation of the core-shell structure. More significantly, based on their superior solubility and stability in water solution, high upconversion efficiency and Gd-doped predominant X-ray absorption, the as-prepared NaYF4:Yb, Er@NaGdF4 core-shell UCNCs exhibited high contrast in in vitro cell imaging and in vivo X-ray computed tomography (CT) imaging, demonstrating great potential as multiplexed luminescent biolabels and CT contrast agents.

  7. 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.

  8. A visualization of threading dislocations formation and dynamics in mosaic growth of GaN-based light emitting diode epitaxial layers on (0001) sapphire

    Science.gov (United States)

    Ravadgar, P.; Horng, R. H.; Ou, S. L.

    2012-12-01

    A clear visualization of the origin and characteristics of threading dislocations (TDs) of GaN-based light emitting diode epitaxial layers on (0001) sapphire substrates have been carried out. Special experimental set up and chemical etchant along with field emission scanning electron microscopy are employed to study the dynamics of GaN TDs at different growth stages. Cross-sectional transmission electron microscopy analysis visualized the formation of edge TDs is arising from extension of coalescences at boundaries of different tilting-twining nucleation grains "mosaic growth." Etch pits as representatives of edge TDs are in agreement with previous theoretical models and analyses of TDs core position and characteristics.

  9. Recent Results on Growth of (211)B CdTe on (211)Si with Intermediate Ge and ZnTe Buffer Layers by Metalorganic Vapor-Phase Epitaxy

    Science.gov (United States)

    Shintri, Shashidhar; Rao, Sunil; Wijewarnasuriya, Priyalal; Trivedi, Sudhir; Bhat, Ishwara

    2012-10-01

    We report on the investigation of epitaxial cadmium telluride grown by metalorganic vapor-phase epitaxy (MOVPE) on (211)Si, with particular emphasis on studying the effect of changing the reactor parameters and thermal annealing conditions on the epilayer quality. The CdTe films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The best CdTe films were observed when the Te/Cd precursor partial pressure ratio was close to 3.1. It was also observed that, though annealing improved the crystal quality, a slight increase in surface roughness was observed. Similar attempts were made to improve the growth conditions of ZnTe intermediate buffer layer, which showed similar trends with changes in precursor flows.

  10. 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

  11. Growth of nitrogen-doped p-type ZnO thin films prepared by atomic layer epitaxy

    Institute of Scientific and Technical Information of China (English)

    LEE Chongmu; LIM Jongmin; PARK Suyoung; KIM Hyounwoo

    2006-01-01

    Nitrogen-doped, p-type ZnO thin films were grown successfully on sapphire (0001) substrates by using atomic layer epitaxy (ALE). Zn(C2H5)2[Diethylzinc,DEZn], H2O and NH3 were used as a zinc precursor, an oxidant and a doping source gas, respectively. The lowest electrical resistivity of the p-type ZnO films grown by ALE and annealed at 1000 ℃ in an oxygen atmosphere for 1 h was 18.3 Ω·m with a hole concentration of 3.71×1017cm-3 . Low temperature-photoluminescence analysis and time-dependent Hall measurement results support that the nitrogen-doped ZnO after annealing is ap-type semiconductor.

  12. Growth and characterization of epitaxial anatase TiO{sub 2}(001) on SrTiO{sub 3}-buffered Si(001) using atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, M.D. [University of Texas at Austin, Department of Chemical Engineering, Austin, TX 78712 (United States); Posadas, A. [University of Texas at Austin, Department of Physics, Austin, TX 78712 (United States); Wang, T. [University of Texas at Austin, Department of Chemical Engineering, Austin, TX 78712 (United States); Demkov, A.A. [University of Texas at Austin, Department of Physics, Austin, TX 78712 (United States); Ekerdt, J.G., E-mail: ekerdt@che.utexas.edu [University of Texas at Austin, Department of Chemical Engineering, Austin, TX 78712 (United States)

    2012-08-31

    Epitaxial anatase titanium dioxide (TiO{sub 2}) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO{sub 2} was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225-250 Degree-Sign C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600 Degree-Sign C in vacuum (10{sup -7} Pa) for 1-2 h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO{sub 2} by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO{sub 2} growth. X-ray diffraction revealed that the TiO{sub 2} films were anatase with only the (004) reflection present at 2{theta} = 38.2 Degree-Sign , indicating that the c-axis is slightly reduced from that of anatase powder (2{theta} = 37.9 Degree-Sign ). Anatase TiO{sub 2} films up to 100 nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates. - Highlights: Black-Right-Pointing-Pointer Epitaxial anatase films are grown by atomic layer deposition (ALD) on Si(001). Black-Right-Pointing-Pointer Four unit cells of SrTiO{sub 3} on silicon create a stable template for ALD. Black-Right-Pointing-Pointer TiO{sub 2} thin films have a compressed c-axis and an expanded a-axis. Black-Right-Pointing-Pointer Up to 100 nm thick TiO{sub 2} films remain highly ordered in the (001) direction.

  13. Large-area, laterally-grown epitaxial semiconductor layers

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jung; Song, Jie; Chen, Danti

    2017-07-18

    Structures and methods for confined lateral-guided growth of a large-area semiconductor layer on an insulating layer are described. The semiconductor layer may be formed by heteroepitaxial growth from a selective growth area in a vertically-confined, lateral-growth guiding structure. Lateral-growth guiding structures may be formed in arrays over a region of a substrate, so as to cover a majority of the substrate region with laterally-grown epitaxial semiconductor tiles. Quality regions of low-defect, stress-free GaN may be grown on silicon.

  14. Seed layer technique for high quality epitaxial manganite films

    Science.gov (United States)

    Graziosi, P.; Gambardella, A.; Calbucci, M.; O’Shea, K.; MacLaren, D. A.; Bergenti, I.; Homonnay, N.; Schmidt, G.; Pullini, D.; Busquets-Mataix, D.; Dediu, V.

    2016-01-01

    We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived. PMID:27648371

  15. Seed layer technique for high quality epitaxial manganite films

    Directory of Open Access Journals (Sweden)

    P. Graziosi

    2016-08-01

    Full Text Available We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

  16. Optical characterization of epitaxial semiconductor layers

    CERN Document Server

    Richter, Wolfgang

    1996-01-01

    The last decade has witnessed an explosive development in the growth of expitaxial layers and structures with atomic-scale dimensions. This progress has created new demands for the characterization of those stuctures. Various methods have been refined and new ones developed with the main emphasis on non-destructive in-situ characterization. Among those, methods which rely on the interaction of electromagnetic radiation with matter are particularly valuable. In this book standard methods such as far-infrared spectroscopy, ellipsometry, Raman scattering, and high-resolution X-ray diffraction are presented, as well as new advanced techniques which provide the potential for better in-situ characterization of epitaxial structures (such as reflection anistropy spectroscopy, infrared reflection-absorption spectroscopy, second-harmonic generation, and others). This volume is intended for researchers working at universities or in industry, as well as for graduate students who are interested in the characterization of ...

  17. Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

    Science.gov (United States)

    Fujikura, Hajime; Konno, Taichiro; Yoshida, Takehiro; Horikiri, Fumimasa

    2017-08-01

    Thick (20-30 µm) layers of highly pure GaN with device-quality smooth as-grown surfaces were prepared on freestanding GaN substrates by using our advanced hydride-vapor-phase epitaxy (HVPE) system. Removal of quartz parts from the HVPE system markedly reduced concentrations of residual impurities to below the limits of detection by secondary-ion mass spectrometry. Appropriate gas-flow management in the HVPE system realized device-quality, smooth, as-grown surfaces with an excellent uniformity of thickness. The undoped GaN layer showed insulating properties. By Si doping, the electron concentration could be controlled over a wide range, down to 2 × 1014 cm-3, with a maximum mobility of 1150 cm2·V-1·s-1. The concentration of residual deep levels in lightly Si-doped layers was in the 1014 cm-3 range or less throughout the entire 2-in. wafer surface. These achievements clearly demonstrate the potential of HVPE as a tool for epitaxial growth of power-device structures.

  18. Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

    Science.gov (United States)

    Li, Liang; Yang, Lin'an; Zhang, Jincheng; Hao, Yue

    2013-09-01

    This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm2/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

  19. Epitaxial Growth of MOF Thin Film for Modifying the Dielectric Layer in Organic Field-Effect Transistors.

    Science.gov (United States)

    Gu, Zhi-Gang; Chen, Shan-Ci; Fu, Wen-Qiang; Zheng, Qingdong; Zhang, Jian

    2017-03-01

    Metal-organic framework (MOF) thin films are important in the application of sensors and devices. However, the application of MOF thin films in organic field effect transistors (OFETs) is still a challenge to date. Here, we first use the MOF thin film prepared by a liquid-phase epitaxial (LPE) approach (also called SURMOFs) to modify the SiO2 dielectric layer in the OFETs. After the semiconductive polymer of PTB7-Th (poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]) was coated on MOF/SiO2 and two electrodes on the semiconducting film were deposited sequentially, MOF-based OFETs were fabricated successfully. By controlling the LPE cycles of SURMOF HKUST-1 (also named Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate), the performance of the HKUST-1/SiO2-based OFETs showed high charge mobility and low threshold voltage. This first report on the application of MOF thin film in OFETs will offer an effective approach for designing a new kind of materials for the OFET application.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Study of growth rate and composition variations in metalorganic vapour phase selective area epitaxy at atmospheric pressure and application to the growth of strained layer DBR lasers

    Science.gov (United States)

    Silvestre, L.; Ougazzaden, A.; Delprat, D.; Ramdane, A.; Daguet, C.; Patriarche, G.

    1997-01-01

    In selective area epitaxy (SAE), a lateral variation of thickness accompanied by a variation of composition occurs because of the presence of dielectric masks on the substrate surface. To take advantage of these behaviours for monolithic integration of electronic devices, a good control of growth rate and composition is necessary. For this aim, different bulk materials InP, InGaAs and InGaAsP have been systematically investigated as a function of the geometry of dielectric masks specially designed for this work. All growths were performed by metalorganic vapour phase epitaxy (MOVPE) at atmospheric pressure. An estimation of growth rate enhancement and composition variation between the open regions in dielectric masks and the unmasked region has been established, allowing the choice of specific mask geometry for each application. Following this study, a strained multiple quantum well (MQW) structure for a distributed Bragg reflector (DBR) laser has been selectively grown. The standard buried ridge structure (BRS) processed presents good characteristics (8 mA threshold current) and we obtained a 7 nm tuning range with a ridge structure, which constitutes the best value reported with SAE.

  5. Si衬底上热壁外延制备GaAs单晶薄膜材料%Growth of Monocrystalline GaAs Layer on Si by Hot Wall Epitaxy

    Institute of Scientific and Technical Information of China (English)

    刘翔; 谭红琳; 吴长树; 张鹏翔; 赵德锐; 陈庭金; 廖世坤; 吴刚; 杨家明

    2000-01-01

    This paper reports the growth of GaAs layer on Si substrate by hot wall epitaxy (HWE). Si surface prior to epitaxy of GaAs layer is activated. Then two - step epitaxy is used to achieve GaAs layer. Finally, intermittent multi - layer cycle annealing (IMCA) is implemented to improve morphology and quality of the epitaxial layer. Measurement and analysis by electron probe micro - analysis (EPMA), Raman spectrum, Hall measurement and photo - luminescence (PL) confirm that GaAs layer with thickness of approximately 4 μm has been obtained.%报道了采用热壁外延(HWE)技术,在Si表面生长GaAs薄膜。先通过活化剂活化Si表面,再采取两步生长法外延GaAs单晶薄膜,最后进行断续多层循环退火(IMCA)。经电子探针(EPMA)、Raman光谱、Hall测量和荧光(PL)光谱测试分析,证实在Si表面获得了近4μm厚的GaAs单晶薄膜。

  6. 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.

  7. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya

    2017-05-10

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  8. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing.

    Science.gov (United States)

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-03

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

  9. Systematic study on dynamic atomic layer epitaxy of InN on/in +c-GaN matrix and fabrication of fine-structure InN/GaN quantum wells: Role of high growth temperature

    Science.gov (United States)

    Yoshikawa, Akihiko; Kusakabe, Kazuhide; Hashimoto, Naoki; Hwang, Eun-Sook; Imai, Daichi; Itoi, Takaomi

    2016-12-01

    The growth kinetics and properties of nominally 1-ML (monolayer)-thick InN wells on/in +c-GaN matrix fabricated using dynamic atomic layer epitaxy (D-ALEp) by plasma-assisted molecular beam epitaxy were systematically studied, with particular attention given to the effects of growth temperature. Attention was also given to how and where the ˜1-ML-thick InN layers were frozen or embedded on/in the +c-GaN matrix. The D-ALEp of InN on GaN was a two-stage process; in the 1st stage, an "In+N" bilayer/monolayer was formed on the GaN surface, while in the 2nd, this was capped by a GaN barrier layer. Each process was monitored in-situ using spectroscopic ellipsometry. The target growth temperature was above 620 °C and much higher than the upper critical epitaxy temperature of InN (˜500 °C). The "In+N" bilayer/monolayer tended to be an incommensurate phase, and the growth of InN layers was possible only when they were capped with a GaN layer. The InN layers could be coherently inserted into the GaN matrix under self-organizing and self-limiting epitaxy modes. The growth temperature was the most dominant growth parameter on both the growth process and the structure of the InN layers. Reflecting the inherent growth behavior of D-ALEp grown InN on/in +c-GaN at high growth temperature, the embedded InN layers in the GaN matrix were basically not full-ML in coverage, and the thickness of sheet-island-like InN layers was essentially either 1-ML or 2-ML. It was found that these InN layers tended to be frozen at the step edges on the GaN and around screw-type threading dislocations. The InN wells formed type-I band line-up heterostructures with GaN barriers, with exciton localization energies of about 300 and 500 meV at 15 K for the 1-ML and 2-ML InN wells, respectively.

  10. 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.

  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. Layer-by-layer epitaxial thin films of the pyrochlore Tb2Ti2O7

    Science.gov (United States)

    Bovo, Laura; Rouleau, Christopher M.; Prabhakaran, Dharmalingam; Bramwell, Steven T.

    2017-02-01

    Layer-by-layer epitaxial growth of the pyrochlore magnet Tb2Ti2O7 on the isostructural substrate Y2Ti2O7 results in high-quality single crystal films of up to 60 nm thickness. Substrate-induced strain is shown to act as a strong and controlled perturbation to the exotic magnetism of Tb2Ti2O7, opening up the general prospect of strain-engineering the diverse magnetic and electrical properties of pyrochlore oxides.

  13. 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.

  14. Multilayer epitaxial growth of lead phthalocyanine and C(70) using CuBr as a templating layer for enhancing the efficiency of organic photovoltaic cells.

    Science.gov (United States)

    Kim, Tae-Min; Shim, Hyun-Sub; Choi, Min-Soo; Kim, Hyo Jung; Kim, Jang-Joo

    2014-03-26

    The molecular orientation and crystallinity of donor and acceptor molecules are important for high-efficiency organic photovoltaic cells (OPVs) because they significantly influence both the absorption of light and charge-transport characteristics. We report that the templating effect extends to multilayers to increase the crystallinity and to modify the orientation of the crystals of lead phthalocyanine (PbPc) and C70 layers at the same time by adopting CuBr as a new templating layer on indium tin oxide (ITO). The formation of a monoclinic phase with a preferred orientation of (320) for PbPc and a fcc phase with a preferred orientation of (220) for C70 on the PbPc layer is revealed by X-ray diffraction (XRD) patterns. The multilayer epitaxy results in an increase of the exciton diffusion lengths from 5.6 to 8.8 nm for PbPc and from 6.9 to 13.8 nm for C70 to enhance the power conversion efficiency (PCE) of the planar heterojunction OPVs composed of PbPc and C70 from 1.4 to 2.3%. The quasi-epitaxy model is proposed to explain the multilayer epitaxy.

  15. 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.

  16. 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.)

  17. Optical Epitaxial Growth of Gold Nanoparticle Arrays.

    Science.gov (United States)

    Huang, Ningfeng; Martínez, Luis Javier; Jaquay, Eric; Nakano, Aiichiro; Povinelli, Michelle L

    2015-09-09

    We use an optical analogue of epitaxial growth to assemble gold nanoparticles into 2D arrays. Particles are attracted to a growth template via optical forces and interact through optical binding. Competition between effects determines the final particle arrangements. We use a Monte Carlo model to design a template that favors growth of hexagonal particle arrays. We experimentally demonstrate growth of a highly stable array of 50 gold particles with 200 nm diameter, spaced by 1.1 μm.

  18. 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.

  19. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses of the initial growth mechanism of CdTe layers on (100) GaAs by metalorganic vapor phase epitaxy

    OpenAIRE

    1990-01-01

    X‐ray photoelectron spectroscopy and Auger electron spectroscopy measurements were performed to investigate the initial growth mechanism and the selection of growth orientations of CdTe layers grown on (100) GaAs by metalorganic vapor phase epitaxy (MOVPE). The surface stoichiometry of the GaAs substrate was found to recover when annealed in a H2 flow atmosphere (500°C, 5 min), although the surface was initially in an As‐rich condition after chemical etching by H2SO4@B:H2O2@B:H2O=5@B:1@B:1. N...

  20. Epitaxial growth of mixed conducting layered Ruddlesden–Popper La{sub n+1}Ni{sub n}O{sub 3n+1} (n = 1, 2 and 3) phases by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Kuan-Ting; Soh, Yeong-Ah; Skinner, Stephen J., E-mail: s.skinner@imperial.ac.uk

    2013-10-15

    Graphical abstract: - Highlights: • High quality epitaxial thin films of layered Ruddlesden–Popper nickelates were prepared. • For the first time this has been achieved by the PLD process. • n = 1, 2 and 3 films were successfully deposited on SrTiO{sub 3} and NdGaO{sub 3} substrates. • c-Axis oriented films were confirmed by XRD analysis. • In-plane and out-of-plane strain effects on lattice are discussed. - Abstract: Layered Ruddlesden–Popper phases of composition La{sub n+1}Ni{sub n}O{sub 3n+1} (n = 1, 2 and 3) have been epitaxially grown on SrTiO{sub 3} (0 0 1) or NdGaO{sub 3} (1 1 0) single crystal substrates using the pulsed laser deposition technique. X-ray diffraction analyses (θ/2θ, rocking curves, and φ-scans) and atomic force microscopy confirms the high-quality growth of the series of films with low surface roughness values (less than 1 nm). In particular, epitaxial growth of the higher order phases (n = 2 and 3) of lanthanum nickelate have been demonstrated for the first time.

  1. X-ray photoelectron spectroscopy studies of initial growth mechanism of CdTe layers grown on (100)GaAs by organometallic vapor phase epitaxy

    OpenAIRE

    1990-01-01

    Variations of the GaAs surface conditions and the adsorption of the precursor elements of Cd and Te on the (100)GaAs substrate were studied by x‐ray photoelectron spectroscopy at the initial stage of CdTe growth by organometallic vapor phase epitaxy. The stoichiometry of GaAs substrates was found to recover by annealing in the H2 environment (500°C, 5 min), while the surface was initially in an As‐rich condition after etching with H2SO4:H2O2:H2O (5:1:1). The preferential adsorption of Te on t...

  2. Atomic layer epitaxy of 3-5 compounds

    Science.gov (United States)

    Dapkus, P. D.; Wittig, C.; Allen, S.

    1986-08-01

    This program is intended to develop a process for the growth of GaAs and related compounds by Atomic Layer Epitaxy (ALE). The program involves fundamental studies of gas phase kinetics of the organometallic and hydrides to be used in the process as well as surface reaction studies to determine the surface of various organometallics. We have chosen in this program to effect ALE growth in a dense H2 atmosphere. We believe that the reactivity of H2 is important to the removal, by hydrogenation, of the alkyl radicals from the growing surface. To better understand the process we are pursuing fundamental information in two areas. First, basic measurements of the reactivity band reaction products of organometallics and hydrides and of photogenerated species with compound semiconductor surfaces are being undertaken that will determine the feasibility of using photoactivation and in thermal catalytic reactions in the gas phase to accomplish ALE. Second, epitaxial growth experiments are being performed to determine the feasibility of an ALE process employing photodecomposition of surface absorbed species as well as thermal catalytic reactions.

  3. Epitaxially Grown Layered MFI–Bulk MFI Hybrid Zeolitic Materials

    KAUST Repository

    Kim, Wun-gwi

    2012-11-27

    The synthesis of hybrid zeolitic materials with complex micropore-mesopore structures and morphologies is an expanding area of recent interest for a number of applications. Here we report a new type of hybrid zeolite material, composed of a layered zeolite material grown epitaxially on the surface of a bulk zeolite material. Specifically, layered (2-D) MFI sheets were grown on the surface of bulk MFI crystals of different sizes (300 nm and 10 μm), thereby resulting in a hybrid material containing a unique morphology of interconnected micropores (∼0.55 nm) and mesopores (∼3 nm). The structure and morphology of this material, referred to as a "bulk MFI-layered MFI" (BMLM) material, was elucidated by a combination of XRD, TEM, HRTEM, SEM, TGA, and N2 physisorption techniques. It is conclusively shown that epitaxial growth of the 2-D layered MFI sheets occurs in at least two principal crystallographic directions of the bulk MFI crystal and possibly in the third direction as well. The BMLM material combines the properties of bulk MFI (micropore network and mechanical support) and 2-D layered MFI (large surface roughness, external surface area, and mesoporosity). As an example of the uses of the BMLM material, it was incorporated into a polyimide and fabricated into a composite membrane with enhanced permeability for CO2 and good CO2/CH4 selectivity for gas separations. SEM-EDX imaging and composition analysis showed that the polyimide and the BMLM interpenetrate into each other, thereby forming a well-adhered polymer/particle microstructure, in contrast with the defective interfacial microstructure obtained using bare MFI particles. Analysis of the gas permeation data with the modified Maxwell model also allows the estimation of the effective volume of the BMLM particles, as well as the CO2 and CH4 gas permeabilities of the interpenetrated layer at the BMLM/polyimide interface. © 2012 American Chemical Society.

  4. Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei, E-mail: weili.unsw@gmail.com; Varlamov, Sergey; Xue, Chaowei

    2014-09-30

    Highlights: • Crystallisation kinetic is used to analyse seed layer surface cleanliness. • Simplified RCA cleaning for the seed layer can shorten the epitaxy annealing duration. • RTA for the seed layer can improve the quality for both seed layer and epi-layer. • Epitaxial poly-Si solar cell performance is improved by RTA treated seed layer. - Abstract: This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, V{sub oc} and J{sub sc} than the one on the seed layer without RTA treatment.

  5. Growth kinetics and structural perfection of (InN)1/(GaN)1-20 short-period superlattices on +c-GaN template in dynamic atomic layer epitaxy

    Science.gov (United States)

    Kusakabe, Kazuhide; Hashimoto, Naoki; Itoi, Takaomi; Wang, Ke; Imai, Daichi; Yoshikawa, Akihiko

    2016-04-01

    The growth kinetics and structural perfection of (InN)1/(GaN)1-20 short-period superlattices (SPSs) were investigated with their application to ordered alloys in mind. The SPSs were grown on +c-GaN template at 650 °C by dynamic atomic layer epitaxy in conventional plasma-assisted molecular beam epitaxy. It was found that coherent structured InN/GaN SPSs could be fabricated when the thickness of the GaN barrier was 4 ML or above. Below 3 ML, the formation of SPSs was quite difficult owing to the increased strain in the SPS structure caused by the use of GaN as a template. The effective or average In composition of the (InN)1/(GaN)4 SPSs was around 10%, and the corresponding InN coverage in the ˜1 ML-thick InN wells was 50%. It was found that the effective InN coverage in ˜1 ML-thick InN wells could be varied with the growth conditions. In fact, the effective In composition could be increased up to 13.5%, i.e., the corresponding effective InN coverage was about 68%, by improving the capping/freezing speed by increasing the growth rate of the GaN barrier layer.

  6. Growth kinetics and structural perfection of (InN){sub 1}/(GaN){sub 1–20} short-period superlattices on +c-GaN template in dynamic atomic layer epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kusakabe, Kazuhide; Hashimoto, Naoki; Wang, Ke; Imai, Daichi [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Itoi, Takaomi [Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Yoshikawa, Akihiko, E-mail: yoshi@faculty.chiba-u.jp [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Graduate School of Engineering, Kogakuin University, Hachioji, Tokyo 192-0015 (Japan)

    2016-04-11

    The growth kinetics and structural perfection of (InN){sub 1}/(GaN){sub 1–20} short-period superlattices (SPSs) were investigated with their application to ordered alloys in mind. The SPSs were grown on +c-GaN template at 650 °C by dynamic atomic layer epitaxy in conventional plasma-assisted molecular beam epitaxy. It was found that coherent structured InN/GaN SPSs could be fabricated when the thickness of the GaN barrier was 4 ML or above. Below 3 ML, the formation of SPSs was quite difficult owing to the increased strain in the SPS structure caused by the use of GaN as a template. The effective or average In composition of the (InN){sub 1}/(GaN){sub 4} SPSs was around 10%, and the corresponding InN coverage in the ∼1 ML-thick InN wells was 50%. It was found that the effective InN coverage in ∼1 ML-thick InN wells could be varied with the growth conditions. In fact, the effective In composition could be increased up to 13.5%, i.e., the corresponding effective InN coverage was about 68%, by improving the capping/freezing speed by increasing the growth rate of the GaN barrier layer.

  7. 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°.

  8. 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.

  9. Epitaxial growth and characterization of Gd2O3-doped HfO2 film on Ge (001) substrates with zero interface layer

    Institute of Scientific and Technical Information of China (English)

    张心强; 屠海令; 魏峰; 熊玉华; 杨萌萌; 赵洪滨; 杜军; 王文武

    2013-01-01

    The GHO (Gd2O3-doped HfO2) films were epitaxially grown on Ge (001) substrates adopting cube-on-cube mode with zero interface layer using pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) and high-resolution transmission electron microscopy (HRTEM) observation revealed a sharp interface of GHO/Ge and orientation relationship corre-sponding to (001)GHO//(001)Ge and [011] GHO//[011]Ge. The band offset for GHO/Ge stack was evaluated to be 3.92 eV for va-lence band and 1.38 eV for conduction band by X-ray photoelectron spectrum. Small equivalent oxide thickness (0.49 nm) and inter-face state density (7×1011 cm-2) were achieved from Au/Ti/GHO/Ge/Al capacitors.

  10. Growth of ferroelectric Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} epitaxial films by ultraviolet pulsed laser irradiation of chemical solution derived precursor layers

    Energy Technology Data Exchange (ETDEWEB)

    Queraltó, A.; Pérez del Pino, A., E-mail: aperez@icmab.es; Mata, M. de la; Tristany, M.; Gómez, A.; Obradors, X.; Puig, T. [Institut de Ciència de Materials de Barcelona, Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia (Spain); Arbiol, J. [Institut de Ciència de Materials de Barcelona, Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08010 Barcelona, Catalonia (Spain)

    2015-06-29

    Highly crystalline epitaxial Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) thin-films are grown on (001)-oriented LaNiO{sub 3}-buffered LaAlO{sub 3} substrates by pulsed laser irradiation of solution derived barium-zirconium-titanium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The structural analyses of the obtained films, studied by X-ray diffractometry and transmission electron microscopy, demonstrate that laser processing allows the growth of tens of nm-thick BST epitaxial films with crystalline structure similar to that of films obtained through conventional thermal annealing methods. However, the fast pulsed nature of the laser employed leads to crystallization kinetic evolution orders of magnitude faster than in thermal treatments. The combination of specific photothermal and photochemical mechanisms is the main responsible for the ultrafast epitaxial laser-induced crystallization. Piezoresponse microscopy measurements demonstrate equivalent ferroelectric behavior in laser and thermally annealed films, being the piezoelectric constant ∼25 pm V{sup −1}.

  11. Strain-induced single-domain growth of epitaxial SrRuO3 layers on SrTiO3: A high-temperature x-ray diffraction study

    NARCIS (Netherlands)

    Vailionis, Arturas; Siemons, Wolter; Koster, Gertjan

    2007-01-01

    Temperature dependent structural phase transitions of SrRuO3 thin films epitaxially grown on SrTiO3(001) single crystal substrates have been studied using high-resolution x-ray diffraction. In contrast to bulk SrRuO3, coherently strained epitaxial layers do not display cubic symmetry up to ∼ 730 °C

  12. 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.

  13. 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.

  14. 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.

  15. Epitaxial Growth of GeGaAs.

    Science.gov (United States)

    1981-06-01

    liquid solvent for epitaxial growth of Ge. Because of the finite solubility of GaAs in Pb (7 x 10-4 atomic fraction at 500°C) relatively fast initial...mixture of Pb and Sn was used as a melt. The solubility of Ge in a PbSn eutetic mixture is significantly higher than the solubility of Ge in pure Pb...shallow donor acceptor levels. Addition of a deep level to the crystal lat- tice at this point would further pin the fermi level near mid-gap

  16. Electric circuit model for strained-layer epitaxy

    Science.gov (United States)

    Kujofsa, Tedi; Ayers, John E.

    2016-11-01

    For the design and analysis of a strained-layer semiconductor device structure, the equilibrium strain profile may be determined numerically by energy minimization but this method is computationally intense and non-intuitive. Here we present an electric circuit model approach for the equilibrium analysis of an epitaxial stack, in which each sublayer may be represented by an analogous configuration involving a current source, a resistor, a voltage source, and an ideal diode. The resulting node voltages in the analogous electric circuit correspond to the equilibrium strains in the original epitaxial structure. This new approach enables analysis using widely accessible circuit simulators, and an intuitive understanding of electric circuits may be translated to the relaxation of strained-layer structures. In this paper, we describe the mathematical foundation of the electrical circuit model and demonstrate its application to epitaxial layers of Si1-x Ge x grown on a Si (001) substrate.

  17. Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

    Science.gov (United States)

    Li, Wei; Varlamov, Sergey; Xue, Chaowei

    2014-09-01

    This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, Voc and Jsc than the one on the seed layer without RTA treatment.

  18. 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.

  19. Epitaxy of layered semiconductor thin films

    Science.gov (United States)

    Brahim Otsmane, L.; Emery, J. Y.; Jouanne, M.; Balkanski, M.

    1993-03-01

    Epilayers of InSe on InSe(00.1) and GaSe(00.1) have been grown by the molecular beam epitaxy (MBE) technique. Raman spectroscopy was used for a characterization of the structure and crystallinity in InSe/InSe(00.1) (homoepitaxy) and InSe/GaSe(00.1) (heteroepitaxy). The Raman spectra of the InSe thin films are identical to those of polytype γ-InSe. An activation of the E(LO) mode at 211 cm -1 is observed in these films here. Scanning electron microscopy (SEM) is also used to investigate surfaces of these films.

  20. Effect of growth conditions on the Al composition and optical properties of Al x Ga 1−x N layers grown by atmospheric-pressure metal organic vapor phase epitaxy

    KAUST Repository

    Soltani, S.

    2017-02-17

    The effect of growth conditions on the Al composition and optical properties of AlxGa1-xN layers grown by atmospheric-pressure metal organic vapor phase epitaxy is investigated. The Al content of the samples is varied between 3.0% and 9.3% by changing the gas flow rate of either trimethylaluminum (TMA) or trimethylgallium (TMG) while other growth parameters are kept constant. The optical properties of the AlxGa1-xN layers are studied by photoreflectance and time-resolved photoluminescence (TR-PL) spectroscopies. A degeneration in the material quality of the samples is revealed when the Al content is increased by increasing the TMA flow rate. When the TMG flow rate is decreased with a fixed TMA flow rate, the Al content of the AlxGa1-xN layers is increased and, furthermore, an improvement in the optical properties corresponding with an increase in the PL decay time is observed. (C) 2017 Elsevier B.V. All rights reserved.

  1. Improved crystalline quality of N-polar GaN epitaxial layers grown with reformed flow-rate-modulation technology

    Science.gov (United States)

    Zhang, Heng; Zhang, Xiong; Wang, Shuchang; Wang, Xiaolei; Zhao, Jianguo; Wu, Zili; Dai, Qian; Yang, Hongquan; Cui, Yiping

    2017-01-01

    A reformed flow-rate-modulation technology was developed for the metalorganic vapor phase epitaxy (MOVPE) growth of the N-polar GaN epitaxial layers. To improve the crystalline quality of the N-polar GaN epitaxial layers, a GaN nucleation layer was grown at relatively low temperature with carefully-controlled pulsed supply of Ga source and showed diverse morphology with atomic force microscope (AFM). Furthermore, the electrical and optical properties of the grown N-polar GaN epitaxial layers were investigated extensively by means of Hall effect, photoluminescence (PL), and X-ray rocking curve (XRC) measurements. The characterization results revealed that as compared with the N-polar GaN epitaxial layer grown over the conventional GaN nucleation layer which was deposited with continuous supply of both N and Ga sources, the electrical and optical properties of the N-polar GaN epitaxial layer grown with optimized supply of Ga source for the GaN nucleation layer were significantly improved.

  2. Atomic layer deposition of epitaxial layers of anatase on strontium titanate single crystals: Morphological and photoelectrochemical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, Theodore J.; Nepomnyashchii, Alexander B.; Parkinson, B. A., E-mail: bparkin1@uwyo.edu [Department of Chemistry, School of Energy Resources, University of Wyoming, Laramie, Wyoming 82071 (United States)

    2015-01-15

    Atomic layer deposition was used to grow epitaxial layers of anatase (001) TiO{sub 2} on the surface of SrTiO{sub 3} (100) crystals with a 3% lattice mismatch. The epilayers grow as anatase (001) as confirmed by x-ray diffraction. Atomic force microscope images of deposited films showed epitaxial layer-by-layer growth up to about 10 nm, whereas thicker films, of up to 32 nm, revealed the formation of 2–5 nm anatase nanocrystallites oriented in the (001) direction. The anatase epilayers were used as substrates for dye sensitization. The as received strontium titanate crystal was not sensitized with a ruthenium-based dye (N3) or a thiacyanine dye (G15); however, photocurrent from excited state electron injection from these dyes was observed when adsorbed on the anatase epilayers. These results show that highly ordered anatase surfaces can be grown on an easily obtained substrate crystal.

  3. 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.

  4. In-situ NC-AFM measurements of high quality AlN(0001 layers grown at low growth rate on 4H-SiC(0001 and Si(111 substrates using ammonia molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Florian Chaumeton

    2015-06-01

    Full Text Available Nitride wide-band-gap semiconductors are used to make high power electronic devices or efficient light sources. The performance of GaN-based devices is directly linked to the initial AlN buffer layer. During the last twenty years of research on nitride growth, only few information on the AlN surface quality have been obtained, mainly by ex-situ characterization techniques. Thanks to a Non Contact Atomic Force Microscope (NC-AFM connected under ultra high vacuum (UHV to a dedicated molecular beam epitaxy (MBE chamber, the surface of AlN(0001 thin films grown on Si(111 and 4H-SiC(0001 substrates has been characterized. These experiments give access to a quantitative determination of the density of screw and edge dislocations at the surface. The layers were also characterized by ex-situ SEM to observe the largest defects such as relaxation dislocations and hillocks. The influence of the growth parameters (substrate temperature, growth speed, III/V ratio and of the initial substrate preparation on the dislocation density was also investigated. On Si(111, the large in-plane lattice mismatch with AlN(0001 (19% induces a high dislocation density ranging from 6 to 12×1010/cm2 depending on the growth conditions. On 4H-SiC(0001 (1% mismatch with AlN(0001, the dislocation density decreases to less than 1010/cm2, but hillocks appear, depending on the initial SiC(0001 reconstruction. The use of a very low growth rate of 10 nm/h at the beginning of the growth process allows to decrease the dislocation density below 2 × 109/cm2.

