bluuebunny/crossref_metadata_2025_split huggingface dataset:
RBS/Chainneling and Ten Analysis of Heteroepitaxial Ge Films on GaAs Crown by Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Parikh N.R. , Hattangady F V , Posthill J.B. , King M.L. , Rudder R.A. , Vitkavage D.J. , Markunas R.J. , Chu W.K. 
Published: March 2011

ABSTRACTWe have deposited thin Ge films on GaAs(111) crystals over a temperature range of 250-400° C by Remote Plasma Enhanced Chemical Vapor Deposition (RPECVD). Rutherford Backscattering (RBS)/channelinf analysis of these heteroepitaxial films were carried out using 2.07 MeV He ions channeled along the <111> axis. RBS/channeling analysis showed that the best Ce films were grown at a substrate temperature of 300° C. The minimum yield for <111> channeling on films deposited at 300° C was 0.08, slightly greater than that of the GaAs crystal. Films grown at temperatures below 300° C showed poor epitaxy. No channeling was observed for the film grown at 250° C. Films grown at substrate temperatures above 350° C showed high dechanneling near the interface and poor epitaxy indicating films are highly defective. The RBS/channeling results are correlated with microstructural characterization using transmission electron microscopy of these films.
X-Ray Diffraction and Sims Studies of Mbe Grown Doping Superlattices in Silicon
Authors: Brown G T , Barnett S J , Blackmore G W , Courtney S J , Houghton D C 
Published: March 2011

ABSTRACTSi-Si(B) doping superlattices (pipi structures) were grown by MBE and studied using double crystal x-ray diffraction and SIMS. Detailed analysis of the complex x-ray rocking curves required comparison of experimental data with theoretically simulated data. It is demonstrated that this technique is sensitive to irregularities in the dopant composition, dopant distribution and superlattice period. The B concentration profile is shown to spread well into the intrinsic layers and the extent and magnitude of the dopant distribution has been quantified. A comparison of this data with SIMS showed good agreement for the distribution of B and reasonable agreement for the peak values of B concentration.
Oxidation of Strained Si-Ge Layers Grown by MBE
Authors: Patton G.L. , Iyer S.S. , Delage S.L. , Ganin E. , Mcintosh R.C. 
Published: March 2011

ABSTRACTThe oxidation of strained SiGe alloy layers grown by Molecular Beam Epitaxy (MBE) was studied. An initial fast growth regime was identified for 800°C steam oxidations, where the growth rate is 2.5 times that of silicon. The oxides formed on SiGe were found to be essentially Ge-free: Ge present in the material is rejected by the oxide, resulting in the formation of a Ge-rich epitaxial layer at the oxide/substrate interface.
Pulsed Laser Crystallization of GexSi1−x Alloy Films on Si(100) Substrates
Authors: Abelson John R. , Weiner Kurt H. , Kim Ki-Bum , Sigmon Thomas W. 
Published: March 2011

ABSTRACTWe demonstrate the fabrication of high quality GexSi1−x heteroepitaxial alloy layers on Si(100) substrates by pulsed laser melting of a-Ge/Si(100) layered structures. First, 50–200Å of germanium are evaporated onto a chemically cleaned silicon wafer. Next, an excimer laser pulse is used to melt the sample surface to a depth of 200–2500Å. Finally, the melt solidifies in 20–100ns producing a heteroepitaxial alloy layer. By varying the thickness of the evaporated Ge film and the laser energy, alloys of 500–1500Å thickness and Ge fraction x=3–20% are obtained. The crystallinity of the layer and interface are found to be excellent as evaluated by Rutherford Backscattering Spectrometry (RBS), ion channeling, and high resolution cross sectional TEM. This technique for producing GexSi1−x alloy layers is insensitive to minor levels of contamination because the original Ge/Si interface is melted through during the laser processing
Photoluminescence of MBE and MOCVD ZnTe Films on GaAs
Authors: Wilson B. A. , Bonner Carl E. , Feldman R. D. , Austin R. F. , Kisker D. W. , Krajewski J. J. , Bridenbaugh P. M. 
Published: March 2011

ABSTRACTWe present low-temperature photoluminescence (PL) spectra of MBE and MOCVD ZnTe layers deposited on (100) GaAs substrates under different growth conditions. Strong bands associated with Zn vacancies are observed in the MBE materials, while the MOCVD spectra are dominated by sharp impurity-related lines. Stress levels less than 0.1 kbar are determined for both the MBE and MOCVD layers. A study of the effects of the Zn:Te ratio in the MBE growth chamber reveals an optimal value of −2.2 for a growth temperature of 325°C.
Layered Structures Composed of Si, Ge, GaAs, and Fluorides
Authors: Ishiwara H. , Asano T. , Tsutsui K. , Lee H. C. , Furukawa S. 
Published: March 2011

