UScholar Works
 
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CreatorTitleDescriptionSubjectDate
1 Stringfellow, Gerald B.Effect of oxygen incorporation in semi-insulating (AlxGa1-x)yIn1-yPDiscusses a study conducted on oxygen-doped, semi-insulating layers of (aluminum-gallium) indium phosphide grown on gallium arsenide using organometallic vapor phase epitaxy. Effect of oxygen doping on semi-insulating layers of the substance; Secondary-ion mass spectrometry measurements; Measured co...Inactive interstitial atoms; Energy-dispersive spectoscopy; intentional oxygen1992
2 Tiwari, AshutoshBand-gap engineering of Zn1-xGaxO nanopowders: synthesis, structural and optical characterizationsWe report the preparation and detailed structural and optical characterizations of single phase gallium doped ZnO nanopowders. A low temperature solution-based technique was developed to synthesize high-purity Zn1−xGaxO (x:0-0.05) nanopowders. Structural and optical characterization experiments we...Zinc gallium oxide; ZnGaO; Nanopowders; Band-gap engineering2008
3 Tiwari, AshutoshOxides for spintronics: a review of engineered materials for spin injectionIn this article we have reviewed the role of oxides in spintronics research, and specifically how these materials stand to further improve the efficiencies and capabilities of spin injection for active spintronic device development. The use of oxides in spintronics is advantageous in that they are s...2014-01-01
4 Liu, FengFabricating artificial nanowells with tunable size and shape by using scanning tunneling microscopyThe authors report a method of precisely fabricating the large-scale nanocrystals with well-defined shape and size. The (111) oriented Pb islands deposited on Si(111)-7x7 substrate were investigated with a manipulation technique based on scanning tunneling microscopy. By applying a series of voltage...Artificial nanowells2006
5 Liu, FengOrbit- and atom-resolved spin textures of intrinsic, extrinsic, and hybridized Dirac cone statesCombining first-principles calculations and spin- and angle-resolved photoemission spectroscopy measurements, we identify the helical spin textures for three different Dirac cone states in the interfaced systems of a two-dimensional (2D) topological insulator (TI) of a Bi(111) bilayer and a three-di...2014-01-01
6 Liu, FengEffects of Li doping on H-diffusion in MgH2: A first-principles studyThe effects of Li doping in MgH2 on H-diffusion process are investigated, using first-principles calculations. We have identified two key effects: (1) The concentration of H vacancy in the þ1 charge state ðVþ1 H Þ can increase by several orders of magnitude upon Li doping, which significantly in...2013-01-01
7 Scarpulla, MichaelEnhanced absorption in optically thin solar cells by scattering from embedded dielectric nanoparticlesAbstract: We present a concept for improving the efficiency of thin-film solar cells via scattering from dielectric particles. The particles are embedded directly within the semiconductor absorber material with sizes on the order of one wavelength. Importantly, this geometry is fully compatible wit...2010
8 Tiwari, AshutoshStructural, electrical, and optical characterizations of epitaxial Zn(1-x)Ga(x)O films grown on sapphire (0001) substrateIn this paper we report the structural, electrical, and optical properties of epitaxial Zn1−xGaxO films (x=0-0.05) grown on single crystal sapphire (0001) substrate by pulsed laser deposition technique. Structural and elemental analysis was performed using high-resolution x-ray diffraction (θ-2...Transparent conductive oxides; Gallium2007
9 Liu, FengConfining P diffusion in Si by an As-doped barrier layerThe miniaturization of Si-based devices requires control of doping profile, which makes the understanding of dopant interaction and diffusion in Si critical. The authors have studied the effect of As doping on P diffusion in Si using first-principles calculations. The authors found a form of As-vaca...P diffusion; Silicon; Arsenic doping; As-doped barrier; Diffusion control2007
10 Liu, FengSuppression of spin polarization in graphene nanoribbon by edge defects and impuritiesWe investigate the effect of edge defects (vacancies) and impurities (substitutional dopants) on the robustness of spin polarization in graphene nanoribbons (GNRs) with zigzag edges by using density-functional-theory calculations. The stability of the spin state and its magnetic moments is found to ...Edge defects; Vacancy; Spin-polarization; Graphene nanoribbon; GNR2008-04
11 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