  5. 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

  6. Optimal Cu buffer layer thickness for growing epitaxial Co overlayers on Si(111)7 x 7

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Yu. P.; Zotov, A. V. [School of Natural Science, Far Eastern Federal University, 690950 Vladivostok (Russian Federation); Institute of Automation and Control Processes, 690041 Vladivostok (Russian Federation); Ilin, A. I.; Davydenko, A. V. [School of Natural Science, Far Eastern Federal University, 690950 Vladivostok (Russian Federation)

    2011-10-15

    Using scanning tunneling microscopy, reflection high energy diffraction and magnetic optical Kerr effect measurements, growth mode and the magnetic properties of epitaxial Co films on Si(111) with epitaxial Cu(111) buffer layers of various thicknesses have been studied. The strained 3.5-monolayer-thick Cu/Si(111) film has been found to be an optimal buffer, in which case an almost ideal layer-by-layer like growth of Co is observed up to six Co monolayers, due to a negligible lattice mismatch. The coercivity of Co films grown in this layer-by-layer like fashion has been determined to be about 10 Oe, testifying to the high quality of the formed Co film and Co/Cu interface. Changeover of the Co film growth mode from layer-by-layer like to multilayer has been found to result in the transition of the film magnetic properties from isotropic to markedly uniaxially anisotropic.

  7. Conductive layer for biaxially oriented semiconductor film growth

    Science.gov (United States)

    Findikoglu, Alp T.; Matias, Vladimir

    2007-10-30

    A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

  8. 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.

  9. 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.

  10. 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.)

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. Epitaxial Techniques for Compound Semiconductor Growth: from LPE to MOVPE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The epitaxial techniques are the most important processes in the production of semiconductor materials and optoelectronic devices. Liquid phase epitaxy (LPE) and metal organic vapor-phase epitaxy (MOVPE) particularly have many applications.The process characteristics and crystalline properties of both LPE and MOVPE techniques were introduced briefly, the compositional space suitable for LPE and MOVPE growth was discussed from the view point of thermodynamic equilibrium. The analysis and comparison show that on the one hand LPE and MOVPE have some advantages and characteristics in common; on the other hand, they may overcome each other′s weaknesses and deficiencies by offering their own special features.

  16. Substrate heater for the growth of epitaxial silicon films

    Science.gov (United States)

    Deming, Matthew; Varhue, Walter; Adams, Edward; Lavoie, Mark

    1999-03-01

    The single wafer processing of epitaxial Si films requires that special attention be paid to the design of the substrate heater assembly. This document describes the evolution and testing of an in situ heater used to deposit epitaxial Si films at temperatures as high as 700 °C. One problem encountered was the production of excessive levels of ultraviolet radiation which contributed to the desorption of water vapor from the vacuum chamber walls during the in situ cleaning process. A second problem involved the formation of a molybdenum containing film that poisoned epitaxial growth. A final proven in situ heater design is presented which avoids these problems.

  17. 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)

  18. 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.

  19. Improved radiation tolerance of MAPS using a depleted epitaxial layer

    Energy Technology Data Exchange (ETDEWEB)

    Dorokhov, A., E-mail: Andrei.Dorokhov@IReS.in2p3.f [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Bertolone, G.; Baudot, J.; Brogna, A.S.; Colledani, C.; Claus, G.; De Masi, R. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Deveaux, M. [Goethe-Universitaet Frankfurt am Main, Senckenberganlage 31, 60325 Frankfurt am Main (Germany); Doziere, G.; Dulinski, W. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Fontaine, J.-C. [Groupe de Recherche en Physique des Hautes Energies (GRPHE), Universite de Haute Alsace, 61, rue Albert Camus, 68093 Mulhouse (France); Goffe, M.; Himmi, A.; Hu-Guo, Ch.; Jaaskelainen, K.; Koziel, M.; Morel, F.; Santos, C.; Specht, M.; Valin, I. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France)

    2010-12-11

    Tracking performance of Monolithic Active Pixel Sensors (MAPS) developed at IPHC (Turchetta, et al., 2001) have been extensively studied (Winter, et al., 2001; Gornushkin, et al., 2002) . Numerous sensor prototypes, called MIMOSA, were fabricated and tested since 1999 in order to optimise the charge collection efficiency and power dissipation, to minimise the noise and to increase the readout speed. The radiation tolerance was also investigated. The highest fluence tolerable for a 10{mu}m pitch device was found to be {approx}10{sup 13}n{sub eq}/cm{sup 2}, while it was only 2x10{sup 12}n{sub eq}/cm{sup 2} for a 20{mu}m pitch device. The purpose of this paper is to show that the tolerance to non-ionising radiation may be extended up to O(10{sup 14}) n{sub eq}/cm{sup 2}. This goal relies on a fabrication process featuring a 15{mu}m thin, high resistivity ({approx}1k{Omega}cm) epitaxial layer. A sensor prototype (MIMOSA-25) was fabricated in this process to explore its detection performance. The depletion depth of the epitaxial layer at standard CMOS voltages (<5V) is similar to the layer thickness. Measurements with m.i.p.s show that the charge collected in the seed pixel is at least twice larger for the depleted epitaxial layer than for the undepleted one, translating into a signal-to-noise ratio (SNR) of {approx}50. Tests after irradiation have shown that this excellent performance is maintained up to the highest fluence considered (3x10{sup 13}n{sub eq}/cm{sup 2}), making evidence of a significant extension of the radiation tolerance limits of MAPS.

  20. High quality GaN-based LED epitaxial layers grown in a homemade MOCVD system

    Institute of Scientific and Technical Information of China (English)

    Yin Haibo; Wang Xiaoliang; Ran Junxue; Hu Guoxin; Zhang Lu; Xiao Hongling; Li Jing; Li Jinmin

    2011-01-01

    A homemade 7 × 2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown.The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%.Using the LED structural epitaxial layers,blue LED chips with area of 350 × 350μm2 were fabricated.Under 20 mA injection current,the optical output power of the blue LED is 8.62 mW.

  1. 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.

  2. 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.

  3. 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}.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Growth and characterization of group iiinitrides by migration-enhanced afterglow epitaxy

    Science.gov (United States)

    Gergova, Rositsa

    The work presented in this thesis investigates the growth and properties of group III- nitride semiconductors that were grown using the Migration Enhanced Afterglow Epitaxy (MEAglow) method. This work was to enhance the understanding of the MEAglow growth process towards the improvement of quality of the layers grown using this technique. The MEAglow technique applies the migration enhanced epitaxy method in a low pressure plasma-based CVD reactor, which has a potential of producing high quality epitaxial group III-nitride layers at relatively low growth temperatures on large deposition areas. The low temperature pulse growth in metal-rich regime, comprising the MME method was employed under growth pressures between 500 mTorr and 3000 mTorr. As the MME method up to this point has been used only for MBE systems, study of the impact of the growth pressure on the materials properties was necessary. In this work the pressure dependence was mapped to an existing surface phase diagram for MBE systems by calculating the number of nitrogen gas phase collisions and the metalorganic bombardment rate, for the specific to the prototype reactor parameters, to a first approximation. This was done in order to achieve an intermediate regime free of metal droplets for growth in metal-rich regime. High quality epitaxial InN layers were accomplished on extremely thin and smooth Ga2O3 buffer layers. These results indicate a potential for the application of Ga2O3 buffers in InN growth. The MEAglow InN layers were further optimized for growth on commercially available GaN buffer layers and excellent two-dimensional growth was achieved for layers grown under metal-rich conditions at 512 °C. Post-growth annealing studies were carried out for InN layers grown at temperatures below 400 °C to study the limiting processes of the removal of excess nitrogen, believed to be a dominant defect in InN films grown in plasma-based systems at very low temperatures. Variations in GaN stoichiometry

  10. 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.

  11. Growth of {110}-one-axis-oriented perovskite-type oxide films using self-aligned epitaxial (101)PdO//(111) Pd double layers

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hiroki [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Kariya, Tetsuro [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Sanyo Special Steel Co., Ltd, 3007, Nakashima, Shikama-ku, Himeji, Hyogo 672-8677 (Japan); Shimizu, Takao [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Uchiyama, Kiyoshi, E-mail: uchiyama@tsuruoka-nct.ac.jp [Department of Creative Engineering, National Institute of Technology, Tsuruoka College, 104 Inooka Sawada, Tsuruoka, Yamagata 997-8511 (Japan); Funakubo, Hiroshi [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan)

    2016-01-29

    Self-aligned (101)-one-axis-oriented PdO layer was obtained on (111) Pd films prepared on (111)Pt/TiO{sub x}/SiO{sub 2}/Si [abbreviated as (111)Pt/Si] substrates by the heat treatment at 750 °C under atmospheric oxygen flow. Films with (110){sub c}-oriented SrRuO{sub 3} with perovskite structure were successfully deposited at 500 °C on a (101)-oriented PdO layer by an RF magnetron sputtering method due to their relatively small lattice mismatch. A (101)-oriented Sr(Zr{sub 0.8}Y{sub 0.2})O{sub 3-δ} (SZYO) film can be successfully prepared on (110){sub c}-oriented SrRuO{sub 3} and its proton conductivity is almost the same as that of (111){sub c}-oriented SZYO but slightly smaller than that of (111){sub c}-oriented one. As the conductivity is strongly affected by the film crystallinity, we can conclude that the newly fabricated (110){sub c}-oriented SZYO has almost the same crystallinity comparing to the films with other orientation. We have successfully demonstrated that the use of (101)PdO//(111)Pd double layer is a good candidate to grow {110}-one-axis-oriented perovskite thin films on Si substrates. - Highlights: • Self-aligned (101)-one-axis-oriented PdO layer were obtained on (111) Pd films • (110){sub c}SrRuO{sub 3} perovskite can be deposited successfully on (101) PdO//Pd double layer • (101){sub c}Sr(Zr{sub 0.8}Y{sub 0.2})O{sub 3–δ} perovskite is also prepared by using (110){sub c} SrRuO{sub 3} layer • (101)PdO//(111)Pd is quite effective for growing {110}-oriented perovskite films.

  12. 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%.

  13. Epitaxial growth of pentacene films on Cu110.

    Science.gov (United States)

    Söhnchen, S; Lukas, S; Witte, G

    2004-07-01

    The molecular structure of thin pentacene (C(22)H(14)) films grown on a Cu(110) surface has been studied by means of He atom scattering, low energy electron diffraction, thermal desorption spectroscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. Depending on the actual film thickness three different crystalline phases have been identified which reveal a characteristic reorientation of the molecular plane relative to the substrate surface. In the monolayer regime the molecules form a highly ordered commensurate (6.5x2) structure with a planar adsorption geometry. For thin multilayers (thickness <2 nm) a second phase is observed which is characterized by a lateral ((-0.65 5.69) ( 1.90 1.37)) structure and a tilting of the molecular plane of about 28 degrees around their long axis which remains parallel to the surface. Finally, when exceeding a thickness of about 2 nm subsequent growth proceeds with an upright molecular orientation and leads to the formation of crystalline films which are epitaxially oriented with respect to the substrate. The present study thus demonstrates that also on metal substrates highly ordered pentacene films with an upright orientation of the molecular planes can be grown. Photoelectron spectroscopy data indicate further that thick films do not grow in a layer-by-layer mode but reveal a significant degree of roughness. (c) 2004 American Institute of Physics.

  14. 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.

  15. Schottky barrier detection devices having a 4H-SiC n-type epitaxial layer

    Science.gov (United States)

    Mandal, Krishna C.; Terry, J. Russell

    2016-12-06

    A detection device, along with methods of its manufacture and use, is provided. The detection device can include: a SiC substrate defining a substrate surface cut from planar to about 12.degree.; a buffer epitaxial layer on the substrate surface; a n-type epitaxial layer on the buffer epitaxial layer; and a top contact on the n-type epitaxial layer. The buffer epitaxial layer can include a n-type 4H--SiC epitaxial layer doped at a concentration of about 1.times.10.sup.15 cm.sup.-3 to about 5.times.10.sup.18 cm.sup.-3 with nitrogen, boron, aluminum, or a mixture thereof. The n-type epitaxial layer can include a n-type 4H--SiC epitaxial layer doped at a concentration of about 1.times.10.sup.13 cm.sup.-3 to about 5.times.10.sup.15 cm.sup.-3 with nitrogen. The top contact can have a thickness of about 8 nm to about 15 nm.

  16. 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.

  17. Epitaxial growth of HgTe by a MOVPE process

    Energy Technology Data Exchange (ETDEWEB)

    Irvine, S.J.C.; Mullin, J.B.; Royle, A. (Royal Signals and Radar Establishment, Malvern (UK))

    1982-03-01

    Epitaxial layers of HgTe have been grown onto insulating CdTe substrates by the pyrolysis of (C/sub 2/H/sub 5/)/sub 2/Te in the presence of Hg vapour using a H/sub 2/ flow system. Temperature-dependent Hall effect and conductivity measurements have shown that the electrical properties of the layers are comparable with good quality bulk HgTe.

  18. 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...

  19. 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.

  20. 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.

  1. Substrate-induced magnetism in epitaxial graphene buffer layers.

    Science.gov (United States)

    Ramasubramaniam, A; Medhekar, N V; Shenoy, V B

    2009-07-08

    Magnetism in graphene is of fundamental as well as technological interest, with potential applications in molecular magnets and spintronic devices. While defects and/or adsorbates in freestanding graphene nanoribbons and graphene sheets have been shown to cause itinerant magnetism, controlling the density and distribution of defects and adsorbates is in general difficult. We show from first principles calculations that graphene buffer layers on SiC(0001) can also show intrinsic magnetism. The formation of graphene-substrate chemical bonds disrupts the graphene pi-bonds and causes localization of graphene states near the Fermi level. Exchange interactions between these states lead to itinerant magnetism in the graphene buffer layer. We demonstrate the occurrence of magnetism in graphene buffer layers on both bulk-terminated as well as more realistic adatom-terminated SiC(0001) surfaces. Our calculations show that adatom density has a profound effect on the spin distribution in the graphene buffer layer, thereby providing a means of engineering magnetism in epitaxial graphene.

  2. 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.

  3. Misfit dislocation generation in SiGe epitaxial layers supersaturated with intrinsic point defects

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I. [Institute for Chemical Problems of Microelectronics, B. Tolmachevsky per. 5, 119017 Moscow (Russian Federation)], E-mail: vivdov@gmail.com; Zakharov, N.D. [Max-Planck-Institut fuer Mikrostrukturphysik, 06120 Halle (Saale) (Germany)], E-mail: zakharov@mpi-halle.mpg.de

    2008-11-03

    Misfit dislocation generation in SiGe/Si(001) heterostructures supersaturated with the vacancies (LT epitaxial growth) or self-interstitials (ion implantation) was studied by transmission electron microscopy. A model of 'optimal' intrinsic point defects (IPDs) for effective strain relaxation is suggested and verified. Supersaturation of compressed SiGe layers with the vacancies ('optimal' IPDs) promotes high strain relaxation, whereas supersaturation with the self-interstitials ('inverse' IPDs) promotes a generation of V-shaped TDs which cannot extend to form MDs.

  4. 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.)

  5. Above bandgap luminescence of p-type GaAs epitaxial layers

    Science.gov (United States)

    Sapriel, J.; Chavignon, J.; Alexandre, F.; Azoulay, R.; Sermage, B.; Rao, K.; Voos, M.

    1991-08-01

    New photoluminescence bands are observed in p-type GaAs epitaxial layers at 300 and 80 K, above the bandgap. These bands are independent of the nature of the dopant (Zn, Be, C) and of the growth technique (MBE or MOCVD). Their intensities increase as a function of the p doping (1 × 10 17 < p < 2 × 10 20cm-3) and peak at energies which correspond to transitions between the Γ 6, L 6 and X 6 minima of the conduction band and the Γ 8 and Γ 7 maxima of the valence band.

  6. Selective epitaxial growth of Ge1-xSnx on Si by using metal-organic chemical vapor deposition

    Science.gov (United States)

    Washizu, Tomoya; Ike, Shinichi; Inuzuka, Yuki; Takeuchi, Wakana; Nakatsuka, Osamu; Zaima, Shigeaki

    2017-06-01

    Selective epitaxial growth of Ge and Ge1-xSnx layers on Si substrates was performed by using metal-organic chemical vapor deposition (MOCVD) with precursors of tertiary-butyl-germane (t-BGe) and tri-butyl-vinyl-tin (TBVSn). We investigated the effects of growth temperature and total pressure during growth on the selectivity and the crystallinity of the Ge and Ge1-xSnx epitaxial layers. Under low total pressure growth conditions, the dominant mechanism of the selective growth of Ge epitaxial layers is the desorption of the Ge precursors. At a high total pressure case, it is needed to control the surface migration of precursors to realize the selectivity because the desorption of Ge precursors was suppressed. The selectivity of Ge growth was improved by diffusion of the Ge precursors on the SiO2 surfaces when patterned substrates were used at a high total pressure. The selective epitaxial growth of Ge1-xSnx layer was also realized using MOCVD. We found that the Sn precursors less likely to desorb from the SiO2 surfaces than the Ge precursors.

  7. 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.

  8. Metal organic vapor phase epitaxy growth of (Al)GaN heterostructures on SiC/Si(111) templates synthesized by topochemical method of atoms substitution

    DEFF Research Database (Denmark)

    Rozhavskaia, Mariia M.; Kukushkin, Sergey A.; Osipov, Andrey

    2017-01-01

    crystalline interfaces with epitaxial relationship between SiC/Si and AlN/SiC layers. Optimization of SiC morphology and AlN seed layer thickness facilitates the growth of GaN layers free of pits (v-defects). It is also found that Si doping eliminates these defects in the case of growth on SiC templates...

  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. 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.

  11. 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.

  12. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    Science.gov (United States)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Posadas, Agham; Demkov, Alexander A.; Ekerdt, John G.

    2015-12-01

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al2O3 and HfO2. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO3), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  13. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G., E-mail: ekerdt@utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-12-15

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al{sub 2}O{sub 3} and HfO{sub 2}. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO{sub 3}), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  14. 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.

  15. 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.

  16. Arsenic-Doped High-Resistivity-Silicon Epitaxial Layers for Integrating Low-Capacitance Diodes

    Directory of Open Access Journals (Sweden)

    Jaber Derakhshandeh

    2011-12-01

    Full Text Available An arsenic doping technique for depositing up to 40-μm-thick high-resistivity layers is presented for fabricating diodes with low RC constants that can be integrated in closely-packed configurations. The doping of the as-grown epi-layers is controlled down to 5 × 1011 cm−3, a value that is solely limited by the cleanness of the epitaxial reactor chamber. To ensure such a low doping concentration, first an As-doped Si seed layer is grown with a concentration of 1016 to 1017 cm−3, after which the dopant gas arsine is turned off and a thick lightly-doped epi-layer is deposited. The final doping in the thick epi-layer relies on the segregation and incorporation of As from the seed layer, and it also depends on the final thickness of the layer, and the exact growth cycles. The obtained epi-layers exhibit a low density of stacking faults, an over-the-wafer doping uniformity of 3.6%, and a lifetime of generated carriers of more than 2.5 ms. Furthermore, the implementation of a segmented photodiode electron detector is demonstrated, featuring a 30 pF capacitance and a 90 Ω series resistance for a 7.6 mm2 anode area.

  17. 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.

  18. 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.

  19. Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Claudel, A., E-mail: arnaud.claudel@grenoble-inp.org [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Fellmann, V. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Gélard, I. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Coudurier, N. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Sauvage, D. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Balaji, M. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Crystal Growth Center, Anna University, Chennai 600025 (India); and others

    2014-12-31

    Thin (0001) epitaxial aluminum nitride (AlN) layers were grown on c-plane sapphire using high temperature hydride vapor phase epitaxy. The experimental set-up consists of a vertical cold-wall quartz reactor working at low pressure in which the reactions take place on a susceptor heated by induction. The reactants used are ammonia and aluminum chlorides in situ formed via hydrogen chloride reaction with high purity aluminum pellets. As-grown AlN layers have been characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence and Raman spectroscopies. The influence of the V/III ratio in the gas phase, from 1.5 to 15, on growth rate, surface morphology, roughness and crystalline quality is investigated in order to increase the quality of thin epitaxial AlN layers grown at high temperature. Typical growth rates of around 0.45 μm/h were obtained for such thin epitaxial AlN layers. The growth rate was unaffected by the V/III ratio. An optimum for roughness, crystalline quality and optical properties seems to exist at V/III = 7.5. As a matter of fact, for a V/III ratio of 7.5, best root mean square roughness and crystalline quality — measured on 0002 symmetric reflection — as low as 6.9 nm and 898 arcsec were obtained, respectively. - Highlights: • Growth of thin epitaxial AlN layers by high temperature hydride vapor phase epitaxy • Influence of V/III ratio on growth rate, morphology and crystalline quality • The effect of surface morphology on strain state and crystal quality is established.

  20. 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.

  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 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...

  3. 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.

  4. 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.

  5. 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.

  6. The role of Energy Deposition in the Epitaxial Layer in Triggering SEGR in Power MOSFETs

    Science.gov (United States)

    Selva, L.; Swift, G.; Taylor, W.; Edmonds, L.

    1999-01-01

    In these SEGR experiments, three identical-oxide MOSFET types were irradiated with six ions of significantly different ranges. Results show the prime importance of the total energy deposited in the epitaxial layer.

  7. Epitaxial growth and dielectric properties of Bi sub 2 VO sub 5 sub . sub 5 thin films on TiN/Si substrates with SrTiO sub 3 buffer layers

    CERN Document Server

    Lee, H Y; Choi, B C; Jeong, J H; Joseph, M; Tabata, H; Kawai, T

    2000-01-01

    Bi sub 2 VO sub 5 sub . sub 5 (BVO) thin films were epitaxially grown on SrTiO sub 3 /TiN/Si substrates by using pulsed laser ablation. A TiN thin film was prepared at 700 .deg. C as a bottom electrode. The TiN film exhibited a high alpha axis orientation and a very smooth morphology. Before the preparation of the BVO thin film, a crystallized SrTiO sub 3 thin film was deposited as a buffer layer on TiN/Si. The BVO thin film grown at a substrate temperature at 700 .deg. C and an oxygen pressure of 50 mTorr was found to be epitaxial along the c-axis. Also, BVO films were observed to have flat surfaces and the step-flow modes. The dielectric constant of the BVO film on STO/TiN/Si was constant at about 8 approx 4 in the applied frequency range between 10 sup 2 and 10 sup 6 Hz.

  8. 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.

  9. Planarization and Processing of Metamorphic Buffer Layers Grown by Hydride Vapor-Phase Epitaxy

    Science.gov (United States)

    Zutter, Brian T.; Schulte, Kevin L.; Kim, Tae Wan; Mawst, Luke J.; Kuech, T. F.; Foran, Brendan; Sin, Yongkun

    2014-04-01

    Hydride vapor-phase epitaxy (HVPE) is a high-growth-rate, cost-effective means to grow epitaxial semiconductor material. Thick HVPE-based metamorphic buffer layers (MBLs) can serve as "pseudosubstrates" with controllable lattice parameter. In our structures, the indium content in In x Ga1- x As is gradually increased from zero to the final composition corresponding to the desired lattice constant, and then a thick (˜10 μm) constant-composition capping layer is grown. This thick capping layer promotes maximum strain relaxation while permitting use of polishing procedures to achieve surface planarity. Lattice-mismatched growth of MBLs invariably results in rough, cross-hatched surface morphology exhibiting up to 200 nm peak-to-valley roughness. This roughness can be eliminated by chemical mechanical planarization, thus creating a suitable surface for subsequent regrowth. Polishing of In x Ga1- x As is complicated by the sensitivity of the surface layer to the polishing parameters, particularly the applied pressure. Polishing at high applied pressure (12 psi) results in the formation of circular asperities hundreds of nanometers high and tens of microns in diameter. When lower applied pressure (4 psi) was used, the cross-hatching height of MBLs was lowered from 200 nm to <10 nm over a 350 μm lateral scale. The successfully planarized In0.20Ga0.80As MBLs were used as a substrate for a superlattice (SL) structure such as that used in quantum cascade lasers. Use of planarization before regrowth of the SL resulted in a reduction of the high-resolution x-ray diffraction peak full-width at half-maximum from 389″ to 159″.

  10. Blanket and Patterned Growth of CdTe on (211)Si Substrates by Metal-Organic Vapor Phase Epitaxy

    Science.gov (United States)

    2012-05-15

    REPORT Blanket and Patterned Growth Of CdTE On (211)Si Substrates By Metal-Organic Vapor Phase Epitaxy 14. ABSTRACT 16. SECURITY CLASSIFICATION OF...Metalorganic vapor phase epitaxy (MOVPE) of (211)B CdTe on (211)Si using intermediate Ge and ZnTe layers has been achieved for use as substrates for the...growth of HgCdTe infrared detector materials. The best (211)B CdTe films grown in this study display a low X-ray diffraction (XRD) rocking-curve

  11. 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...

  12. 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...

  13. Growth and characterization of YAG:Cr4+epitaxial films

    Science.gov (United States)

    Ubizskii, Sergii B.; Syvorotka, Igor M.; Melnyk, Sergii S.; Matkovskii, Andrej O.; Kopczynski, Krzysztof; Mierczyk, Zygmunt; Frukacz, Zygmunt

    1999-03-01

    Epitaxial films with thickness of 10 - 250 micrometers of yttrium aluminum garnet (YAG) doped with Cr were grown by liquid phase epitaxy technique on YAG:Nd substrates. Co-doping with Mg2+ is used to force the Cr4+ valent state formation. Dependence of absorption spectra of obtained films on melt-solution composition, growth conditions and thermal treatment in reducing and oxidizing atmospheres is studied. A very intensive absorption band in UV region with maximum at 275 nm was found both in co-doped and YAG:Mg2+ epifilms caused probably by oxygen vacancies compensating the excess charge of Mg2+. Its intensity correlates with Cr4+ content in the film in that way: it decreases with Cr4+ entering in the film. The absorption being characteristic for YAG:Cr4+ crystals is found in co-doped films grown at higher temperatures (1000 - 1100 degree(s)C). The processes occurring during annealing are discussed.

  14. Hafnium nitride buffer layers for growth of GaN on silicon

    Science.gov (United States)

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16

    Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

  15. Undoped and in-situ B doped GeSn epitaxial growth on Ge by atmospheric pressure-chemical vapor deposition

    DEFF Research Database (Denmark)

    Vincent, B.; Gencarelli, F.; Bender, H.

    2011-01-01

    In this letter, we propose an atmospheric pressure-chemical vapor deposition technique to grow metastable GeSn epitaxial layers on Ge. We report the growth of defect free fully strained undoped and in-situ B doped GeSn layers on Ge substrates with Sit contents up to 8%. Those metastable layers stay...

  16. Si(111)衬底上多层石墨烯薄膜的外延生长%Epitaxial Growth of Multi-layer Graphene on the Substrate of Si(111)

    Institute of Scientific and Technical Information of China (English)

    李利民; 唐军; 康朝阳; 潘国强; 闫文盛; 韦世强; 徐彭寿

    2011-01-01

    Graphene thin films were epitaxial grown on Si(111) substrates by depositing carbon atoms with solid source molecular beam epitaxy (SSMBE). The structural properties of the samples deposited at different substrate temperature (400, 600, 700 and 800℃) were investigated by reflection high energy electron diffraction (RHEED),Fourier transform infrared spectroscope (FTIR), Raman spectroscope (RAMAN) and near-edge X-ray absorption fine-structure (NEXAFS). RAMAN and NEXAFS results indicated that the thin film deposited at 800℃ exhibited the characteristic of graphene, while the thin films deposited at 400℃, 600℃ and 700℃ were attributed to amorphous or polycrystalline carbon thin films. RHEED and FTIR results indicated that C atoms did not bond with Si atoms at the substrate temperature below 600℃, however, above 700℃, C atoms reacted with Si atoms and formed the SiC buffer layer. Furthermore, the better quality of SiC buffer layer could be obtained at 800℃. Thus, high substrate temperature and high-quality SiC buffer layers are essential to the formation of the graphene layers on the Si substrates.%利用固源分子束外延(SSMBE)技术,在Si(111)衬底上沉积碳原子外延生长石墨烯薄膜,通过反射式高能电子衍射(RHEED)、红外吸收谱(FTIR)、拉曼光谱(RAMAN)和X射线吸收精细结构谱(NEXAFS)等手段对不同衬底温度(400、600、700、800℃)生长的薄膜进行结构表征.RAMAN和NEXAFS结果表明:在800℃下制备的薄膜具有石墨烯的特征,而400、600和700℃生长的样品为非晶或多晶碳薄膜.RHEED和FTIR结果表明,沉积温度在600℃以下时C原子和衬底Si原子没有成键,而衬底温度提升到700℃以上,沉积的C原子会先和衬底Si原子反应形成SiC缓冲层,且在800℃沉积时缓冲层质量较好.因此在Si衬底上制备石墨烯薄膜需要较高的衬底温度和高质量的SiC缓冲层.

  17. 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.

  18. Electrical transport in thin BeSeTe/Si epitaxial layers

    Science.gov (United States)

    Clark, Kevin; Maldonado, Eduardo; Basit, Nasir; Sandu, Titus; Bate, Robert; Kirk, Wiley

    2003-03-01

    Beryllium selenide telluride BeSe_0.41Te_0.59 is a II-VI semiconductor lattice-matched to silicon. For Si-based optoelectronic heterostructures, BeSeTe has planar epitaxial growth, covalent fault-resistant bonding, and thermal and chemical stability. BeSeTe has an indirect bandgap of 3.0eV, from a tight-binding model alloy of the indirect-gap constituents BeTe (2.7eV) and BeSe (4.5eV). Growth, fabrication, and vertical transport measurements were done for several thin ˜30-100ÅBeSeTe/Si structures in a range of compositions and thicknesses. I-V and I-T characteristics of the thinnest layers were modeled by direct tunneling while thicker layers were modeled by trap-assisted transport. Excess current was remarkably suppressed in composite films with a BeSeTe interface and a zinc chalcogenide (ZnS, ZnSe) cap layer. C-V measurements showed growth of low interface-state density BeSeTe/Si interfaces requires avoiding any excess Te flux at the interface.

  19. 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.

  20. Epitaxial growth of ZnO nanorod arrays via a self-assembled microspheres lithography

    Science.gov (United States)

    Lin, Bo-Cheng; Ku, Ching-Shun; Lee, Hsin-Yi; Wu, Albert T.

    2017-08-01

    Through a simple hydrothermal method, well-aligned and periodic honeycomb-like ZnO nanorod arrays were fabricated on a c-plane sapphire with an aluminum-doped ZnO (AZO) seed layer. Vertical and highly ordered ZnO nanostructures with the orientation were synthesized by employing a self-assembled monolayer of polystyrene (PS) microspheres as a mask. The optimal growth conditions allowed the growth of only one rod in the confined space between the microspheres. A ϕ-scan exhibited six-fold symmetry, which indicates a favorable epitaxial relationship between the ZnO nanorods, seed layer, and c-plane sapphire substrate. The epitaxial relation is as follows: [0001]ZnO∥[0001]AZO∥[0001]c-planesapphire. These results indicate that the AZO seed layer acts as a buffer layer that can relax the strain between ZnO and c-plane sapphire generated by the large lattice mismatch of 18%. The size of the resulting ZnO nanorods of diameter 20-90 nm could be tuned by varying the concentration of the solution, pH, and duration of reaction. The large aspect ratio of the ZnO nanorod arrays can serve as a template for high-surface-area applications.

  1. Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template

    Science.gov (United States)

    Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

    2016-01-01

    Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi2Se3 epitaxial heterostructures by using two-dimensional (2D) Bi2Se3 nanoplates as soft templates. The dangling bond–free surface of 2D Bi2Se3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi2Se3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi2Se3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi2Se3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi2Se3 nanoplates. We further show that the resulted PbSe/Bi2Se3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi2Se3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions. PMID:27730211

  2. Real structure of the ZnO epitaxial films on (0001) leucosapphire substrates coated by ultrathin gold layers

    Energy Technology Data Exchange (ETDEWEB)

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kolymagin, A. B.; Vasilyev, A. L.; Kanevsky, V. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2016-01-15

    The real structure of ZnO films formed by magnetron sputtering on (0001) leucosapphire substrates coated by an ultrathin (less than 0.7 nm) Au buffer layer has been studied by high-resolution microscopy. It is shown that modification of the leucosapphire substrate surface by depositing ultrathin Au layers does not lead to the formation of Au clusters at the film–substrate interface but significantly improves the structural quality of ZnO epitaxial films. It is demonstrated that the simplicity and scalability of the technique used to modify the substrate surface in combination with a high (above 2 nm/s) film growth rate under magnetron sputtering make it possible to obtain high-quality (0001) ZnO epitaxial films with an area of 5–6 cm{sup 2}.

  3. 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.

  4. Control of epitaxial growth at a-Si:H/c-Si heterointerface by the working pressure in PECVD

    Science.gov (United States)

    Shen, Yanjiao; Chen, Jianhui; Yang, Jing; Chen, Bingbing; Chen, Jingwei; Li, Feng; Dai, Xiuhong; Liu, Haixu; Xu, Ying; Mai, Yaohua

    2016-11-01

    The epitaxial-Si (epi-Si) growth on the crystalline Si (c-Si) wafer could be tailored by the working pressure in plasma-enhanced chemical vapor deposition (PECVD). It has been systematically confirmed that the epitaxial growth at the hydrogenated amorphous silicon (a-Si:H)/c-Si interface is suppressed at high pressure (hp) and occurs at low pressure (lp). The hp a-Si:H, as a purely amorphous layer, is incorporated in the lp-epi-Si/c-Si interface. We find that: (i) the epitaxial growth can also occur at a-Si:H coated c-Si wafer as long as this amorphous layer is thin enough; (ii) with the increase of the inserted hp layer thickness, lp epi-Si at the interface is suppressed, and the fraction of a-Si:H in the thin films increases and that of c-Si decreases, corresponding to the increasing minority carrier lifetime of the sample. Not only the epitaxial results, but also the quality of the thin films at hp also surpasses that at lp, leading to the longer minority carrier lifetime of the hp sample than the lp one although they have the same amorphous phase. Project supported by the Natural Science Foundation of Hebei Province, China (Grant No. E2015201203) and the International Society for Theoretical Chemical Physics of China (Grant No. 2015DFE62900).

  5. 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}.

  6. Atomic layer deposition of metastable β-Fe₂O₃ via isomorphic epitaxy for photoassisted water oxidation.

    Science.gov (United States)

    Emery, Jonathan D; Schlepütz, Christian M; Guo, Peijun; Riha, Shannon C; Chang, Robert P H; Martinson, Alex B F

    2014-12-24

    We report the growth and photoelectrochemical (PEC) characterization of the uncommon bibyite phase of iron(III) oxide (β-Fe2O3) epitaxially stabilized via atomic layer deposition on an conductive, transparent, and isomorphic template (Sn-doped In2O3). As a photoanode, unoptimized β-Fe2O3 ultrathin films perform similarly to their ubiquitous α-phase (hematite) counterpart, but reveal a more ideal bandgap (1.8 eV), a ∼0.1 V improved photocurrent onset potential, and longer wavelength (>600 nm) spectral response. Stable operation under basic water oxidation justifies further exploration of this atypical phase and motivates the investigation of other unexplored metastable phases as new PEC materials.

  7. Segregation of Sb in Ge epitaxial layers and its usage for the selective doping of Ge-based structures

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, A. V.; Drozdov, M. N.; Novikov, A. V., E-mail: anov@ipmras.ru; Yurasov, D. V. [Institute for Physics of Microstructures of the Russian Academy of Sciences (Russian Federation)

    2015-11-15

    The segregation of Sb in Ge epitaxial layers grown by the method of molecular beam epitaxy on Ge (001) substrates is investigated. For a growth temperature range of 180–325°C, the temperature dependence is determined for the segregation ratio of Sb in Ge, which shows a sharp increase (by more than three orders of magnitude) with increasing temperature. The strong dependence of the segregation properties of Sb on the growth temperature makes it possible to adapt a method based on the controlled use of segregation developed previously for the doping of Si structures for the selective doping of Ge structures with a donor impurity. Using this method selectively doped Ge:Sb structures, in which the bulk impurity concentration varies by an order of magnitude at distances of 3–5 nm, are obtained.

