bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reflection High-Energy Electron Diffraction Study of Arsenic Incorporation in Metalorganic Molecular Beam Epitaxy of GaAs
Authors: Dong H. K. , Hung S. C. H. , Tu C. W. 
Published: April 2011

ABSTRACTMetalorganic molecular beam epitaxy (MOMBE) of GaAs using triethylgallium (TEGa) and As4 has been studied by reflection high-energy electron diffraction (RHEED). The effect of varying the group-Ill flow rates and group-V beam flux on the growth rate has been investigated over a wide range of substrate temperatures. For a given arsenic flux, the GaAs growth rate first increases linearly as the TEGa flow rate increases. This linear relation extends up to a certain TEGa flow rate, where the growth rate reaches its maximum value. When the TEGa flow rate is increased above this critical value, the growth rate decreases and reaches a stabilized value. From a study of both group-Ill and group-V induced RHEED intensity oscillations, we find that the V/Ill incorporation ratio is unity at the transition point. Compared to conventional molecular beam epitaxy (MBE), MOMBE behaves differently when the V/Ill incorporation ratio is less than unity. The transition region between V/III>I and V/III<1 is gradual and no excess gallium accumulates on the surface during growth. The arseniccontrolled growth rate obtained from conventional group-V induced oscillations where excess Ga atoms are present is greater than the growth rate in the stabilization region where V/IIl<1.
ETCH Rate and Thickness Measurements of Layered GaAs, AlAs and AlGaAs Structures Using a Laser Reflectance Technique
Authors: Grober Louise H. , Hong M. , Grober R.D. , Mannaerts J.P. , Freund R.S. 
Published: April 2011

ABSTRACTLaser reflectometry has been shown to be a useful tool for etch depth measurements during etching of multiple layer structures. We have extended the use of laser reflectometry to accurately determine the etch rates of GaAs, Al0.4Ga0.6As and AlAs as a function of temperature and to verify layer thickness in-situ. By use of computer simulation we compare a theoretical model to actual data to determine layer thicknesses and accurate etch rates. We compare our data to previously published work for GaAs etching.
Cross-Sectional Scanning Tunneling Microscopy of III-V Heterostructures Grown by Molecular-Beam Epitaxy
Authors: Lew A.Y. , Yu E.T. , Chow D.H. , Miles R.H. 
Published: April 2011

ABSTRACTCross-sectional scanning tunneling microscopy and spectroscopy have been used to characterize InAs/Ga1-x InxSb strained-layer superlattices grown by molecular-beam epitaxy. Atomic-resolution constant-current images of the epitaxial layers reveal monolayer roughness at the superlattice interfaces. An asymmetry in electronic structure between interfaces in which InAs has been grown on Ga1-x InxSb and those in which Ga1-x InxSb has been grown on InAs has also been observed in these images. Close inspection of the images reveals increased growthdirection lattice spacings in the Ga1-x InxSb layers compared to the InAs layers, as well as even larger lattice spacings at the InAs/Ga1-x InxSb interfaces. The latter is consistent with the formation of primarily InSb-like interfaces. Current-voltage spectra obtained while tunneling into the superlattice layers are found to be strongly influenced by extended superlattice electronic states.
High-Quality InAs/A1Sb Superlattices with AlAs and InSb Interfaces
Authors: Bennett Brian R. , Shanabrook B.V. , Glaser E.R. , Wagner R.J. 
Published: April 2011

ABSTRACTThe presence of two species of both cations and anions permits the construction of InAs/AlSb heterostructures with either AlAs- or InSb-like interfaces. InAs/AlSb superlattices with both types of interfaces were grown using migration-enhanced epitaxial techniques. The layer quality and control of interfacial composition were confirmed by x-ray diffraction, Raman spectroscopy, and photoluminescence measurements. We demonstrate that high-quality superlattices with both InSb- and AlAs-bonded interfaces can be achieved with appropriate growth temperatures.
A Study of Traps in Semi-Insulating III-V Epitaxial Films by Zero Bias Transient Current Spectroscopy
Authors: Lau W. S. , Goo C. H. , Chong T. C. , Tan C. T. 
Published: April 2011