ABSTRACTRecent progress in the heteroepitaxial growth of layered structures of Si, Ge, GaAs, and alkaline earth fluorides is reviewed. Effectiveness of the predeposition technique, in which a thin Si layer is deposited on the CaF2 surface at room temperature prior to the growth of a thick Si film at 800°C, is shown for the growth of Si films on CaF2/Si structures. In case of the overgrowth of Ge and GaAs films on (111) substrates, modification of the fluoride surface by electron beam exposure is effective to increase the wettability between fluoride and semiconductor films and to improve the crystallinity and surface morphology of the films. Finally, antiphase disorder in the GaAs(l00) films grown on fluorides is experimentally studied and the generation mechanisms are discussed.
Hot Electron Transistors Using Si/CoSi2
Authors: Levi A. F. J. , Tung R. T. , Batstone J. L. , Anzlowar M. 
Published: March 2011

ABSTRACTWe have explored the possibility of fabricating a metal base transistor in the Si/CoSi2 material system. Utilizing recent advances in the growth of thin, pinhole free, CoSi2 layers on Si(111) we have measured the transistor characteristics of a Si/CoSi2/Si structure. The observed low common emitter current gain is attributed to an absence of current carrying states in the CoSi2 transistor base.
Buried Silicide Synthesis and Strain in Cobalt-Implanted Silicon
Authors: Barbour J.C. , Picraux S.T. , Doyle B.L. 
Published: March 2011

ABSTRACTSilicon (001) substrates were implaynted with 350 keV Co at room temperature and 450°C with fluence of from l×l017 Co/cm2 to 6×1017 Co/cm . All samples were annealed at 1000°C in order to form the CoSi2 phase Concentration profiles were determined with Rutherford backscattering spectrometry (RBS), and the associated strain profiles were analyzed with double-crystal X-ray rocking curve measurements. Ion channeling was also used to characterize the silicide formation and crystal quality. An implantation of 6×1017 Co/cm2 at 450°C forms a single-crystal CoSi2 layer while lower fluences do not. A continuous, buried CoSi2 single-crystal layer is formed for the 3×1017 Co/cm2 sample implanted at 450°C and annealed at 1000°C. The continous CoSi2 layer is thicker than the critical layer thickness for a fully coherent film, and therefore the layer partially relaxes. A relaxation of 50% of the fully coherent value is observed for this buried silicide system.
Nucleation and Growth of Cosi2 on (001) and (111) Si
Authors: Bulle-Lieuwma C.W.T. , Van Ommen A.H. , Hornstra J. 
Published: March 2011

ABSTRACTNucleation and growth of epitaxial CoSi2 on Si by the thermal reaction of vapour deposited Co on (001) and (111) Si have been studied by transmission electron microscopy (TEM). On (001)-Si the layer consists of CoSi2 grains. Apart from an aligned (a)-orientation, CoSi2 occurs in a number of orientations, including a (110) preferential (b)-orientation. On (111) Si, single-crystalline layers are obtained, predominantly in the B-type orientation, which is rotated through 180° relative to the aligned (111)-orientation (A-type). The interfacial defect structure consists of misfit dislocations of edge-type with Burgers vector b=a/6<112>, running in <110> directions. The observations for both (001) and (111) Si are related to geometrical lattice match between CoSi2 and Si. In addition to the experimental results, a computer program has been made which calculates the matching between various orientations of CoSi2 and Si. The nucleation of B-type CoSi2 for (111) Si and the different oriented grains for (001) Si are discussed in terms of a nucleation mechanism at steps at the interface in combination with a relatively large mismatch.
The Effect of Formation Conditions on the Structural and Electrical Properties of Ultrathin Cobalt Silicide Films
Authors: Phillips Julia M. , Batstone J. L. , Hensel J. C. , Cerullo M. , Unterwald F. C. 
Published: March 2011