  8. Spin transport in epitaxial magnetic manganite/ruthenate heterostructures with an LaMnO{sub 3} layer

    Energy Technology Data Exchange (ETDEWEB)

    Petrzhik, A. M., E-mail: petrzhik@hitech.cplire.ru; Ovsyannikov, G. A.; Shadrin, A. V. [Russian Academy of Sciences, Kotel’nikov Institute of Radio Engineering and Electronics (Russian Federation); Khaidukov, Yu. N.; Mustafa, L. [Max-Plank Institute for Solid State Research (Germany)

    2014-12-15

    Epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/LaMnO{sub 3}/SrRuO{sub 3} (LSMO/LMO/SRO) heterostructures with an LMO layer 0–35 nm thick are grown by laser ablation on an NdGaO{sub 3} substrate at a high temperature. X-ray diffraction and transmission electron microscopy demonstrate sharp interfaces and epitaxial growth of the LSMO and SRO layers in the heterostructures at an LMO layer thickness of 0–35 nm. SQUID measurements of the magnetic moment of the heterostructures with an LMO layer and the data obtained with reflectometry of polarized neutrons show that the manganite LMO layer is a ferromagnet at a temperature below 150 K and strongly affects the magnetic moment of the heterostructures at low temperatures. The magnetoresistance of the mesostructure created from the heterostructure using lithography and ion etching decreases with increasing LMO layer thickness and weakly depends on the direction of an applied magnetic field. If the LMP layer is absent, a negative magnetoresistance is detected; it is likely to be caused by a negative magnetization of the SRO layer.

  9. The use of helium ion RBS for profiling epitaxial layers of Cd sub x Hg sub 1-x Te

    Energy Technology Data Exchange (ETDEWEB)

    Avery, A.J.; Diskett, D.J.; Lane, D.W. (Royal Military Coll. of Science, Shrivenham, Swindon, Wiltshire (UK)); Giess, J.; Irvine, S.J.C. (Royal Signals and Radar Establishment, Malvern, Worcestershire (UK))

    1990-01-01

    This paper describes the application of helium ion RBS and channelling to the characterization of an epitaxial layer of Cd{sub x}Hg{sub 1-x}Te. The layer was grown by MOVPE on a substrate of GaAs as part of a programme for developing infrared detector materials. The use of RBS with the aid of computer techniques is discussed for obtaining compositional (x) profiles both within the layers and, in particular, in the near-surface region. Conventional- and grazing-geometry measurements have been used to establish layer quality and interfacial abruptness. Variations in composition close to the surface have been correlated with the conditions under which layer growth was terminated. Channelling measurements are presented for the assessment of the layer crystalline quality. (orig.).

  10. Defect and dislocation structures in low-temperature-grown Ge and Ge{sub 1−x}Sn{sub x} epitaxial layers on Si(110) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kidowaki, Shohei [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Asano, Takanori [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Research Fellow of Japan Society for the Promotion of Science, 5-3-1, Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Shimura, Yosuke [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kurosawa, Masashi [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Taoka, Noriyuki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nakatsuka, Osamu, E-mail: nakatuka@alice.xtal.nagoya-u.ac.jp [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2016-01-01

    We have investigated the epitaxial growth and crystalline properties of Ge{sub 1−x}Sn{sub x} layers on a Si(110) substrate. We found that the twin growth in the Ge epitaxial layer deposited on the Si(110) using molecular beam epitaxy at a low temperature of 200 °C can be effectively suppressed by the incorporation of 2.0% Sn. We also examined the strain relaxation of annealed Ge{sub 1−x}Sn{sub x}/Si(110) samples. The degree of strain relaxation is enhanced by the annealing process, and the threading dislocation in the Ge{sub 1−x}Sn{sub x} layers decreases from 10{sup 11} cm{sup −2} to 10{sup 10} cm{sup −2} because of the propagation of misfit dislocations. We also observed misfit dislocations formed at the Ge{sub 1−x}Sn{sub x}/Si interface, which would effectively promote isotropic strain relaxation in the Ge{sub 1−x}Sn{sub x} layers. - Highlights: • Suppression of twin in GeSn growth on Si(110) substrate • Isotropic strain relaxation of Ge and GeSn layers by misfit dislocation network • Achievement of high quality GeSn epitaxial layers on Si(110) by post deposition annealing.

  11. 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.

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

    Science.gov (United States)

    Chang, Y. Austin; Yang, Jianhua Joshua

    2008-11-11

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

  14. Growth, structural, and electrical properties of germanium-on-silicon heterostructure by molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Aheli Ghosh

    2017-09-01

    Full Text Available The growth, morphological, and electrical properties of thin-film Ge grown by molecular beam epitaxy on Si using a two-step growth process were investigated. High-resolution x-ray diffraction analysis demonstrated ∼0.10% tensile-strained Ge epilayer, owing to the thermal expansion coefficient mismatch between Ge and Si, and negligible epilayer lattice tilt. Micro-Raman spectroscopic analysis corroborated the strain-state of the Ge thin-film. Cross-sectional transmission electron microscopy revealed the formation of 90  ° Lomer dislocation network at Ge/Si heterointerface, suggesting the rapid and complete relaxation of Ge epilayer during growth. Atomic force micrographs exhibited smooth surface morphology with surface roughness < 2 nm. Temperature dependent Hall mobility measurements and the modelling thereof indicated that ionized impurity scattering limited carrier mobility in Ge layer. Capacitance- and conductance-voltage measurements were performed to determine the effect of epilayer dislocation density on interfacial defect states (Dit and their energy distribution. Finally, extracted Dit values were benchmarked against published Dit data for Ge MOS devices, as a function of threading dislocation density within the Ge layer. The results obtained were comparable with Ge MOS devices integrated on Si via alternative buffer schemes. This comprehensive study of directly-grown epitaxial Ge-on-Si provides a pathway for the development of Ge-based electronic devices on Si.

  15. 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

  16. 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

  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. Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

    Directory of Open Access Journals (Sweden)

    Rui Sun

    2016-06-01

    Full Text Available We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100 substrates with a TiN buffer layer. A 50-nm-thick (200-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large IcRN product of 3.8 mV, a sharp quasiparticle current rise with a ΔVg of 0.4 mV, and a small subgap leakage current. The junction quality factor Rsg/RN was about 23 for the junction with a Jc of 47 A/cm2 and was about 6 for the junction with a Jc of 3.0 kA/cm2. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200-orientated TiN buffer layer and had a highly crystalline structure with the (200 orientation.

  19. Bulk growth and surface characterization of epitaxy ready cadmium zinc telluride substrates for use in IR imaging applications

    Science.gov (United States)

    Flint, J. P.; Martinez, B.; Betz, T. E. M.; MacKenzie, J.; Kumar, F. J.; Bindley, G.

    2016-05-01

    Cadmium Zinc Telluride (CZT) is an important compound semiconductor material upon which Mercury Cadmium Telluride (MCT) layers are deposited epitaxially to form structures that are used in high performance detectors covering a wide infrared (IR) spectral band. The epitaxial growth of high quality MCT layers presents many technical challenges and a critical determinant of material performance is the quality of the underlying bulk CZT substrate. CZT itself is a difficult material to manufacture where traditional methods of bulk growth are complex and low yielding, which constrains the supply of commercially available substrates. In this work we report on the epitaxy-ready finishing of Travelling Heather Method (THM) grown Cd0.96Zn0.04Te substrates. The THM method is well established for the growth of high quality CZT crystals used in nuclear, X-ray and spectroscopic imaging applications and in this work we demonstrate the application of this technique to the growth of IR specification CZT substrates with areas of up to 5 cm x 5 cm square. We will discuss the advantages of the THM method over alternative methods of bulk CZT growth where the high yield and material uniformity advantages of this technique will be demonstrated. Chemo-mechanical polishing (CMP) of 4 cm x 4 cm CZT substrates reveals that III-V (InSb/GaSb) like levels of epitaxy-ready surface finishing may be obtained with modified process chemistries. Surface quality assessments will be made by various surface analytical and microscopy techniques from which the suitability of the material for subsequent assessment of quality by epitaxial growth will be ascertained.

  20. Weakly doped InP layers prepared by liquid phase epitaxy using a modulated cooling rate

    Science.gov (United States)

    Krukovskyi, R.; Mykhashchuk, Y.; Kost, Y.; Krukovskyi, S.; Saldan, I.

    2017-04-01

    Epitaxial structures based on InP are widely used to manufacture a number of devices such as microwave transistors, light-emitting diodes, lasers and Gunn diodes. However, their temporary instability caused by heterogeneity of resistivity along the layer thickness and the influence of various external or internal factors prompts the need for the development of a new reliable technology for their preparation. Weak doping by Yb, Al and Sn together with modulation of the cooling rate applied to prepare InP epitaxial layers is suggested to be adopted within the liquid phase epitaxy (LPE) method. The experimental results confirm the optimized conditions created to get a uniform electron concentration in the active n-InP layer. A sharp profile of electron concentration in the n+-InP(substrate)/n-InP/n+-InP epitaxial structure was observed experimentally at the proposed modulated cooling rate of 0.3 °С-1.5 °С min-1. The proposed technological method can be used to control the electrical and physical properties of InP epitaxial layers to be used in Gunn diodes.

  1. 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.

  2. Structural Properties of Alternate Monatomic Layered [Fe/Co]n Epitaxial Films on MgO Substrate

    Science.gov (United States)

    Chu, In Chang; Saki, Yoshinobu; Kawasaki, Shohei; Doi, Masaaki; Sahashi, Masashi

    2008-06-01

    Body-centered-cubic (bcc) Fe50Co50 material is reported to show a high bulk spin scattering coefficient on current perpendicular to plane-giant magneto-resistance (CPP-GMR) system. But the origin of that phenomenon does not make sure yet. We prepared artificially alternate monatomic layered (AML) [Fe/Co] 41 MLs epitaxial films (Ts: 75, 250 °C) by monatomic deposition method and investigated the topology of AML [Fe/Co]n epitaxial films on MgO substrate with different orientation (001), (011) by the scanning tunnel microscopy (STM) and reflection high energy electron diffraction (RHEED), which we could confirm Frank-van der Merwe (FM) growth mode for AML [Fe/Co]n on MgO(001) and Volmer-Weber (VW) growth mode for that on Mg(011). The roughness of surface, Ra (0.20 nm) of AML [Fe/Co] 41 MLs epitaxial film grown at 75 °C on MgO(001) is smaller than that (0.46 nm) of AML [Fe/Co] grown at 250 °C on MgO(001), which has the large terraces of over 50 nm (Ra: 0.17 nm), even though there are some valleys between large terraces. Moreover we confirmed the structural properties of trilayered epitaxial films with AML [Fe/Co]n (Ra: 0.18 nm) and Fe50Co50 alloy epitaxial film on Au electrode by RHEED before confirming the characteristics of CPP-GMR devices.

  3. Methods for improved growth of group III nitride buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  4. Methods for improved growth of group III nitride buffer layers

    Science.gov (United States)

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

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

    Energy Technology Data Exchange (ETDEWEB)

    Cerio, Frank

    2013-09-14

    The DOE has set aggressive goals for solid state lighting (SSL) adoption, which require manufacturing and quality improvements for virtually all process steps leading to an LED luminaire product. The goals pertinent to this proposed project are to reduce the cost and improve the quality of the epitaxial growth processes used to build LED structures. The objectives outlined in this proposal focus on achieving cost reduction and performance improvements over state-of-the-art, using technologies that are low in cost and amenable to high efficiency manufacturing. The objectives of the outlined proposal focus on cost reductions in epitaxial growth by reducing epitaxy layer thickness and hetero-epitaxial strain, and by enabling the use of larger, less expensive silicon substrates and would be accomplished through the introduction of a high productivity reactive sputtering system and an effective sputtered aluminum-nitride (AlN) buffer/nucleation layer process. Success of the proposed project could enable efficient adoption of GaN on-silicon (GaN/Si) epitaxial technology on 150mm silicon substrates. The reduction in epitaxy cost per cm{sup 2} using 150mm GaN-on-Si technology derives from (1) a reduction in cost of ownership and increase in throughput for the buffer deposition process via the elimination of MOCVD buffer layers and other throughput and CoO enhancements, (2) improvement in brightness through reductions in defect density, (3) reduction in substrate cost through the replacement of sapphire with silicon, and (4) reduction in non-ESD yield loss through reductions in wafer bow and temperature variation. The adoption of 150mm GaN/Si processing will also facilitate significant cost reductions in subsequent wafer fabrication manufacturing costs. There were three phases to this project. These three phases overlap in order to aggressively facilitate a commercially available production GaN/Si capability. In Phase I of the project, the repeatability of the performance

  6. 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

  7. Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented β-Y2Si2O7 Layer and Epitaxial ZrO2

    Science.gov (United States)

    Wisniewski, Wolfgang; Seidel, Sabrina; Patzig, Christian; Rüssel, Christian

    2017-03-01

    The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3 is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7 (YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2 (Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2 and ε-YS is proven and multiple twinning relationships occur in the YS phases.

  8. Heat resistive dielectric multi-layer micro-mirror array in epitaxial lateral overgrowth gallium nitride.

    Science.gov (United States)

    Huang, Chen-Yang; Ku, Hao-Min; Liao, Wei-Tsai; Chao, Chu-Li; Tsay, Jenq-Dar; Chao, Shiuh

    2009-03-30

    Ta2O5 / SiO2 dielectric multi-layer micro-mirror array (MMA) with 3mm mirror size and 6mm array period was fabricated on c-plane sapphire substrate. The MMA was subjected to 1200 degrees C high temperature annealing and remained intact with high reflectance in contrast to the continuous multi-layer for which the layers have undergone severe damage by 1200 degrees C annealing. Epitaxial lateral overgrowth (ELO) of gallium nitride (GaN) was applied to the MMA that was deposited on both sapphire and sapphire with 2:56 mm GaN template. The MMA was fully embedded in the ELO GaN and remained intact. The result implies that our MMA is compatible to the high temperature growth environment of GaN and the MMA could be incorporated into the structure of the micro-LED array as a one to one micro backlight reflector, or as the patterned structure on the large area LED for controlling the output light.

  9. 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.

  10. Epitaxial TiO 2/SnO 2 core-shell heterostructure by atomic layer deposition

    KAUST Repository

    Nie, Anmin

    2012-01-01

    Taking TiO 2/SnO 2 core-shell nanowires (NWs) as a model system, we systematically investigate the structure and the morphological evolution of this heterostructure synthesized by atomic layer deposition/epitaxy (ALD/ALE). All characterizations, by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction and Raman spectra, reveal that single crystalline rutile TiO 2 shells can be epitaxially grown on SnO 2 NWs with an atomically sharp interface at low temperature (250 °C). The growth behavior of the TiO 2 shells highly depends on the surface orientations and the geometrical shape of the core SnO 2 NW cross-section. Atomically smooth surfaces are found for growth on the {110} surface. Rough surfaces develop on {100} surfaces due to (100) - (1 × 3) reconstruction, by introducing steps in the [010] direction as a continuation of {110} facets. Lattice mismatch induces superlattice structures in the TiO 2 shell and misfit dislocations along the interface. Conformal epitaxial growth has been observed for SnO 2 NW cores with an octagonal cross-section ({100} and {110} surfaces). However, for a rectangular core ({101} and {010} surfaces), the shell also derives an octagonal shape from the epitaxial growth, which was explained by a proposed model based on ALD kinetics. The surface steps and defects induced by the lattice mismatch likely lead to improved photoluminescence (PL) performance for the yellow emission. Compared to the pure SnO 2 NWs, the PL spectrum of the core-shell nanostructures exhibits a stronger emission peak, which suggests potential applications in optoelectronics. © The Royal Society of Chemistry 2012.

  11. Characterization of thick epitaxial GaAs layers for X-ray detection

    CERN Document Server

    Samic, H; Donchev, V; Nghia, N X; Gandouzi, M; Zazoui, M; Bourgoin, J C; El-Abbassi, H; Rath, S; Sellin, P J

    2002-01-01

    We have studied the current-voltage and capacitance-voltage characteristics of p/i/n structures made on non-intentionally doped epitaxial GaAs layers grown by the chemical reaction method. Deep level transient spectroscopy demonstrates that these layers contain a low defect concentration. X-ray photoconductivity shows that the diffusion length is large. The homogeneity of the properties of these layers, which has been evaluated over large area (cm sup 2), is confirmed by photoluminescence mapping.

  12. Advances in modeling semiconductor epitaxy: Contributions of growth orientation and surface reconstruction to InN metalorganic vapor phase epitaxy

    Science.gov (United States)

    Kusaba, Akira; Kangawa, Yoshihiro; Kempisty, Pawel; Shiraishi, Kenji; Kakimoto, Koichi; Koukitu, Akinori

    2016-12-01

    We propose a newly improved thermodynamic analysis method that incorporates surface energies. The new theoretical approach enables us to investigate the effects of the growth orientation and surface reconstruction. The obtained knowledge would be indispensable for examining the preferred growth conditions in terms of the contribution of the surface state. We applied the theoretical approach to study the growth processes of InN(0001) and (000\\bar{1}) by metalorganic vapor phase epitaxy. Calculation results reproduced the difference in optimum growth temperature. That is, we successfully developed a new theoretical approach that can predict growth processes on various growth surfaces.

  13. 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.

  14. 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.

  15. 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.

  16. Low-energy electron diffraction investigation of epitaxial growth: Pt and Pd on Pd(100)

    Energy Technology Data Exchange (ETDEWEB)

    Flynn-Sanders, D.

    1990-09-21

    We investigate the epitaxial growth of Pt and Pd and Pd(100) via spot profile analysis using conventional low-energy electron diffraction (LEED). We resolve a central-spike and diffuse component in the spot profiles, reflecting the layer-occupations and pair-correlations, respectively. Kinetic limitations inhibit layer-by-layer growth at low temperatures. Our data suggest diffusion switches on at ca. 150 K for Pt and ca. 170 K for Pd indicating activation barriers to surface diffusion of ca. 10 and ca. 13 kcal/mol, respectively. To clarify the role of diffusion in determining the resulting film morphology, we develop a growth model that incorporates the adsorption-site requirement and predicts intensity oscillations. We present a new procedure to experimentally determine out-of-phase scattering conditions. At these energies, ring-structure is evident in the profiles during Pd growth between ca. 200 and 400 K. We report ring intensity oscillations as a function of coverage, which demonstrate the filling of individual layers.

  17. Structural differences between capped GaSb nanostructures grown by Stranski-Krastanov and droplet epitaxy growth modes

    Science.gov (United States)

    DeJarld, Matt; Yan, Lifan; Luengo-Kovac, Marta; Sih, Vanessa; Millunchick, Joanna

    2017-01-01

    Droplet epitaxy (DE) has emerged as an alternative to Stranski-Krastanov (SK) as a method for epitaxial nanostructure formation. We find significant structural differences of similar sized nanostructures embedded in GaAs between the two methods. Atomic force microscopy and atom probe tomography measurements reveal that uncapped and capped SK structures resemble each other. However, the DE nanostructures appear as rings topographically but are quantum dots compositionally. A GaSb wetting layer is present regardless of the growth method and shares a nearly identical Sb concentration profile. DE nanostructures are shown to have a lower Sb concentration, and transmission electron microscopy measurements reveal that they produce less strain on the capping layer. Despite significant structural differences, SK and DE nanostructures exhibit the same photoluminescence response, suggesting that the emission is from a shared feature such as the wetting layer, rather than the nanostructures.

  18. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  19. 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...

  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.

  1. Strain and crystalline defects in epitaxial GaN layers studied by high-resolution X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Chierchia, Rosa

    2007-07-01

    This thesis treats strain and dislocations in MOVPE GaN layers. The mosaic structure of metalorganic vapour phase epitaxy (MOVPE)-grown GaN layers was studied in dependence on the grain diameter utilizing high-resolution XRD. Different models for the defect structure were analyzed, the edge type TD densities were calculated under the assumption that the dislocations are not randomly distributed but localized at the grain boundaries. Moreover, in situ measurements have shown that the layers are under tension in the c-plane when a nucleation layer is used. The second part of this thesis treats a particular approach to reduce dislocations in MOVPE GaN layers, i.e. maskless pendeo epitaxial growth of MOVPE GAN layers. FE simulations assuming the strain to be completely induced during cooling of the structures after growth agree only partly with experimental data. The strain state of single layers and stripes of GaN grown on SiC was studied to exploit the evolution of the strain in the different phases of the PE growth. The biaxial compressive stress, due to the lattice mismatch between the GaN layer and the AlN nucleation layer is plastically relieved before overgrowth. Temperature dependent measurements show a linear reduction of the wing tilt with increasing temperature varying from sample to sample. Bent TDs have been observed in TEM images of maskless PE samples. Stress induced from the mismatch between the AlN buffer layer and the GaN also contributes to the remaining part of the wing tilt not relieved thermally. It has to be noted that the rest tilt value varies from sample to sample at the growth temperature. In fact some of the data indicate that the wing tilt decreases with increasing V/III ratio. In the last Chapter the application of X-ray techniques for the analysis of strain and composition in layers of inhomogeneous composition is explored. In the first part of the Chapter the strain state and the Al content of AlGaN buffer layers grown directly on (0001

  2. Direct growth of hexagonal boron nitride/graphene heterostructures on cobalt foil substrates by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhongguang; Khanaki, Alireza; Tian, Hao; Zheng, Renjing; Suja, Mohammad; 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); Zheng, Jian-Guo [Irvine Materials Research Institute, University of California, Irvine, California 92697-2800 (United States)

    2016-07-25

    Graphene/hexagonal boron nitride (G/h-BN) heterostructures have attracted a great deal of attention because of their exceptional properties and wide variety of potential applications in nanoelectronics. However, direct growth of large-area, high-quality, and stacked structures in a controllable and scalable way remains challenging. In this work, we demonstrate the synthesis of h-BN/graphene (h-BN/G) heterostructures on cobalt (Co) foil by sequential deposition of graphene and h-BN layers using plasma-assisted molecular beam epitaxy. It is found that the coverage of h-BN layers can be readily controlled on the epitaxial graphene by growth time. Large-area, uniform-quality, and multi-layer h-BN films on thin graphite layers were achieved. Based on an h-BN (5–6 nm)/G (26–27 nm) heterostructure, capacitor devices with Co(foil)/G/h-BN/Co(contact) configuration were fabricated to evaluate the dielectric properties of h-BN. The measured breakdown electric field showed a high value of ∼2.5–3.2 MV/cm. Both I-V and C-V characteristics indicate that the epitaxial h-BN film has good insulating characteristics.

  3. Efficient Exciton Diffusion and Resonance-Energy Transfer in Multi-Layered Organic Epitaxial Nanofibers

    DEFF Research Database (Denmark)

    Tavares, Luciana; Cadelano, Michele; Quochi, Francesco;

    2015-01-01

    Multi-layered epitaxial nanofibers are exemplary model systems for the study of exciton dynamics and lasing in organic materials due to their well-defined morphology, high luminescence efficiencies, and color tunability. We resort to temperature-dependent cw and picosecond photoluminescence (PL) ...

  4. 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.

  5. GaAs Solar Cells Grown by Hydride Vapor-Phase Epitaxy and the Development of GaInP Cladding Layers

    Energy Technology Data Exchange (ETDEWEB)

    Simon, John; Schulte, Kevin L.; Young, David L.; Haegel, Nancy M.; Ptak, Aaron J.

    2016-01-01

    The high cost of high-efficiency III-V photovoltaic devices currently limits them to niche markets. Hydride vapor-phase epitaxy (HVPE) growth of III-V materials recently reemerged as a low-cost, high-throughput alternative to conventional metal- organic vapor-phase epitaxy (MOVPE) growth of high-efficiency solar cells. Previously, we demonstrated unpassivated HVPEgrown GaAs p-n junctions with good quantum efficiency and high open-circuit voltage (Voc). In this work, we demonstrate the growth of GaInPby HVPE for use as a high-quality surface passivation layer to GaAs solar cells. Solar cells grown with GaInP window layers show significantly improved quantum efficiency compared with unpassivated cells, increasing the short-circuit current (JSC) of these low-cost devices. These results show the potential of low-cost HVPE for the growth of high-quality III-V devices.

  6. Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Cariou, R., E-mail: romain.cariou@polytechnique.edu [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); III-V lab a joint laboratory between Alcatel-Lucent Bell Labs France, Thales Research and Technology and CEA-LETI, route de Nozay, 91460, Marcoussis, France. (France); Ruggeri, R. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy); Tan, X.; Nassar, J.; Roca i Cabarrocas, P. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); Mannino, Giovanni [CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy)

    2014-07-15

    We report on unusual low temperature (175 °C) heteroepitaxial growth of germanium thin films using a standard radio-frequency plasma process. Spectroscopic ellipsometry and transmission electron microscopy (TEM) reveal a perfect crystalline quality of epitaxial germanium layers on (100) c-Ge wafers. In addition direct germanium crystal growth is achieved on (100) c-Si, despite 4.2% lattice mismatch. Defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and threading dislocation density (TDD) values as low as 10{sup 6} cm{sup −2} are obtained. Misfit stress is released fast: residual strain of −0.4% is calculated from Moiré pattern analysis. Moreover we demonstrate a striking feature of low temperature plasma epitaxy, namely the fact that crystalline quality improves with thickness without epitaxy breakdown, as shown by TEM and depth profiling of surface TDD.

  7. 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.)

  8. A step-by-step experiment of 3C-SiC hetero-epitaxial growth on 4H-SiC by CVD

    Science.gov (United States)

    Xin, Bin; Jia, Ren-Xu; Hu, Ji-Chao; Tsai, Cheng-Ying; Lin, Hao-Hsiung; Zhang, Yu-Ming

    2015-12-01

    To investigate the growth mechanism of hetero-epitaxial SiC, a step-by-step experiment of 3C-SiC epitaxial layers grown on 4H-SiC on-axis substrates by the CVD method are reported in this paper. Four step experiments with four one-quarter 4H-SiC wafers were performed. Optical microscopy and atomic force microscopy (AFM) were used to characterize the morphology of the epitaxial layers. It was previously found that the main factor affecting the epilayer morphology was double-positioning boundary (DPB) defects, which normally were in high density with shallow grooves. However, a protrusive regular "hill" morphology with a much lower density was shown in our experiment in high-temperature growth conditions. The anisotropic migration of adatoms is regarded as forming the morphology of DPB defects, and a new "DPB defects assist epitaxy" growth mode has been proposed based on the Frank-van der Merwe growth mode. Raman spectroscopy and X-ray diffraction were used to examine the polytypes and the quality of the epitaxial layers.

  9. Atomic layer epitaxy of hematite on indium tin oxide for application in solar energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Martinson, Alex B.; Riha, Shannon; Guo, Peijun; Emery, Jonathan D.

    2016-07-12

    A method to provide an article of manufacture of iron oxide on indium tin oxide for solar energy conversion. An atomic layer epitaxy method is used to deposit an uncommon bixbytite-phase iron (III) oxide (.beta.-Fe.sub.2O.sub.3) which is deposited at low temperatures to provide 99% phase pure .beta.-Fe.sub.2O.sub.3 thin films on indium tin oxide. Subsequent annealing produces pure .alpha.-Fe.sub.2O.sub.3 with well-defined epitaxy via a topotactic transition. These highly crystalline films in the ultra thin film limit enable high efficiency photoelectrochemical chemical water splitting.

  10. The role of defects in fluorescent silicon carbide layers grown by sublimation epitaxy

    DEFF Research Database (Denmark)

    Schimmel, Saskia; Kaiser, Michl; Jokubavicius, Valdas;

    lifetimes, high nonradiative lifetimes are crucial for efficient light conversion. Despite the excellent crystalline quality that can generally be obtained by sublimation epitaxy according to XRD measurements, the role of defects in f-SiC is not yet well understood. Recent results from room temperature...... photoluminescence, charge carrier lifetime measurements by microwave detected photoconductivity and internal quantum efficiency measurements suggest that the internal quantum efficiency of f-SiC layers is significantly affected by the incorporation of defects during epitaxy. Defect formation seems to be related...

  11. 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

  12. Growth of epitaxial semiconductor alloys and superlattices with continuously variable composition by pulsed-laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    McCamy, J.W. [Tennessee Univ., Knoxville, TN (United States). Dept. of Materials Science; Lowndes, D.H. [Oak Ridge National Lab., TN (United States)

    1993-08-01

    We describe a new method to grow epitaxial semiconductor alloys with continuously variable composition, while using a single pulsed laser ablation target of fixed composition. Epitaxial ZnSe{sub 1{minus}x}S{sub x} films with continuously variable sulfur content ``x`` were grown by ablating a ZnSe target through low-pressure ambient H{sub 2}S gas. The sulfur content was easily controlled by varying the H{sub 2}S partial pressure. The composition of ZnSe{sub 1{minus}x}S{sub x} films differs by as much as x = 0.52 from the pure ZnSe target. We have used this method to grow heteroepitaxial structures with either continuously graded or periodically repeating, abrupt compositional changes (compositional superlattices). Structures that simultaneously incorporate both types of compositional modulation also have been grown. This development removes the principal barrier to convenient pulsed-laser ablation (PLA) growth of compositionally graded semiconductor thin-film materials, namely that the film and target normally have the same composition. The method appears to have broad application for PLA growth of other compound semiconductor films and heterostructures, as well as for doping individual layers.

  13. Epitaxial composite layers of electron donors and acceptors from very large polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Samorí, Paolo; Severin, Nikolai; Simpson, Christopher D; Müllen, Klaus; Rabe, Jürgen P

    2002-08-14

    Large polycyclic aromatic hydrocarbons (PAHs) can be considered as nanographenes, whose electron donating or accepting properties are controlled by their size and shape as well as functionalities in their periphery. Epitaxial thin films of them are targets for optoelectronic applications; however, large PAHs are increasingly difficult to process. Here we show that epitaxial layers of very large unsubstituted PAHs (C(42)H(18) and C(132)H(34)), as well as a mixed layer of C(42)H(18) with an electron acceptor, can be obtained by self-assembly from solution. The C(132)H(34) is by far the largest nanographene that up to now has been processed into ordered thin films; due to its size it cannot be sublimed in a vacuum. Scanning tunneling microscopy (STM) studies reveal that the interaction with the substrate induces a strong perturbation of the electronic structure of the pure donor in the first epitaxial monolayer. In a second epitaxial layer with a donor acceptor stoichiometry of 2:1 the molecules are unperturbed.

  14. 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.

  15. 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.).

  16. Van der Waals epitaxial growth of MoS2 on SiO2/Si by chemical vapor deposition

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    Recently, single layer MoS2 with a direct band gap of 1.9 eV has been proposed as a candidate for two dimensional nanoelectronic devices. However, the synthetic approach to obtain high-quality MoS2 atomic thin layers is still problematic. Spectroscopic and microscopic results reveal that both single layers and tetrahedral clusters of MoS2 are deposited directly on the SiO2/Si substrate by chemical vapor deposition. The tetrahedral clusters are mixtures of 2H- and 3R-MoS2. By ex situ optical analysis, both the single layers and tetrahedral clusters can be attributed to van der Waals epitaxial growth. Due to the similar layered structures we expect the same growth mechanism for other transition-metal disulfides by chemical vapor deposition. © 2013 The Royal Society of Chemistry.

  17. Electronic and material characterization of silicon-germanium and silicon-germanium-carbon epitaxial layers

    Science.gov (United States)

    Peterson, Jeffrey John

    This dissertation presents results of material and electronic characterization of strained SiGe and SiGeC epitaxial layers grown on (100) silicon using Atmospheric Pressure Chemical Vapor Deposition and Reduced Pressure Chemical Vapor Deposition. Fabrication techniques for SiGe and SiGeC are also presented. Materials characterization of epitaxial SiGe and SiGeC was done to characterize crystallinity using visual, microscopic, and Rutherford Backscattering (RBS) characterization. Surface roughness was characterized and found to correspond roughly with epitaxial crystal quality. Spectroscopic ellipsometry was used to study epitaxial layer composition and thickness, requiring development of models for nSiGe and nSiGeC versus composition (the first published for nSiGeC) and generation of ellipsometric nomograms. X-ray diffraction (XRD) measurements of epitaxial strain and relaxation showed Ge composition dominates the stress, although strain compensation due to C was observed. XRD, Raman, and Fourier Transform Infrared (FTIR) characterization were done to characterize substitutional C in SiGeC epitaxial layers, finding that C incorporation into SiGeC saturates for C contents >1%. Fabrication techniques for SiGe and SiGeC were examined. Low thermal budget processing of strained layers were investigated as well as fabrication techniques using advantageous material properties of SiGe and SiGeC. Ti/Al contacts were developed and characterized for electrical contact to SiGe and SiGeC. Schottky contacts of Pt silicide on SiGe and SiGeC was done; formation and resistivity were characterized. Four separate resistivity characterization structures have been fabricated using mesa-etch and Si etch-stop techniques. A NPN Heterojunction Bipolar transistor has been fabricated using successive mesa-etches and SiGe (or SiGeC) etch-stops. Electronic characterization of in-situ doped SiGe and SiGeC epitaxial layers was done to determine resistivity, mobility, and bandgap. Resistivities

  18. Comparative study of polar and semipolar (112⁻2) InGaN layers grown by metalorganic vapour phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-21

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

  19. 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...

  20. 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...

  1. MBE growth and design of II-VI heterostructures for epitaxial lift-off

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, Ian A.; Vallance, Erin C.; Prior, Kevin A. [School of Engineering and Physical Science, Heriot-Watt University, Edinburgh (United Kingdom); Moug, Richard T.; Tamargo, Maria C. [Department of Chemistry, City College of New York, New York, NY (United States)

    2012-08-15

    Epitaxial lift-off (ELO) is a post-growth process that allows the active part of a semiconductor structure to be transferred from its growth substrate to a new one. This is a well established technique for III-V semiconductors, and has previously been demonstrated for ZnSe-based alloys grown on GaAs using a metastable MgS sacrificial layer, taking advantage of the huge difference in etch rates of MgS and ZnSe. We report here the first successful extension of this process to II-VI layers grown on InP by using a MgSe sacrificial layer. By using the correct etching conditions, MgSe has been found to work effectively as a sacrificial layer. 5 x 5 mm{sup 2} square pieces of material can be lifted and deposited on glass substrates without any deterioration in the structural or optical properties; as confirmed by optical microscopy and photoluminescence (PL) measurements. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

    Directory of Open Access Journals (Sweden)

    Takeo Ohno and Yutaka Oyama

    2012-01-01

    Full Text Available In this article we review the fundamental properties and applications of sidewall GaAs tunnel junctions. Heavily impurity-doped GaAs epitaxial layers were prepared using molecular layer epitaxy (MLE, in which intermittent injections of precursors in ultrahigh vacuum were applied, and sidewall tunnel junctions were fabricated using a combination of device mesa wet etching of the GaAs MLE layer and low-temperature area-selective regrowth. The fabricated tunnel junctions on the GaAs sidewall with normal mesa orientation showed a record peak current density of 35 000 A cm-2. They can potentially be used as terahertz devices such as a tunnel injection transit time effect diode or an ideal static induction transistor.