ABSTRACTSemi-insulating Al0.3Ga0.7AS epitaxial films grown by molecular beam epitaxy at 400°C have been characterised by a recently proposed technique known as zero quiescent bias voltage transient current spectroscopy (ZBTCS). Separated electron trap spectra and hole trap spectra are obtained by ZBTCS. From these spectra, a prominent hole trap with an activation energy of 1.01eV, a prominent electron trap with an activation energy of 0.86eV and a continuum of states are detected. The trap concentrations of the detected hole trap and electron trap are calculated to be about 3.6x1015cm−3 and 9.7x1015cm−3 respectively. The continuum of states is believed to be due to the surface states of the Al0.3Ga0.7AS film. By passivating the surface with (NH4)2S solution, the magnitudes of the continuums in the spectra reduce significantly. With the reduction of the surface states, hole injections that interfere the electron trap spectra are suppressed, and consequently electron trap spectra with more pronounced peaks are produced.
The Characteristics of the Lateral Thickness Modulation in Strained Layer GaxIn1-xAs Multiple Quantum Well Structures Grown by MOVPE
Authors: Zhou X. , Charsley P. , Smith A. D. , Briggs A. T. R. 
Published: April 2011

ABSTRACTSimilar phenomena associated with the lateral thickness modulation have been observed in two different types of GaxIn1-x strained layer multiple quantum well structures grown on InP by MOVPE. The thickness modulations were always quasi-periodic and developed anisotropically in the [110] direction. It has been found that lattice distortions were caused by such thickness modulations, resulting probably in overall surface elastic relaxation. Once the thickness modulation had started at some stage of the growth, it would continue in the subsequent layer with approximately the same modulation period and an amplified amplitude. This is attributed to the effect of the lattice deformation at the growth surface on the deposition rate of the subsequent layer. The effect of such factors as the magnitude of strain, the growth temperature and the V/III gas ratio on the onset of the thickness modulation is discussed.
Heterostructural Characterization of Pseudomorphic, Partially Strained, and Highly Mismatched Semiconductors Using Double Crystal X-Ray Diffraction, TEM, and SEM
Authors: Kim Hyung Mun , Kim Sang-Gi , Nahm Sahn , Park Hyung-Ho , Lee Hae-Kwon , Lee Jae-Jin , Cho Kyung-Ik , Choo Heung Ro , Kim Hong Man , Park Hyung Moo , Park Sin-Chong 
Published: April 2011

ABSTRACTHeterostructural properties of pseudomorphic (AlGaAs/GaAs), partially strained (GaInAs/GaAs), and highly strained (GaAs/Si) semiconductor systems have been studied using High Resolution Double-Crystal X-ray Diffraction (DXRD), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). Using the high resolution DXRD with CuKα1 and two-reflection Si (220) monochromator, we obtained (004) symmetric and (115) or (224) asymmetric reflection rocking curves for samples grown by molecular beam epitaxy. With 0.5 μm thick samples, perpendicular and in-plane lattice mismatches were calculated using elastic theory and compared with each other. The different degree of relaxation for these samples was observed and correlated with the lattice mismatch, X-ray layer peak broadening (i.e., full width at half maximum), and SEM surface morphology. For a GaInAs/GaAs sample, the strain relaxation along one of the <110> directions was more than the other direction, that is, the strain relaxation is not isotrophic. Also we observed that the lines were mainly parallel in one direction, i.e., they did not form a cross-hatch pattern. TEM images from both cross-sectional and planar views of the samples will be presented.
Anisotropic Structural and Electronic Properties of InGaAs/GaAs Heterojunctions
Authors: Goldman R.S. , Rammohan K. , Raisanen A. , Goorsky M. , Brillson L.J. , Rich D.H. , Wieder H.H. , Kavanagh K.L. 
Published: April 2011

ABSTRACTWe have investigated the structural and electronic properties of partially strain-relaxed InxGal-xAs/GaAs heterojunctions, grown by molecular beam epitaxy (MBE) on both misoriented and nominally flat (001) GaAs substrates. Mobility measurements using Hall bars aligned along the [110] and [110] in-plane directions reveal an asymmetry in bulk InGaAs electron mobility. This asymmetry is correlated with an anisotropic bulk strain relaxation and interfacial misfit dislocation density, determined from high-resolution x-ray rocking curves (XRC), as well as a polarization anisotropy in cathodoluminescence (CL).
Kinetic Monte Carlo Simulations of Ge Segregation During Epitaxial Growth of Si-SixGel-x Heterostructures
Authors: Deppe J. , Lill J. V. , Godbey D. J. , Hobart K. D. 
Published: April 2011

