UScholar Works
 
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CreatorTitleDescriptionSubjectDate
51 Stringfellow, Gerald B.Effects of V/III ratio on ordering in GaInP: atomic scale mechanismsGa0.5In0.5P layers have been grown by organometallic vapor-phase epitaxy using various values of input V/III ratio for two phosphorus precursors, phosphine, the conventional precursor, and tertiarybutylphosphine (TBP), a newly developed, less-hazardous precursor. For growth on nominally (001) GaAs s...Photoabsorption spectroscopy; Transmission electron diffraction; Phosphorus precursor1996-05-01
52 Stringfellow, Gerald B.InAsSbBi alloys grown by organometallic vapor-phase epitaxyProvides information on a study on the growth of InAsSbBi alloys by organometallic vapor-phase epitaxy. Experiment; Results and discussion; Conclusion.Alloys; Epitaxy; Organometallic Compounds1994
53 Stringfellow, Gerald B.Spectroscopic study of surfactant enhanced organometallic vapor phase epitaxy growth of GaInPSamplen s of GaxIn1-xP grown by organometallic vapor phase epitaxy on (001) GaAs substrates by addition of TESb demonstrating a lateral superlattice compositional modulation (CM) have been studied by low temperature polarized photoluminescence (PL), power dependent PL, and photoluminescence excitati...Organometallic vapor; Photoluminescence excitation; Spectroscopy2001
54 Liu, FengMechanism for nanotube formation from self-bending nanofilms driven by atomic-scale surface-stress imbalanceWe demonstrate, by theoretical analysis and molecular dynamics simulation, a mechanism for fabricating nanotubes by self-bending of nanofilms under intrinsic surface-stress imbalance due to surface reconstruction. A freestanding Si nanofilm may spontaneously bend itself into a nanotube without exter...Nanotube formation; Self-bending nanofilms; Surface-stress imbalance2007-04
55 Scarpulla, MichaelBandgap and band offsets determination of semiconductor heterostructures using three-terminal ballistic carrier spectroscopyAmong the most important properties of semiconductors are their bandgaps and how the total bandgap difference distributes between the conduction band offset ΔEC and the valence band offset ΔEV at the heterojunction (HJ) interface between two semiconductors. Understanding such properties is crucial...Bandgaps; Band offsets; Gallium arsenide2009
56 Liu, FengElectronic and elastic properties of edge dislocations in SiAb initio, tight-binding, and classical calculations have been done for (a/2)( 110) edge dislocation dipoles in Si at separations of 7.5-22.9 A in unit cells comprising 32-288 atoms. These calculations show states associated with the cores relatively deep in the band gap (~ 0.2 eV) despite the abse...Edge dislocations1995-06
57 Liu, FengBending of nanoscale ultrathin substrates by growth of strained thin films and islandsMechanical bending is ubiquitous in heteroepitaxial growth of thin films where the strained growing film applies effectively an "external" stress to bend the substrate. Conventionally, when the deposited film is much thinner than the substrate, the bending increases linearly with increasing film th...Nanoscale ultrathin substrates; Strained thin films; Islands; Heteroepitaxial growth; Si substrate; Ge film2005-08
58 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
59 Tiwari, AshutoshEpitaxial growth of magnetic nickel nanodots by pulsed laser depositionEpitaxial nickel magnetic nanodots were obtained by pulsed laser deposition (PLD) technique on Si (100) substrate using epitaxial TiN film as the template. Characterization methods include: high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) Z-...Nanodots; TiN; Nickel2003
60 Stringfellow, Gerald B.Influence of tellurium doping on step bunching of GaAs (001) vicinal surfaces grown by organometallic vapor phase epitaxyAtomic force microscopy has been used to investigate the influence of controlled tellurium Te incorporation on the step structure of GaAs grown by organometallic vapor phase epitaxy on vicinal 001 surfaces. Te doping, using the precursor diethyltelluride, is found to markedly decrease the surface r...Epitaxial growth; Misorientation; Organometallic vapor phase epitaxy1998
61 Stringfellow, Gerald B.Long wavelength lattice dynamics for quaternary alloys: GaInPSb and AlGaAsSbPresents information on a study which investigated the long wavelength lattice dynamics of quaternary alloys. Theory of the random cell isodisplacement model; Secular equation developed; Results and discussion.Lattice dynamics; Quaternary alloys1992
62 Stringfellow, Gerald B.; Shurtleff, James KevinAdsorption and desorption of the surfactant Sb on GaInP grown by organometallic vapor phase epitaxyIt has been determined that ordering has a profound effect on the bandgap energy of many compound semiconductor alloys. Therefore, ordering must be controlled for devices such as solar cells, light emitting diodes and diode lasers. Since ordering depends on the surface properties during organomet...Time dependent surface photoabsorption (SPA); Compound semiconductor alloys2000