  3. Controlling the growth of epitaxial graphene on metalized diamond (111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Cooil, S. P., E-mail: simon.cooil@ntnu.no [Department of Physics, Aberystwyth University, Aberystwyth SY23 3BZ (United Kingdom); Department of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim (Norway); Wells, J. W. [Department of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim (Norway); Hu, D.; Evans, D. A. [Department of Physics, Aberystwyth University, Aberystwyth SY23 3BZ (United Kingdom); Niu, Y. R.; Zakharov, A. A. [MAX IV Laboratory, Lund University, 221 00 Lund (Sweden); Bianchi, M. [Department of Physics and Astronomy and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus DK-8000 (Denmark)

    2015-11-02

    The 2-dimensional transformation of the diamond (111) surface to graphene has been demonstrated using ultrathin Fe films that catalytically reduce the reaction temperature needed for the conversion of sp{sup 3} to sp{sup 2} carbon. An epitaxial system is formed, which involves the re-crystallization of carbon at the Fe/vacuum interface and that enables the controlled growth of monolayer and multilayer graphene films. In order to study the initial stages of single and multilayer graphene growth, real time monitoring of the system was preformed within a photoemission and low energy electron microscope. It was found that the initial graphene growth occurred at temperatures as low as 500 °C, whilst increasing the temperature to 560 °C was required to produce multi-layer graphene of high structural quality. Angle resolved photoelectron spectroscopy was used to study the electronic properties of the grown material, where a graphene-like energy momentum dispersion was observed. The Dirac point for the first layer is located at 2.5 eV below the Fermi level, indicating an n-type doping of the graphene due to substrate interactions, while that of the second graphene layer lies close to the Fermi level.

  4. Epitaxial Growth of beta-Silicon Carbide (SiC) on a Compliant Substrate via Chemical Vapor Deposition (CVD)

    Science.gov (United States)

    Mitchell, Sharanda L.

    1996-01-01

    Many lattice defects have been attributed to the lattice mismatch and the difference in the thermal coefficient of expansion between SiC and silicon (Si). Stacking faults, twins and antiphase boundaries are some of the lattice defects found in these SiC films. These defects may be a partial cause of the disappointing performance reported for the prototype devices fabricated from beta-SiC films. The objective of this research is to relieve some of the thermal stress due to lattice mismatch when SiC is epitaxially grown on Si. The compliant substrate is a silicon membrane 2-4 microns thick. The CVD process includes the buffer layer which is grown at 1360 C followed by a very thin epitaxial growth of SiC. Then the temperature is raised to 1500 C for the subsequent growth of SiC. Since silicon melts at 1415 C, the SiC will be grown on molten Silicon which is absorbed by a porous graphite susceptor eliminating the SiC/Si interface. We suspect that this buffer layer will yield less stressed material to help in the epitaxial growth of SiC.

  5. 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.

  6. Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface

    Science.gov (United States)

    Li, Ming-Yang; Shi, Yumeng; Cheng, Chia-Chin; Lu, Li-Syuan; Lin, Yung-Chang; Tang, Hao-Lin; Tsai, Meng-Lin; Chu, Chih-Wei; Wei, Kung-Hwa; He-Hau, Jr.; Chang, Wen-Hao; Suenaga, Kazu; Li, Lain-Jong

    2015-07-01

    Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.

  7. Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface

    KAUST Repository

    Li, Ming Yang

    2015-07-30

    Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.

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

    OpenAIRE

    Gerbaux, X.; Pianelli, A.; Hadni, A.; Jeanniard, C.; Strimer, P.

    1980-01-01

    The growth of CdTe oriented thin films by the ENSH method - i.e. Epitaxial Nucleation in Sub-microscopic Holes of an intermediate layer closely applied on a bulk single crystal — has been recently described. The CdTe films are generally difficult to detach from the bulk crystal. However free films are needed to study the infrared transmission in the spectral region of high absorption. To get them, the vitreous or amorphous thin intermediate layers are substituted by quite soluble an oriented ...

  9. Study of near-surface nanostructures in silicon systems after ion implantation and in the epitaxial growth by means of X-ray scattering

    CERN Document Server

    Beck, U W L

    1999-01-01

    In this thesis sample systems on silicon base, the doped regions of which were fabricated by ion implantation respectively by epitaxial layer growth, were studied by means of surface-sensitive X-ray scattering. In the foreground thereby lies the identification and characterization of defects and real structures, which influence the electronic properties.

  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. Efficient Exciton Diffusion and Resonance-Energy Transfer in Multi-Layered Organic Epitaxial Nanofibers

    DEFF Research Database (Denmark)

    Tavares, Luciana; Cadelano, Michele; Quochi, Francesco

    2015-01-01

    ) spectroscopy to quantify exciton diffusion and resonance-energy transfer (RET) processes in multi-layered nanofibers consisting of alternating layers of para-hexaphenyl (p6P) and α-sexithiophene (6T), serving as exciton donor and acceptor material, respectively. The high probability for RET processes...... is confirmed by Quantum Chemical calculations. The activation energy for exciton diffusion in p6P is determined to be as low as 19 meV, proving p6P epitaxial layers also as a very suitable donor material system. The small activation energy for exciton diffusion of the p6P donor material, the inferred high p6P...

  12. 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.

  13. Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Delabie, Annelies; Billen, Arne [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Dekkers, Harold; Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Caymax, Matty [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [KU Leuven, Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, Marc [KU Leuven, Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2015-01-01

    Highlights: • Atomic layer is deposited by O{sub 3} chemisorption reaction on H-terminated Si(100). • O-content has critical impact on the epitaxial thickness of the above-deposited Si. • Oxygen atoms at dimer/back bond configurations enable epitaxial Si on O atomic layer. • Oxygen atoms at hydroxyl and more back bonds, disable epitaxial Si on O atomic layer. - Abstract: Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-15

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

  15. Growth of (111)-oriented epitaxial and textured ferroelectric Y-doped HfO2 films for downscaled devices

    Science.gov (United States)

    Katayama, Kiliha; Shimizu, Takao; Sakata, Osami; Shiraishi, Takahisa; Nakamura, Syogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Uchida, Hiroshi; Funakubo, Hiroshi

    2016-09-01

    In this study, the growth of (111)-oriented epitaxial and textured YO1.5-HfO2 (0.07:0.93 ratio) films using the pulsed laser deposition method is presented. Epitaxial films were prepared on ITO//(111)yttria-stabilized zirconia (YSZ) substrates (ITO: Sn-doped In2O3; YSZ: yttria-stabilized zirconia), while textured films were prepared on (111)Pt/TiOx/SiO2//Si substrates with and without an ITO buffer layer via the grain on grain coherent growth. Inserting an ITO layer increased the volume fraction of the ferroelectric orthorhombic phase. Both the epitaxial and uniaxially textured films exhibited similar ferroelectricity with a remanent polarization of around 10 μC/cm2 and a coercive field of 1.9 to 2.0 MV/cm. These results present us with a way of obtaining stable and uniform ferroelectric properties for each grain and device cells consisting of a small number of grains. This opens the door for ultimately miniaturized ferroelectric devices, such as ferroelectric field effect transistors with small gate length and resistive random access memory using ferroelectric tunnel junctions.

  16. Direct Growth of a-Plane GaN on r-Plane Sapphire Substrate by Metalorganic Vapor Phase Epitaxy

    Science.gov (United States)

    Araki, Masahiro; Mochimizo, Noriaki; Hoshino, Katsuyuki; Tadatomo, Kazuyuki

    2007-02-01

    We have investigated the direct growth of nonpolar a-plane GaN layers on an r-plane sapphire substrate by metalorganic vapor-phase epitaxy (MOVPE). A high-density nucleation of GaN islands was obtained on the r-plane sapphire substrate at the initial stage of the high-temperature growth without a buffer layer, which resulted in a two-dimensional (2D) growth mode. We studied the effects of V/III ratio growth conditions on the surface morphology and growth features of an a-plane GaN layer. The results showed that a high density of pits with an inverse-pyramidal shape were formed at a high V/III ratio, whereas a relatively low density of pits were formed at a low V/III ratio due to the increase in the rate of lateral growth along the c-axis direction. We successfully grew a-plane GaN layers with a flat and pit-free surface using the “two-step growth method”. The method consisted of growing a first layer at a high V/III ratio and growing a second layer at a low V/III ratio. We found that the first layer plays an important role in GaN layer growth. The formation of a void-free GaN layer with sidewall facets in the first step leads to a flat and pit-free layer grown at a high rate of lateral growth along the c-axis direction in the second step.

  17. 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.

  18. Analysis of the Band-Structure in (Ga, Mn)As Epitaxial Layers by Optical Methods

    OpenAIRE

    Yastrubchak, O.

    2012-01-01

    The ternary III-V semiconductor (Ga, Mn)As has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, Mn)As layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE) technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy...

  19. Theoretical Investigation of the Effect of Growth Orientation on Indium Incorporation Efficiency during InGaN Thin Film Growth by Metal-Organic Vapor Phase Epitaxy

    Science.gov (United States)

    Yayama, Tomoe; Kangawa, Yoshihiro; Kakimoto, Koichi

    2013-08-01

    The effect of growth orientation on In incorporation efficiency in InGaN films grown by metal-organic vapor phase epitaxy (MOVPE) is theoretically investigated. We propose a new theoretical model that explains the role of the surface N-H layer in In incorporation based on first-principles calculations. During III-nitride MOVPE, N-terminated reconstruction with N dangling bonds passivated by H is stable. A surface N-H layer that covers a group-III (In, Ga) atomic layer prevents In atoms from desorbing and being replaced by Ga atoms. In incorporation is therefore more efficient for higher N-H layer coverage and stability. To investigate this relationship, the enthalpy change for the decomposition of a N-H layer was calculated. This enthalpy change which depends on growth orientations is in good agreement with the experimental In content.

  20. MgO/Cu2O Superlattices: Growth of Epitaxial Two-Dimensional Nanostructures

    Science.gov (United States)

    Yang, M. J.; Wadekar, P. V.; Hsieh, W. C.; Huang, H. C.; Lin, C. W.; Chou, J. W.; Liao, C. H.; Chang, C. F.; Seo, H. W.; You, S. T.; Tu, L. W.; Lo, I. K.; Ho, N. J.; Yeh, S. W.; Liao, H. H.; Chen, Q. Y.; Chu, W. K.

    2016-12-01

    Alternated stacking of dissimilar layers can produce novel superlattice materials with multiple functionalities. The majority of such work reported in literature on epitaxial superlattices has been on alternating layers with the same space group (SG) and crystal structure (CS), whereas superlattices with the same CS but different SG have not been studied as much. We have grown superlattices with two well-known oxide materials, viz. cuprite (Cu2O, CS = cubic and SG = Pn bar{3} m) and magnesium oxide (MgO, CS = cubic, SG = Fm bar{3} m). An MgO buffer layer grown near 650°C at the film-substrate interface was found to be essential to achieving reasonable long-range atomic order. Grazing-angle x-ray diffraction, x-ray reflectivity, and electron diffraction analyses as well as transmission electron microscopy were used to investigate the interface abruptness, smoothness, and general crystallinity of the individual layers. Interdiffusion between MgO and Cu2O near interfacial regions places a limit of 250°C on the growth temperature for fabrication of superlattices with reasonably sharp interfaces.

  1. Growth of Strain Free GaN Layers on (0001) Oriented Sapphire by Using Quasi-Porous GaN Template

    Institute of Scientific and Technical Information of China (English)

    XIE Xin-Jian; CHEN Jia-Rong; CAO Xian-Cun; ZHONG Fei; QIU Kai; LIU Gui-Feng; YIN Zhi-Jun; WANG Yu-Qi; LI Xin-Hua; JI Chang-Jian; HAN Qi-Fen

    2006-01-01

    We report the reduced-strain gallium-nitride (GaN) epitaxial growth on (0001) oriented sapphire by using quasi-porous GaN template. A GaN film in thickness of about 1μm was initially grown on a (0001) sapphire substrate by molecular beam epitaxy. Then it was dealt by putting, into 45% NaOH solution at 100°C for Wmin. By this process a quasi-porous GaN Rim was formed. An epitaxial GaN layer was grown on the porous GaN layer at 1050°C in the hydride vapour phase epitaxy reactor. The epitaxial layer grown on the porous GaN is found to have no cracks on the surface. That is much improved from many cracks on the surface of the GaN epitaxial layer grown on the sapphire as the same as on GaN buffer directly.

  2. 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...

  3. 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.

  4. Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Metaferia, Wondwosen; Sun, Yan-Ting, E-mail: yasun@kth.se; Lourdudoss, Sebastian [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, KTH—Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Pietralunga, Silvia M. [CNR-Institute for Photonics and Nanotechnologies, P. Leonardo da Vinci, 32 20133 Milano (Italy); Zani, Maurizio; Tagliaferri, Alberto [Department of Physics Politecnico di Milano, P. Leonardo da Vinci, 32 20133 Milano (Italy)

    2014-07-21

    Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 μm/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 μm polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III–V semiconductor layers on low cost and flexible substrates for solar cell applications.

  5. Growth of NaCl on thin epitaxial KCl films on Ag(100) studied by SPA-LEED

    Science.gov (United States)

    Marquardt, Christian; Paulheim, Alexander; Sokolowski, Moritz

    2015-11-01

    We investigated the growth of NaCl on thin (100)-oriented films of KCl by spot profile analysis of low energy electron diffraction (SPA-LEED). The underlying question of this investigation was how the system accommodates to the misfit of - 10% between the NaCl and KCl lattices. The KCl films (3 atomic layers thick) were epitaxially grown on a Ag(100) single crystal. We studied the heteroepitaxial growth of NaCl on KCl at 300 K and at 500 K, respectively. At 300 K, the first NaCl monolayer (ML) grows pseudomorphically on the KCl film. From the second layer onward, the NaCl lattice relaxes. The NaCl multilayers roughen, and a small rotational disorder (± 4°) of the NaCl domains is observed. The roughening results from the formation of multilayer islands of limited lateral size due to the misfit to the pseudomorphic first NaCl layer. At a growth temperature of 500 K, no pseudomorphic NaCl layer forms, instead relaxed multilayer island growth of NaCl is observed from the first layer onward. Similarly to the growth at 300 K, we find NaCl multilayer islands of limited lateral size. For both temperatures, we explain this growth behavior by the misfit that makes the adsorption sites at the island edges of the first relaxed NaCl layer less favorable for larger islands, promoting nucleation of multilayer islands.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Integrated DFB-DBR laser modulator grown by selective area metalorganic vapor phase epitaxy growth technique

    Science.gov (United States)

    Tanbun-Ek, T.; Chen, Y. K.; Grenko, J. A.; Byrne, E. K.; Johnson, J. E.; Logan, R. A.; Tate, A.; Sergent, A. M.; Wecht, K. W.; Sciortine, P. F.; Chu, S. N. G.

    1994-12-01

    A device quality of selective epitaxy growth of InGaAsP/InP multiple quantum well (MQW) structure using low-pressure metalorganic vapor phase epitaxy (MOVPE) technique is described. The technique is applied to a monolithically integrated electroabsorption modulator with distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers. Superior device characteristics such as efficient modulation, low threshold current and high efficiency operation of the integrated devices are obtained.

  11. 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.

  12. Molecular beam epitaxy growth and structure of self-assembled Bi2Se3/Bi2MnSe4 multilayer heterostructures

    Science.gov (United States)

    Hagmann, Joseph A.; Li, Xiang; Chowdhury, Sugata; Dong, Si-Ning; Rouvimov, Sergei; Pookpanratana, Sujitra J.; Yu, Kin Man; Orlova, Tatyana A.; Bolin, Trudy B.; Segre, Carlo U.; Seiler, David G.; Richter, Curt A.; Liu, Xinyu; Dobrowolska, Margaret; Furdyna, Jacek K.

    2017-08-01

    We demonstrate that the introduction of an elemental beam of Mn during the molecular beam epitaxial growth of Bi2Se3 results in the formation of layers of Bi2MnSe4 that intersperse between layers of pure Bi2Se3. This study revises the assumption held by many who study magnetic topological insulators (TIs) that Mn incorporates randomly at Bi-substitutional sites during epitaxial growth of Mn:Bi2Se3. Here, we report the formation of thin film magnetic TI Bi2MnSe4 with stoichiometric composition that grows in a self-assembled multilayer heterostructure with layers of Bi2Se3, where the number of Bi2Se3 layers separating the single Bi2MnSe4 layers is approximately defined by the relative arrival rate of Mn ions to Bi and Se ions during growth, and we present its compositional, structural, and electronic properties. We support a model for the epitaxial growth of Bi2MnSe4 in a near-periodic self-assembled layered heterostructure with Bi2Se3 with corresponding theoretical calculations of the energetics of this material and those of similar compositions. Computationally derived electronic structure of these heterostructures demonstrates the existence of topologically nontrivial surface states at sufficient thickness.

  13. Droplet epitaxy growth of telecom InAs quantum dots on metamorphic InAlAs/GaAs(111)A

    Science.gov (United States)

    Ha, Neul; Mano, Takaaki; Kuroda, Takashi; Mitsuishi, Kazutaka; Ohtake, Akihiro; Castellano, Andrea; Sanguinetti, Stefano; Noda, Takeshi; Sakuma, Yoshiki; Sakoda, Kazuaki

    2015-04-01

    We demonstrated the droplet epitaxial growth of InAs quantum dots on a GaAs(111)A substrate, which emitted at telecommunication wavelengths. A high-quality metamorphic In0.52Al0.48As layer was formed by inserting three monolayers of InAs between GaAs(111)A and InAlAs. InAs quantum dots were grown on the InAlAs surface by droplet epitaxy. They exhibited a laterally symmetrical shape owing to the C3v symmetry of the {111} surface. The photoluminescence signals of capped quantum dots indicated broadband spectra covering wavelengths from 1.3 to 1.55 µm. Thus, our dots are potentially useful for constructing entangled photon sources compatible with current telecommunication networks.

  14. Effect of low-temperature annealing on the electronic- and band-structures of (Ga,Mn)As epitaxial layers

    Science.gov (United States)

    Yastrubchak, O.; Wosinski, T.; Gluba, L.; Andrearczyk, T.; Domagala, J. Z.; Żuk, J.; Sadowski, J.

    2014-01-01

    The effect of outdiffusion of Mn interstitials from (Ga,Mn)As epitaxial layers, caused by post-growth low-temperature annealing, on their electronic- and band-structure properties has been investigated by modulation photoreflectance (PR) spectroscopy. The annealing-induced changes in structural and magnetic properties of the layers were examined with high-resolution X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. They confirmed an outdiffusion of Mn interstitials from the layers and an enhancement in their hole concentration, which were more efficient for the layer covered with a Sb cap acting as a sink for diffusing Mn interstitials. The PR results demonstrating a decrease in the band-gap-transition energy in the as-grown (Ga,Mn)As layers, with respect to that in the reference GaAs one, are interpreted by assuming a merging of the Mn-related impurity band with the GaAs valence band. Whereas an increase in the band-gap-transition energy caused by the annealing treatment of the (Ga,Mn)As layers is interpreted as a result of annealing-induced enhancement of the free-hole concentration and the Fermi level location within the valence band. The experimental results are consistent with the valence-band origin of itinerant holes mediating ferromagnetic ordering in (Ga,Mn)As, in agreement with the Zener model for ferromagnetic semiconductors.

  15. Application of advanced sensors to the liquid phase epitaxy (LPE) growth of MCT

    Science.gov (United States)

    Westphal, Glenn H.; Colombo, Luigi; Anderson, Jeff M.

    1994-07-01

    Liquid phase epitaxy (LPE) of (Hg,Cd)Te (MCT) is the technique of choice for the preparation of the materials used for high performance focal plane arrays. Its successful development requires the development of advanced sensors and process controls. We detail here progress on the application of four sensor technologies to the LPE process for growth of MCT layers from Te rich melts on CdZnTe substrates. These include: (1) electron beam microprobe/wavelength dispersive x-ray analysis (WDX) for the rapid measurement of film composition immediately after growth; (2) an RTD based precision temperature control system that controls the melt temperature to better than +/- 0.005 degree(s)C and the Hg reservoir temperature to better than +/- 0.020 degree(s)C; (3) UV/visible optical absorption spectroscopy for the determination of the Hg partial pressure over the melt; and (4) CCD imaging for the detection of the liquid temperature of the LPE growth solution. The impact of each of the sensors on process yield is discussed. The application of the CCD camera to Hg rich high pressure LPE growth is also briefly mentioned.

  16. 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.

  17. Comparative study of single InGaN layers grown on Si(111) and GaN(0001) templates: The role of surface wetting and epitaxial constraint

    Science.gov (United States)

    Gómez, V. J.; Gačević, Ž.; Soto-Rodríguez, P. E. D.; Aseev, P.; Nötzel, R.; Calleja, E.; Sánchez-García, M. A.

    2016-08-01

    This work presents a comparative study, based mainly on X-ray diffraction analysis, of compact (~100 nm thick) and uniform single crystal InGaN layers (In content <35%) grown by plasma-assisted molecular beam epitaxy. InGaN layers have been grown directly on Si(111) substrates and on commercially available GaN(0001)-on-sapphire templates.. A high reactivity of atomic N with Si leads to a formation of amorphous SiN on Si substrate, i.e. an indirect crystal-to-crystal InGaN/SiN/Si contact; the weak InGaN interaction with the underlying substrate (weak epitaxial constraint) further leads to poor surface "wetting" and consequent 3D nucleation. The InGaN growth on GaN is, on the other hand, characterized by a direct crystal-to-crystal InGaN/GaN contact; the strong InGaN interaction with the underlying substrate (strong epitaxial constraint) leads to good surface "wetting" and consequent 2D nucleation. All studied InGaN layers show single epitaxial relationship to both Si(111) and GaN(0001)-on-sapphire substrates as well as a relatively good compositional uniformity (no trace of InGaN phase separation). However, layers grown on Si show significantly lower strain and inferior crystallographic uniformity i.e. higher disorder in crystallographic tilt and twist. The surface "wetting" (poor vs. good) and epitaxial constraint (weak vs. strong) are suggested as the main origins of these discrepancies.

  18. 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].

  19. Evaluation of methods for application of epitaxial layers of superconductor and buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-06-01

    The recent achievements in a number of laboratories of critical currents in excess of 1.0x10{sup 6} amp/cm{sup 2} at 77K in YBCO deposited over suitably textured buffer/substrate composites have stimulated interest in the potential applications of coated conductors at high temperatures and high magnetic fields. As of today, two different approaches for obtaining the textured substrates have been identified. These are: Los Alamos National Laboratory`s (LANL) ion-beam assisted deposition called IBAD, to obtain a highly textured yttria-stabilized zirconia (YSZ) buffer on nickel alloy strips, and Oak Ridge National Laboratory`s (ORNL) rolling assisted, bi-axial texturized substrate option called RABiTS. Similarly, based on the published literature, the available options to form High Temperature Superconductor (HTS) films on metallic, semi-metallic or ceramic substrates can be divided into: physical methods, and non-physical or chemical methods. Under these two major groups, the schemes being proposed consist of: - Sputtering - Electron-Beam Evaporation - Flash Evaporation - Molecular Beam Epitaxy - Laser Ablation - Electrophoresis - Chemical Vapor Deposition (Including Metal-Organic Chemical Vapor Deposition) - Sol-Gel - Metal-Organic Decomposition - Electrodeposition, and - Aerosol/Spray Pyrolysis. In general, a spool- to-spool or reel-to-reel type of continuous manufacturing scheme developed out of any of the above techniques, would consist of: - Preparation of Substrate Material - Preparation and Application of the Buffer Layer(s) - Preparation and Application of the HTS Material and Required Post-Annealing, and - Preparation and Application of the External Protective Layer. These operations would be affected by various process parameters which can be classified into: Chemistry and Material Related Parameters; and Engineering and Environmental Based Parameters. Thus, one can see that for successful development of the coated conductors manufacturing process, an

  20. 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.

  1. (abstract) All Epitaxial Edge-geometry SNS Devices with Doped PBCO and YBCO Normal Layers

    Science.gov (United States)

    Barner, J. B.; Hunt, B. D.; Foote, M. C.

    1995-01-01

    We will present our results on tapered-edge-geometry SNS weak link fabricated from c-axis oriented base-, counterelectrode and normal layers using a variety of processing conditions. To date, we have employed a variety of different normal materials (Co-doped YBCO, Y-doped PBCO, Ca-doped PBCO). We have been examining the junction fabrication process in detail and we will present our methods. In particular, we have been examining both epitaxial and non-epitaxial milling mask overlayers and we will present a comparison of both methods. These devices behave similar to the expectations of the resisively shunted junction model and conventional SNS proximity effect models but with some differences which will be discussed. We will present the detailed systematics of our junctions including device parameters versus temperature, rf and dc magnetic response for the various processing conditions.

  2. 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.

  3. 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.

  4. Growth of wurtzite InP/GaP core-shell nanowires by metal-organic molecular beam epitaxy

    Science.gov (United States)

    Halder, Nripendra N.; Kelrich, Alexander; Kauffmann, Yaron; Cohen, Shimon; Ritter, Dan

    2017-04-01

    We report on the selective area vapor-liquid-solid (SA-VLS) growth of InP/GaP core shell nano-wires (NWs) by metal organic molecular beam epitaxy. Wurtzite crystal structure of the core InP was transferred to the GaP shell through layer by layer radial growth which eliminated bending of the NWs in random directions. Low growth temperature restricted surface segregation and kept the shell free from indium. Strain in the GaP shell was partially relaxed through formation of periodic misfit dislocations. From the periodicity of Moiré fringes and splitting of the fast-Fourier-transform of the transmission electron micrographs, the radial and axial strain were determined as 4.5% and 6.2%, respectively.

  5. Design of Strain-Compensated Epitaxial Layers Using an Electrical Circuit Model

    Science.gov (United States)

    Kujofsa, Tedi; Ayers, John E.

    2017-08-01

    The design of heterostructures that exhibit desired strain characteristics is critical for the realization of semiconductor devices with improved performance and reliability. The control of strain and dislocation dynamics requires an understanding of the relaxation processes associated with mismatched epitaxy, and the starting point for this analysis is the equilibrium strain profile, because the difference between the actual strain and the equilibrium value determines the driving force for dislocation glide and relaxation. Previously, we developed an electrical circuit model approach for the equilibrium analysis of semiconductor heterostructures, in which an epitaxial layer may be represented by a stack of subcircuits, each of which involves an independent current source, a resistor, an independent voltage source, and an ideal diode. In this work, we have applied the electrical circuit model to study the strain compensation mechanism and show that, for a given compositionally uniform device layer with fixed mismatch and layer thickness, a buffer layer may be designed (in terms of thickness and mismatch) to tailor the strain in the device layer. A special case is that in which the device layer will exhibit zero residual strain in equilibrium (complete strain compensation). In addition, the application of the electrical circuit analogy enables the determination of exact expressions for the residual strain characteristics of both the buffer and device layers in the general case where the device layer may exhibit partial strain compensation. On the basis of this framework, it is possible to develop design equations for the tailoring of the strain in a device layer grown on a uniform composition buffer.

  6. Threading dislocations in GaAs epitaxial layers on various thickness Ge buffers on 300 mm Si substrates

    Science.gov (United States)

    Bogumilowicz, Y.; Hartmann, J. M.; Rochat, N.; Salaun, A.; Martin, M.; Bassani, F.; Baron, T.; David, S.; Bao, X.-Y.; Sanchez, E.

    2016-11-01

    We have grown GaAs epitaxial layers on Ge buffers, themselves on Si (001) substrates, using an Applied Materials 300 mm metal organic chemical vapor deposition tool. We varied the Ge buffer thickness between 0.36 and 1.38 μm and studied the properties of a 0.27 μm thick GaAs layer on top. We found that increasing the Ge buffer thickness yielded smoother GaAs films with an rms surface roughness as low as 0.5 nm obtained on a 5×5 μm2 area. The bow of the substrate increased following a linear law with the epitaxial stack thickness up to 240 μm for a 1.65 μm stack. We have also characterized the threading dislocations present in the GaAs layers using X-ray diffraction and cathodoluminescence. Increasing the Ge buffer thickness resulted in lower threading dislocation densities, enabling us to obtain anti-phase boundary - free GaAs films with a threading dislocation density as low as 3×107 cm-2. In addition, atomic force microscopy surface topology measurements showed the presence of pits in the GaAs layers whose density agreed well with other threading dislocation density assessments. It thus seems that threading dislocations can in certain cases induce some growth rate variations, making them visible in as-grown GaAs films. Using thicker Ge buffers results in smoother films with less threading dislocations, with the side effect of increasing the bow on the wafer. If bow is not an issue, this is a practical approach to improve the GaAs (on Ge buffer) on silicon quality.

  7. Effect of the Ammonia Flow on the Formation of Microstructure Defects in GaN Layers Grown by High-Temperature Vapor Phase Epitaxy

    Science.gov (United States)

    Barchuk, M.; Lukin, G.; Zimmermann, F.; Röder, C.; Motylenko, M.; Pätzold, O.; Heitmann, J.; Kortus, J.; Rafaja, D.

    2016-12-01

    High-temperature vapor phase epitaxy (HTVPE) is a physical vapor transport technology for a deposition of gallium nitride (GaN) layers. However, little is known about the influence of the deposition parameters on the microstructure of the layers. In order to fill this gap, the influence of the ammonia (NH3) flow applied during the HTVPE growth on the microstructure of the deposited GaN layers is investigated in this work. Although the HTVPE technology is intended to grow GaN layers on foreign substrates, the GaN layers under study were grown on GaN templates produced by metal organic vapor phase epitaxy in order to be able to separate the growth defects from the defects induced by the lattice misfit between the foreign substrate and the GaN layer. The microstructure of the layers is characterized by means of high-resolution x-ray diffraction (XRD), transmission electron microscopy and photoluminescence. In samples deposited at low ammonia flow, planar defects were detected, along which the nitrogen atoms are found to be substituted by impurity atoms. The interplay between these planar defects and the threading dislocations is discussed. A combination of XRD and micro-Raman spectroscopy reveals the presence of compressive residual stress in the samples.

  8. 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...

  9. 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.

  10. 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...

  11. 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...

  12. Defect structure of erbium-doped <1 1 1> silicon layers formed by solid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kyutt, R.N.; Sobolev, Nikolai A. E-mail: nick@sobolev.ioffe.rssi.ru; Nikolaev, Yu. A.; Vdovin, V.I

    2001-01-01

    Erbium-doped layers have been produced on <1 1 1>-oriented silicon wafers using high-energy amorphizing Er implants and solid phase epitaxy (SPE). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques, used to study the microstructure of these layers, revealed the presence of microtwins and dislocations. The twins were found to be platelets with lateral dimensions of 15-30 nm and a thickness of about 2-9 nm, and their density throughout the regrown layer was nonuniform. The dislocation densities observed in the regrown layers were very high with densities exceeding 10{sup 10} cm{sup -2}. Within the implant fluence range studied, between 1x10{sup 14} and 9x10{sup 14} Er cm{sup -2}, the twin and dislocation densities were observed to increase with fluence, while the twin dimensions were found to decrease.

  13. Photoluminescence efficiency of BGaN epitaxial layers with high boron content

    Energy Technology Data Exchange (ETDEWEB)

    Jurkevičius, J.; Mickevičius, J., E-mail: juras.mickevicius@ff.vu.lt; Kadys, A.; Kolenda, M.; Tamulaitis, G.

    2016-07-01

    High-boron-content epitaxial layers of BGaN intended for lattice-matching with AlGaN in UV light emitters were grown on SiC substrate and GaN and AlN templates on sapphire. Photoluminescence (PL) of these layers was studied under quasi-steady-state conditions by varying temperature and excitation intensity. The PL spectra in the samples with different boron content and their dynamics evidence formation of boron-rich regions occupying a small fraction of the total layer volume and acting as the emission killers. The room-temperature PL efficiency of the BGaN epilayers was estimated and shown to drastically decrease at increasing boron content with no significant correlation with either the type of substrate/template or technological conditions of the layer deposition.

  14. Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gencarelli, F., E-mail: federica.gencarelli@imec.be [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium); Shimura, Y. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Kumar, A. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Vincent, B.; Moussa, A.; Vanhaeren, D.; Richard, O.; Bender, H. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, W. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Caymax, M.; Loo, R. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, M. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium)

    2015-09-01

    In this work, we discuss the characteristics of particular island-type features with an amorphous core that are developed during the low temperature epitaxial growth of Ge and GeSn layers by means of chemical vapor deposition with Ge{sub 2}H{sub 6}. Although further investigations are needed to unambiguously identify the origin of these features, we suggest that they are originated by the formation of clusters of H and/or contaminants atoms during growth. These would initially cause the formation of pits with crystalline rough facets over them, resulting in ring-shaped islands. Then, when an excess surface energy is overcome, an amorphous phase would nucleate inside the pits and fill them. Reducing the pressure and/or increasing the growth temperature can be effective ways to prevent the formation of these features, likely due to a reduction of the surface passivation from H and/or contaminant atoms. - Highlights: • Island features with amorphous cores develop during low T Ge(Sn) CVD with Ge{sub 2}H{sub 6.} • These features are thoroughly characterized in order to understand their origin. • A model is proposed to describe the possible evolution of these features. • Lower pressures and/or higher temperatures avoid the formation of these features.

  15. 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.

  16. Optical properties of pure and Ce{sup 3+} doped gadolinium gallium garnet crystals and epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Syvorotka, I.I. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Sugak, D. [Scientific Research Company “Carat”, 202 Stryjska Street, Lviv 79031 (Ukraine); Lviv Polytechnic National University, 12, S. Bandera Street, Lviv, 79013 (Ukraine); Wierzbicka, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Wittlin, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Cardinal Stefan Wyszyński University in Warsaw, ul. Dewajtis 5, 01-815 Warsaw (Poland); Przybylińska, H. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barzowska, J. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Barcz, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Berkowski, M.; Domagała, J. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Mahlik, S.; Grinberg, M. [Institute of Experimental Physics, Gdańsk University, ul. Wita Stwosza 57, Gdańsk (Poland); Ma, Chong-Geng [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); and others

    2015-08-15

    Results of X-ray diffraction and low temperature optical absorption measurements of cerium doped gadolinium gallium garnet single crystals and epitaxial layers are reported. In the region of intra-configurational 4f–4f transitions the spectra of the bulk crystals exhibit the signatures of several different Ce{sup 3+} related centers. Apart from the dominant center, associated with Ce substituting gadolinium, at least three other centers are found, some of them attributed to the so-called antisite locations of rare-earth ions in the garnet host, i.e., in the Ga positions. X-ray diffraction data prove lattice expansion of bulk GGG crystals due to the presence of rare-earth antisites. The concentration of the additional Ce-related centers in epitaxial layers is much lower than in the bulk crystals. However, the Ce-doped layers incorporate a large amount of Pb from flux, which is the most probable source of nonradiative quenching of Ce luminescence, not observed in crystals grown by the Czochralski method. - Highlights: • Ce{sup 3+} multicenters found in Gadolinium Gallium Garnet crystals and epitaxial layers. • High quality epitaxial layers of pure and Ce-doped GGG were grown. • Luminescence quenching of Ce{sup 3+} by Pb ions from flux detected in GGG epitaxial layers. • X-ray diffraction allows measuring the amount of the rare-earth antisites in GGG.

  17. Scanning proximal microscopy study of the thin layers of silicon carbide-aluminum nitride solid solution manufactured by fast sublimation epitaxy

    Directory of Open Access Journals (Sweden)

    Tománek P.

    2013-05-01

    Full Text Available The objective of the study is a growth of SiC/(SiC1−x(AlNx structures by fast sublimation epitaxy of the polycrystalline source of (SiC1−x(AlNx and their characterisation by proximal scanning electron microscopy and atomic force microscopy. For that purpose optimal conditions of sublimation process have been defined. Manufactured structures could be used as substrates for wide-band-gap semiconductor devices on the basis of nitrides, including gallium nitride, aluminum nitride and their alloys, as well as for the production of transistors with high mobility of electrons and also for creation of blue and ultraviolet light emitters (light-emitted diodes and laser diodes. The result of analysis shows that increasing of the growth temperature up to 2300 K allows carry out sublimation epitaxy of thin layers of aluminum nitride and its solid solution.