ABSTRACTWe have studied the dependence of the structural and electrical properties of ultrathin cobalt silicide films on the annealing temperature and deposited Co thickness.We recently reported that coherent, electrically continuous films of CoSi2 could be grown on Si(111) with thicknesses as small as 1 nm.1 The thinnest of these films had a high density of pinholes which covered about 20% of the area of the substrate. The resistivity of the films increased dramatically with decreasing thickness in a manner which was qualitatively consistent with quantum size effects. In order to investigate the dependence of both the pinhole density and the resistivity of ultrathin CoSi2 films on Si(111), we have deposited different thicknesses of Co onto near room temperature (<100°C) Si(111) substrates and have annealed the samples at different temperatures in order to study the effect of silicide formation conditions on the structural and electrical properties of the resulting films.Co layers were deposited onto Si(111) wafers in a molecular beam epitaxy apparatus as described previously.1 In our earlier work, CoSi2 was formed by heating the sample to ∼600°C for a few seconds after Co deposition. Because higher temperature anneals are known to lead to pinhole formation in thicker films,2 annealing temperatures in the present experiments were constrained to be 600° or less. The reaction time was on the order of 5 minutes. The layers were examined using plan-view transmission electron microscopy (TEM) in order to avoid beam heating and ion beam mixing effects which might cause artefacts in cross-section TEM observation.The results of our experiments are summarized in Figure 1. The figure indicates the silicide phases found in a film as a function of deposited Co thickness and annealing temperature. The numbers in each square correspond to the residual resistivity, ρo, measured for each film. Perhaps the most striking finding of this study is the abrupt change in the structure of the films between 0.7 and 1.4 nm of deposited Co. For all temperatures investigated (including near room temperature), films formed by depositing less than 1 nm of Co form CoSi2 immediately upon deposition. (For films approaching this thickness, there is also a small amount of Co2Si which persists at all temperatures
Molecular Beam Epitaxial Growth Over Multiple Wafers Using an Indium-Free Mounting Technique
Authors: Igarashi T. , Saito J. , Okamoto Y. , Ishikawa T. , Kondo K. 
Published: March 2011

ABSTRACTAn indium-free substrate mounting technique was developed for a 190-mm diameter substrate holder on which three 3-inch GaAs substrates are mounted. Reduction of the heat conduction between the substrates and the holder kept the temperature variation in the substrate within ±5° C. Highly uniform epitaxial layers were grown with low residual impurity concentrations using this technique. The variations in layer thickness and carrier concentration of Si-doped GaAs and AlGaAs epitaxial layers were within ±1% over the substrate holder. High mobility of a two-dimensional electron gas in a selectively doped GaAs/N-AlGaAs heterostructure was obtained uniformly over three 3-inch wafers. Since the holder was designed to hold the wafers without stress, no stress-related degradation of the surface morphology was observed.
Observation of GaAs/Si Interface by Tem: Effect of Annealing on the Structure
Authors: Heral H. , Rocher A. , Charasse M. N. , Georgakilas A. , Chazelas J. , Hirtz J. P. , Blancka H. , Siejka J. 
Published: March 2011

ABSTRACTWe present in this paper the effect of heat treatments applied to a 400 nm GaAs layer grown by MBE on a (001) Silicon substrate. These heat treatments have been applied during or after the growth of the GaAs, in order to improve the crystalline quality of the layer. RBS and TEM observations have been performed to study the improvement of the crystalline quality of the GaAs layer. Specimens, prepared by cross-section technique along both (110) and (170) planes and plane view, have been studied by TEM. Observations of cross-section by HREM show an interface roughness of about 1.5 nm before and after heat treatments. A roughness, observed also by RHEED, appears in the first stage of growth. Although the density of threading dislocations decreases after heat treatments.
The Growth of AIGaAs/GaAs Heterostructures By Atomic Layer Epitaxy
Authors: Denbaars S. P. , Hariz A. , Beyler C. , Maa B. Y. , Chen Q. , Dapkus P. D. 
Published: March 2011

ABSTRACTThe kinetics of atomic layer epitaxy (ALE) of GaAs utilizing trimethylgallium and arsine are described. The results show that saturated monolayer growth can be achieved-in the temperature range 445°C -485°C and that high quality materials can be grown.. Hybrid A1GaAs/GaAs heterostructures have been grown utilizing ALE for the active regions and conventional metalorganic chemical vapor deposition (MOCVD) for the confining regions that yield high quality quantum wells and low threshold quantum well lasers.
TEM and TED Studies of Ordering in GaInP
Authors: Coral J. P. , Al-Jassim M. M. , Olson J. N. , Kibbler A. 
Published: March 2011

ABSTRACTTransmission electron microscopy (TEM) and transmission electron diffraction (TED) studies have shown the presence of long range CuPt-type cationic ordering 4n GaInP grown by MOCVD on (001) GaAs. Domains regions (on order of 104nm2) exhibit a double periodicity along the [111] and [110] directions.
Transmission Electron Microscope Study of An Ordered Structure in GaAs0.5 Sb0.5 Grown By Molecular Beam Epitaxy
Authors: Ihm Y. E. , Otsuka N. , Hirotsu Y. , Klem J. , Morkoc H. 
Published: March 2011