63 Liu, FengSelf-assembly of two-dimensional islands via strain-mediated coarseningWe demonstrate two distinctive effects of strain-induced island-island interaction on island size and spatial distribution during coarsening of 2D islands. When coarsening proceeds via only mass transport between islands, the interaction broadens the island size distribution, leading to a power-law...Two-dimensional islands; Strain-mediated coarsening2001-08
64 Tiwari, AshutoshCopper diffusion characteristics in single-crystal and polycrystalline TaNWe have investigated the diffusivity of copper in single-crystal (NaCl-structured) and polycrystalline TaN thin films grown by pulsed-laser deposition. Polycrystalline TaN films were grown directly on Si(100), while single-crystal films were grown with TiN buffer layers. Both poly- and single-crysta...Diffusion barriers; Copper diffusion; Tantalum nitride2002
65 Liu, FengStrain effect on adatom binding and diffusion in homo- and heteroepitaxies of Si and Ge on (001) SurfacesStrain dependence of adatom binding energies and diffusion barriers in homo- and heteroepitaxies of Si and Ge on s001d surface has been studied using first-principles calculations. In general, Si adatom binding energies and diffusion barriers are larger on Sis001d and Ges001d surfaces than a Ge ada...Strain effect; Adatom binding; Adatom diffusion; Adatoms; Heteroepitaxies; Homoepitaxies; (001) surfaces; Si; Ge2004-10
66 Liu, FengStep-induced magnetic-hysteresis anisotropy in ferromagnetic thin filmsWe investigate the quasistatic magnetic hysteresis of ferromagnetic thin films grown on a vicinal substrate, using Monte Carlo simulations within a two-dimensional XY model. Intrinsic in-plane anisotropy is assigned to surface sites according to their local symmetry. The simulated hysteresis loops s...Magnetic hysteresis; Ferromagnetic thin films; Step-induced2002
67 Tiwari, AshutoshGrowth of epitaxial ZnO films on Si(111)Epitaxial ZnO films have been grown on Si(l 11) substrates by employing a A1N buffer layer during a pulsed laser-deposition process. The epitaxial structure of A1N on Si(l 11) substrate provides a template for ZnO growth. The resultant films are evaluated by transmission electron microscopy, x-ray ...Buffer layers; Aluminum nitride; Silicon substrate2002
68 Scarpulla, MichaelDiluted II-VI oxide semiconductors with multiple band gapsWe report the realization of a new mult-band-gap semiconductor. Zn1-yMnyOxTe1-x alloys have been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of ...Highly mismatched alloys; Zinc telluride2003-12
69 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
70 Tiwari, AshutoshElectrical transport in ZnO1-δ films: transition from band-gap insulator to Anderson localized insulatorWe have thoroughly investigated the effect of oxygen nonstoichiometry on the electrical transport characteristics of ZnO1−δ films. These films were grown on optical grade quartz substrates by using a pulsed laser deposition technique. In order to alter the amount of oxygen nonstoichiometry (δ), ...Anderson localized insulators2004
71 Liu, FengModification of Si(001) substrate bonding by adsorbed Ge or Si dimer islandsHigh-resolution scanning tunneling microscopy studies of the Si(100)-(2 X 1) surface show a heretofore unrecognized distortion of the substrate structure when islands form during the initial stage of growth of either Si or Ge. The distortion, reflecting the influence of strain, extends at least thre...Si(001); Adsorbed Ge; Adsorbed Si; Dimer islands; Substrate bonding; Distortion1998-09
72 Liu, FengBending of nanoscale thin Si film induced by growth of Ge islands: hut vs. domeWe perform atomistic simulations to compute bending of freestanding nanoscale thin Si film induced by strained Ge islands. We show that a larger Ge dome island can induce smaller bending than a smaller hut island and explain the surprising experimental observation for growth of Ge islands on pattern...Bending; Nanoscale thin Si film; Ge islands; Hut islands; Dome islands; Atomistic simulations2004
73 Scarpulla, MichaelElectrical transport and ferromagnetism in Ga1−xMnxAs synthesized by ion implantation and pulsed-laser meltingWe present a detailed investigation of the magnetic and magnetotransport properties of thin films of ferromagnetic Ga1−xMnxAs synthesized using ion implantation and pulsed-laser melting (II-PLM). The field and temperature-dependent magnetization, magnetic anisotropy, temperature-dependent resist...GaMnAs; Gallium arsenide2008
74 Tiwari, AshutoshSingle crystal TaN thin films on TiN/Si heterostructureWe have successfully grown epitaxial cubic (Bl-NaCl structure) tantalum nitride films on Si (100) and (111) substrate using a pulsed laser deposition technique. A thin layer of titanium nitride was used as a buffer medium. We characterized these films using X-ray diffraction, high resolution transmi...Tantalum nitride; Diffusion barriers; Copper diffusion2002
75 Liu, FengFirst-principles calculation of interaction between interstitial O and As dopant in heavily As-doped SiWe investigate the interaction between interstitial oxygen (Oi) and As dopant in heavily As-doped Si using first-principles total-energy calculations. The interaction between Oi and As (substitutional) is found to be short ranged. The most stable configuration is with As and Oi as second nearest nei...First-principles calculation; Interstitial oxygen; As dopant; As-doped Si; Oxygen diffusion; Oi2007
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