  18. Hydrogen-surfactant-mediated epitaxy of Ge1- x Sn x layer and its effects on crystalline quality and photoluminescence property

    Science.gov (United States)

    Nakatsuka, Osamu; Fujinami, Shunsuke; Asano, Takanori; Koyama, Takeshi; Kurosawa, Masashi; Sakashita, Mitsuo; Kishida, Hideo; Zaima, Shigeaki

    2017-01-01

    The effect of hydrogen-surfactant-mediated molecular beam epitaxy (MBE) growth of Ge1- x Sn x layer on Ge(001) substrate on crystalline quality and photoluminescence (PL) property has been investigated. The effect of irradiation of atomic hydrogen (H) generated by dissociating molecular hydrogen (H2) were examined during the MBE growth. H irradiation significantly improves the surface morphology with the enhancement of the two-dimensional growth of the Ge1- x Sn x epitaxial layer. Enhanced diffuse scattering is observed in the X-ray diffraction profile, indicating a high density of point defects. In the PL spectrum of the H2-irradiated Ge1- x Sn x layer, two components are observed, suggesting the radiative recombination with both indirect and direct transitions, while one component related to the direct transition is observable in the H-irradiated sample. The postdeposition annealing in nitrogen ambient at as low as 220 °C decreases the PL intensity of the H-irradiated Ge1- x Sn x layer, although the intensity is recovered after annealing at 300 °C, suggesting the annihilation of point defects in the Ge1- x Sn x layer.

  19. 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.

  20. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R.G.; Kringhoj, P. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1993-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-03-26

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

  2. Terahertz absorption in GaN epitaxial layers under lateral electric field

    Science.gov (United States)

    Balagula, R. M.; Vinnichenko, M. Ya; Melentev, G. A.; Moldavskaya, M. D.; Shalygin, V. A.; Vorobjev, L. E.; Firsov, D. A.; Danilov, S. N.; Suihkonen, S.

    2016-08-01

    Variation of absorption of terahertz radiation in lateral electric field was investigated in GaN epitaxial layers. Different behaviour of the absorption modulation in electric field was observed for radiation polarized along electric field and perpendicular to it. Joint analysis of optical and transport measurements let us obtain field dependencies of mobility, electron concentration and absorption cross-section. For terahertz radiation polarized perpendicular to the electric field, results are in accordance with Drude model of free electron absorption. Another polarization demonstrates significant deviation that is yet to be studied more thoroughly.

  3. Deposition of HgTe by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-04-01

    Full Text Available and Received 17 November 2005; received in revised 0022-0728/$ - see front matter � 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jelechem.2006.02.006 l atomic layer epitaxy (EC-ALE) n Jayaraju a, Stephen M. Cox b, Mathe a, John L. Stickney a... (1983). [7] N.H. Karam, R.G. Wolfson, I.B. Bhat, H. Ehsani, S.K. Ghandhi, Thin Solid Films 225 (1993) 261. [8] M.A.M. Seyam, A. Elfalaky, Vacuum 57 (2000) 31–41. [9] C. Janowitz, N. Orlowski, R. Manzke, Z. Golacki, J. Alloy. Compd. 328 (2001) 84...

  4. Increasing the radiation resistance of single-crystal silicon epitaxial layers

    Directory of Open Access Journals (Sweden)

    Kurmashev Sh. D.

    2014-12-01

    Full Text Available The authors investigate the possibility of increasing the radiation resistance of silicon epitaxial layers by creating radiation defects sinks in the form of dislocation networks of the density of 109—1012 m–2. Such networks are created before the epitaxial layer is applied on the front surface of the silicon substrate by its preliminary oxidation and subsequent etching of the oxide layer. The substrates were silicon wafers KEF-4.5 and KDB-10 with a diameter of about 40 mm, grown by the Czochralski method. Irradiation of the samples was carried out using electron linear accelerator "Electronics" (ЭЛУ-4. Energy of the particles was 2,3—3,0 MeV, radiation dose 1015—1020 m–2, electron beam current 2 mA/m2. It is shown that in structures containing dislocation networks, irradiation results in reduction of the reverse currents by 5—8 times and of the density of defects by 5—10 times, while the mobility of the charge carriers is increased by 1,2 times. Wafer yield for operation under radiation exposure, when the semiconductor structures are formed in the optimal mode, is increased by 7—10% compared to the structures without dislocation networks. The results obtained can be used in manufacturing technology for radiation-resistant integrated circuits (bipolar, CMOS, BiCMOS, etc..

  5. Thin film solar cells based on layered chalcogenides: Fundamentals and perspectives of van der Waals epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Jaegermann, W.; Pettenkofer, C.; Lang, O.; Schlaf, R.; Tiefenbacher, S.; Tomm, Y. [Hahn-Meitner-Inst., Berlin (Germany)

    1994-12-31

    The preparation of thin films of layered chalcogenide semiconductors as MX and MX{sub 2} (X = S, Se) based on the concept of van der Waals epitaxy (VDWE) is presented for different substrate/overlayer combinations as GaSe, InSe, SnSe{sub 2}, WS{sub 2} on WSe{sub 2}, GaSe, MoTe{sub 2}, graphite and mica. In all cases stoichiometric films are formed either as epitaxial layers or strongly textured films with the c-axis aligned in spite of strong lattice mismatch. The interfaces are non-reactive and atomically abrupt. The electronic properties of the interfaces are mostly ideal showing band offsets according to the electron affinity rule and no operative interface states. However, doping of the films is still a problem which limits the band bending and the attainable surface photovoltage. The perspectives and preconditions for the further development of layered semiconductor VDWE films for solar cells will be critically discussed.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Properties of heavily impurity-doped PbSnTe liquid-phase epitaxial layers grown by the temperature difference method under controlled Te vapor pressure

    Science.gov (United States)

    Yasuda, Arata; Takahashi, Yatsuhiro; Suto, Ken; Nishizawa, Jun-ichi

    2017-07-01

    We propose the use of heavily impurity-doped Pb1-xSnxTe/PbTe epitaxial layers grown via the temperature difference method under controlled vapor pressure (TDM-CVP) liquid-phase epitaxy (LPE) for the preparation of IV-VI compounds for mid- to far-infrared optical device applications. A flat surface morphology and the distribution of a constant Sn concentration for 0.05 ≤ x ≤ 0.33 were observed in the epitaxial layers using electron-probe microanalysis. The segregation coefficient of Sn in Pb1-xSnxTe grown via TDM-CVP LPE (Tg = 640 °C) was xSSn?xLSn = 0.28. The appearance of the Fermi level pinning and persistent photoconductivity effects in In-doped PbSnTe were also proposed; we estimated that the activation energies of these processes were 2.8 and 39.7 meV, respectively, based on the In-doped Pb1-xSnxTe carrier profile as a function of ambient temperature. In Hall mobility measurements, Sn was assumed to be a main scattering center in the Pb1-xSnxTe epitaxial crystals. The impurity effect was also observed in Pb1-xSnxTe epitaxial growth, similar to the effects observed for Tl-doped PbTe bulk crystals. We concluded that the heavily doped Pb1-xSnxTe crystals grown via TDM-CVP LPE can be used to fabricate high-performance mid- to far-infrared optical devices.

  12. Growth of epitaxial Pt thin films on (0 0 1) SrTiO{sub 3} by rf magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kahsay, A. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Polo, M.C., E-mail: mcpolo@ub.edu [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Ferrater, C.; Ventura, J. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Rebled, J.M. [Departament d’Electrònica, Universitat de Barcelona Institut de Nanociència i Nanotecnologia IN 2UB, 08028 Barcelona (Spain); Varela, M. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain)

    2014-07-01

    The growth of platinum thin film by rf magnetron sputtering on SrTiO{sub 3}(0 0 1) substrates for oxide based devices was investigated. Platinum films grown at temperatures higher than 750 °C were epitaxial ([1 0 0]Pt(0 0 1)//[1 0 0]STO(0 0 1)), whereas at lower temperatures Pt(1 1 1) films were obtained. The surface morphology of the Pt films showed a strong dependence on the deposition temperature as was revealed by atomic force microscopy (AFM). At elevated temperatures there is a three-dimensional (3D) growth of rectangular atomically flat islands with deep boundaries between them. On the other hand, at low deposition temperatures, a two-dimensional (2D) layered growth was observed. The transition from 2D to 3D growth modes was observed that occurs for temperatures around 450 °C. The obtained epitaxial thin films also formed an atomically sharp interface with the SrTiO{sub 3}(0 0 1) substrate as confirmed by HRTEM.

  13. High perpendicular hard magnetic properties of nanocomposite Co-rich Co-Pt/Pt double-layered films by epitaxial deposition without capped layer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S.C., E-mail: chensc@mail.mcut.edu.t [Department of Materials Engineering, MingChi University of Technology, Taipei 243, Taiwan (China); Kuo, P.C.; Shen, C.L.; Hsu, S.L.; Fang, Y.H.; Lin, G.P.; Huang, K.T. [Institute of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China)

    2009-07-01

    The HRTEM cross-sectional lattice image shows that a well epitaxial growth of hcp Co-rich Co-Pt (002) on Pt (111) underlayer leads to good perpendicular magnetic anisotropy of Co-rich Co-Pt film. It is found that both the perpendicular coercivity (Hc{sub perpendicular}) and perpendicular squareness (S{sub perpendicular}) of Co-rich Co-Pt films without Pt capped layer are larger than that of Co-rich Co-Pt films with Pt capped layer. The cross-sectional TEM-EDS and AES analysis confirm that the oxygen atoms will diffuse from film surface into the Co-rich Co-Pt film without adding Pt capped layer, and it react with cobalt atoms to form CoO, which is detected by XPS analysis. The increase in perpendicular hard magnetic properties of Co-rich Co-Pt film without Pt capped layer is mainly due to form CoO in the Co-rich Co-Pt film.

  14. 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.

  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 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...

  17. 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.

  18. 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.)

  19. Band Gap Opening Induced by the Structural Periodicity in Epitaxial Graphene Buffer Layer.

    Science.gov (United States)

    N Nair, Maya; Palacio, Irene; Celis, Arlensiú; Zobelli, Alberto; Gloter, Alexandre; Kubsky, Stefan; Turmaud, Jean-Philippe; Conrad, Matthew; Berger, Claire; de Heer, Walter; Conrad, Edward H; Taleb-Ibrahimi, Amina; Tejeda, Antonio

    2017-04-12

    The epitaxial graphene buffer layer on the Si face of hexagonal SiC shows a promising band gap, of which the precise origin remains to be understood. In this work, we correlate the electronic to the atomic structure of the buffer layer by combining angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and high-resolution scanning transmission electron microscopy (HR-STEM). We show that the band structure in the buffer has an electronic periodicity related to the structural periodicity observed in STM images and published X-ray diffraction. Our HR-STEM measurements show the bonding of the buffer layer to the SiC at specific locations separated by 1.5 nm. This is consistent with the quasi 6 × 6 periodic corrugation observed in the STM images. The distance between buffer C and SiC is 1.9 Å in the bonded regions and up to 2.8 Å in the decoupled regions, corresponding to a 0.9 Å corrugation of the buffer layer. The decoupled regions are sp(2) hybridized. Density functional tight binding (DFTB) calculations demonstrate the presence of a gap at the Dirac point everywhere in the buffer layer, even in the decoupled regions where the buffer layer has an atomic structure close to that of graphene. The surface periodicity also promotes band in the superperiodic Brillouin zone edges as seen by photoemission and confirmed by our calculations.

  20. Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer

    Science.gov (United States)

    Dong, K. F.; Deng, J. Y.; Peng, Y. G.; Ju, G.; Chow, G. M.; Chen, J. S.

    2016-09-01

    The microstructure and magnetic properties of the FePt films grown on large mismatched ZrN (15.7%) intermediate layer were investigated. With using ZrN intermediate layer, FePt 10 nm films exhibited (001) texture except for some weaker FePt (110) texture. Good epitaxial relationships of FePt (001) //ZrN (001) //TiN (001) among FePt and ZrN/TiN were revealed from the transmission electron microscopy (TEM) results. As compared with TiN intermediate layer, although FePt-SiO2-C films grown on ZrN/TiN intermediate layer showed isotropic magnetic properties, the large interfacial energy and lattice mismatch between FePt and ZrN would lead to form columnar structural FePt films with smaller grain size and improved isolation. By doping ZrN into the TiN layer, solid solution of ZrTiN was formed and the lattice constant is increased comparing with TiN and decreased comparing with ZrN. Moreover, FePt-SiO2-C films grown on TiN 2 nm-20 vol.% ZrN/TiN 3 nm intermediate layer showed an improved perpendicular magnetic anisotropy. Simultaneously, columnar structure with smaller grain size retained.

  1. Epitaxial SrO interfacial layers for HfO2-Si gate stack scaling

    Science.gov (United States)

    Marchiori, C.; Frank, M. M.; Bruley, J.; Narayanan, V.; Fompeyrine, J.

    2011-01-01

    We discuss the structural and electrical properties of scaled 2 nm HfO2/SrO gate stacks. Thin SrO layers are deposited by molecular beam epitaxy onto (001) p-Si substrates as alternative passivating interfacial layers (ILs) to SiO2. X-ray photoelectron spectroscopy and transmission electron microscopy show that, despite some HfO2-SrO intermixing, the SrO IL acts as a barrier against HfxSiy and SiO2 formation during high-κ deposition. Electrical measurements on metal-oxide-semiconductor capacitors with TiN metal gates integrated in a low-temperature process flow reveal an equivalent oxide thickness of 5 Å with competitive leakage current and hysteresis and a negative flat band voltage shift, suitable for n-channel transistors.

  2. Half Layer By Half Layer Growth of a Blue Phosphorene Monolayer on a GaN(001) Substrate

    Science.gov (United States)

    Zeng, Jiang; Cui, Ping; Zhang, Zhenyu

    2017-01-01

    Black phosphorene (BlackP), consisting of a vertically corrugated yet single layer of phosphorus atoms, is a latest member of the expanding two-dimensional (2D) materials family with high carrier mobility and immense application potentials. Blue phosphorene (BlueP), an allotrope of BlackP with appealing properties of its own, consists of a more flatly arranged layer of phosphorus atoms. To date, direct growth of either BlackP or BlueP remains a daunting challenge. Using first-principles approaches, here we establish a novel kinetic pathway for fabricating BlueP via epitaxial growth. Our systematic energetic studies reveal that both BlackP and BlueP monolayers can be readily stabilized on Cu(111), Au(111), and GaN(001) substrates. The semiconducting GaN(001) is further shown to be superior for fabricating BlueP, through an intriguing half-layer-by-half-layer (HLBHL) growth mechanism. Within this scheme, the GaN(001) surface is first preferentially covered by a half layer of phosphorus adatoms, followed by the addition of the other half. Once formed, such a BlueP monolayer is thermodynamically stable, as tested using ab initio molecular dynamics simulations. The HLBHL growth mechanism discovered here may enable mass production of high-quality BlueP, and could also be instrumental in achieving epitaxial growth of BlackP and other 2D materials.

  3. Impact of LT-GaAs layers on crystalline properties of the epitaxial GaAs films grown by MBE on Si substrates

    Science.gov (United States)

    Petrushkov, M. O.; Putyato, M. A.; Gutakovsky, A. K.; Preobrazhenskii, V. V.; Loshkarev, I. D.; Emelyanov, E. A.; Semyagin, B. R.; Vasev, A. V.

    2016-08-01

    GaAs films with low-temperature GaAs (LT-GaAs) layers were grown by molecular beam epitaxy (MBE) method on vicinal (001) Si substrates oriented 6° off towards [110]. The grown structures were different with the thickness of LT-GaAs layers and its arrangement in the film. The processes of epitaxial layers nucleation and growth were controlled by reflection high energy electron diffraction (RHEED) method. Investigations of crystalline properties of the grown structures were carried out by the methods of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystalline perfection of the GaAs films with LT-GaAs layers and the GaAs films without ones was comparable. It was found that in the LT- GaAs/Si layers the arsenic clusters are formed, as it occurs in the LT-GaAs/GaAs system without dislocation. It is shown that large clusters are formed mainly on the dislocations. However, the clusters have practically no effect on the density and the propagation path of threading dislocations. With increasing thickness of LT-GaAs layer the dislocations are partly bent along the LT-GaAs/GaAs interface due to the presence of stresses.

  4. 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.

  5. 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.

  6. Comeback of epitaxial graphene for electronics: large-area growth of bilayer-free graphene on SiC

    Science.gov (United States)

    Kruskopf, Mattias; Momeni Pakdehi, Davood; Pierz, Klaus; Wundrack, Stefan; Stosch, Rainer; Dziomba, Thorsten; Götz, Martin; Baringhaus, Jens; Aprojanz, Johannes; Tegenkamp, Christoph; Lidzba, Jakob; Seyller, Thomas; Hohls, Frank; Ahlers, Franz J.; Schumacher, Hans W.

    2016-12-01

    We present a new fabrication method for epitaxial graphene on SiC which enables the growth of ultra-smooth defect- and bilayer-free graphene sheets with an unprecedented reproducibility, a necessary prerequisite for wafer-scale fabrication of high quality graphene-based electronic devices. The inherent but unfavorable formation of high SiC surface terrace steps during high temperature sublimation growth is suppressed by rapid formation of the graphene buffer layer which stabilizes the SiC surface. The enhanced nucleation is enforced by decomposition of deposited polymer adsorbate which acts as a carbon source. Unique to this method are the conservation of mainly 0.25 and 0.5 nm high surface steps and the formation of bilayer-free graphene on an area only limited by the size of the sample. This makes the polymer-assisted sublimation growth technique a promising method for commercial wafer scale epitaxial graphene fabrication. The extraordinary electronic quality is evidenced by quantum resistance metrology at 4.2 K showing ultra-high precision and high electron mobility on mm scale devices comparable to state-of-the-art graphene.

  7. In situ photoemission study of interface and film formation during epitaxial growth of Er2O3 film on Si(001) substrate

    Institute of Scientific and Technical Information of China (English)

    ZHU Yanyan; FANG Zebo; LIU Yongsheng; LIAO Can; CHEN Sheng

    2008-01-01

    Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si(001) interface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maxi-mum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.

  8. STM studies of GeSi thin layers epitaxially grown on Si(111)

    Science.gov (United States)

    Motta, N.; Sgarlata, A.; De Crescenzi, M.; Derrien, J.

    1996-08-01

    Ge/Si alloys were prepared in UHV by solid phase epitaxy on Si(111) substrates. The alloy formation, as a function of the evaporation rate and the Ge layer thickness has been followed in situ by RHEED and scanning tunneling microscopy. The 5 × 5 surface reconstruction appeared after annealing at 450°C Ge layers (up to 10 Å thick), obtained from a low rate Knudsen cell evaporator. In this case a nearly flat and uniform layer of reconstructed alloy was observed. When using an e-gun high rate evaporator we needed to anneal the Ge layer up to 780°C to obtain a 5 × 5 reconstruction. The grown layer was not flat, with many steps and Ge clusters; at high coverages (10 Å and more) large Ge islands appeared. Moreover, we then succeeded in visualizing at atomic resolution the top of some of these Ge islands which displayed a 2 × 1 reconstruction, probably induced from the high compressive strain due to the lattice mismatch with the substrate. We suggest that this unusual behavior could be connected to the high evaporation rate, which helped the direct formation of Ge microcrystals on the Si substrate during the deposition process.

  9. 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.

  10. 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

  11. Zinc sulfide and terbium-doped zinc sulfide films grown by traveling wave reactor atomic layer epitaxy

    CERN Document Server

    Yun, S J; Nam, K S

    1998-01-01

    Zinc sulfide (ZnS) and terbium-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (ALE). In the present work, ZnCl sub 2 , H sub 2 S, and tris (2,2,6,6-tetramethyl-3,5-heptandionato) terbium (Tb(tmhd) sub 3) were used as the precursors. The dependence of crystallinity and Cl content of ZnS films was investigated on the growth temperature. ZnS and ZnS:Tb films grown at temperatures ranging from 400 to 500 .deg. C showed a hexagonal-2H crystalline structure. The crystallinity of ZnS film was greatly enhanced as the temperature increased. At growth temperatures higher than 450.deg.C, the films showed preferred orientation with mainly (002) diffraction peak. The Cl content decreased from approximately 9 to 1 at.% with the increase in growth temperature from 400 to 500 .deg. C. The segregation of Cl near the surface region and the incorporation of O from Tb(tmhd) sub 3 during ALE process were also observed using Auger electron spectroscopy. The ALE-grown ZnS and ZnS:Tb films re...

  12. SYNTHESIS OF THICK GALLIUM NITRIDE LAYERS BY METHOD OF MULTI-STAGE GROWTH ON SUBSTRATES WITH COLUMN STRUCTURE

    Directory of Open Access Journals (Sweden)

    Marina G. Mynbaeva

    2016-11-01

    Full Text Available Subject of Research.The paper deals with processes of formation and transformation of defects during multi-stage growth of thick gallium nitride layers with hydride vapor phase epitaxy on GaN/Al2O3 substrates with buried column pattern formed with the use of metal-organic vapor phase epitaxy. Methods. The growth of initial GaN layers was performed with the use of metal-organic vapor phase epitaxy. On the surface of the initial layers columns with the height of 800 nm were generated by means of ion etching. These columns were overgrown with 3-4 µm-thick GaN layers. On thus formed substrate multi-stage growth of GaN layers was performed with the use of hydride vapor-phase epitaxy. The total thickness of GaN layers was 100-1500 µm. The grown layers were studied by optical and electron microscopy and Raman spectroscopy. Main Results. Density of threading dislocations in the layers grown by hydride vapor-phase epitaxy was (3-6·107 cm-2, that was one order of magnitude lower than in the used substrate, and two to three orders lower than dislocation density in typical GaN layers grown on commercial sapphire substrates. Raman spectroscopy data were indicative of low level of mechanical stress in the layers and their high structural uniformity. It was established that under multi-stage growth conditions, non-catastrophic cracks (those that do not cause sample destruction are able to transform into macropores and appear to be an important structural element, serving to stress relaxation in the bulk of thick gallium nitride layers grown on foreign substrates. Practical Relevance. The results of the study can be used in the development of III-nitride heterostructures for optoelectronics and high-power and high-frequency microelectronics.

  13. 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.

  14. Metalorganic vapor phase epitaxy of GaAs on Si using II a-flouride buffer layers

    Science.gov (United States)

    Tiwari, A. N.; Freundlich, A.; Beaumont, B.; Blunier, S.; Zogg, H.; Teodoropol, S.; Vèrié, C.

    1992-11-01

    Metalorganic vapor phase epitaxy has been used for the first time to grow epitaxial GaAs layers on (111) and (100) oriented Si either using CaF 2 or stacked (Ca,Sr)F 2/CaF 2 as a buffer. The GaAs layers show sharp and well resolved electron channeling patterns. The Rutherford backscattering (RBS) ion channeling minimum yield is 5% for (111) orientation and 6% for (100) orientation. The GaAs(111) layers are untwinned. The strain in the GaAs layer has been measured with RBS and X-ray diffraction and it is found that the thermal mismatch-induced strain in the GaAs layer is considerably lower than in similar GaAs films grown without flouride buffer.

  15. Dynamic atomic layer epitaxy of InN on/in +c-GaN matrix: Effect of “In+N” coverage and capping timing by GaN layer on effective InN thickness

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, Akihiko, E-mail: yoshi@faculty.chiba-u.jp [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Graduate School of Engineering, Kogakuin University, Hachioji, Tokyo 192-0015 (Japan); Kusakabe, Kazuhide; Hashimoto, Naoki [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Hwang, Eun-Sook; Itoi, Takaomi [Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2016-01-11

    The growth front in the self-organizing and self-limiting epitaxy of ∼1 monolayer (ML)-thick InN wells on/in +c-GaN matrix by molecular beam epitaxy (MBE) has been studied in detail, with special attention given to the behavior and role of the N atoms. The growth temperatures of interest are above 600 °C, far higher than the typical upper critical temperature of 500 °C in MBE. It was confirmed that 2 ML-thick InN wells can be frozen/inserted in GaN matrix at 620 °C, but it was found that N atoms at the growth front tend to selectively re-evaporate more quickly than In atoms at temperatures higher than 650 °C. As a result, the effective thickness of inserted InN wells in the GaN matrix at 660–670 °C were basically 1 ML or sub-ML, even though they were capped by a GaN barrier at the time of 2 ML “In+N” coverage. Furthermore, it was found that the N atoms located below In atoms in the dynamic atomic layer epitaxy growth front had remarkably weaker bonding to the +c-GaN surface.

  16. Characterization of GaN Buffer Layers and Its Epitaxial Layers Grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Low-pressure MOCVD has been used to investigate the properties of low-temperature buffer layer deposition conditions and their influence on the properties of high-temperature GaN epilayers grown subsequently. It is found that the surface morphology of the as-grown buffer layer after thermal annealing at 1030℃ and 1050℃ depends strongly on the thickness of the buffer layer. In particular when a thick buffer layer is used, large trapezoidal nuclei are formed after annealing.

  17. Influence of layer thickness on the structure and the magnetic properties of Co/Pd epitaxial multilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Tobari, Kousuke, E-mail: tobari@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo 112-8551 (Japan); Ohtake, Mitsuru; Nagano, Katsumasa; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2012-03-15

    Co/Pd epitaxial multilayer films were prepared on Pd(111){sub fcc} underlayers hetero-epitaxially grown on MgO(111){sub B1} single-crystal substrates at room temperature by ultra-high vacuum RF magnetron sputtering. In-situ reflection high energy electron diffraction shows that the in-plane lattice spacing of Co on Pd layer gradually decreases with increasing the Co layer thickness, whereas that of Pd on Co layer remains unchanged during the Pd layer formation. The CoPd alloy phase formation is observed around the Co/Pd interface. The atomic mixing is enhanced for thinner Co and Pd layers in multilayer structure. With decreasing the Co and the Pd layer thicknesses and increasing the repetition number of Co/Pd multilayer film, stronger perpendicular magnetic anisotropy is observed. The relationships between the film structure and the magnetic properties are discussed. - Highlights: Black-Right-Pointing-Pointer Epitaxial Co/Pd multilayer films are prepared on Pd(111){sub fcc} underlayers. Black-Right-Pointing-Pointer Lattice strain in Co layer and CoPd-alloy formation are noted around the interface. Black-Right-Pointing-Pointer Magnetic property dependence on layer thickness is reported.

  18. 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.

  19. 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.

  20. 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.

  1. Epitaxial Growth of Cubic Crystalline Semiconductor Alloys on Basal Plane of Trigonal or Hexagonal Crystal

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

    2011-01-01

    Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.

  2. Multiple release layer study of the intrinsic lateral etch rate of the epitaxial lift-off process

    NARCIS (Netherlands)

    Voncken, M.M.J.; Schermer, J.J.; Bauhuis, G.J.; Mulder, P.; Larsen, P.K.

    2004-01-01

    The lateral etch rate of AlGaAs in HF in the 'Epitaxial Lift-Off' (ELO) process consists of two parts, an intrinsic and a radius-induced part. The intrinsic part is studied with a new approach in which multiple release layers are introduced in one sample. By letting an essential ELO process paramete

  3. Epitaxial growth of Fe/Ag single crystal superlattices and their magnetic properties

    Institute of Scientific and Technical Information of China (English)

    Yu Gu; Fei Zeng; Fang Lv; Yuli Cu; Pei-yong Yang; Feng Pan

    2009-01-01

    Single crystal Fe/Ag(001) superlattices with various periodicities were fabricated using ultrahigh vacuum evaporation de-position.It was found that single crystal bcc Fe layers and single crystal fcc Ag layers can epitaxially grow on a single crystal Ag buffer layer alternately,which was deposited on NaCl single crystal chips by ion beam assisted deposition.The magnetic measure-ments of the superlattices reveal an oscillation coupling between ferromagnetism and antiferromagnetism as a function of the Ag layer thickness.The oscillation period,which is 1 nm (5 Ag layers),is in good agreement with the calculated values when the Ag thickness is greater than 1.5 nm.While the thickness of the Ag spacer layer decreases to 1 nm,the oscillation coupling varies from calculations,which can be attributed to the intermixing of the interlayers according to the annealing results.

  4. Growth mechanism and electronic properties of epitaxial In{sub 2}O{sub 3} films on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ch. Y.; Kirste, L.; Roehlig, C. C.; Koehler, K.; Cimalla, V.; Ambacher, O. [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany); Morales, F. M.; Manuel, J. M.; Garcia, R. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica, Facultad de Ciencias, Universidad de Cadiz, Puerto Real, Cadiz 11510 (Spain)

    2011-11-01

    In this work, we report on the epitaxial growth of high-quality cubic indium oxide thick films on c-plane sapphire substrates using a two-step growth process. The epitaxial relationship of In{sub 2}O{sub 3} on (0001) Al{sub 2}O{sub 3} has been investigated. The (222) plane spacing and lattice parameter of a most strain-relaxed high-quality In{sub 2}O{sub 3} film have been determined to be 292.58 pm and 1013.53 pm, respectively. The electronic properties in dependence of the film thickness are interpreted using a three-region model. The density at the surface and interface totals (3.3{+-}1.5)x10{sup 13}cm{sup -2}, while the background electron density in the bulk was determined to be (2.4{+-}0.5)x10{sup 18}cm{sup -3}. Furthermore, post treatments such as irradiation via ultraviolet light and ozone oxidation have been found to influence only the surface layer, while the bulk electronic properties remain unchanged.

  5. Lattice sites of diffused gold and platinum in epitaxial ZnSe layers

    Science.gov (United States)

    Seppälä, A.; Salonen, R.; Slotte, J.; Ahlgren, T.; Rauhala, E.; Räisänen, J.

    2000-03-01

    The lattice location of diffused gold and platinum in zinc selenide (ZnSe) epitaxial layers was studied using the Rutherford backscattering (RBS) channeling technique. Thin Au and Pt films were evaporated onto ZnSe samples. The Au/ZnSe samples were annealed at 525°C and the residual Au film was removed by etching. Channeling angular scan measurements showed that about 30% of Au atoms were close to substitutional site (displaced about 0.2 Å). In the case of the Pt/ZnSe samples the annealing temperatures ranged from 600°C to 800°C. The Pt minimum yields along direction were close to the random value, varying from 80% to 90%. The measured Pt angular scans along and directions indicated a random location.

  6. Quantitative analysis of HOLZ line splitting in CBED patterns of epitaxially strained layers

    Energy Technology Data Exchange (ETDEWEB)

    Houdellier, F. [Centre d' Elaboration de Materiaux et d' Etudes Structurales, C.N.R.S., 29, Rue Jeanne Marvig, BP 94347 31055 Toulouse Cedex 4 (France)]. E-mail: florent@cemes.fr; Roucau, C. [Centre d' Elaboration de Materiaux et d' Etudes Structurales, C.N.R.S., 29, Rue Jeanne Marvig, BP 94347 31055 Toulouse Cedex 4 (France); Clement, L. [CEA, Departement de Recherche Fondamentale sur la Matiere Condensee, SP2M, 17, Rue des Martyrs, 38054 Grenoble (France); Rouviere, J.L. [CEA, Departement de Recherche Fondamentale sur la Matiere Condensee, SP2M, 17, Rue des Martyrs, 38054 Grenoble (France); Casanove, M.J. [Centre d' Elaboration de Materiaux et d' Etudes Structurales, C.N.R.S., 29, Rue Jeanne Marvig, BP 94347 31055 Toulouse Cedex 4 (France)

    2006-08-15

    A SiGe layer epitaxially grown on a silicon substrate is experimentally studied by convergent beam electron diffraction (CBED) experiments and used as a test sample to analyse the higher-order Laue zones (HOLZ) line splitting. The influence of surface strain relaxation on the broadening of HOLZ lines is confirmed. The quantitative fit of the observed HOLZ line profiles is successfully achieved using a formalism particularly well-adapted to the case of a z-dependent crystal potential (z being the zone axis). This formalism, based on a time-dependent perturbation theory approach, proves to be much more efficient than a classical Howie-Whelan approach, to reproduce the complex HOLZ lines profile in this heavily strained test sample.

  7. Synchrotron X-ray diffraction analysis of epitaxial GaN layer laterally overgrown

    CERN Document Server

    Feng Gan; Wang Yu Tian; Yang Hui; Liang Jun Wu; Zheng Wen Li; Jia Quan Jie

    2002-01-01

    The GaN layer grown by epitaxial lateral overgrowth on sapphire (0001) has been investigated by synchrotron X-ray diffraction. The results show that ELO GaN stripes bend towards the SiN sub x mask in directions perpendicular to the stripe direction. This lead to the GaN (0001) crystal planes in the 'wings' (overgrown GaN) exhibit crystallographic tilts away from those in the 'window' (seed) regions. The GaN (0002) diffraction was used to determine the grain sizes in the wing region and window region, respectively. It is found that the grain size in the wing region increases about three times comparing to those in window region

  8. Temperature Dependence of 1/f Noise in Gallium Nitride Epitaxial Layer

    Directory of Open Access Journals (Sweden)

    Ashutosh Kumar

    2011-01-01

    Full Text Available 1/f noise investigation was performed on n-GaN epitaxial layer grown on sapphire. The variation of spectral power density of voltage fluctuations density was observed as a function of frequency (100-50 Hz and it showed the 1/f spectra. This type of behavior was attributed to the presence of traps. The variation in spectral power density of voltage fluctuations with temperature was also observed with in the temperature range 80 K and 300 K and it was found to be slightly increasing with temperature. It was attributed to the trapping-detrapping process of charge carriers by the defects. Four probe configuration was used for noise measurement and contacts were made with indium. To check the stability and ohmic behavior of contacts, I-V measurements were performed with in the temperature range 80-325 K.

  9. Incorporation of La in epitaxial SrTiO3 thin films grown by atomic layer deposition on SrTiO3-buffered Si (001) substrates

    Science.gov (United States)

    McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Karako, Christine M.; Bruley, John; Frank, Martin M.; Narayanan, Vijay; Demkov, Alexander A.; Ekerdt, John G.

    2014-06-01

    Strontium titanate, SrTiO3 (STO), thin films incorporated with lanthanum are grown on Si (001) substrates at a thickness range of 5-25 nm. Atomic layer deposition (ALD) is used to grow the LaxSr1-xTiO3 (La:STO) films after buffering the Si (001) substrate with four-unit-cells of STO deposited by molecular beam epitaxy. The crystalline structure and orientation of the La:STO films are confirmed via reflection high-energy electron diffraction, X-ray diffraction, and cross-sectional transmission electron microscopy. The low temperature ALD growth (˜225 °C) and post-deposition annealing at 550 °C for 5 min maintains an abrupt interface between Si (001) and the crystalline oxide. Higher annealing temperatures (650 °C) show more complete La activation with film resistivities of ˜2.0 × 10-2 Ω cm for 20-nm-thick La:STO (x ˜ 0.15); however, the STO-Si interface is slightly degraded due to the increased annealing temperature. To demonstrate the selective incorporation of lanthanum by ALD, a layered heterostructure is grown with an undoped STO layer sandwiched between two conductive La:STO layers. Based on this work, an epitaxial oxide stack centered on La:STO and BaTiO3 integrated with Si is envisioned as a material candidate for a ferroelectric field-effect transistor.

  10. 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.

  11. L10 ordering at different stages of Fe0.5Pd0.5 epitaxial growth

    Science.gov (United States)

    Halley, D.; Auric, P.; Bayle-Guillemaud, P.; Gilles, B.; Marty, A.; Jalabert, D.

