UScholar Works
 
Filters: Department: "Materials Science & Engineering" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
251 Liu, FengSurface mobility difference between Si and Ge and its effect on growth of SiGe alloy films and islandsBased on first-principles calculations of surface diffusion barriers, we show that on a compressive Ge(001) surface the diffusivity of Ge is 102-103 times higher than that of Si in the temperature range of 300 to 900 K, while on a tensile surface, the two diffusivities are comparable. Consequently, ...Surface mobility; SiGe film; Strained thin films; Surface diffusion barriers2006-01
252 Stringfellow, Gerald B.Surface photo-absorption studies of the chemical structure of GaInP grown by organometallic vapor phase epitaxyThe surface structure of Ga0.52In0.48P was studied by surface photoabsorption. An absorption peak due to P dimers on Ga0.52In0.48P was observed at 400 nm, shorter than for InP (430 nm). From comparison with results for GaAs and InP, the data are interpreted to indicate that at a tertiarybutylphos...Absorption peak; Ordering; Substrate orientation1995
253 Stringfellow, Gerald B.Surface photoabsorption study of the effect of substrate misorientation on ordering in GaInPSubstrate orientation strongly affects Cu-Pt ordering in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. In situ surface photoabsorption SPA measurements were used to measure the concentration of 1 10-oriented P dimers, characteristic of the 2 4 reconstructed surface, as a functio...P-dimer concentration; Photoluminescence measurements; Surface reconstruction1996-04-15
254 Stringfellow, Gerald B.Surface photoabsorption study of the effect of V/III ratio on ordering in GaInPCu-Pt ordering is widely observed in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. The degree of order is a strong function of the input partial pressure of the phosphorus precursor, i.e., the V/III ratio, during growth. By observing the surface structure using in situ surface p...Degree of order; Photoluminescence; Transmission electron microscopy1996
255 Stringfellow, Gerald B.Surface photoabsorption study of the effects of growth temperature and V/III ratio on ordering in GaInPSurface photoabsorption (SPA) measurements were used to clarify the Cu-Pt ordering mechanism in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. The Cu-Pt ordering is strongly affected by the growth temperature and the input partial pressure of the phosphorus precursor, i.e., the V/II...P-dimer concentration; Oriented phosphorus dimers; Surface reconstruction1996-05-01
256 Stringfellow, Gerald B.Surface photoabsorption transients and ordering in GaInPHeterostructures and quantum wells can be produced in GaInP without changing the solid composition by simply varying the order parameter. Since CuPt ordering reduces the band-gap energy, changes in the order parameter induced by changes in growth conditions result in heterostructures with band-ga...Order parameters; Quantum wells; P-dimers1998-03-15
257 Scarpulla, MichaelSurface stoichiometry of pulsed ultraviolet laser treated polycrystalline CdTeThe effects of nanosecond pulsed ultraviolet laser annealing on the surface stoichiometry of close-space sublimated polycrystalline thin films are investigated using angle-resolved x-ray photoemission spectroscopy (XPS). The raw data suggest the formation of a Cd-rich surface layer, but this is coun...2014-01-01
258 Liu, FengSurface stress-induced island shape transition in Si(001) homoepitaxyA low-energy electron microscopy study of two-dimensional Si(001) island shapes near thermal equilibrium on 10315 mm2 large single-domain terraces reveals a continuous increase of island aspect ratio and a shape transition from elliptical to ‘‘American-football''-like with increasing island size...Si(001); Homoepitaxy; Island shape transition; Single-domain terraces2001-11
259 Stringfellow, Gerald B.Surfactant controlled growth of GaInP by organometallic vapor phase epitaxyThe effect of the surfactant Sb has been studied for GaInP semiconductor alloys grown by organometallic vapor phase epitaxy. Dramatic changes in the optical and electrical properties of GaInP with CuPt ordering have been observed. A small concentration of triethylantimony TESb in the vapor is fou...Semiconductors; Surface active agents2000
260 Stringfellow, Gerald B.; Shurtleff, James KevinSurfactant effects on doping of GaAs grown by organometallic vapor phase epitaxyRecently, the addition of the isoelectronic surfactant Sb during organometallic vapor phase epitaxy (OMVPE) of GaInP was shown to eliminate ordering, resulting in a significant change in the band gap energy. These results suggest that surfactants added during growth could have profound affects on ot...Gallium arsenide; Surfactants; Semiconductors2001
261 Tiwari, AshutoshSynthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrixSingle domain magnetic nickel nanocrystals were embedded in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out at the atomic level using scanning transmission electron microscopy with atomic number contrast (STEM-Z) in conjunction with electron energy ...Nanophase magnetic materials; Alumina2002
262 Scarpulla, MichaelSynthesis and optical properties of II-O-VI highly mismatched alloysWe have synthesized ternary and quaternary diluted II-VI oxides using the combination of O ion implantation and pulsed laser melting. CdOxTe12x thin films with x up to 0.015, and the energy gap reduced by 150 meV were formed by O1-implantation in CdTe followed by pulsed laser melting. Quaternary Cd0...Highly mismatched alloys; Cadmium telluride; Zinc telluride; Thermal annealing; Anticrossing; Photomodulation spectroscopy2004