12 Liu, FengInfluence of quantum size effects on Pb island growth and diffusion barrier oscillationsQuantum size effects are successfully exploited in manipulating the growth of (111) oriented Pb islands on Si(111) substrate with a scanning tunneling microscope. The growth dynamics and morphology displayed can be well controlled through the quantum size effects defined by the island thicknesses ...Quantum size effects; QSE; Pb island; Diffusion barrier oscillations2006-08
13 Tiwari, AshutoshObservation of the inverse spin hall effect in ZnO thin films: an all-electrical approach to spin injection and detectionThe inverse spin Hall effect (ISHE) is a newly discovered, quantum mechanical phenomenon where an applied spin current results in the generation of an electrical voltage in the transverse direction. It is anticipated that the ISHE can provide a more simple way of measuring spin currents in spintroni...2014-01-01
14 Liu, FengPrediction of a Dirac state in monolayer TiB2We predict the existence of a Dirac state in a monolayer TiB2 sheet (m-TiB2), a two-dimensionalmetal diboride, based on first-principles calculations. The band structure of m-TiB2 is found to be characterized with anisotropic Dirac cones with the largest Fermi velocity of 0.57 × 106 m/s, which is a...2014-01-01
15 Liu, FengElectronic strengthening of graphene by charge dopingGraphene is known as the strongest 2D material in nature, yet we show that moderate charge doping of either electrons or holes can further enhance its ideal strength by up to 17%, based on first-principles calculations. This unusual electronic enhancement, versus conventional structural enhancement,...2012-01-01
16 Liu, FengPressure-induced hard-to-soft transition of a single carbon nanotubeWe demonstrate a hydrostatic pressure-induced hard-to-soft transition of an isolated single wall carbon nanotube, using classical and ab initio constant-pressure molecular-dynamics simulations and continuum elastic theory analysis. At low pressure, the carbon tube is hard. Above a critical pressur...Carbon nanotubes; Hard-to-soft transition2004-10
17 Liu, FengStrain-engineered surface transport in Si(001): complete isolation of the surface state via tensile strainBy combining density functional theory, nonequilibrium Green's function formulism and effective- Hamiltonian approaches, we demonstrate strain-engineered surface transport in Si(001), with the complete isolation of the Si surface states from the bulk bands. Our results show that sufficient tensile s...2013-01-01
18 Liu, FengA three-layer-mesh bridging domain for coupled atomistic-continuum simulations at finite temperature: formulation and testingAlthough concurrent multiscale methods have been well developed for zero-temperature simulations, improvements are needed to meet challenges pertaining to finite-temperature simulations. Bridging domain method (BDM) is one of the most efficient and widely-used multiscale atomistic-continuum techniqu...2014-01-01
19 Tiwari, AshutoshShape of the Hanle curve in spin-transport structures in the presence of an ac driveResistance between two ferromagnetic electrodes coupled to a normal channel depends on their relative magnetizations. The spin-dependent component, R, of the resistance changes with magnetic field, B, normal to the directions of magnetizations. In the field of spin transport, this change, R(B), orig...2014-01-01
20 Liu, FengExceptional optoelectronic properties of hydrogenated bilayer siliceneSilicon is arguably the best electronic material, but it is not a good optoelectronic material. By employing first-principles calculations and the cluster-expansion approach, we discover that hydrogenated bilayer silicene (BS) shows promising potential as a new kind of optoelectronic material. Most ...2014-01-01
21 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
22 Scarpulla, MichaelInvestigation of combinatorial coevaporated thin film Cu 2ZnSnS4 (II): Beneficial cation arrangement in Cu-rich growthCu2ZnSn(S,Se)4 (CZTSSe) is an earth-abundant semiconductor with potential for economical photovoltaic power generation at terawatt scales. In this work, we use Raman scattering to investigate phase coexistence in combinatorial CZTS thin films grown at 325 or 470 C. The surface of the samples grown a...2014-01-01
23 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
24 Stringfellow, Gerald B.Step structure and ordering in Zn-doped GaInPPresents the results of a study of Zinc dopant effects on both step structure and ordering in GaInP in an effort to further clarify the disordering mechanism. Comparison of the results obtained for Zinc with those reported for tellurium; Experiment; Results; Discussion; Conclusion.Gallium Compounds; Zinc; Ordering1999
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