    2002-06-01

    FePd layers deposited by molecular beam epitaxy at 620 K on a (001) Pd buffer are investigated. At this growth temperature, an L10 structure is expected; we compare the crystal ordering at different depths in these thin films. 57Fe is used as a local probe at an atomic scale, located at different places within an equimolar FePd layer. The relationship between the alloy structure and the magnetic anisotropy of the films is investigated by Mossbauer spectroscopy. The possible decrease of the L10 ordering during growth is not observed. On the contrary, the quality of the L10 structure seems to improve, as confirmed by the low number of near-neighbors for iron atoms located on the top level of the alloy layer. Iron-rich clusters shaping into large vertical defects across the whole alloy layer are also observed; these clusters correspond to chemically disordered areas within the film. At the buffer interface, disordered, and dilute iron alloys (mean composition: Fe0.25 Pd0.75) with in-plane momenta are identified and explained assuming iron atom diffusion through about 1 nm thick Pd buffer, due to Pd segregation. Some iron rich aggregates could be the consequence of iron homocoordination or Pd surface segregation. The L10 structure is assumed to occur after about 1.7 nm alloy deposit.

  12. Temperature dependence of photoluminescence from ordered GaInP{sub 2} epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T. [Instituto de Ciencias, BUAP, Apartado Postal 207, 72000 Puebla, Pue. (Mexico); Pelosi, C. [IMEM/CNR, Parco Area delle Scienze 37/A, 43010 Parma (Italy)

    2010-01-15

    The temperature behavior of the integrated intensity of photoluminescence (PL) emission from ordered GaInP{sub 2} epitaxial layer was measured at temperatures of 10 - 300 K. Within this temperature range the PL emission is dominated by band-to-band radiative recombination. The PL intensity temperature dependence has two regions: at low temperatures it quenches rapidly as the temperature increases, and above 100 K it reduces slowly. This temperature behavior is compared with that of disordered GaInP{sub 2} layer. The specter of the PL emission of the disordered layer has two peaks, which are identified as due to donor-accepter (D-A) and band-to-band recombination. The PL intensity quenching of these spectral bands is very different: With increasing temperature, the D-A peak intensity remains almost unchanged at low temperatures and then decreases at a higher rate. The intensity of the band-to-band recombination peak decays gradually, having a higher rate at low temperatures than at higher temperatures. Comparing these temperature dependencies of these PL peaks of ordered and disordered alloys and the temperature behavior of their full width at half maximum (FWHM), we conclude that the different morphology of these alloys causes their different temperature behavior. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. 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.

  14. 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.

  15. Reduced growth temperature of Bi6FeCoTi3O18 thin films by conductive bottom layers

    Science.gov (United States)

    Yun, Yu; Huang, Haoliang; Meng, Dechao; Cui, Zhangzhang; Wang, Jianlin; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

    2016-11-01

    The Aurivillius layered oxide homologous series attract wide interests due to their room temperature multiferroic properties. Unfortunately, the synthesis of such layered oxide epitaxial thin films has been a major challenge owing to the occurrence of growth defects and narrow growth temperature window. To obtain high quality epitaxial Bi6FeCoTi3O18 (BFCTO) thin films, the effects of insulating and conductive bottom layers were studied by laser molecular beam epitaxy. We found that the optimal deposition temperature for growth on conductive bottom layers is more than 90 °C lower than that on insulating bottom layers, which indicates the interface between BFCTO and conductive bottom layers has smaller interfacial energy than the interface between BFCTO and insulating bottom layers. The magnetic and ferroelectric properties of the optimized BFCTO thin films on insulating substrate and conductive bottom layers were studied. This study is important to control the growth of complex layered oxide thin films and exploit the applications for future room temperature multiferroic devices.

  16. 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.

  17. 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.)

  18. 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.

  19. 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.

  20. Growth of transition metals on cerium tungstate model catalyst layers

    Science.gov (United States)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  1. Thermal degradation of InGaN/GaN quantum wells in blue laser diode structure during the epitaxial growth

    Science.gov (United States)

    Zhou, Kun; Ikeda, Massao; Liu, Jianping; Li, Zengcheng; Ma, Yi; Gao, Songxin; Ren, Huaijin; Tang, Chun; Sun, Yi; Sun, Qian; Yang, Hui

    2016-01-01

    True blue nitride laser diodes (LDs) are one of the key challenges for epitaxy of nitrides due to the variety of its potential applications. The growth of high temperature p-type layers may cause thermal degradation of the InGaN-based multiple quantum wells (MQWs) active region because of the annealing effect, since thick p-AlGaN layers were introduced as upper optical cladding layer in the LDs. The degradation was found in blue LDs grown on both Si and sapphire substrate. In the degraded LD wafer samples, "Dark" non-radiative MQWs regions were observed by microscopic photoluminescence. Formation of metallic indium precipitates and voids in these regions were confirmed by transmission electron microscope. The thermal degradation is attributed to the decomposition of indium-rich InGaN materials in the MQWs. The indium-rich InGaN materials were supposed to be accumulated at dislocation related V-shaped pits according to the surface morphology by atomic force microscope. To obtain high quality InGaN-based MQWs, one of the four methods can be introduced to eliminate the degradation. A lower thermal budget can suppress the decomposition of indium-rich InGaN clusters by a lower p-cladding layer growth temperature. The use of low threading dislocation density substrates results in low density indium-rich InGaN clusters. The introducing of H2 carrier gas during the quantum barriers growth or a 2-step growth scheme with a higher quantum barrier growth temperature etches off the indium-rich InGaN clusters. The suppression of the thermal degradation in the MQWs makes it possible for lasing of blue laser diode directly grown on Si.

  2. Reduction of background carrier concentration and lifetime improvement for 4H-SiC C-face epitaxial growth

    Science.gov (United States)

    Nishio, Johji; Kushibe, Mitsuhiro; Asamizu, Hirokuni; Kitai, Hidenori; Kojima, Kazutoshi

    2017-08-01

    Reduction of background carrier concentration was investigated for 4H-SiC C-face epitaxial growth in order to realize ultrahigh-voltage power devices. The quantitative contribution of each epitaxial growth parameter was studied, and it has been found that the growth rate increase and the pressure decrease were more effective than the C/Si ratio. Optimizing the parameters has made it possible to achieve a background carrier concentration of 7.6 × 1013 cm-3 within the whole area of specular 3-in. wafers. In addition to the background carrier concentration reduction, it has been confirmed that small epitaxial film thickness variation, low surface defect density and carrier lifetime fulfill the requirements for the devices. Moreover, in-process propane annealing has been found effective in improving the carrier lifetime. As a result, the longest lifetime value to date of 1.6 µs was obtained for a C-face epitaxial film.

  3. DOE-EPSCoR. Exchange interactions in epitaxial intermetallic layered systems

    Energy Technology Data Exchange (ETDEWEB)

    LeClair, Patrick R. [Univ. of Alabama, Tuscaloosa, AL (United States); Gary, Mankey J. [Univ. of Alabama, Tuscaloosa, AL (United States)

    2015-05-25

    The goal of this research is to develop a fundamental understanding of the exchange interactions in epitaxial intermetallic alloy thin films and multilayers, including films and multilayers of Fe-Pt, Co-Pt and Fe-P-Rh alloys deposited on MgO and Al2O3 substrates. Our prior results have revealed that these materials have a rich variety of ferromagnetic, paramagnetic and antiferromagnetic phases which are sensitive functions of composition, substrate symmetry and layer thickness. Epitaxial antiferromagnetic films of FePt alloys exhibit a different phase diagram than bulk alloys. The antiferromagnetism of these materials has both spin ordering transitions and spin orienting transitions. The objectives include the study of exchange-inversion materials and the interface of these materials with ferromagnets. Our aim is to formulate a complete understanding of the magnetic ordering in these materials, as well as developing an understanding of how the spin structure is modified through contact with a ferromagnetic material at the interface. The ultimate goal is to develop the ability to tune the phase diagram of the materials to produce layered structures with tunable magnetic properties. The alloy systems that we will study have a degree of complexity and richness of magnetic phases that requires the use of the advanced tools offered by the DOE-operated national laboratory facilities, such as neutron and x-ray scattering to measure spin ordering, spin orientations, and element-specific magnetic moments. We plan to contribute to DOE’s mission of producing “Materials by Design” with properties determined by alloy composition and crystal structure. We have developed the methods for fabricating and have performed neutron diffraction experiments on some of the most interesting phases, and our work will serve to answer questions raised about the element-specific magnetizations using the magnetic x-ray dichroism techniques and interface magnetism in layered structures

  4. Determination of the types and densities of dislocations in GaN epitaxial layers of different thicknesses by optical and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kravchuk, K. S. [Moscow State Institute of Steel and Alloys (Russian Federation); Mezhennyi, M. V. [Institute of Chemical Problems for Microelectronics (Russian Federation); Yugova, T. G., E-mail: p_Yugov@mail.ru [Institute of Rare Metals (Russian Federation)

    2012-03-15

    The change in the dislocation density on the surface of GaN epitaxial layers, which were grown by hydride vapor-phase epitaxy on sapphire substrates with c and r orientations, has been investigated by optical and atomic force microscopy (AFM). It is shown that the observed decrease in the density of threading dislocations with an increase in the layer thickness is related to the annihilation of mixed dislocations. The experimental and theoretical data on the change in the density of mixed dislocations with an increase in the epitaxial-layer thickness are in good correspondence.

  5. 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.

  6. Epitaxial growth of ZnO on quartz substrate by sol-gel spin-coating method

    Science.gov (United States)

    Chebil, W.; Boukadhaba, M. A.; Fouzri, A.

    2016-07-01

    ZnO thin films grown on Quartz substrates using sol-gel method were synthesized and annealing at different temperature (700 °C, 900 °C and 1000 °C). The structural, optical and morphological comparison of ZnO layers elaborated with that obtained by the sophisticated and expensive technique MOCVD demonstrates the success of the ZnO epitaxial growth on quartz substrate by sol-gel process. Sol-gel ZnO film deposited on quartz substrate annealed at 1000 °C exhibit only (00l) XRD peak which is similar to the diffraction patterns of epitaxial ZnO grown on sapphire by MOCVD. The Surface morphology was examined by SEM which revealed that the grain size becomes larger and faceted as increasing annealing temperature. Pl emission peak of sol-gel ZnO annealed at 1000 °C revealed a close similarity with that obtained by MOCVD ZnO but with a weaker intensity.

  7. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    SUN Bing; CHANG Hu-Dong; LU Li; LIU Hong-Gang; WU De-Xin

    2012-01-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained.An XRD rocking curve scan of the Ge(111) diffraction peak shovs a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600℃ with a ramp-up rate of 20℃/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  8. Erratic Dislocations within Funnel Defects in AlN Templates for AlGaNEpitaxial Layer Growth

    Energy Technology Data Exchange (ETDEWEB)

    Hawkridge, Michael E; Liliental-Weber, Zuzanna; Jin Kim, Hee; Choi, Suk; Yoo, Dongwon; Ryou, Jae-Hyun; Dupuis, Russel D

    2009-03-13

    We report our transmission electron microscopy observations of erraticdislocation behavior within funnel-like defects in the top of AlN templates filled withAlGaN from an overlying epitaxial layer. This dislocation behavior is observed inmaterial where phase separation is also observed. Several bare AlN templates wereexamined to determine the formation mechanism of the funnels. Our results suggest that they are formed prior to epitaxial layer deposition due to the presence of impuritiesduring template re-growth. We discuss the erratic dislocation behavior in relation to thepresence of the phase-separated material and the possible effects of these defects on the optoelectronic properties.

  9. Analysis of the Band-Structure in (Ga, MnAs Epitaxial Layers by Optical Methods

    Directory of Open Access Journals (Sweden)

    O. Yastrubchak

    2012-03-01

    Full Text Available The ternary III-V semiconductor (Ga, MnAs has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, MnAs layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy and the electronic structure in ferromagnetic (Ga, MnAs are still a matter of controversy. The photoreflectance (PR spectroscopy was applied to study the band-structure evolution in (Ga, MnAs layers with increasing Mn content. We have investigated thick (800-700 nm and 230-300 nm (Ga, MnAs layers with Mn content in the wide range from 0.001 % to 6 % and, as a reference, undoped GaAs layer, grown by LT-MBE on semi-insulating (001 GaAs substrates. Our findings were interpreted in terms of the model, which assumes that the mobile holes residing in the valence band of ferromagnetic (Ga, MnAs and the Fermi level position determined by the concentration of valence-band holes. The ternary III-V semiconductor (Ga, MnAs has recently drawn a lot of attention as the model diluted ferromagnetic semiconductor, combining semiconducting properties with magnetism. (Ga, MnAs layers are usually gown by the low-temperature molecular-beam epitaxy (LT-MBE technique. Below a magnetic transition temperature, TC, substitutional Mn2+ ions are ferromagnetically ordered owing to interaction with spin-polarized holes. However, the character of electronic states near the Fermi energy and the electronic structure in ferromagnetic (Ga, MnAs are still a matter of controversy. The photoreflectance (PR spectroscopy was applied to study the band-structure evolution in (Ga, MnAs layers with increasing Mn content. We have investigated thick (800-700 nm and 230-300 nm (Ga

  10. Epitaxial growth of ZnO thin films on AlN substrates deposited at low temperature by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Rahmane, S.; Soussou, A.; Gautron, E.; Jouan, P.Y.; Le Brizoual, L.; Barreau, N.; Djouadi, M.A. [Institut des Materiaux Jean Rouxel -IMN-, UMR CNRS 6502, Nantes (France); Abdallah, B. [Institut des Materiaux Jean Rouxel -IMN-, UMR CNRS 6502, Nantes (France); Atomic Energy Commission Syrian (AECS), Damascus (Syria); Soltani, A. [IEMN, UMR CNRS 8520, USTL, Villeneuve d' Ascq (France)

    2010-07-15

    Hexagonal aluminium nitride (AlN) and zinc oxide (ZnO) thin films have been deposited by DC and RF reactive magnetron sputtering at room temperature. For a first set of samples, sputtered AlN films were deposited on silicon ZnO substrate. For a second set, ZnO films were deposited on AlN substrate. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis of the synthesized AlN film on ZnO buffer layer have shown some amorphous zones close to the interface followed by a nanocrystalline layer exhibiting (10-10) and (0002) orientations of the hexagonal AlN crystalline phase. At the top of the film, a relatively well-crystallized layer with a single (0002) orientation has been observed. We have related the relatively bad interface to the presence of oxygen coming from ZnO substrate. This behaviour was different for the growth of ZnO film when AlN was used as substrate. In fact, we have observed thanks to HRTEM images and selected area electron diffraction patterns, that the ZnO film deposited on AlN substrate exhibits an epitaxial growth which is strongly dependent on the crystalline quality of AlN film. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Step driven competitive epitaxial and self-limited growth of graphene on copper surface

    Directory of Open Access Journals (Sweden)

    Lili Fan

    2011-09-01

    Full Text Available The existence of surface steps was found to have significant function and influence on the growth of graphene on copper via chemical vapor deposition. The two typical growth modes involved were found to be influenced by the step morphologies on copper surface, which led to our proposed step driven competitive growth mechanism. We also discovered a protective role of graphene in preserving steps on copper surface. Our results showed that wide and high steps promoted epitaxial growth and yielded multilayer graphene domains with regular shape, while dense and low steps favored self-limited growth and led to large-area monolayer graphene films. We have demonstrated that controllable growth of graphene domains of specific shape and large-area continuous graphene films are feasible.

  12. Effect of double AlN buffer layer on the qualities of GaN films grown by radio-frequency molecular beam epitaxy

    Institute of Scientific and Technical Information of China (English)

    Li Xin-Hua; Zhong Fei; Qiu Kai; Yin Zhi-Jun; Ji Chang-Jian

    2008-01-01

    This paper reports that the GaN thin films with Ga-polarity and high quality were grown by radio-frequency molecular beam epitaxy on sapphire (0001) substrate with a double A1N buffer layer. The buffer layer consists of a high-temperature (HT) AlN layer and a low-temperature (LT) AlN layer grown at 800℃ and 600℃, respectively. It is demonstrated that the HT-AlN layer can result in the growth of GaN epilayer in Ga-polarity and the LT-AlN layer is helpful for the improvement of the epilayer quality. It is observed that the carrier mobility of the GaN epilayer increases from 458 to 858cm2/V.s at room temperature when the thickness of LT-AlN layer varies from 0 to 20nm. The full width at half maximum of x-ray rocking curves also demonstrates a substantial improvement in the quality of GaN epilayers by the utilization of LT-AlN layer.

  13. 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.

  14. 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

  15. Epitaxial growth and magnetic properties of ultraviolet transparent Ga2O3/(Ga1-xFex)2O3 multilayer thin films

    Science.gov (United States)

    Guo, Daoyou; An, Yuehua; Cui, Wei; Zhi, Yusong; Zhao, Xiaolong; Lei, Ming; Li, Linghong; Li, Peigang; Wu, Zhenping; Tang, Weihua

    2016-04-01

    Multilayer thin films based on the ferromagnetic and ultraviolet transparent semiconductors may be interesting because their magnetic/electronic/photonic properties can be manipulated by the high energy photons. Herein, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films were obtained by alternating depositing of wide band gap Ga2O3 layer and Fe ultrathin layer due to inter diffusion between two layers at high temperature using the laser molecular beam epitaxy technique. The multilayer films exhibits a preferred growth orientation of crystal plane, and the crystal lattice expands as Fe replaces Ga site. Fe ions with a mixed valence of Fe2+ and Fe3+ are stratified distributed in the film and exhibit obvious agglomerated areas. The multilayer films only show a sharp absorption edge at about 250 nm, indicating a high transparency for ultraviolet light. What’s more, the Ga2O3/(Ga1-xFex)2O3 multilayer epitaxial thin films also exhibits room temperature ferromagnetism deriving from the Fe doping Ga2O3.

  16. Layer by layer three-dimensional tissue epitaxy by cell-laden hydrogel droplets.

    Science.gov (United States)

    Moon, SangJun; Hasan, Syed K; Song, Young S; Xu, Feng; Keles, Hasan Onur; Manzur, Fahim; Mikkilineni, Sohan; Hong, Jong Wook; Nagatomi, Jiro; Haeggstrom, Edward; Khademhosseini, Ali; Demirci, Utkan

    2010-02-01

    The ability to bioengineer three-dimensional (3D) tissues is a potentially powerful approach to treat diverse diseases such as cancer, loss of tissue function, or organ failure. Traditional tissue engineering methods, however, face challenges in fabricating 3D tissue constructs that resemble the native tissue microvasculature and microarchitectures. We have developed a bioprinter that can be used to print 3D patches of smooth muscle cells (5 mm x 5 mm x 81 microm) encapsulated within collagen. Current inkjet printing systems suffer from loss of cell viability and clogging. To overcome these limitations, we developed a system that uses mechanical valves to print high viscosity hydrogel precursors containing cells. The bioprinting platform that we developed enables (i) printing of multilayered 3D cell-laden hydrogel structures (16.2 microm thick per layer) with controlled spatial resolution (proximal axis: 18.0 +/- 7.0 microm and distal axis: 0.5 +/- 4.9 microm), (ii) high-throughput droplet generation (1 s per layer, 160 droplets/s), (iii) cell seeding uniformity (26 +/- 2 cells/mm(2) at 1 million cells/mL, 122 +/- 20 cells/mm(2) at 5 million cells/mL, and 216 +/- 38 cells/mm(2) at 10 million cells/mL), and (iv) long-term viability in culture (>90%, 14 days). This platform to print 3D tissue constructs may be beneficial for regenerative medicine applications by enabling the fabrication of printed replacement tissues.

  17. 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.

  18. Defect structure of epitaxial layers of III nitrides as determined by analyzing the shape of X-ray diffraction peaks

    Science.gov (United States)

    Kyutt, R. T.

    2017-04-01

    The shape of X-ray diffraction epitaxial layers with high dislocation densities has been studied experimentally. Measurements with an X-ray diffractometer were performed in double- and triple-crystal setups with both Cu K α and Mo K α radiation. Epitaxial layers (GaN, AlN, AlGaN, ZnO, etc.) with different degrees of structural perfection grown by various methods on sapphire, silicon, and silicon carbide substrates have been examined. The layer thickness varied in the range of 0.5-30 μm. It has been found that the center part of peaks is well approximated by the Voigt function with different Lorentz fractions, while the wing intensity drops faster and may be represented by a power function (with the index that varies from one structure to another). A well-marked dependence on the ordering of dislocations was observed. The drop in intensity in the majority of structures with a regular system and regular threading dislocations was close to the theoretically predicted law Δθ-3; the intensity in films with a chaotic distribution decreased much faster. The dependence of the peak shape on the order of reflection, the diffraction geometry, and the epitaxial layer thickness was also examined.

  19. EuO and Gd-doped EuO thin films. Epitaxial growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Sutarto, Ronny

    2009-07-06

    this respect the quality of many of the doped EuO samples used in the past bulk studies. The focus of this thesis is on the preparation and the properties of high-quality single-crystalline EuO and Gd-doped EuO thin films. The so-called Eu-distillation-assisted molecular beam epitaxy (MBE) has been employed to achieve full control of the stoichiometry. The films have been epitaxially grown on yttria-stabilized cubic zirconia (YSZ) (001) substrates. By a systematic variation of the oxygen deposition rates, we have been able to observe sustained oscillations in the intensity of the reflection high-electron energy diffraction (RHEED) pattern during growth. We thus have demonstrated that layer-by-layer growth has been achieved for the first time. We also have confirmed that YSZ indeed supplies oxygen during the initial stages of growth, yet the EuO stoichiometry can still be well maintained. In the case of Gd-doped EuO films, the presence of Gd even helps to stabilize the layer-by-layer growth mode. It is important to achieve this growth mode, since it enables the preparation of films with very smooth and at surfaces. This in turn facilitates the capping of the films with a thin Al overlayer in order to protect the films against degradation under ambient conditions. More important, the smoothness of the lm will enable the preparation of high quality device structures. By using ex-situ soft x-ray absorption spectroscopy (XAS) at the Eu and Gd M{sub 4,5} edges, we have confirmed that the films are completely free from Eu{sup 3+} contaminants, and we were able to determine reliably the actual Gd concentration. This actual Gd concentration could in fact significantly deviate from the nominal Gd/Eu evaporation ratio. From magnetization and susceptibility measurements, we found the Curie temperature to increase smoothly as a function of doping from 69 K up to a maximum of 125 K, all with a saturation moment of 7 {mu}B. A threshold behavior was not observed for Gd concentrations

  20. 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.

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

    Science.gov (United States)

    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.

  2. 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.

  3. The influence of epitaxial Ti buffer layers for fabricating as-grown MgB{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Oba, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan)]. E-mail: t3806005@iwate-u.ac.jp; Sun, P. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Harada, Y. [JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan); Takahashi, T. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Seki, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Noguchi, S. [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); JST-CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ishida, T. [Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); JST-CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan)

    2007-03-15

    We have measured the magnetic field dependence of the resistivity using a 35T pulsed magnet for the as-grown MgB{sub 2} films fabricated on the epitaxial Ti buffer layer grown on c-plane ZnO and Al{sub 2}O{sub 3} substrates by molecular beam epitaxy (MBE). We will report the upper critical fields (H{sub c2}) along H||c-axis and H||ab-plane. The anisotropy ratio were obtained from these H{sub c2} values. The effects of Ti buffer layer on the H{sub c2} and the anisotropy of MgB{sub 2} film were discussed.

  4. Molecular beam epitaxy of free-standing wurtzite AlxGa1-xN layers

    Science.gov (United States)

    Novikov, S. V.; Staddon, C. R.; Martin, R. W.; Kent, A. J.; Foxon, C. T.

    2015-09-01

    Recent developments with group III nitrides present AlxGa1-xN based LEDs as realistic devices for new alternative deep ultra-violet light sources. Because there is a significant 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). Thick wurtzite AlxGa1-xN films were grown by PA-MBE on 2-in. GaAs (111)B substrates and were removed from the GaAs substrate after growth to provide free standing AlxGa1-xN samples. X-ray microanalysis measurements confirm that the AlN fraction is uniform across the wafer and mass spectroscopy measurements show that the composition is also uniform in depth. We have demonstrated that free-standing wurtzite AlxGa1-xN wafers can be achieved by PA-MBE for a wide range of AlN fractions. In order to develop a commercially viable process for the growth of wurtzite AlxGa1-xN substrates, we have used a novel Riber plasma source and have demonstrated growth rates of GaN up to 1.8 μm/h on 2-in. diameter GaAs and sapphire wafers.

  5. Changing of micromorphology of silicon-on-sapphire epitaxial layer surface at irradiation by subthreshold energy X-radiation

    CERN Document Server

    Kiselev, A N; Skupov, V D; Filatov, D O

    2001-01-01

    The morphology of silicon-on-sapphire epitaxial layer surface after pulse irradiation by the X-rays with the energy of <= 140 keV is studied. The study on the irradiated material surface is carried out by the methods of the atomic force microscopy and ellipsometry. The average roughness value after irradiation constitutes 7 nm. The change in the films surface microrelief occurs due to reconstruction of their dislocation structure under the action of elastic waves, originating in the X radiation

  6. Internal equilibrium layer growth over forest

    DEFF Research Database (Denmark)

    Dellwik, E.; Jensen, N.O.

    2000-01-01

    the magnitude of the scatter. Different theoretical friction velocity profiles for the Internal Boundary Layer (IBL) are tested against the forest data. The results yield information on the Internal Equilibrium Layer (IEL) growth and an equation for the IEL height fur neutral conditions is derived. For stable...

  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. The growth of thin film epitaxial oxide-metal heterostructures

    CERN Document Server

    Wang, C

    1998-01-01

    films with lowest IR emissivity are those made from the purest targets despite their having comparable roughnesses to films from lower purity targets. The lowest emissivity achieved was in the range of 1.64% to 1.72% measured at 3.8 mu m for 1.5 to 1.8 mu m thick films. Modifications to standard idealized Drude theory have been made which, in a phenomenological way, take account of imperfections in the sputtered Al film, oxidation state and roughness. in electric properties of the Nb film and the reduction in crystalline quality of the MgO layer. The reduction of transition temperature to the superconducting state, Tc, and the similarly systematic increase in the Nb lattice parameter were observed consistent with oxygen content data reported in the literature, as the Nb became heavily oxidized. Examination of the surface of clean and oxidized Nb by atomic force microscopy, and deposition of MgO in UHV onto a previously oxidized Nb surface, suggested that the decrease in crystalline quality of the MgO can be a...

  9. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, June Key, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok [Department of Materials Science and Engineering, and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Ryu, Sang-Wan [Department of Physics and Optoelectronics Convergence Research Center, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Jeong, Tak [Korea Photonics Technology Institute, Gwangju 500-460 (Korea, Republic of); Jung, Eunjin; Kim, Hyunsoo, E-mail: junekey@jnu.ac.kr, E-mail: hskim7@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2015-05-14

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ∼35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  10. Fabricating Buffer Layers for YBa2Cu3Oy Coated Conductor by Surface Oxidation Epitaxy

    Institute of Scientific and Technical Information of China (English)

    Yang Jian; Liu Huizhou; Gu Hongwei; Qu Fei; Fan Hongyan

    2005-01-01

    NiO buffer layers were formed on a tape of Ni for making YBCO coated conductor by surface-oxidation epitaxy (SOE) process. Different oxidizing conditions such as temperature and duration were studied for Ni tapes. It is found that the texture of NiO could be affected directly by the orientation and surface of substrate. X-ray diffraction (XRD) 2-2θ scan, φ-scan, and pole figure were employed to characterize the in-plane alignment and cube texture. X-ray φ-scan shows that NiO film is formed on Ni tape with high cube texture and a typical value at the full width at half maximum (FWHM) is ≤7.5°. Scanning electron microscopy was used to study the surface morphology of NiO films. No crack is found and the films appear dense. Such technique is simple and of low cost with perfect reproducibility, promising for developing long tapes.

  11. Luminescence studies in InxGa1-xN epitaxial layers with different indium contents

    Science.gov (United States)

    Wu, T. Y.; Chang, C. C.; Tiong, K. K.; Lee, Y. C.; Hu, S. Y.; Lin, L. Y.; Lin, T. Y.; Feng, Z. C.

    2013-08-01

    The optical properties of InxGa1-xN epitaxial layers (x = 0.02, 0.04, 0.11, 0.15, 0.30 and 0.33) grown by metalorganic chemical vapor deposition (MOCVD) have been investigated by temperature-dependent photoluminescence (PL) measurement. The surface morphologies of InGaN samples are studied by scanning electron microscopy (SEM) images. The PL feature at 12 K has shown an increase in full-width at half-maximum (FWHM) with increasing In content. An anomalous S-shaped temperature dependence of the PL peak energy exhibited by InGaN films with higher In content enabled the evaluation of the exciton localization energy. The broadened FWHM and S-shaped emission shift are attributed to larger compositional fluctuation due to compositional inhomogeneity of In. Additionally, the luminescence mechanism relating to the phase separation has to be considered for the much larger FWHM value and the pronounced S-shaped behavior for the InGaN samples with In content of 0.30 and 0.33.

  12. Thermodynamic analysis of the deposition of GaAs epitaxial layers prepared by the MOCVD method

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, J.; Mikulec, J. (Dept. of Materials for Electronics, Prague Inst. of Chemical Tech. (Czechoslovakia)); Vonka, P. (Dept. of Physical Chemistry, Prague Inst. of Chemical Tech. (Czechoslovakia)); Stejskal, J.; Hladina, R.; Klima, P. (TESLA Research Inst. of Radiocommunication, Prague (Czechoslovakia))

    1991-06-01

    On the basis of a detailed thermodynamic analysis of the Ga-As-C-H system, the initial conditions have been determined, under which the reaction of trimethylgallium (TMGa) and arsine in a hydrogen atmosphere produces a single condensed phase - solid GaAs. Liquid gallium with a small amount of dissolved arsenic is formed simultaneously when the initial ratio of the elements is B{sup V}/A{sup III}<1, whereas solid graphite is simultaneously deposited at a high initial concentration of TMGa, especially at an elevated temperature and a decreased pressure. The equilibrium concentrations of the gaseous substances are strongly influenced by the initial B{sup V}/A{sup III} ratio. As{sub 2}, As{sub 4}, and CH{sub 4} are the dominant species if B{sup V}/A{sup III}>1, while CH{sub 4}, GaCH{sub 3}, GaH and GaH{sub 2} are the most abundant if B{sup V}/A{sup III} < 1. The calculated deposition diagrams are in good qualitative agreement with experimental results published in the literature. A comparison of the calculated composition of the gaseous phase and the results of experiments under the conditions used for the deposition of GaAs epitaxial layers leads to the conclusion that the course and results of the deposition process are significantly affected by transport and kinetic phenomena. (orig.).

  13. Virtual substrates for epitaxial growth and methods of making the same

    Science.gov (United States)

    Atwater, Harry A.; Leite, Marina S.; Warmann, Emily C.; Callahan, Dennis M.

    2016-09-27

    A virtual substrate includes a handle support and a strain-relieved single crystalline layer on the handle support. A method of making the virtual substrate includes growing a coherently-strained single crystalline layer on an initial growth substrate, removing the initial growth substrate to relieve the strain on the single crystalline layer, and applying the strain-relieved single crystalline layer on a handle support.

  14. Effects of surface reconstruction on the epitaxial growth of III-Sb on GaAs using interfacial misfit array

    Science.gov (United States)

    Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt

    2017-03-01

    The effects of pre-growth Sb reconstruction on a GaAs surface on the epitaxial growth of III-Sb (GaSb and InSb) on a (100) GaAs substrate using interfacial misfit array were investigated. All samples exhibited smooth surface with a root mean square (r.m.s.) roughness below 1.5 nm and nearly 100% relaxation. Modeling indicated that the distribution and types of misfit dislocations can be evaluated using a reciprocal space map (RSM) of the x-ray measurements. The interfacial misfit (IMF) arrays in III-Sb/GaAs samples were characterized by RSMs of high-resolution x-ray diffraction (XRD) and transmission electron microscopy (TEM). The RSM results suggest that all samples exhibited highly uniformly distributed misfit dislocations, and pre-growth (2 × 8) Sb surface reconstruction promoted the formation of 90° dislocations in an IMF array. Hall measurements of unintentionally doped GaSb and InSb layers also suggested that the highest motilities at both 77 K and 300 K were achieved at the samples grown on GaAs with pre-growth (2 × 8) Sb reconstruction.

  15. Role of lateral growth on the structural properties of high temperature GaN layer

    Institute of Scientific and Technical Information of China (English)

    GAO ZhiYuan; HAO Yue; LI PeiXian; ZHANG JinCheng

    2009-01-01

    The role of lateral growth on the structural properties of high temperature (HT) GaN epitaxial layer has been investigated by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD).Variations of the lateral growth rate of HT GaN in metal-organic chemical vapor deposition (MOCVD)can be obtained by changing the Ⅴ/Ⅲ ratio. It is found that under higher lateral growth rate, dislocation is easier to bend into subgrains away from c axis, and the position where bend occurs is closer to the buffer layer, however, dislocation density does not show to monotonically vary with increasing lateral growth rate. A model concerning the GaN growth dynamics and dislocation bending mechanics has been proposed to explain the correlation between lateral growth and the structural properties of GaN.

  16. Role of lateral growth on the structural properties of high temperature GaN layer

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The role of lateral growth on the structural properties of high temperature(HT) GaN epitaxial layer has been investigated by means of transmission electron microscopy(TEM) and X-ray diffraction(XRD).Variations of the lateral growth rate of HT GaN in metal-organic chemical vapor deposition(MOCVD) can be obtained by changing the V/Ⅲ ratio.It is found that under higher lateral growth rate,dislocation is easier to bend into subgrains away from c axis,and the position where bend occurs is closer to the buffer layer,however,dislocation density does not show to monotonically vary with increasing lateral growth rate.A model concerning the GaN growth dynamics and dislocation bending mechanics has been proposed to explain the correlation between lateral growth and the structural properties of GaN.

  17. Surface segregation as a means of gettering Cu in liquid-phase-epitaxy silicon thin layers grown from Al-Cu-Si solutions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, T.H.; Ciszek, T.F.; Reedy, R.; Asher, S.; King, D. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    The authors demonstrate that, by using the natural surface segregation phenomenon, Cu can be gettered to the surface from the bulk of silicon layers so that its concentrations in the liquid-phase-epitaxy (LPE) layers are much lower than its solubility at the layer growth temperature and the reported 10{sup 17} cm{sup {minus}3} degradation threshold for solar-cell performance. Secondary-ion mass spectroscopy (SIMS) analysis indicates that, within a micron-deep sub-surface region, Cu accumulates even in as-grown LPE samples. Slower cooling after growth to room temperature enhances this Cu enrichment. X-ray photoelectron spectroscopy (XPS) measurement shows as much as 3.2% Cu in a surface region of about 50 {Angstrom}. More surface-sensitive, ion-scattering spectroscopy (ISS) analysis further reveals about 7% of Cu at the top surface. These results translate to an areal gettering capacity of about 1.0 x 10{sup 16} cm{sup {minus}2}, which is higher than the available total-area density of Cu in the layer and substrate (3.6 x 10{sup 15} cm{sup {minus}2} for a uniform 1.2 x 10{sup 17}cm{sup {minus}3} Cu throughout the layer and substrate with a total thickness of 300 {mu}m).

  18. 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).

  19. 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)

  20. 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.

  1. 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.)

  2. 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.

  3. 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.

  4. 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.

  5. Spiral growth of few-layer MoS2 by chemical vapor deposition

    Science.gov (United States)

    Dong, X.; Yan, C.; Tomer, D.; Li, C. H.; Li, L.

    2016-08-01

    Growth spirals exhibit appealing properties due to a preferred layer stacking and lack of inversion symmetry. Here, we report spiral growth of MoS2 during chemical vapor deposition on SiO2/Si and epitaxial graphene/SiC substrates, and their physical and electronic properties. We determine the layer-dependence of the MoS2 bandgap, ranging from 2.4 eV for the monolayer to a constant of 1.3 eV beyond the fifth layer. We further observe that spirals predominantly initiate at the step edges of the SiC substrate, based on which we propose a growth mechanism driven by screw dislocation created by the coalescence of two growth fronts at steps.