ABSTRACTThe ordered structure in a (100) GaAs0.5 Sb0.5 epilayer grown by molecular beam epitaxy has been studied by transmission electron microscopy. Domain structures are observed in dark field images of superstructure reflections. The ordered structure is derived by the analysis of diffraction patterns taken from single domains. The ordered structure is described as an alternate stacking of As and Sb planes in the <111> direction of the FCC sublattice. The alternate stacking of As and Sb plane is directly observed by high resolution electron microscopy.
Pre-Cracking and Plasma Enhanced Metalorganic Chemical Vapor Deposition Processes for Epitaxial Hg1−xCdxTe and HgTe-CdTe Superlattice Growth
Authors: Lu P.-Y. , Williams L. M. , Wang C.-H. , Chu S. N. G. , Ross M. H. 
Published: March 2011

ABSTRACTTwo low temperature metalorganic chemical vapor deposition growth techniques, the pre-cracking method and the plasma enhanced method, will be discussed. The pre-cracking technique enables one to grow high quality epitaxial Hg1−xCdxTe on CdTe or CdZnTe substrates at temperatures around 200–250°C. HgTe-CdTe superlattices with sharp interfaces have also been fabricated. Furthermore, for the first time, we have demonstrated that ternary Hg1−xCdTe compounds and HgTe-CdTe superlattices can be successfully grown by the plasma enhanced process at temperatures as low as 135 to 150°C. Material properties such as surface morphology, infrared transmission, Hall mobility, and interface sharpness will be presented.
Glancing Angle EXAFS Studies of Tungsten-Carbon Multilayers
Authors: Lamble G. M. , Heald S. M. , Sayers D. E. , Ziegler D E. 
Published: March 2011

ABSTRACTResults are presented from glancing angle EXAFS studies of three tungsten-carbon multilayer systems, of different W/C thickness ratios, by monitoring the fine structure above the tungsten L3-edge. The purpose of the investigations was to determine the structural changes occurring in the multilayer as a result of moderate annealing. Surprisingly, dramatic changes are observed in the structural environment of the W atoms as a result of heating to temperatures as low as 350°C for 3 hours. It is found that, when the W layer is sufficiently thick, and the W/C layer thickness favorable, W2C is preferentially formed and crystallization is extensive.The experiment demonstrates the suitablility of the EXAFS technique for the study of multilayer systems since, 1) contribution to the signal from the interface is significant and 2) the phenomenon is not dependent on the existence of long range order.
X-Ray Scattering (Modeling and Experiment) of InxGa1-xAs/GaAs Multiple Quantum Wells
Authors: Jeong Jichai , Lee J. C. , Shahid M. A. , Schlesinger T. E. , Milnes A. G. 
Published: March 2011

ABSTRACTX-ray diffraction, transmission electron microscopy (TEM), and photoluminescence measurements have been made on strained InxGa1-xAs/GaAs quantum well structures. The well widths measured from TEM are 187, 115 and 69 Å for an interrupted growth, and 218, 126, 60 Å for a non-interrupted growth. In the measured x-ray diffraction patterns, the Pendellosung fringes due to GaAs barriers are modulated by a broad weak peak mostly coming from the thickest InxGa1-xAs well layer and is fairly symmetric for the noninterrupted sample. For the interrupted quantum well, the x-ray diffraction pattern is less symmetric, since there is further modulation by another broader and weaker peak. This results show that the In content in the InxGa1-xAs well layers are not well controlled for the interrupted quantum well. Using actual thickness measured from TEM, x-ray diffraction patterns are calculated and good agreement is obtained between the measured and the calculated x-ray diffraction patterns. The three strained InxGa1-xAs/Gaks quantum wells grown without interruption produce high intensity and narrow full-width at half-maximum (FWHIM) of 2.9 meV of the photoluminescence peak. The photoluminescence peaks for the interrupted quantum well are relatively broad and asymmetric, and have lower intensities, indicating that better quality InxGa1-xAs/GaAs quantum wells can be grown without interruption.
Fe-W Supernirrors for Polarizing Neutrons
Authors: Majkrzak C. F. , Neumann D. A. , Copley J. R. D. , Dinardo R. P. 
Published: March 2011