ABSTRACTThe temperature dependence of germanium surface segregation during growth by solid source SiGe molecular beam epitaxy was studied by x-ray photoelectron spectroscopy and kinetic Monte Carlo (KMC) modeling. Germanium segregation persisted at temperatures 60ºC below that predicted by a two-state exchange model. KMC simulations, where film growth, surface diffusion, and surface segregation are modeled consistently, successfully describe the low temperature segregation of germanium. Realistic descriptions of MBE must follow the physical rates of the growth, surface diffusion, and surface segregation processes. A specific, step mediated exchange mechanism is also considered and shown to lead to surface segregation. While this model of Ge segregation seems possible, more work is necessary to obtain a consistent set of energy barriers.
Gas Source Molecular Beam Epitaxy of ZnSe on (In,Ga)P
Authors: Lu K. , Fisher P.A. , Ho E. , House J.L. , Petrich G.S. , Kolodziejski L.A. 
Published: April 2011

ABSTRACTThe wide bandgap semiconductor ZnSe has been nucleated on epitaxial (In,Ga)P buffer layers (on GaAs substrates) having various In compositions, and hence various lattice constants. The III-V ternary alloy offers a wide range of lattice constants for the heteroepitaxy of a multitude of potential II-VI light emitting devices, such as blue pn injection lasers composed of the (Zn,Mg)(S,Se) material system. Since the II-VI and III-V layers are grown using gas source molecular beam epitaxy in separate dedicated reactors, the technique of amorphous As deposition is employed to passivate the (In,Ga)P surface prior to the ex situ transfer. High resolution double crystal x-ray diffraction measurements on the ZnSe/(In,Ga)P/GaAs heterostructures indicate that for In compositions of 50-52%, the buffer layers with a thickness of 4 μm were only partially relaxed on the GaAs substrates, with the residual mismatch remaining at the ZnSe/III-V heterointerface. The critical thickness of (In,Ga)P, with In concentrations near 52-56%, on GaAs greatly exceeds the predicted critical thickness from either the energy balancing or force balancing model. For an In composition of 56% (and a film thickness of 4 μm), the buffer layers contain an in-plane lattice constant equal to that of ZnSe, and therefore represent the lattice-matched condition, even though the film is not fully relaxed. For (In,Ga)P buffer layers lattice-matched to ZnSe, but mismatched to GaAs, the surface exhibits the expected cross-hatched surface morphology. The occurrence of the cross-hatched surface is significantly alleviated by the addition of a pseudomorphic layer of GaAs positioned between the ZnSe and (In,Ga)P layer.
Low Pressure MOVPE Photo-Assisted Growth of ZnxCd1-xS
Authors: Dumont Hervé , Fujita Shizuo , Fujita Shigeo 
Published: April 2011

ABSTRACTWe will report the photo-assisted heteroepitaxial growth of Znx Cdl-xS by Metalorganic Vapor Phase Epitaxy (MOVPE). Sources materials were diethylzinc, dimethylcadmium and tertiaributylmercarptan. We have studied the effect of light intensity on the change of the Zn composition, crystalline quality and optical properties of epitaxial layers grown on (100) GaAs substrates. The Zn composition of the films could be increased by ≃ 15% by illuminating layers during the growth at 400°C. Concerning the characterization of epilayers, we observed a bright luminescence peak at E = 2.80 eV for x≃ 0.4. Epilayers with the best crystalline quality we could grown exhibited a full width at half maximum of ≃ 70 arsec by x-ray diffraction rocking curves when grown at 380°C.
Structural Characterization of InAlAs/InGaAs Layers Grown on InP Patterned Substrates
Authors: Peiro F. , Cornet A. , Morante J.R. , Zekentes K. , Georgakilas A. 
Published: April 2011

ABSTRACTIn this work we present structural characterization by both Scanning and Transmission Electron Microscopy of InAlAs/InGaAs heterostructures grown on InP substrates. Our attention is devoted to study the two main problems limiting the application of these structures as devices: the presence of defects on the epilayer and the growth habit at theedges of the well. Our results show that a different faceting between the two <110> orthogonal directions develops during the growth and that a high density of defects is observed just at the intersection between the layers grown inside the windows and on the walls. Moreover, the presence of a polycrystalline layer developing over the mask indicates that a selective growth occurs.
Thermodynamic Calculations on Vapour Phase Species in Halogen Doped CDTE
Authors: Schwarz R. , Laasch M. , Benz K.W. 
Published: April 2011