  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. Seeded epitaxy of Co/Au(1 1 1) multilayers on {alpha}-Al{sub 2}O{sub 3}(0 0 0 1): Influence of Co seed layer

    Energy Technology Data Exchange (ETDEWEB)

    Kamiko, Masao [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)], E-mail: kamiko@iis.u-tokyo.ac.jp; Yamamoto, Ryoichi [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2007-06-25

    The influence of a Co seed layer on the structural and magnetic properties of Co/Au(1 1 1) multilayers grown onto {alpha}-Al{sub 2}O{sub 3}(0 0 0 1) single crystal substrates by molecular beam epitaxy has been studied by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and vibrating a sample magnetometer (VSM). The initial deposition of the Co seed layer onto Al{sub 2}O{sub 3}(0 0 0 1) prior to the deposition of an Au buffer layer yielded high-quality fcc-Au(1 1 1) oriented epitaxial films and a well-known (23 x 1) surface reconstruction structure. The RHEED results proved that the Co seed layer enhanced the layer-by-layer growth of the Co/Au multilayer on Au(1 1 1). The Co seed layer also improved the crystalline quality of the consequent Co/Au(1 1 1) multilayer. The results of XRD revealed that interfaces of the Co/Au multilayers with the Co seed layer were sharper than those without a seed layer. The magnetic anisotropy energy of the Co/Au multilayers was increased by using the Co seed layer. This indicated that a high structural quality resulted in a greater perpendicular magnetic anisotropy. However, this structural control was the result of the decrease in the coercive force and remanent magnetization.

  8. Atomic layer epitaxy of Ruddlesden-Popper SrO(SrTiO{sub 3}){sub n} films by means of metalorganic aerosol deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jungbauer, M.; Hühn, S.; Moshnyaga, V. [Erstes Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Egoavil, R.; Tan, H.; Verbeeck, J.; Van Tendeloo, G. [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium)

    2014-12-22

    We report an atomic layer epitaxial growth of Ruddlesden-Popper (RP) thin films of SrO(SrTiO{sub 3}){sub n} (n = ∞, 2, 3, 4) by means of metalorganic aerosol deposition (MAD). The films are grown on SrTiO{sub 3}(001) substrates by means of a sequential deposition of Sr-O/Ti-O{sub 2} atomic monolayers, monitored in-situ by optical ellipsometry. X-ray diffraction and transmission electron microscopy (TEM) reveal the RP structure with n = 2–4 in accordance with the growth recipe. RP defects, observed by TEM in a good correlation with the in-situ ellipsometry, mainly result from the excess of SrO. Being maximal at the film/substrate interface, the SrO excess rapidly decreases and saturates after 5–6 repetitions of the SrO(SrTiO{sub 3}){sub 4} block at the level of 2.4%. This identifies the SrTiO{sub 3} substrate surface as a source of RP defects under oxidizing conditions within MAD. Advantages and limitations of MAD as a solution-based and vacuum-free chemical deposition route were discussed in comparison with molecular beam epitaxy.

  9. ’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

  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. 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.)

  12. Realization of high quality epitaxial current- perpendicular-to-plane giant magnetoresistive pseudo spin-valves on Si(001 wafer using NiAl buffer layer

    Directory of Open Access Journals (Sweden)

    Jiamin Chen

    2016-05-01

    Full Text Available In this letter, we report a NiAl buffer layer as a template for the integration of epitaxial current-perpendicular-plane-giant magnetoresistive (CPP-GMR devices on a Si(001 single crystalline substrate. By depositing NiAl on a Si wafer at an elevated temperature of 500 °C, a smooth and epitaxial B2-type NiAl(001 layer was obtained. The surface roughness was further improved by depositing Ag on the NiAl layer and applying subsequent annealing process. The epitaxial CPP-GMR devices grown on the buffered Si(001 substrate present a large magnetoresistive output comparable with that of the devices grown on an MgO(001 substrate, demonstrating the possibility of epitaxial spintronic devices with a NiAl templated Si wafer for practical applications.

  13. 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.

  14. Material-dependent amorphization and epitaxial crystallization in ion-implanted AlAs/GaAs layer structures

    Energy Technology Data Exchange (ETDEWEB)

    Cullis, A.G.; Chew, N.G.; Whitehouse, C.R. (Royal Signals and Radar Establishment, St. Andrews Road, Malvern, Worcestershire WR14 3PS, United Kingdom (GB)); Jacobson, D.C.; Poate, J.M.; Pearton, S.J. (AT T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey 07974)

    1989-09-18

    When AlAs/GaAs layer samples are subjected to Ar{sup +} ion bombardment at liquid-nitrogen temperature, it is shown that very different damage structures are produced in the two materials. While the GaAs is relatively easily amorphized, the AlAs is quite resistant to damage accumulation and remains crystalline for the ion doses employed in these investigations. Epitaxial regrowth of buried amorphous GaAs layers of thicknesses up to 150 nm can be induced by rapid thermal annealing. It is demonstrated that differences in the initial damage state have a strong influence upon the nature of lattice defects produced by annealing.

  15. Growth of epitaxial orthorhombic YO1.5-substituted HfO2 thin film

    Science.gov (United States)

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Funakubo, Hiroshi

    2015-07-01

    YO1.5-substituted HfO2 thin films with various substitution amounts were grown on (100) YSZ substrates by the pulsed laser deposition method directly from the vapor phase. The epitaxial growth of film with different YO1.5 amounts was confirmed by the X-ray diffraction method. Wide-area reciprocal lattice mapping measurements were performed to clarify the crystal symmetry of films. The formed phases changed from low-symmetry monoclinic baddeleyite to high-symmetry tetragonal/cubic fluorite phases through an orthorhombic phase as the YO1.5 amount increased from 0 to 0.15. The additional annular bright-field scanning transmission electron microscopy indicates that the orthorhombic phase has polar structure. This means that the direct growth by vapor is of polar orthorhombic HfO2-based film. Moreover, high-temperature X-ray diffraction measurements showed that the film with a YO1.5 amount of 0.07 with orthorhombic structure at room temperature only exhibited a structural phase transition to tetragonal phase above 450 °C. This temperature is much higher than the reported maximum temperature of 200 °C to obtain ferroelectricity as well as the expected temperature for real device application. The growth of epitaxial orthorhombic HfO2-based film helps clarify the nature of ferroelectricity in HfO2-based films (186 words/200 words).

  16. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process.

    Science.gov (United States)

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-07-28

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor-liquid-solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core-shell structure that consists of a single-crystalline Si core along the direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires.

  17. Epitaxial growth of Al-Cr-N thin films on MgO(111)

    Energy Technology Data Exchange (ETDEWEB)

    Willmann, H. [Materials Center Leoben, 8700 Leoben (Austria); IFM Material Physics, Division of Thin Film Physics, Linkoeping University, 58183 Linkoeping (Sweden)], E-mail: herwi@ifm.liu.se; Beckers, M. [IFM Material Physics, Division of Thin Film Physics, Linkoeping University, 58183 Linkoeping (Sweden); Birch, J. [IFM Material Physics, Division of Thin Film Physics, Linkoeping University, 58183 Linkoeping (Sweden)], E-mail: jens.birch@ifm.liu.se; Mayrhofer, P.H.; Mitterer, C. [Department of Physical Metallurgy and Materials Testing, University of Leoben, 8700 Leoben (Austria); Hultman, L. [IFM Material Physics, Division of Thin Film Physics, Linkoeping University, 58183 Linkoeping (Sweden)

    2008-11-28

    Cubic rock salt structure Al{sub 0.60}Cr{sub 0.40}N and Al{sub 0.68}Cr{sub 0.32}N films of different thicknesses were grown epitaxially onto MgO(111) substrates by reactive unbalanced magnetron sputtering at 500 deg. C . Rutherford backscattering spectroscopy reveals stoichiometric nitrides with Al/Cr ratios close to the ones of the used compound targets of 60/40 and 70/30. High resolution X-ray diffraction proves epitaxial growth over the whole film thickness up to thicknesses of {approx} 1.8 {mu}m. Reciprocal space maps and selected area electron diffraction show that the Al{sub x}Cr{sub 1-x}N films grow fully relaxed. Scanning and transmission electron microscopy imaging reveals columnar microstructures with column widths between 12-16 nm and {l_brace}001{r_brace} surface faceting on individual columns. The fully relaxed growth and the columnar structure can be attributed to limited ad-atom mobility on the initial Al{sub x}Cr{sub 1-x}n (111) growth surface.

  18. Growth dynamics and an order-disorder transition in epitaxial alloy semiconductors

    Science.gov (United States)

    Nakayama, Hiroshi; Takeguchi, Tohru; Nishino, Taneo

    1996-08-01

    A stochastic theory describing epitaxial growth dynamics in binary alloy systems has been proposed. Considering the "atom correlation" in surface adsorption and diffusion processes, the effective Ising Hamilton of binary elements and the stochastic differential equation (master equation) are combined in a unified manner. Monte-Carlo (MC) calculations made on the basis of the stochastic equation of a binary growing system have successfully revealed the growth dynamics and the evolution of short-range ordering (SRO) and long-range ordering (LRO) during the epitaxial processes. It has been discovered that the LRO parameter shows a peak at a certain temperature below the order-disorder transition temperature. The presence of the peak in the LRO parameter in the order-disorder transition is caused by the interplay of adsorption and diffusion processes involving atom correlation among the surface atoms. As an example, it is noted that the experimental data relating to LRO parameter variation as a function of the growth temperature in a (In,Ga)P pseudobinary alloy exhibits such an order-disorder transition, showing a peak in the LRO value just below the order-disorder transition temperature.

  19. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    Energy Technology Data Exchange (ETDEWEB)

    Oguchi, Hiroyuki, E-mail: oguchi@nanosys.mech.tohoku.ac.jp [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Micro System Integration Center (muSIC), Tohoku University, Sendai 980-0845 (Japan); Ikeshoji, Tamio; Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Kuwano, Hiroki [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2014-11-24

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al{sub 2}O{sub 3} substrates indicated polycrystalline films with a LiAlO{sub 2} secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides.

  20. Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN

    NARCIS (Netherlands)

    Bohnen, T.

    2010-01-01

    Chemical vapor deposition (CVD); hydride vapor phase epitaxy (HVPE); gallium nitride (GaN); indium gallium nitride (InGaN); scandium nitride (ScN); scandium aluminum nitride (ScAlN); semiconductors; thin films; nanowires; III nitrides; crystal growth - We studied the HVPE growth of different III ni

  1. Van der Waals epitaxial double heterostructure: InAs/single-layer graphene/InAs.

    Science.gov (United States)

    Hong, Young Joon; Yang, Jae Won; Lee, Wi Hyoung; Ruoff, Rodney S; Kim, Kwang S; Fukui, Takashi

    2013-12-17

    Van der Waals (vdW) epitaxial double heterostructures have been fabricated by vdW epitaxy of InAs nanostructures on both sides of graphene. InAs nanostructures diametrically form on/underneath graphene exclusively along As-polar direction, indicating polarity inversion of the double heterostructures. First-principles and density functional calculations demonstrate how and why InAs easily form to be double heterostructures with polarity inversion.

  2. 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.

  3. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J. [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

    1996-12-31

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

  4. Structural properties of GaN(0001) epitaxial layers revealed by high resolution X-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    High-resolution X-ray diffraction has been used to analyze GaN(0001) epitaxial layers on sapphire substrates. Several structural properties of GaN, including the lattice constants, strains, and dislocation densities are revealed by the technique of X-ray dffraction (XRD). Lattice constants calculated from the omega/2theta scan are c=0.5185 nm and a=0.3157 nm. Also, the in-plane strain is -1.003%, while out of the plane, the epitaxial film is almost relaxed. Several methods are used to deduce the mosaicity and dislocation density of GaN, showing that the edge type dislocations are the overwhelming majority.

  5. Electrical and Structural Characteristics of High-k Gate Dielectrics with Epitaxial Si3N4 Interfacial Layer on Si(111)

    Science.gov (United States)

    Sim, Hyunjun; Samantaray, Chandan B.; Lee, Taeho; Yeom, Hanwoong; Hwang, Hyunsang

    2004-12-01

    In this study, the electrical and structural characteristics of Gd2O3 gate dielectrics with an epitaxial Si3N4 interfacial layer grown on Si(111) were investigated. Compared with control Gd2O3 gate dielectrics deposited on HF-last treated Si (111), the Gd2O3 gate dielectrics with an epitaxial Si3N4 interfacial layer exhibited excellent electrical characteristics such as low leakage current density and low interface state density. These characteristics are due to a high-quality interfacial layer formation on Si. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were employed to analyze the structures of the gate dielectrics and interfacial layer. High-k gate dielectrics with an epitaxial Si3N4 interfacial layer have considerable potential for future use in sub-0.1 μm metal oxide semiconductor field-effect transistors (MOSFETs).

  6. Growth of Catalyst-Free Epitaxial InAs Nanowires on Si Wafers Using Metallic Masks.

    Science.gov (United States)

    Soo, M Teng; Zheng, Kun; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Zou, Jin

    2016-07-13

    Development of heteroepitaxy growth of catalyst-free vertical III-V nanowires on Si wafers is highly desirable for future nanoscale Si-based electronic and optoelectronic devices. In this study, a proof-of-concept approach is developed for catalyst-free heteroepitaxy growth of InAs nanowires on Si wafers. Before the growth of InAs nanowires, a Si-compatible metallic film with a thickness of several tens of nanometers was predeposited on a Si wafer and then annealed to form nanosize openings so as to obtain a metallic mask. These nano-openings exposed the surface of the Si wafer, which allowed subsequent nucleation and growth of epitaxial InAs nanowires directly on the surface of the Si wafer. The small size of the nano-openings limits the lateral growth of the nanostructures but promotes their axial growth. Through this approach, catalyst-free InAs nanowires were grown on both Si (111) and (001) wafers successfully at different growth temperatures. In particular, ultralong defect-free InAs nanowires with the wurtzite structure were grown the Si (111) wafers at 550 °C using the Ni mask. This study offers a simple, cost-effective, and scalable method to grow catalyst-free III-V nanowires on Si wafers. The simplicity of the approach opens a new avenue for the growth and integration of catalyst-free high-quality heteroepitaxial III-V nanowires on Si wafers.

  7. Epitaxial growth and high-frequency properties of YBa{sub 2}Cu{sub 3}O{sub 7} electrodes on LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, F.; Ferrater, C.; Garcia-Cuenca, M.V.; Varela, M. [Dept. de Fisica Aplicada i Optica, Univ. de Barcelona, Barcelona (Spain); Collado, C.; Mateu, J.; Menendez, O.; O' Callaghan, J.M. [Dept. de Teoria del Senyal i Comunicacions, Campus Nord UPC, Barcelona (Spain); Fabrega, L.; Rubi, R.; Fontcuberta, J. [Inst. de Ciencia de Materials de Barcelona (CSIC), Campus de la UAB, Bellaterra (Spain)

    2003-07-01

    Epitaxial YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) thin films were deposited on electro-optic X-cut LiNbO{sub 3} (LNO) single crystals by pulsed laser deposition. A double buffer layer of yttria-stabilized zirconia (YSZ) and CeO{sub 2} was found necessary to grow high quality superconducting films. The YSZ layer prevents diffusion from the substrate to the YBCO, although promotes the formation of LiNb{sub 3}O{sub 8} at the interface. The CeO{sub 2} top buffer layer is required to avoid the nucleation of two different YBCO crystal domains, 45 rotated. When growth is on the double buffer layer, the YBCO films are epitaxial, with the c axis perpendicular to the surface and single in-plane orientation. The films are superconducting at temperatures above 85 K, with critical current densities of 3 x 10{sup 5} A/cm{sup 2} at 77 K (6 x 10{sup 6} A/cm{sup 2} at 5 K). A surface resistance below 1.5 m{omega} was measured at 8 GHz and 65 K, making these films promising candidates as electrodes in photonic and acoustic devices. (orig.)

  8. 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.

  9. 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.

  10. Integration of in situ RHEED with magnetron sputter deposition for atomic layer controlled growth

    Science.gov (United States)

    Podkaminer, Jacob P.

    Epitaxial thin films continue to be one of the most promising topics within electronic materials research. Sputter deposition is one process by which these films can be formed and is a widely used growth technique for a large range of technologically important material systems. Epitaxial films of carbides, nitrides, metals, oxides and more can all be formed during the sputter process which offers the ability to deposit smooth and uniform films from the research level up to an industrial scale. This tunable kinematic deposition process excels in easily adapting for a large range of environments and growth procedures. Despite the vast advantages associated with sputter deposition, there is a significant lack of in situ analysis options during sputtering. In particular, the area of real time atomic layer control is severely deficient. Atomic layer controlled growth of epitaxial thin films and artificially layered superlattices is critical for both understanding their emergent phenomena and engineering novel material systems and devices. Reflection high-energy electron diffraction (RHEED) is one of the most common in situ analysis techniques during thin film deposition that is rarely used during sputtering due to the strong permanent magnets in magnetron sputter sources and their effect on the RHEED electron beam. In this work we have solved this problem and designed a novel way to deter the effect of the magnets for a wide range of growth geometries and demonstrate the ability for the first time to have layer by layer control during sputter deposition by in situ RHEED. A novel growth chamber that can seamlessly change between pulsed laser deposition and sputtering with RHEED for the growth of complex heterostructures has been designed and implemented. Epitaxial thin films of LaAlO3, La1-xSrxMnO3, and SrRuO3 have all been deposited by sputtering and shown to exhibit clear and extended RHEED oscillations. To solve the magnet issue, a finite element model has been

  11. 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.

  12. 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.

  13. Influences of Pressure and Substrate Temperature on Epitaxial Growth of γ-Mg2SiO4 Thin Films on Si Substrates

    Institute of Scientific and Technical Information of China (English)

    KANG Lin; GAO Ju; XU Hua-Rong; ZHAO Shao-Qi; CHEN Hong; WU Pei-Heng

    2007-01-01

    An epitaxial,γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films.For high temperature superconducting multilayer structures,hopefully it can be taken as an insulating layer to replace the widely used MgO film.To explore such possibilities,we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si(100) substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent.With the substrate temperature kept at 500℃and the pressure changing from 10Pa to 15Pa,in the XRD spectra the γ-Mg2SiO4(400) peak grows drastically while the MgO(200)peak is suppressed.Keeping the pressure at 15 Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy,while working at 780℃ and 11 Pa seems to give very good results.X-ray photoelectronic spectroscopy and φscan are used to characterize the stoichiometry,crystallinity,and in-plane growth of the samples.

  14. Ultra-thin crystalline silicon films produced by plasma assisted epitaxial growth on silicon wafers and their transfer to foreign substrates*

    Directory of Open Access Journals (Sweden)

    Cabarrocas P. Roca i

    2010-10-01

    Full Text Available We have developed a new process to produce ultra-thin crystalline silicon films with thicknesses in the range of 0.1 − 1 μm on flexible substrates. A crystalline silicon wafer was cleaned by SiF4 plasma exposure and without breaking vacuum, an epitaxial film was grown from SiF4, H2 and Ar gas mixtures at low substrate temperature (Tsub ≈ 200 °C in a standard RF PECVD reactor. We found that H2 dilution is a key parameter for the growth of high quality epitaxial films and modification of the structural composition of the interface with the c-Si wafer, allowing one to switch from a smooth interface at low hydrogen flow rates to a fragile one, composed of hydrogen-rich micro-cavities, at high hydrogen flow rates. This feature can be advantageously used to separate the epitaxial film from the crystalline Si wafer. As a example demonstration, we show that by depositing a metal film followed by a spin-coated polyimide layer and applying a moderate thermal treatment to the stack, the fragile interface breaks down and allows one to obtain an ultrathin crystalline wafer on the flexible polyimide support.

  15. 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.

  16. Carbon nanofiber growth on thin rhodium layers

    NARCIS (Netherlands)

    Chinthaginjala, J.K.; Unnikrishnan, S.; Smithers, M.A.; Kip, G.A.M.; Lefferts, L.

    2012-01-01

    A thinlayer of carbon nanofibers (CNFs) was synthesized on a thin polycrystalline rhodium (Rh) metal layer by decomposing ethylene in the presence of hydrogen. Interaction of Rh crystals with carbon results in fragmentation and formation of Rh-nanoparticles, facilitating CNF growth. CNFs are immobil

  17. Epitaxial growth and electrical transport properties of La0.5Sr0.5CoO3 thin films prepared by pulsed laser deposition

    Institute of Scientific and Technical Information of China (English)

    李美亚; 熊光成; 王忠烈; 范守善; 赵清太; 林揆训

    1999-01-01

    Epitaxial growth of the La0.5Sr0.5CoO3(LSCO) thin films has been realized on LaAlO3, SrTiO3 and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaAlO3 substrates at about 700℃ possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made.

  18. Epitaxial growth of higher transition-temperature VO2 films on AlN/Si

    Directory of Open Access Journals (Sweden)

    Tetiana Slusar

    2016-02-01

    Full Text Available We report the epitaxial growth and the mechanism of a higher temperature insulator-to-metal-transition (IMT of vanadium dioxide (VO2 thin films synthesized on aluminum nitride (AlN/Si (111 substrates by a pulsed-laser-deposition method; the IMT temperature is TIMT ≈ 350 K. X-ray diffractometer and high resolution transmission electron microscope data show that the epitaxial relationship of VO2 and AlN is VO2 (010 ‖ AlN (0001 with VO2 [101] ‖   AlN   [ 2 1 ̄ 1 ̄ 0 ] zone axes, which results in a substrate-induced tensile strain along the in-plane a and c axes of the insulating monoclinic VO2. This strain stabilizes the insulating phase of VO2 and raises TIMT for 10 K higher than TIMT single crystal ≈ 340 K in a bulk VO2 single crystal. Near TIMT, a resistance change of about four orders is observed in a thick film of ∼130 nm. The VO2/AlN/Si heterostructures are promising for the development of integrated IMT-Si technology, including thermal switchers, transistors, and other applications.

  19. 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.

  20. Growth of 3C-SiC on 150-mm Si(100) substrates by alternating supply epitaxy at 1000 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Wang Li, E-mail: l.wang@griffith.edu.au; Dimitrijev, Sima; Han, Jisheng; Iacopi, Alan; Hold, Leonie; Tanner, Philip; Harrison, H. Barry

    2011-07-29

    To lower deposition temperature and reduce thermal mismatch induced stress, heteroepitaxial growth of single-crystalline 3C-SiC on 150 mm Si wafers was investigated at 1000 deg. C using alternating supply epitaxy. The growth was performed in a hot-wall low-pressure chemical vapor deposition reactor, with silane and acetylene being employed as precursors. To avoid contamination of Si substrate, the reactor was filled in with oxygen to grow silicon dioxide, and then this thin oxide layer was etched away by silane, followed by a carbonization step performed at 750 deg. C before the temperature was ramped up to 1000 deg. C to start the growth of SiC. Microstructure analyses demonstrated that single-crystalline 3C-SiC is epitaxially grown on Si substrate and the film quality is improved as thickness increases. The growth rate varied from 0.44 to 0.76 {+-} 0.02 nm/cycle by adjusting the supply volume of SiH{sub 4} and C{sub 2}H{sub 2}. The thickness nonuniformity across wafer was controlled with {+-} 1%. For a prime grade 150 mm virgin Si(100) wafer, the bow increased from 2.1 to 3.1 {mu}m after 960 nm SiC film was deposited. The SiC films are naturally n type conductivity as characterized by the hot-probe technique.

  1. Chemical order and selection of the mechanism for strain relaxation in epitaxial FePd(Pt) thin layers

    Science.gov (United States)

    Halley, D.; Marty, A.; Bayle-Guillemaud, P.; Gilles, B.; Attane, J. P.; Samson, Y.

    2004-11-01

    We observed that the relaxation mechanism of the epitaxial strain is dramatically dependent on the chemical ordering within the L10 structure in FePd(Pt) thin films. In disordered or weakly ordered layers, the relaxation takes place though perfect (1)/(2)[101] dislocations, whereas well-ordered films relax through the partial 1/6[112] Shockley dislocations, piled-up within microtwins, with a huge impact on both the morphology and the magnetic properties of the film. We show that the antiphase boundary energy is the key factor preventing the propagation of perfect dislocations in ordered alloys.

  2. The structural transition from epitaxial Fe/Pt multilayers to an ordered FePt film using low energy ion beam sputtering deposition with no buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chih-Hao, E-mail: chlee@mx.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Yu-Sheng [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Liu, Li-Jung [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Huang, J.C.A. [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2014-11-03

    An epitaxial L1{sub 0} FePt thin film grown from an [Fe(10 Å)/Pt(10 Å)]{sub 15} multilayer with the orientation of (001) was prepared by an ion beam sputtering deposition method without buffer layer. From the measurement data of X-ray diffraction and X-ray reflectivity, the multilayer structure was totally disappeared and a uniform FePt alloy thin film was formed at temperatures higher than 600 °C. For the as-deposited thin film grown at 100 °C, the multilayer already possesses an epitaxial structure. The epitaxial relation is FePt(001)[100]//MgO(001)[100] and this epitaxial relation persists after sequential high temperature annealing. An epitaxial L1{sub 0} ordered FePt(001) film with order parameter of 0.95 was obtained when the annealing temperature reached 650 °C. The ordered FePt(001) thin film has a perpendicular magnetic anisotropy with a squareness of 0.95 ± 0.03 on the magnetic hysteresis loop. This experiment demonstrates that the low energy ion beam sputtering deposition will preserve the epitaxial relation with no buffer layer between multilayer and substrate. - Highlights: • The Fe/Pt films using ion sputtering deposition with no buffer layer is epitaxial. • Multilayer structure was totally disappeared at temperatures higher than 600 °C. • Order parameter reach 0.95 after annealing at 650 °C. • Interfacial epitaxial FePt alloy already formed at 100 °C.

  3. 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.

  4. Epitaxial growth of Ti{sub 3}SiC{sub 2} thin films with basal planes parallel or orthogonal to the surface on {alpha}-SiC

    Energy Technology Data Exchange (ETDEWEB)

    Drevin-Bazin, A.; Barbot, J. F.; Alkazaz, M.; Cabioch, T.; Beaufort, M. F. [Institut Pprime, UPR 3346, CNRS-Universite de Poitiers-ENSMA, Departement de Physique et Mecanique des Materiaux, SP2MI, Teleport 2, Bd M. et P. Curie, BP 30179, F-86962 Futuroscope-Chasseneuil (France)

    2012-07-09

    The growth of Ti{sub 3}SiC{sub 2} thin films were studied onto {alpha}-SiC substrates differently oriented by thermal annealing of TiAl layers deposited by magnetron sputtering. For any substrate's orientation, transmission electron microscopy coupled with x-ray diffraction showed the coherent epitaxial growth of Ti{sub 3}SiC{sub 2} films along basal planes of SiC. Specifically for the (1120) 4H-SiC, Ti{sub 3}SiC{sub 2} basal planes are found to be orthogonal to the surface. The continuous or textured nature of Ti{sub 3}SiC{sub 2} films does not depend of the SiC stacking sequence and is explained by a step-flow mechanism of growth mode. The ohmic character of the contact was confirmed by current-voltage measurements.

  5. Monitoring of elastic stresses with optical system for measuring the substrate curvature in growth of III-N heterostructures by molecular-beam epitaxy

    Science.gov (United States)

    Zolotukhin, D. S.; Nechaev, D. V.; Ivanov, S. V.; Zhmerik, V. N.

    2017-03-01

    An original optical system for measuring substrate curvature (OSMSC) is described. The system enables a high-precision analysis of the processes of generation and relaxation of elastic stresses in growth of heterostructures (HSs) based on nitride compounds III-N by plasma-assisted molecular-beam epitaxy (PA-MBE). The application of OSMSC to analyze the growth of GaN/AlN/Si(111) HSs made it possible not only to observe in detail the variation dynamics of elastic stresses in this structure in its metal-enriched growth by low-temperature PA-MBE, but also to develop an HS design eliminating the effect of layer cracking by controlling the compressive stresses.

  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. Synthesis of Indium Nitride Epitaxial Layers on a Substrate of Porous Indium Phosphide

    Directory of Open Access Journals (Sweden)

    J.A. Suchikova

    2015-10-01

    Full Text Available The paper presents a technique to obtain InN films on porous InP substrates by radical-beam gettering epitaxy. According to the results of the Auger spectroscopy, InN film thickness ranged from 100 nm to 0.5 microns depending on the etching conditions.

  8. 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.

  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. Growth and characterization of ultrathin epitaxial MnO film on Ag(001)

    Science.gov (United States)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-07-01

    We present here a comprehensive growth procedure to obtain a well-ordered MnO(001) ultrathin film on Ag(001) substrate. Depending upon the oxygen partial pressure during the growth, different phases of manganese oxide have been detected by Low Energy Electron Diffraction (LEED) and X-ray Photoelectron Spectroscopic (XPS) studies. A modified growth scheme has been adopted to get well-ordered and stoichiometric MnO(001) ultrathin film. The detailed growth mechanism of epitaxial MnO film on Ag(001) has been studied step by step, using LEED and XPS techniques. Observation of sharp (1 × 1) LEED pattern with a low inelastic background, corresponds to a long-range atomic order with low defect densities indicating the high structural quality of the film. The Mn 2p and Mn 3s core-level spectra confirm the oxidation state as well as the stoichiometry of the grown MnO films. Apart from the growth optimization, the evolution of strain relaxation of the MnO(001) film with film thickness has been explored.

  11. Electrodeposition of a Pt monolayer film: using kinetic limitations for atomic layer epitaxy.

    Science.gov (United States)

    Brimaud, Sylvain; Behm, R Jürgen

    2013-08-14

    A new and facile one-step method to prepare a smooth Pt monolayer film on a metallic substrate in the absence of underpotential deposition-type stabilizations is presented as a general approach and applied to the growth of Pt monolayer films on Au. The strongly modified electronic properties of these films were demonstrated by in situ IR spectroscopy at the electrified solid-liquid interface with adsorbed carbon monoxide serving as a probe molecule. The Pt monolayer on Au is kinetically stabilized by adsorbed CO, inhibiting further Pt deposition in higher layers.

  12. Low temperature growth of high quality CdTe polycrystalline layers

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, I R B [Departamento de Fisica, Universidade Federal de Vicosa, Vicosa, MG (Brazil); Suela, J [Departamento de Fisica, Universidade Federal de Vicosa, Vicosa, MG (Brazil); Oliveira, J E [Departamento de Fisica, Universidade Federal de Vicosa, Vicosa, MG (Brazil); Ferreira, S O [Departamento de Fisica, Universidade Federal de Vicosa, Vicosa, MG (Brazil); Motisuke, P [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, SP (Brazil)

    2007-08-07

    We have investigated the growth of CdTe thin films on glass substrates by hot wall epitaxy. The layers have been characterized by scanning electron microscopy, atomic force microscopy, profilometry, x-ray diffraction and optical transmission. The grown samples are polycrystalline with a high preferential [1 1 1] orientation. Atomic force microscopy and scanning electron microscopy reveal pyramidal grain shapes with a size of around 0.3 {mu}m. The surface roughness increases with sample thickness and growth temperature, reaching about 200 nm for 10 {mu}m thick layers grown at 300 deg. C. Samples with a thickness of 2 {mu}m grown at 150 deg. C showed a roughness of less than 40 nm. Optical transmission measurements demonstrate layers with high optical quality.

  13. Low temperature growth of high quality CdTe polycrystalline layers

    Science.gov (United States)

    Ribeiro, I. R. B.; Suela, J.; Oliveira, J. E.; Ferreira, S. O.; Motisuke, P.

    2007-08-01

    We have investigated the growth of CdTe thin films on glass substrates by hot wall epitaxy. The layers have been characterized by scanning electron microscopy, atomic force microscopy, profilometry, x-ray diffraction and optical transmission. The grown samples are polycrystalline with a high preferential [1 1 1] orientation. Atomic force microscopy and scanning electron microscopy reveal pyramidal grain shapes with a size of around 0.3 µm. The surface roughness increases with sample thickness and growth temperature, reaching about 200 nm for 10 µm thick layers grown at 300 °C. Samples with a thickness of 2 µm grown at 150 °C showed a roughness of less than 40 nm. Optical transmission measurements demonstrate layers with high optical quality.

  14. Atomic layer epitaxy of group 4 materials: Surface processes, thin films, devices and their characterization

    Science.gov (United States)

    Davis, Robert F.

    1994-06-01

    The viability of Si2Cl6, C2H2 and C2H4 as precursors for chemically self-limiting ALE of SiC has been investigated via XPS and LEED. Si2Cl6 readily adsorbs in a self-limiting manner on a Si(100) surface; however, neither hydrocarbon will adsorb or react with a Cl-terminated Si surface to 475 deg C. Conversely, partial chlorination of Si(100) saturated with C2H2 and C2H4 does occur and implies that Si2Cl6 will adsorb/react with a hydrocarbon terminated surface. Layer-by-layer growth of Beta-SiC on Si(100) or 6H-SiC has been achieved with a carrier concentration of approx. 10(exp 17)/cu cm. P-type doping with Al has allowed the achievement of hole concentrations of 4 x 10(exp 18) - 2 10(exp 20)/cu cm. Efforts to produce an HBT using Beta-SiC emitters is described. Ni3Si has been employed for the deposition of diamond because of the close lattice match. Under the same growth conditions, diamond particles were obtained on the Ni3Si, but only diamond-like C and graphite on pure Ni substrates. Evidence of oriented particles was observed. REED and TEM of cerium oxide films grown on Si(111) substrates has revealed the formation of a dual amorphous layer of CeOx and SiO2 at the Si interface followed by a layer of CeO2. Post annealing in dry oxygen caused the CeOx layer to disappear and the SiO2 layer to thicken. D(sub it) = 6 x 10(exp 11)/sq cm and Q sub f = 5 x 10(exp 11)/sq cm. The structure exhibits a high capacitance due to the large dielectric constant of CeO2 and has electrical properties comparable with those of other reported gate insulators on Si.

  15. 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.

  16. 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.

  17. Epitaxial growth of a single-domain hexagonal boron nitride monolayer.

    Science.gov (United States)

    Orlando, Fabrizio; Lacovig, Paolo; Omiciuolo, Luca; Apostol, Nicoleta G; Larciprete, Rosanna; Baraldi, Alessandro; Lizzit, Silvano

    2014-12-23

    We investigate the structure of epitaxially grown hexagonal boron nitride (h-BN) on Ir(111) by chemical vapor deposition of borazine. Using photoelectron diffraction spectroscopy, we unambiguously show that a single-domain h-BN monolayer can be synthesized by a cyclic dose of high-purity borazine onto the metal substrate at room temperature followed by annealing at T=1270 K, this method giving rise to a diffraction pattern with 3-fold symmetry. In contrast, high-temperature borazine deposition (T=1070 K) results in a h-BN monolayer formed by domains with opposite orientation and characterized by a 6-fold symmetric diffraction pattern. We identify the thermal energy and the binding energy difference between fcc and hcp seeds as key parameters in controlling the alignment of the growing h-BN clusters during the first stage of the growth, and we further propose structural models for the h-BN monolayer on the Ir(111) surface.

  18. 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.

  19. Reaction mechanisms in the organometallic vapor phase epitaxial growth of GaAs

    Science.gov (United States)

    Larsen, C. A.; Buchan, N. I.; Stringfellow, G. B.

    1988-01-01

    The decomposition mechanisms of AsH3, trimethylgallium (TMGa), and mixtures of the two have been studied in an atmospheric-pressure flow system with the use of D2 to label the reaction products which are analyzed in a time-of-flight mass spectrometer. AsH3 decomposes entirely heterogeneously to give H2. TMGa decomposes by a series of gas-phase steps, involving methyl radicals and D atoms to produce CH3D, CH4, C2H6, and HD. TMGa decomposition is accelerated by the presence of AsH3. When the two are mixed, as in the organometallic vapor phase epitaxial growth of GaAs, both compounds decompose in concert to produce only CH4. A likely model is that of a Lewis acid-base adduct that forms and subsequently eliminates CH4.