263 Scarpulla, MichaelSynthesis and properties of highly mismatched II-O-I alloysTernary and quaternary dilute II-VI oxides were synthesised using a highly nonequilibrium method: the combination of O ion implantation and pulsed-laser melting. CdOxTe12x thin films have been produced with x up to 0.015 and with the energy gap reduced by 0.15 eV. Optical transitions corresponding t...Highly mismatched alloys; Cadmium telluride; Zinc telluride; Anticrossing2004
264 Scarpulla, MichaelSynthesis of GaNxAs1-x thin films by pulsed laser melting and rapid thermal annealing of N+-implanted GaAsWe present a systematic investigation on the formation of the highly mismatched alloy GaNxAs1-x using N1-implantation followed by a combination of pulsed laser melting and rapid thermal annealing. Thin films of GaNxAs1-x with x as high as 0.016 and an activation efficiency of the implanted N up to 5...Highly mismatched alloys; Gallium arsenide2003
265 Tiwari, AshutoshTb2O3 thin films: An alternative candidate for high-k dielectric applicationsWe are reporting the growth and structural, optical, and dielectric properties of Tb2O3, a relatively unexplored high-k dielectric material. A pulsed-laser deposition technique was used to grow Tb2O3 thin-films on four different substrates: Si(100), SrTiO3(100), LaAlO3(100), and MgO(100). High resol...2014-01-01
266 Stringfellow, Gerald B.Te doping of GaInP: ordering and step structureThe donor Te has been added to GaInP during organometallic vapor phase epitaxial growth using the precursor diethyltelluride. In agreement with previous studies, the addition of high Te concentrations leads to the elimination of the CuPt ordering observed in undoped layers. The degree of order is es...Epitaxial growth; Heterostructures; Growth parameters1999-04-01
267 Scarpulla, MichaelTe-rich CdTe surface by pulsed UV laser treatment for ohmic back contact formationPulsed UV laser treatments have recently been applied to polycrystalline CdTe solar cells to create an ohmic back contact. In this work, we investigate the surface stoichiometry variations produced by pulsed laser excitation using X-ray photoelectron spectroscopy (XPS). These results reveal surfaces...2014-01-01
268 Scarpulla, MichaelTemperature dependence of equivalent circuit parameters used to analyze admittance spectroscopy and application to CZTSe devicesWe present a device physics and equivalent circuit model for admittance spectroscopy of CZTSe based photovoltaic devices. The experimental variations of the capacitance and conductance in the depletion width are reproduced for state of the art coevaporated CZTSe devices. We will show that simple Arr...2014-01-01
269 Scarpulla, MichaelTemperature dependent conductivity of polycrystalline Cu 2ZnSnS 4 thin filmsThe temperature-dependent conductivity of Cu2ZnSnS4 (CZTS) thin films prepared by sulfurization of different sputtered ZnS/Cu/Sn stacks and also of the same stack annealed for different times was investigated from 30-300 K. Fitting of the through-thickness conductivity requires a model including Mot...2012-01-01
270 Bedrov, Dmitro; Smith, Grant D.Temperature dependent shear viscosity coefficient of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX ): a molecular dynamics simulation studyEquilibrium molecular dynamics methods were used in conjunction with linear response theory and a recently published potential-energy surface [J. Phys. Chem. B 103, 3570 (1999)] to compute the liquid shear viscosity and self-diffusion coefficient of the high explosive HMX (octahydro-1,3,5,7-tetran...Polymer melts; HMX; Shear viscosity coefficient; Plastic-bonded explosives2000
271 Stringfellow, Gerald B.Tertiarybutyldimethylantimony: a new Sb source for low temperature organometallic vapor phase epitaxial growth of InSbThis article investigates tertiarybutyldimethylantimony as a source for low-temperature organometallic vapor phase epitaxial growth of indium antimonide (InSB); extraction of good surface morphology InSb layers; efficiency of InSB growth; and, presence of a negligible parasitic reaction between trim...Tertiarybutyldimethylantimony; Indium antimonide crystals1992
272 Liu, FengTheory of directed nucleation of strained islands on patterned substratesWe develop a theoretical model to elucidate the nucleation of strained islands on patterned substrates. We show that island nucleation is directed to the preferred sites by a much lower energy barrier and smaller critical size. Strain relaxation directs island nucleation to the bottom of a pit rat...Directed nucleation; Strained islands; Patterned substrates2008-11
273 Liu, FengTheory of equilibrium shape of an anisotropically strained island: thermodynamic limits for growth of nanowiresUsing continuum elastic theory, we show that strain anisotropy removes the shape instability existing for an isotropically strained island. An anistropically strained island has always an anisotropic shape, elongating along the less-strained direction and adopting a narrow width in the more-strain...Strained islands; Equilibrium shape; Growth; Thermodynamic limits2004-11
274 Liu, FengTheory of hydrogen pairing in yttriumThe energetics of hydrogen atoms interacting with yttrium have been investigated using the self-consistent cluster model and the local-density approximation. Our results provide a theoretical understanding of a range of novel phenomena observed recently in resistivity, neutron scattering, NMR, and ...Hydrogen pairing; Self-consistent cluster model; Local-density approximation; Energetics1989-09
275 Bedrov, Dmitro; Smith, Grant D.Thermal conductivity of molecular fluids from molecular dynamics simulations: application of a new imposed-flux methodWe have applied a new nonequilibrium molecular dynamics (NEMD) method [F. Müller-Plathe, J. Chem. Phys. 106, 6082 (1997)] previously applied to monatomic Lennard-Jones fluids in the determination of the thermal conductivity of molecular fluids. The method was modified in order to be applicable to...Thermal conductivity; Molecular fluids; Heat flux; Imposed-flux NEMD method2000
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