ABSTRACTA thermodynamic analysis of the vapour phase species occurring in the undoped CdTe and doped CdTe:X (X = Cl, Br, I) systems is given. Calculations are performed using a Gibbs energy minimizer software (EPC), which offers the possibility of receiving relativly prompt results allowing for the change in experimental conditions as well as the consideration of even spurious species.In each system, the dopant - transporting species are the cadmiumdihalogenides CdX2. Contrary, in the CdTe:I vapour phase two more species (Tel and I) have to be considered at the growing phase boundary afffecting transport and interface kinetics.
Electronic and Photonic Device Applications of In0.5Ga0.5P and In0.5Al0.5P Grown by Gas Source Molecular Beam Epitaxy
Authors: Kuo Jenn-Ming 
Published: April 2011

ABSTRACTAdvances in gas-source molecular beam epitaxial (GSMBE) growth techniques have allowed the successful fabrication of electronic and photonic devices based on In0.5Ga0.5P and In0.5A10.5P heterostructures lattice matched to GaAs. Basically the interest in In0.5Ga0.5P and In0.5A10.5P derives from their unique material properties as well as their band alignment to GaAs. In this paper, we review the growth, fabrication, and performance of In0.5A10.5P/In0.2Ga0.8As pseudomorphic high electron mobility transistors (HEMT's), InO.5A10.5P/GaAs heterojunction bipolar transistors (HBT's), and In0.5Ga0.5P red light emitting diodes (LED's) grown on Ge/graded GexSil-x/Si substrates. The results provide a solid demonstration of the feasibility of using In0.5Ga0.5P and In0.5A10.5P prepared by GSMBE for manufacturing GaAs-based optoelectronic devices.
In-Situ Surface Photo-Absorption Study of Movpe Surface
Authors: Kobayashi Naoki 
Published: April 2011

ABSTRACTIn-situ surface photo-absorption (SPA) method was applied to study the dynamic surface processes and the static surface structures during metal-organic vapor phase epitaxy (MOVPE). Observed spectra in near-ultaviolet and visible regions consist of an anisotropic dielectric response due to surface dimer-bonds as well as an isotropic response probably due to surface back-bonds. Time-resolved spectra showing dynamic changes of surface can be measured by the use of optical multichannel analyzer. The rate of surface decomposition of source molecule was measured as the change of reflectivity at a fixed wavelength. The decomposition of source molecule was characterized quantitatively, and various effects on the decomposition were studied. The style of decomposition and the activation energy depended on the substituent of source molecule and the rate of decomposition was affected by the surface potential and the strain.
Ag Films Deposited by Ionized Cluster Beam Deposition
Authors: Ren Zhong-Min , Du Yuan-Cheng , Ying Zhi-Feng , Xiong Xia-Xing , He Mao-Qi , Li Fu-Ming 
Published: April 2011

ABSTRACTIonized cluster beam deposition (ICBD) technique has been used to deposit Ag films on both Si(111) and Si(100) substrates. Sizes of clusters in ionized cluster beam are found to distribute in a range of 100–600 atoms/cluster. X-ray diffraction (XRD), and α-step profile methods are used to analyze the properties of Ag films. As a comparison, Ag films deposited by conventional evaporation are also investigated. Highly textured Ag films with strong (111) orientation on Si (111) have been obtained at high accelerating voltage Va=4kV. The crystallinity and surface flatness of Ag films can be improved by ICBD at high accelerating voltages.
Segregation Effect and its Influence on Grain Boundary Diffusion in Thin Metallic Films
Authors: Aleshin A. N. , Bokstein B. S. , Egorov V. K. , Kurkin P. V. 
Published: April 2011

ABSTRACTThe diffusion in Au-Cu and Pt-Cu thin films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic regime “B” (within the temperature interval of 175–290°C) and “C” (room temperature). The 1,5-2,0 MeV He+ RBS spectra were taken using 14–18 keV resolution. The RBS spectra were changed to depth-concentration profiles for both bulk and grain boundary (GB) diffusion. Under the kinetic regime “C” the absolute values of GB diffusion coefficients were obtained. Under the kinetic regime “B” the triple products δKDb, (δ is the GB width, Db is the GB diffusion coefficient, K is the enrichment ratio) were obtained using Whipple’s and Gilmer-Farrell’s models. The activation energies for both GB diffusion and bulk diffusion were determined for Au-Cu system as well as for Pt-Cu system. The comparison between the data on the GB diffusion for kinetics “B” extrapolated to room temperature and the data on the GB diffusion for the kinetics “C” enables one to derive the product δK and to separate the contribution of segregation into the parameters of GB diffusion for systems under study.
Liquid Metal Penetration along Grain Boundaries
Authors: Fradkov V. E. 
Published: April 2011