  20. 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.

  1. Wetting of microstructured alumina fabricated by epitaxial growth of Al4B2O9 whiskers

    Science.gov (United States)

    Wang, Yifeng; Feng, Jicai; Chen, Zhe; Song, Xiaoguo; Cao, Jian

    2015-12-01

    Topographical microstructures were fabricated on alumina by epitaxial growth of Al4B2O9 whiskers in air. The products were characterized via scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The whiskers were found to grow along the [0 0 1] crystallographic direction, and the lattice mismatch between Al2O3 and Al4B2O9 was determined to be 0.03%. The wetting of the Al4B2O9-whisker-coated surfaces by Ag-36.7Cu-8.0Ti at.% alloy was studied. The time needed to reach the equilibrium stage reduced as the temperature increased, and the final contact angle for liquid alloy on the rough surface was 27° at 880 °C. The wetting dynamics of the whiskers coated surfaces was investigated. After wetting, a whisker-interconnected region was formed between alumina and the alloy.

  2. 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.

  3. 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.

  4. A new approach to grow C-doped GaN thick epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Gogova, D.; Siche, D.; Albrecht, M.; Irmscher, K.; Rost, H.J.; Fornari, R. [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Rudko, G.Yu. [V. Lashkarev Institute of Semiconductors Physics, 03028 Kiev (Ukraine)

    2011-07-15

    In this study we employ a new method for growth of carbon-doped wurtzite crystalline GaN (GaN:C) based on vapour phase transport of Ga by the pseudohalide hydrogen cyanide HCN. GaN:C layers with a thicknesses from 10 to 100 {mu}m and up to 19 mm in size were grown from gallium melt and ammonia as feeding materials in a carbon-containing equipment. The properties of the GaN:C layers were characterized by low-temperature photoluminescence (LTPL), High-Resolution X-ray Diffraction (HRXRD), Secondary Ion Mass Spectrometry (SIMS) and room-temperature Hall effect and Raman spectroscopy measurements. HRXRD studies demonstrated good crystalline quality of the thick GaN layers (the Rocking curve FWHMs are 570 arcsec for the (0004) reflection and 561 arcsec for the (10-14) reflection for 10 {mu}m thick samples). The LTPL and Raman spectroscopy confirmed the good optical and structural quality of the material. The carbon concentration measured by SIMS was 6x10{sup 18} cm{sup -3}, however, the room-temperature Hall effect experiments showed n-type conductivity. Carbon acceptor incorporation into GaN (from the transport agent) as well as the reason of its electrical overcompensation by unintentional impurities like oxygen and silicon is discussed. Ways of technological process improvement are proposed. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Scaling analysis of self-assembled structures and related morphological information in epitaxial growth

    Science.gov (United States)

    Blel, Sonia; Hamouda, Ajmi B. H.; Mahjoub, Brahim; Hoggan, Philip; Oujia, Brahim

    2017-02-01

    Using kinetic Monte-Carlo simulations, we have performed a qualitative and quantitative study of the homo-epitaxial growth for two materials Cu and Ag. Based on their dynamic scaling properties, a relationship between the resultant growth morphology and its computed scaling exponents is found to play a key role in the surface self-assembled at long time (hundreds of monolayer) and also at early time (sub-monolayer regime) of growth. Then, the effect of next-nearest-neighbor (NNN) interactions on the scaling exponents, as well as the surface morphology, is discussed. NNN interactions are found to affect the scaling exponents in the case of Cu rather than Ag. We also show that the higher the local roughness, the best 1-D nanostructures are obtained; which is confirmed by the measurement of filling rate of nanowires at step-edge on vicinal surfaces. Our results were compared to the available experimental and theoretical results and seem advantageous for a better understanding of the growth dynamics.

  6. Growth temperature-dependent metal–insulator transition of vanadium dioxide epitaxial films on perovskite strontium titanate (111) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liangxin; Zhao, Jiangtao; Hong, Bin; Hu, Kai; Luo, Zhenlin [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230029 (China); Yang, Yuanjun, E-mail: yangyuanjun@ustc.edu.cn, E-mail: cgao@ustc.edu.cn; Gao, Chen, E-mail: yangyuanjun@ustc.edu.cn, E-mail: cgao@ustc.edu.cn [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230029 (China); Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Peng, Jinlan; Zhang, Haibin; Wen, Xiaolei; Li, Xiaoguang [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2016-04-14

    Vanadium dioxide (VO{sub 2}) epitaxial films were grown on perovskite single-crystal strontium titanate (SrTiO{sub 3}) substrates by reactive radio-frequency magnetron sputtering. The growth temperature-dependent metal–insulator transition (MIT) behavior of the VO{sub 2} epitaxial films was then investigated. We found that the order of magnitude of resistance change across the MIT increased from 10{sup 2} to 10{sup 4} with increasing growth temperature. In contrast, the temperature of the MIT does not strongly depend on the growth temperature and is fairly stable at about 345 K. On one hand, the increasing magnitude of the MIT is attributed to the better crystallinity and thus larger grain size in the (010)-VO{sub 2}/(111)-SrTiO{sub 3} epitaxial films at elevated temperature. On the other hand, the strain states do not change in the VO{sub 2} films deposited at various temperatures, resulting in stable V-V chains and V-O bonds in the VO{sub 2} epitaxial films. The accompanied orbital occupancy near the Fermi level is also constant and thus the MIT temperatures of VO{sub 2} films deposited at various temperatures are nearly the same. This work demonstrates that high-quality VO{sub 2} can be grown on perovskite substrates, showing potential for integration into oxide heterostructures and superlattices.

  7. Current Transport Behaviour of Au/n-GaAs Schottky Diodes Grown on Ge Substrate With Different Epitaxial Layer Thickness Over a Wide Temperature Range

    Directory of Open Access Journals (Sweden)

    N. Padha

    2011-01-01

    Full Text Available The work presents temperature dependent forward and reverse current-voltage (I-V analyses of n-GaAs/Au Schottky Diodes grown on n+ Ge substrate with different epitaxial layer thicknesses. While some of the Schottky diodes follow TED mechanism, others exceed significantly from this theory due to existence of patches of reduced barrier height embedded in the Schottky interface. The zero bias barrier heights (φbo increase (0.649 to 0.809 eV while the ideality factors (η decrease (1.514 to 1.052 with increase in epitaxial layer thickness (1-4 μm, thus, indicating similar behaviour to that observed for the I-V characteristics of the undertaken Schottky diodes with decreasing temperature. It all indicated the existence of barrier inhomogenities over the M-S interface. The breakdown behaviour analysis of these diodes showed some interesting results; the breakdown voltage (VBR decreases with temperature and shows ‘Defect Assisted Tunneling’ phenomenon through surface or defect states in the 1 μm thick epitaxial layer Schottky diode while VBR increases with temperature in 3 μm and 4 μm thick epitaxial layer Schottky diodes which demonstrate ‘Avalanche Multiplication’ mechanism responsible for junction breakdown. The reverse breakdown voltage is also seen to increase (2.7-5.9 Volts with the increase in epitaxial layer thickness of the diodes. The undertaken diodes have been observed to follow TFE mechanism at low temperatures (below 200 K in which the tunneling current component increases with epitaxial layer thickness which has been ascribed as an impact of GaAs/Ge hetero-interface over the Au/n-GaAs Schottky barrier.

  8. Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

    Energy Technology Data Exchange (ETDEWEB)

    Malinverni, M., E-mail: marco.malinverni@epfl.ch; Lamy, J.-M.; Martin, D.; Grandjean, N. [ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Feltin, E.; Dorsaz, J. [NOVAGAN AG, CH-1015 Lausanne (Switzerland); Castiglia, A.; Rossetti, M.; Duelk, M.; Vélez, C. [EXALOS AG, CH-8952 Schlieren (Switzerland)

    2014-12-15

    We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH{sub 3}-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10{sup −4} Ω cm{sup 2}, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH{sub 3}-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm{sup 2} ridge dimension and a threshold current density of ∼5 kA cm{sup −2} in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al{sub 0.06}Ga{sub 0.94}N:Mg despite the low growth temperature.

  9. 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.

  10. Laser-induced fluorescence analysis of plasmas for epitaxial growth of YBiO3 films with pulsed laser deposition

    Science.gov (United States)

    Orsel, Kasper; Groenen, Rik; Bastiaens, Bert; Koster, Gertjan; Rijnders, Guus; Boller, Klaus-J.

    2016-12-01

    We record the two-dimensional laser-induced fluorescence (LIF) on multiple plasma constituents in a YBiO3 plasma. This allows us to directly link the influence of oxygen present in the background gas during pulsed laser deposition to the oxidation of plasma species as well as the formation of epitaxial YBiO3 films. With spatiotemporal LIF mapping of the plasma species (Y, YO, Bi, and BiO) in different background gas compositions, we find that little direct chemical interaction takes place between the plasma plume constituents and the background gas. However, a strong influence of the background gas composition can be seen on the YBO film growth, as well as a strong correlation between the oxygen fraction in the background gas and the amount of YO in the plasma plume. We assign this correlation to a direct interaction between the background gas and the target in between ablation pulses. In an O2 background, an oxygen-rich surface layer forms in between ablation pulses, which provides additional oxygen for the plasma plume during target ablation. This differs from our previous observations in STO and LAO plasmas, where species oxidation primarily takes place during propagation of the plasma plume towards the substrate.

  11. Laser-induced fluorescence analysis of plasmas for epitaxial growth of YBiO3 films with pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Kasper Orsel

    2016-12-01

    Full Text Available We record the two-dimensional laser-induced fluorescence (LIF on multiple plasma constituents in a YBiO3 plasma. This allows us to directly link the influence of oxygen present in the background gas during pulsed laser deposition to the oxidation of plasma species as well as the formation of epitaxial YBiO3 films. With spatiotemporal LIF mapping of the plasma species (Y, YO, Bi, and BiO in different background gas compositions, we find that little direct chemical interaction takes place between the plasma plume constituents and the background gas. However, a strong influence of the background gas composition can be seen on the YBO film growth, as well as a strong correlation between the oxygen fraction in the background gas and the amount of YO in the plasma plume. We assign this correlation to a direct interaction between the background gas and the target in between ablation pulses. In an O2 background, an oxygen-rich surface layer forms in between ablation pulses, which provides additional oxygen for the plasma plume during target ablation. This differs from our previous observations in STO and LAO plasmas, where species oxidation primarily takes place during propagation of the plasma plume towards the substrate.

  12. 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.

  13. Morphology and optical properties of InN layers grown by molecular beam epitaxy on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Grandal, J.; Sanchez-Garcia, M.A.; Calle, F.; Calleja, E. [Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)

    2005-05-01

    This work reports on the morphology and photoluminescence (PL) properties of wurtzite InN layers grown by plasma assisted molecular beam epitaxy (PA-MBE) on AlN-buffered 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 columnar InN layers, to stoichiometric conditions leading to coalesced InN layers. X-Ray Diffraction (XRD) rocking curves around the InN (002) reflection yield a minimum value of 682 arcsec full width at half maximum (FWHM) for a coalesced InN layer. PL intensity from columnar InN samples is two orders of magnitude stronger than that corresponding to coalesced material, pointing to a much higher crystalline quality of the former. PL spectra in columnar InN layers reveal an emission at 0.75 eV (16 K) that follows the typical band-gap temperature dependence and shows a linear trend with the excitation power, suggesting a band-edge recombination that yields an estimate of the energy gap for InN around 0.72 eV at room temperature. No other emissions are observed at higher energies. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Depth-dependent phase change in Gd{sub 2}O{sub 3} epitaxial layers under ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Mejai, N.; Debelle, A., E-mail: aurelien.debelle@u-psud.fr; Thomé, L.; Sattonnay, G. [Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Univ. Paris-Sud, CNRS, Université Paris-Saclay, Bâtiment 108, 91405 Orsay Cedex (France); Gosset, D. [CEA-Saclay, DEN-DMN-SRMA-LA2M, Gif/Yvette (France); Boulle, A. [Science des Procédés Céramiques et de Traitements de Surface CNRS UMR 7315, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges (France); Dargis, R.; Clark, A. [Translucent Inc., 952 Commercial St., Palo Alto, California 94303 (United States)

    2015-09-28

    Epitaxial Gd{sub 2}O{sub 3} thin layers with the cubic structure were irradiated with 4-MeV Au{sup 2+} ions in the 10{sup 13}–10{sup 15} cm{sup −2} fluence range. X-ray diffraction indicates that ion irradiation induces a cubic to monoclinic phase change. Strikingly, although the energy-deposition profile of the Au{sup 2+} ions is constant over the layer thickness, this phase transformation is depth-dependent, as revealed by a combined X-ray diffraction and ion channeling analysis. In fact, the transition initiates very close to the surface and propagates inwards, which can be explained by an assisted migration process of irradiation-induced defects. This result is promising for developing a method to control the thickness of the rare-earth oxide crystalline phases.

  15. Effects of Sb incorporation in GaAsSb-capping layer on the optical properties of InAs/GaAs QDs grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Salhi, A.; Alshaibani, S.; Alhamdan, M.; Albrithen, H.; Alyamani, A.; El-Desouki, M.

    2017-01-01

    We have investigated the effect of antimony incorporation in GaAsSb as a capping layer on the optical properties of InAs quantum dots grown by Molecular Beam Epitaxy. Atomic Force Microscopy (AFM), High Resolution X-Ray Diffraction (HRXRD), photoluminescence (PL) and power dependent PL at 77 K and 300 K have been used for the characterization of the grown samples. Our analysis showed that the emission wavelength increases with Sb content and reaches ∼1.5 μm for Sb concentration of 22%. To achieve this wavelength, a reduction of the growth temperature of the GaAsSb layer from 500 °C to 440 °C was necessary. The wavelength increase is accompanied by a transition from a type I to type II band alignment and a broadening of the PL spectrum to a value of ∼237 nm for an excitation power of 100 mW. This broadening is attributed to the QD size inhomogeneity increase and Sb atoms redistribution during the in-situ annealing during the growth of the barriers at elevated temperature. Our results show the potential of the InAs/GaAsSb system in the development of broadband light sources and super-luminescent light emitting diodes in 1.2-1.5 μm wavelength range.

  16. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    Science.gov (United States)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  17. Growth and characterization of epitaxial SrF2 on InP(100)

    Science.gov (United States)

    Sinharoy, S.; Hoffman, R. A.; Rieger, J. H.; Warner, J. D.; Bhasin, K. B.

    1986-01-01

    The epitaxial growth of 100-262.5-nm SrF2 films on n-type and p-type (100)InP in a conventional baked UHV system at base pressure about 200 ptorr, temperature 250-350 C, and growth rate from less than 100 to about 200 pm/s. Substrates are chemicomechanically polished, degreased, bombarded with 500-eV Ar ions for 3-4 min at 350 C, and annealed for 23-30 min at 350 C, producing a slightly In-rich (In/P = 1.02) In-island-free surface with a (4 x 1) or (1 x 1) LEED structure. Films grown at 350 C and less than 100 pm/s are found to be smooth and free of cracks in most cases, with a highly faceted (1 x 1) LEED structure. The electrical properties of the SrF2 films are found to be acceptable only when the ohmic contacts are applied prior to the substrate prior to SrF2 growth.

  18. 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.

  19. Diffusion-driven growth of nanowires by low-temperature molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Rueda-Fonseca, P.; Orrù, M. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Institut NEEL, F-38000 Grenoble (France); CEA, INAC, F-38000 Grenoble (France); Bellet-Amalric, E.; Robin, E. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, INAC, F-38000 Grenoble (France); Den Hertog, M.; Genuist, Y.; André, R.; Tatarenko, S.; Cibert, J., E-mail: joel.cibert@neel.cnrs.fr [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Institut NEEL, F-38000 Grenoble (France)

    2016-04-28

    With ZnTe as an example, we use two different methods to unravel the characteristics of the growth of nanowires (NWs) by gold-catalyzed molecular beam epitaxy at low temperature. In the first approach, CdTe insertions have been used as markers, and the nanowires have been characterized by scanning transmission electron microscopy, including geometrical phase analysis and energy dispersive electron spectrometry; the second approach uses scanning electron microscopy and the statistics of the relationship between the length of the tapered nanowires and their base diameter. Axial and radial growth are quantified using a diffusion-limited model adapted to the growth conditions; analytical expressions describe well the relationship between the NW length and the total molecular flux (taking into account the orientation of the effusion cells), and the catalyst-nanowire contact area. A long incubation time is observed. This analysis allows us to assess the evolution of the diffusion lengths on the substrate and along the nanowire sidewalls, as a function of temperature and deviation from stoichiometric flux.

  20. Epitaxial growth and electric properties of γ-Al2O3(110) films on β-Ga2O3(010) substrates

    Science.gov (United States)

    Hattori, Mai; Oshima, Takayoshi; Wakabayashi, Ryo; Yoshimatsu, Kohei; Sasaki, Kohei; Masui, Takekazu; Kuramata, Akito; Yamakoshi, Shigenobu; Horiba, Koji; Kumigashira, Hiroshi; Ohtomo, Akira

    2016-12-01

    Epitaxial growth and electrical properties of γ-Al2O3 films on β-Ga2O3(010) substrates were investigated regarding the prospect of a gate oxide in a β-Ga2O3-based MOSFET. The γ-Al2O3 films grew along the [110] direction and inherited the oxygen sublattice from β-Ga2O3 resulting in the unique in-plane epitaxial relationship of γ-Al2O3 [\\bar{1}10] ∥ β-Ga2O3[001]. We found that the γ-Al2O3 layer had a band gap of 7.0 eV and a type-I band alignment with β-Ga2O3 with conduction- and valence-band offsets of 1.9 and 0.5 eV, respectively. A relatively high trap density (≅ 2 × 1012 cm-2 eV-1) was found from the voltage shift of photoassisted capacitance-voltage curves measured for a Au/γ-Al2O3/β-Ga2O3 MOS capacitor. These results indicate good structural and electric properties and some limitations hindering the better understanding of the role of the gate dielectrics (a γ-Al2O3 interface layer naturally crystallized from amorphous Al2O3) in the β-Ga2O3 MOSFET.

  1. Effect of initial growth on the quality of GaN on patterned sapphire substrate with ex situ physical vapor deposition AlN seed layer

    Science.gov (United States)

    Wang, Hongbo; Daigo, Yoshiaki; Seino, Takuya; Ishibashi, Sotaro; Sugiyama, Masakazu

    2016-10-01

    GaN epitaxy was explored on a cone-patterned sapphire substrate with an ex situ AlN seed layer prepared by physical vapor deposition (PVD). The effect of initial growth on the quality of the GaN epilayer was investigated using both ex situ PVD-AlN seed layers with various thicknesses and various deposition parameters such as temperature and reactor pressure in metal-organic vapor-phase epitaxy (MOVPE). It was found that the quality of GaN is insensitive to both the thickness of the ex situ PVD-AlN seed layer and the MOVPE growth conditions. A high-quality GaN film was realized, as indicated by room-temperature CL mapping (dark spot density of 1.6 × 108 cm-2), on a patterned sapphire substrate with a wide growth condition window by simply employing an ex situ PVD-AlN seed layer.

  2. Photoconductivity of ultra-thin Ge(GeSn) layers grown in Si by low-temperature molecular beam epitaxy

    Science.gov (United States)

    Talochkin, A. B.; Chistokhin, I. B.; Mashanov, V. I.

    2016-04-01

    Photoconductivity (PC) spectra of Si/Ge(GeSn)/Si structures with the ultra-thin (1.0-2.3 nm) Ge and GeSn alloy layers grown by the low-temperature (T = 100 °C) molecular beam epitaxy are studied. Photoresponse in the range of 1.2-0.4 eV related to light absorption in the buried Ge(GeSn) layer is observed. It is shown that in case of lateral PC, a simple diffusion model can be used to determine the absorption coefficient of this layer α ˜ 105 cm-1. This value is 100 times larger than that of a single Ge quantum dot layer and is reached significantly above the band gap of most bulk semiconductors. The observed absorption is caused by optical transitions between electron and hole states localized at the interfaces. The anomalous high value of α can be explained by the unusual state of Ge(GeSn) layer with high concentration of dangling bonds, the optical properties of which have been predicted theoretically by Knief and von Niessen (Phys. Rev. B 59, 12940 (1999)).

  3. Full compensation of oxygen vacancies in EuTiO3 (001) epitaxial thin film stabilized by a SrTiO3 surface protection layer

    Science.gov (United States)

    Shimamoto, K.; Hatabayashi, K.; Hirose, Y.; Nakao, S.; Fukumura, T.; Hasegawa, T.

    2013-01-01

    We fabricated highly insulating EuTiO3 (001) epitaxial thin films capped with SrTiO3 protection layers on SrTiO3 (001) substrates by combining pulsed laser deposition and post-annealing processes. The epitaxial SrTiO3 protection layer played a significant role in compensation of oxygen vacancies in the EuTiO3 thin films by preventing excess oxidation of the films and by "locking" the EuTiO3 perovskite structure in an epitaxial manner from the top during the air-annealing process. The obtained EuTiO3 thin films demonstrated an antiferromagnetic transition at 5.4 K, quantum paraelectricity down to ˜25 K, and a magnetoelectric coupling comparable to that of bulk EuTiO3.

  4. Selective-area growth of GaN nanowires on SiO{sub 2}-masked Si (111) substrates by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kruse, J. E.; Doundoulakis, G. [Department of Physics, University of Crete, P. O. Box 2208, 71003 Heraklion (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, N. Plastira 100, 70013 Heraklion (Greece); Lymperakis, L. [Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Eftychis, S.; Georgakilas, A., E-mail: alexandr@physics.uoc.gr [Department of Physics, University of Crete, P. O. Box 2208, 71003 Heraklion (Greece); Adikimenakis, A.; Tsagaraki, K.; Androulidaki, M.; Konstantinidis, G. [Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, N. Plastira 100, 70013 Heraklion (Greece); Olziersky, A.; Dimitrakis, P.; Ioannou-Sougleridis, V.; Normand, P. [Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Patriarchou Grigoriou and Neapoleos 27, 15310 Aghia Paraskevi, Athens (Greece); Koukoula, T.; Kehagias, Th.; Komninou, Ph. [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2016-06-14

    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 SiO{sub 2} 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.

  5. 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.

  6. Model for computing kinetics of the graphene edge epitaxial growth on copper

    Science.gov (United States)

    Khenner, Mikhail

    2016-06-01

    A basic kinetic model that incorporates a coupled dynamics of the carbon atoms and dimers on a copper surface is used to compute growth of a single-layer graphene island. The speed of the island's edge advancement on Cu[111] and Cu[100] surfaces is computed as a function of the growth temperature and pressure. Spatially resolved concentration profiles of the atoms and dimers are determined, and the contributions provided by these species to the growth speed are discussed. Island growth under the conditions of a thermal cycling is studied.

  7. 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

  8. 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.

  9. 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.

  10. Epitaxial growth of diindenoperylene ultrathin films on Ag(111) investigated by LT-STM and LEED.

    Science.gov (United States)

    Huang, Han; Sun, Jia-Tao; Feng, Yuan Ping; Chen, Wei; Wee, Andrew Thye Shen

    2011-12-21

    The epitaxial growth of the 1st and 2nd monolayer (ML) diindenoperylene (DIP) on Ag(111) has been systematically investigated using low temperature scanning tunneling microscopy, low energy electron diffraction and first-principles calculations. At one ML regime, DIP molecules commensurately arrange in either herringbone or brick-wall superstructures, depending on the deposition rate. Tip-induced structural transformation from herringbone to brick-wall is observed. Calculations based on density functional theory reveal that the top site of Ag(111) is energetically favorable for both superstructures. The 2nd ML DIP aggregate in either herringbone or brick-wall superstructures depending on the arrangements of the 1st ML DIP, indicating that the structural properties of DIP thin films on Ag(111) are sensitive to growth conditions. The observed variation in DIP ultrathin film structure may result in different electronic properties and have implications for DIP-based organic electronic devices, such as organic field-effect transistors or organic photovoltaic cells.

  11. Epitaxial growth and structure of monolayer cerium oxide films on Rh(111)

    Science.gov (United States)

    Chan, Lap Hong; Yuhara, Junji

    2017-07-01

    We prepared monolayer cerium (Ce) oxide films on Rh(111) to investigate their growth and structure using scanning tunneling microscopy (STM), low-energy electron diffraction, X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. For quantitative analysis of Ce-oxide films, we used the combined techniques of XPS and Rutherford backscattering spectrometry to determine the concentration of Ce and O atoms. We prepared a monolayer (ML) Ce-oxide film by annealing a metallic Ce film at 0.3 ML coverage in an oxygen atmosphere. A well-ordered Ce-oxide phase with a (4×4) unit cell was obtained. The epitaxially grown Ce-oxide film aligned along the azimuthal direction of Rh(111). The number of Ce and O atoms in the (4×4) unit cell was estimated. The STM images indicated that the two-dimensional island growth of the p(4×4) phase with p3m1 symmetry can be explained using the missing Ce atoms model. A simulated STM image of the p(4×4) structural model was in good agreement with the experimental STM image. The formation of Ce-oxide films on Rh(111) at submonolayer coverage was discussed on the basis of the results of DFT+U calculations.

  12. Epitaxial AlN layers on sapphire and diamond; Epitaktische AlN-Schichten auf Saphir und Diamant

    Energy Technology Data Exchange (ETDEWEB)

    Hermann, Martin

    2009-04-27

    In this work, epitaxial AlN layers deposited by molecular beam epitaxy on sapphire and diamond substrates were investigated. Starting from this AlN, the dopant silicon was added. The influence of the silicon doping on the structural properties of the host AlN crystal was investigated using high resolution X-ray diffraction. Once the silicon concentration exceeds 1 x 10{sup 19} cm{sup -3}, a significant change of the AlN:Si crystal can be observed: increasing the silicon concentration up to 5 x 10{sup 20} cm{sup -3} results in a decrease of the a lattice parameter by approximately 1.2 pm and an increase of the c lattice parameter by about 1.0 pm. The crystal is stressed additionally by adding silicon resulting in a increase of the biaxial compressive stress of up to 2.0 GPa. Further increase of the silicon concentration leads to lattice relaxation. This result from X-ray diffraction was independently confirmed by Raman spectroscopy investigations. Further increase of the silicon concentration leads to the generation of polycrystalline phases within the epitaxial layer. XTEM measurements detected these polycrystalline phases. In addition, XTEM investigations confirmed also the increase of the lateral crystal size with increasing silicon concentration, as well as a great reduction of the screw dislocation density by more than one order of magnitude as found by X-ray diffraction: in undoped, nitrogen rich grown AlN layers the screw dislocation density is about 3 x 10{sup 8} cm{sup -2}, while AlN layers with a silicon concentration of 5 x 10{sup 20} cm{sup -3} show a screw dislocation density of only 1 x 10{sup 7} cm{sup -2}. In low-doped AlN:Si ([Si]{approx}2 x 10{sup 19} cm{sup -3}) the activation energy of the electronic conductivity is about 250 meV. Increasing the silicon concentration to about 1 x 10{sup 21} cm{sup -3} leads to an increase of the activation energy up to more than 500 meV in the now much more stressed AlN:Si epilayer. Studies of the absorption

  13. Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Schou, Jørgen

    ), to the growth of dense, gas impermeable 10 mol% gadolinia-doped ceria (CGO10) solid electrolyte can be overcome by the seeding process. In order to evaluate the seed layer preparation, the effects of different thermal annealing treatments on the morphology, microstructure and surface roughness of ultrathin CGO...... the preparation of ultrathin seed layers in the first stage of the deposition process is often envisaged to control the growth and physical properties of the subsequent coating. This work suggests that the limitations of conventional pulsed laser deposition (PLD), performed at moderate temperature (400°C...

  14. Epitaxial Cu{sub 2}ZnSnSe{sub 4} layers by annealing of Sn/Cu/ZnSe(001) precursors on GaAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Krämmer, Christoph, E-mail: Christoph.Kraemmer@kit.edu [Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe (Germany); Sachs, Johannes [Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe (Germany); Pfaffmann, Lukas [Laboratory for Electron Microscopy, KIT (Germany); Musiol, Timo; Lang, Mario; Gao, Chao [Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe (Germany); Gerthsen, Dagmar [Laboratory for Electron Microscopy, KIT (Germany); Kalt, Heinz [Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe (Germany); Powalla, Michael [Light Technology Institute, KIT (Germany); Zentrum für Sonnenenergie-und Wasserstoff-Forschung Baden-Württemberg (ZSW), 70565 Stuttgart (Germany); Hetterich, Michael [Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe (Germany)

    2015-05-01

    We report on the fabrication of epitaxial Cu{sub 2}ZnSnSe{sub 4} films by a two-step fabrication approach. An epitaxial ZnSe(001) layer on GaAs(001) is grown by molecular-beam epitaxy followed by sequential deposition of Cu and Sn. The Sn/Cu/ZnSe(001) precursor is then thermally annealed in a selenium atmosphere. Raman spectroscopy confirms the presence of the kesterite phase. Electron microscopy shows that the films exhibit monocrystalline regions of several micrometers in size with inclusions of smaller grains with a different chemical composition. The latter is confirmed by electron backscatter diffraction measurements which prove the conservation of the crystal orientation defined by the cubic ZnSe/GaAs(001) precursor structure throughout the whole CZTSe film. - Highlights: • Two-step fabrication approach to obtain epitaxial kesterite layers is presented. • Kesterite phase formation is confirmed by Raman spectroscopy. • SnSe{sub x} compounds are identified to be the main secondary phase. • Electron backscatter diffraction proves epitaxial orientation of the films.

  15. Real-time and in situ monitoring of sputter deposition with RHEED for atomic layer controlled growth

    Directory of Open Access Journals (Sweden)

    J. P. Podkaminer

    2016-08-01

    Full Text Available Sputter deposition is a widely used growth technique for a large range of important material systems. Epitaxial films of carbides, nitrides, metals, oxides and more can all be formed during the sputter process which offers the ability to deposit smooth and uniform films from the research level up to an industrial scale. This tunable kinematic deposition process excels in easily adapting for a large range of environments and growth procedures. Despite the vast advantages, there is a significant lack of in situ analysis options during sputtering. In particular, the area of real time atomic layer control is severely deficient. Atomic layer controlled growth of epitaxial thin films and artificially layered superlattices is critical for both understanding their emergent phenomena and engineering novel material systems and devices. Reflection high-energy electron diffraction (RHEED is one of the most common in situ analysis techniques during thin film deposition that is rarely used during sputtering due to the effect of the strong permanent magnets in magnetron sputter sources on the RHEED electron beam. In this work we have solved this problem and designed a novel way to deter the effect of the magnets for a wide range of growth geometries and demonstrate the ability for the first time to have layer-by-layer control during sputter deposition by in situ RHEED.

  16. Real-time and in situ monitoring of sputter deposition with RHEED for atomic layer controlled growth

    Science.gov (United States)

    Podkaminer, J. P.; Patzner, J. J.; Davidson, B. A.; Eom, C. B.

    2016-08-01

    Sputter deposition is a widely used growth technique for a large range of important material systems. Epitaxial films of carbides, nitrides, metals, oxides and more can all be formed during the sputter process which offers the ability to deposit smooth and uniform films from the research level up to an industrial scale. This tunable kinematic deposition process excels in easily adapting for a large range of environments and growth procedures. Despite the vast advantages, there is a significant lack of in situ analysis options during sputtering. In particular, the area of real time atomic layer control is severely deficient. Atomic layer controlled growth of epitaxial thin films and artificially layered superlattices is critical for both understanding their emergent phenomena and engineering novel material systems and devices. Reflection high-energy electron diffraction (RHEED) is one of the most common in situ analysis techniques during thin film deposition that is rarely used during sputtering due to the effect of the strong permanent magnets in magnetron sputter sources on the RHEED electron beam. In this work we have solved this problem and designed a novel way to deter the effect of the magnets for a wide range of growth geometries and demonstrate the ability for the first time to have layer-by-layer control during sputter deposition by in situ RHEED.

  17. The Influence of Deposition Temperature on the Epitaxial Growth of La0. 7 Ca0.3 MnO3 Thin Film

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The growth conditions epitaxial thin film are investigated of Lao. 7 Cao. 3 MnO3 ( LCMO ) The results indicate that the deposition temperature plays a crucial role on the growth mode of LCMO thin film. There is an optimal deposition temperature, To, for the epitaxial growth of LCMO thin film. Just only at the To, the real epitaxial LCMO thin film can be obtained. When the deposition temperature deviates from the T,,, the thin film tends to be polycrystalline, although it orientes growth along a certain direction (a or c axis). Moreover, the experimental results show that just only for the epitaxial thin film the ferromagnetic-paramagnetic transition temperature (i. e. the Courier temperature T ) equals to the metal-semiconductor transition temperature ( To ). The ferromagnetic state shows metallicity and the paramagnetic state exhibits semiconducting character.

  18. A benchmark of co-flow and cyclic deposition/etch approaches for the selective epitaxial growth of tensile-strained Si:P

    Science.gov (United States)

    Hartmann, J. M.; Veillerot, M.; Prévitali, B.

    2017-10-01

    We have compared co-flow and cyclic deposition/etch processes for the selective epitaxial growth of Si:P layers. High growth rates, relatively low resistivities and significant amounts of tensile strain (up to 10 nm min-1, 0.55 mOhm cm and a strain equivalent to 1.06% of substitutional C in Si:C layers) were obtained at 700 °C, 760 Torr with a co-flow approach and a SiH2Cl2 + PH3 + HCl chemistry. This approach was successfully used to thicken the sources and drains regions of n-type fin-shaped Field Effect Transistors. Meanwhile, the (Si2H6 + PH3/HCl + GeH4) CDE process evaluated yielded at 600 °C, 80 Torr even lower resistivities (0.4 mOhm cm, typically), at the cost however of the tensile strain which was lost due to (i) the incorporation of Ge atoms (1.5%, typically) into the lattice during the selective etch steps and (ii) a reduction by a factor of two of the P atomic concentration in CDE layers compared to that in layers grown in a single step (5 × 1020 cm-3 compared to 1021 cm-3).

  19. 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.

  20. Self-limiting growth when using trimethyl bismuth (TMBi) in the metal-organic vapor phase epitaxy (MOVPE) of GaAs1-yBiy

    Science.gov (United States)

    Forghani, Kamran; Guan, Yingxin; Wood, Adam W.; Anand, Amita; Babcock, Susan E.; Mawst, Luke J.; Kuech, Thomas F.

    2014-06-01

    Theoretical and experimental studies have confirmed that the GaAs1-yBiy semiconductor alloy system has potential for long wavelength applications and devices with improved performance over other materials emitting at similar wavelengths. The growth of GaAs1-yBiy by metal-organic vapor phase epitaxy (MOVPE) remains a challenge; bismuth is not easily incorporated into the GaAs matrix due the large difference in electronegativity and covalent radii between As and Bi. These differences often lead to Bi surface segregation or very low incorporation rates of Bi into the GaAs matrix. We have studied the growth of GaAs1-yBiy quantum well structures using trimethyl bismuth as the Bi source. A reduced growth rate is observed with increasing Bi precursor flux into the growth reactor. Additionally, an increase in the growth time for the Bi-containing layer at very low growth temperatures does not lead to a corresponding increase in layer thickness, which is indicative of a near self-limiting growth. Complex compositional profiles deduced from combining x-ray diffraction analysis with the transmission electron microscopy investigations are used to develop a phenomenological model of the MOVPE growth of GaAs1-yBiy heterostructures which includes a complex interplay of the chemical surface species. The presence of a methyl-terminated surface, associated with the use of trimethyl Bi, particularly at low growth temperatures, leads to an effective “site blocking” by Bi precursor inhibiting the growth of GaAs1-yBiy hetero-structures.