ABSTRACTThin film bilayers of ferromagnetic Fe and nonmagnetic W have been deposited by sputtering on flat glass substrates according to a sequence of gradually varying bilayer thicknesses which in effect extends the critical angle for external mirror reflection for neutrons of one spin state when the Fe is magnetized in the plane of the film. The measured reflectivity of this Fe-W multilayer system is compared with that of other supermirror polarizers consisting of different materials and layer sequences.
Techniques for Characterising Artificial Layer Structures using Transmission Electron Microscopy
Authors: Stobbs W. M. 
Published: March 2011

ABSTRACTT.E.M. methods are described for the quantitative characterisation of the compositional and structural changes at interfaces and in homo- and hetero-phase multilayer structures. Many of the newer approaches described including the Fresnel and Centre Stop Dark Field Imaging Methods were developed specifically for such characterisations. The range of applications of each of the techniques is assessed as is the importance of delineating the limiting effects of inelastic and inelastic/elastic multiple scattering.
Evidence for Instability in Pb1-x EuxTe Alloys
Authors: Salamanca-Young L. , Wuttig M. , Partin D. L. , Heremans J. 
Published: March 2011

ABSTRACTWe have used transmission electron microscopy to study the structure of Pb1-xEuxTe alloys grown by molecular beam epitaxy. We have observed ordered solid solutions of the Pb1-x EuxTe alloys as well as spinodal decomposition for 0.35≤x<0.75. The spinodal decomposition corresponds to a modulation of both the composition and the lattice spacing of the Pb1-x EuxTe alloy. These modulated structures have periodicities of ∼18Å along the <111> and <110> directions and indicate that the solid solution of Pb1-x Eux Te is unstable in this range of compositions.
Interface Structure and Solid State Reactions of Fe/Zr Multilayers
Authors: Clemens Bruce M. , Williamson D. L. 
Published: March 2011

ABSTRACTIron zirconium multilayer films were prepared by electron beam evaporation and by sputter deposition. Layer thicknesses were varied from 50 monolayers of each constituent down to 2 monolayers. Conversion electron Mössbauer spectroscopy, x-ray diffraction, and Auger spectroscopy have been used to characterize multilayers in the as-deposited and annealed state. Amorphous phase formation occurs during thermal anneals, and samples with layer thicknesses of 5 monolayers or less of each constituent are amorphous as deposited. Amorphous interfaces are observed in all samples, with this interface region being larger in the electron beam evaporated samples than in the sputter deposited samples.
Epitaxial Growth of Rare Earths on Rare Earth Fluorides and Rare Earth Fluorides on Rare Earths: Two New Epitaxial Systems Accessed by MBE
Authors: Farrow R. F. C. , Parkin S. S. P. , Lang M. , Roche K. P. 
Published: March 2011

ABSTRACTWe report two new epitaxial systems, prepared by MBE: basal plane epitaxy of the rare earth metal Dy onto LaF3 films and vice versa. SQUID magnetometry studies indicate that buried epitaxial Dy films, of ∼300Å thick, order ferromagnetically at similar temperatures to bulk Dy crystals.These epitaxial systems are one member of a new family of epitaxial systems of basal plane epitaxy of rare earth metals on rare earth fluorides and vice versa. Such systems may be used to probe the effects of strain and dimensionality on magnetic ordering in rare earth metal films and multilayers.
A Solid State Amorphisation Reaction in Ti-Si Diffusion Couples: The Phase Field
Authors: Raaijmakers Ivo J. M. M. , Oosting Piet H. , Reader Alec H. 
Published: March 2011

ABSTRACTThe reactions in sputter deposited Si-Ti-Si diffusion couples were investigated with X-ray diffraction, Auger electron spectroscopy and cross-section transmission electron microscopy. Anneals at a temperature of 400°C resulted in the growth of an amorphous phase at the Si-Ti interfaces. Crystalline silicides were only found after an anneal at temperatures of 500°C or higher.It was demonstrated that an amorphous layer of approximately 8 nm thickness sustained a concentration gradient from about 73% Si at the Si side to about 28% Si at the Ti side of the diffusion couple. The measured width of the phase field agreed with the width predicted from a calculated free energy versus composition diagram. Actually the observed phase field was found to be so wide, that it contains the stoichiometry of all equilibrium silicides. The consequences of our results for the explanation of silicide first phase nucleation were discussed.
Light Scattering Analysis of Strained-Layer Superlattices
Authors: Schwartz G. P. , Gualtieri G. J. , Sunder W. A. 
Published: March 2011

ABSTRACTRaman scattering has been used to examine strained-layer GaSb/AlSb superlattices for a variety of growth imperfections. Analysis of zone-folded acoustic phonon spectra permit a determination of the superlattice period, the individual layer widths, some estimate of the interfacial widths, and evidence for variations in layer thicknesses.