ABSTRACTLiquid metal grain boundary corrosion is discussed in terms of grain boundary etching profiles with equilibrium dihedral angles at the vertex of the grooves close to zero. It is shown that if the liquid solution is in equilibrium with the solid, then only grain boundary grooving occurs, producing small grooves growing in time as t½. However, if the equilibrium cannot be reached, a long liquid filled canal develops along the grain boundary, rapidly propagating with constant velocity. To stop such rapid grain boundary corrosion certain measures should be taken to reach the equilibrium state. This explains, for example, why removal of oxygen from the Nb(s)-Li(l) system prevents rapid grain boundary corrosion of Nb.
Scanning X-Ray Diffraction: A Technique With High Compositional Resolution for Studying Phase Formation in Co-Deposited Thin Films
Authors: Selinder T.I. , Miller D.J. , Gray K.E. , Beno M.A. , Knapp G.S. 
Published: April 2011

ABSTRACTInvestigation of the formation of new metastable phases in alloy thin films requires ways of quickly determining the crystalline structure of samples with different compositions. We report a novel technique for acquiring structural information from films intentionally grown with a composition gradient. For example, binary metal alloy films were deposited using a phase-spread sputtering method. In this way essentially the entire composition range could be grown in a single deposition. By using a narrow incident x-ray beam and a translating sample stage combined with a position sensitive x-ray detector technique, detailed information of the metastable phase diagram can be obtained rapidly. Compositional resolution of the order of ±0.2% can be achieved, and is limited by the brightness of the x-ray source. Initial results from studies of phase formation in Zr-Ta alloys will be presented. Extensions of the analysis technique to ternary systems will be discussed.
Fine Structure of Sputtered Ni/Ti Multilayered Thin Films Studied by HREM
Authors: Casanove M. J. , Snoeck E. , Roucau C. , Hutchison J. L. , Jiang Z. , Vidal B. 
Published: April 2011

ABSTRACTNi/Ti multilayered thin films can be efficient neutron guides and are therefore of great interest in neutron optics. Ni/Ti and NiC/Ti multilayers with various layer thicknesses were fabricated by magnetron sputtering and characterized by high resolution transmission electron microscopy (TEM). The TEM studies, performed on cross-sectional specimens, revealed that both kinds of layers were textured and snowed coherence in the growth direction. The presence of a 2 nra thick amorphous zone at the Ni/Ti interface in the carbon free thin films was also confirmed. On the contrary, sharp interfaces were obtained in NiC/Ti multilayers. The fine structure of the different layers will also be reported.
The Effect of Microstructure on the Magnetic Properties of Thin Film Magnetic Media
Authors: Yamashita T. , Ranjan R. , Chan L.H. , Lu M. , Ross C.A. , Chang J. , Tarnopolsky G. 
Published: April 2011

ABSTRACTMagnetic recording media used today are based on sputtered cobalt alloy films with thicknesses in the order of 50 nm. As recording density is increased, the microstructure of the film must be controlled with increasing level of sophistication to achieve the magnetic properties necessary for good recording performance. Recording density has been increasing at the compound annual rate of 30%, and in recent years at a higher rate. Already, 1 Gb/in2 has been achieved in the laboratory [1], and 10 Gb/in2 is being contemplated [2]. In order to achieve such densities, microstructural characteristics such as grain morphology, size distribution, crystallographic orientation, and grain separation must be controlled with great precision, and their relationship to magnetic properties must be understood. The paper will describe the effect of sputter process conditions and the selection of magnetic alloys on the film microstructure and describe what might be required to achieve high recording densities. Particular attention will be paid to grain size distribution and grain separation. Grain separation is important for low noise performance of the media. Alloy selection and sputtering conditions can be manipulated to achieve different levels of separation between the grains.
Effect of Ion Irradiation on the Artificial Structure and the Interlayer Coupling of Copper-Cobalt Multilayers
Authors: Bobo J-F. , Snoeck E. , Piecuch M. , Casanove M-J. 
Published: April 2011

ABSTRACTStructural defects like local ferromagnetic short-circuits are responsible for large reductions of the intrinsic interlayer coupling in the case of antiferromagnetically (AF) coupled multilayers (ML). We have investigated the role of such point defects in AF-coupled Cu-Co ML’s with tCu=8Å and tCo=12Å which have been irradiated with various doses of 200 keV xenon ions. A significant decrease of the giant magnetoresistance and of the saturation field is observed when the density of defects is increased. These results are compared with a micromagnetic model that takes into account local discontinuities of the AF coupling in an ideally AF-coupled ML. Evidence for the presence of such defects is investigated by TEM on cross-sectional specimens.