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1 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
2 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
3 Stringfellow, Gerald B.Effects of V/III ratio on ordering and antiphase boundaries in GaInP layersTransmission electron microscope (TEM) and transmission electron diffraction (TED) studies have been performed to investigate the effects of V/III ratio on ordering and antiphase boundaries (APBs) in organometallic vapor phase epitaxial Ga0.5In0.5P layers grown onto (001) GaAs vicinal substrates ...Antiphase boundaries; APB; Heterostructures; Organometallics1997
4 Liu, FengInterplay of stress, structure, and stoichiometry in Ge-covered Si(001)By calculating the evolution of surface energies and surface stress tensors of Ge-covered Si(001) with increasing Ge coverage, we derive the most probable Ge stoichiometry in the subsurface regions beyond 1 monolayer coverage. We compare the calculated surface reconstruction and surface stress at th...Ge-covered; Si(001); Stress; Structure; Surface stress tensors1996-04
5 Scarpulla, MichaelAir shear driven flow of thin perfluoropolyether polymer filmsWe have studied the wind driven movement of thin perfluoropolyether (PFPE) polymer films on silicon wafers and CNx overcoats using the blow-off technique. The ease with which a liquid polymer film moves across a surface when sheared is described by a shear mobility xS , which can be interpreted both...Perfluoropolyether; Polymer films; Air shear; Shear mobility2003
6 Tiwari, AshutoshGrowth of epitaxial NdNiO3 and integration with Si(100)We have grown epitaxial NdNiO3 films on Si(100) substrate under ambient oxygen pressure using a pulsed-laser deposition method. The integration of NdNiO3 with Si(100) was accomplished by lattice-matching epitaxy of MgO and SrTiO3 and domain matching epitaxy of TiN on Si(100). During domain matching...NdNiO3; SrTiO3; Silicon substrate2002
7 Stringfellow, Gerald B.Effect of growth rate on step structure and ordering in GaInPCuPt ordering is widely observed in GaInP epitaxial layers grown by organometallic vapor phase epitaxy. The formation of this spontaneously ordered structure during epitaxial growth is intimately related to the atomic-scale physical processes occurring on the surface, specifically surface reconst...Atomic force microscopy; Organometallic vapor phase; Crystallographic plane1997
8 Liu, FengMagnetism in small vanadium clustersUsing the self-consistent-field molecular-orbital theory and the density-functional approximation, we show that vanadium could become magnetic if its size and dimension were constrained. This is illustrated for vanadium forming clusters with body-centered-cubic (bcc) geometry as well as for linear c...Vanadium clusters; Molecular-orbital theory; Density-functional approximation; Stoner criterion1991-04
9 Liu, FengMagnetism in nanopatterned graphite filmUsing first-principles calculations, we show that nanopatterned graphite films (NPGFs) can exhibit magnetism in analogy to graphene-based nanostructures (GBNs). In particular, graphite films with patterned nanoscale triangular holes and channels with zigzag edges all have ferromagnetic ground state...Nanopatterned graphite; Graphite films; NPGF2008
10 Liu, FengSimple theory of the electronic structure: clusters to crystalsA simple scheme based upon a cross between the molecular clusters and the tight-binding theory has been developed to calculate the electronic structure of a large class of systems ranging from molecules to solids. The method is applied to study the variations in the magnetic moments of Fe and Ni for...Clusters; Tight-binding theory; Magnetic moment1988-09
11 Liu, FengQuantum size effect on adatom surface diffusionUsing scanning tunneling microscopy, we demonstrate that the nucleation density of Fe islands on the surface of nanoscale Pb films oscillates with the film thickness, providing a direct manifestation of the quantum size effect on surface diffusion. The Fe adatom diffusion barriers were derived to be...Quantum size effect; QSE; Adatoms; Surface diffusion; Fe islands; Nanoscale metallic structures; Epitaxial growth; Pb films2006-12
12 Liu, FengSelf-consistent tight-binding methodA self-consistent tight-binding formalism is described. The self-consistency is achieved by the introduction of a chemical hardness matrix and a generalization of the Huckel model to make the tight-binding Hamiltonian an implicit functional of the charge density. Studies of the band structures of d...Tight-binding method; Self-consistency; Huckel model1995-10
13 Chaudhuri, Reaz A.Interlaminar shear stresses around an internal part-through hole in a stretched laminated composite plateThe equilibrium/compatibility method, which is a semi-analytical post-processing method, is employed for computation of hitherto unavailable through-thickness variation of interlaminar (transverse) shear stresses in the vicinity of the bi-layer interface circumferential re-entrant corner line of an...2010-03
14 Liu, FengMechanical stability of ultrathin Ge/Si film on SiO2: the effect of Si/SiO2 interfaceWe perform two-dimensional linear elastic finite element analysis to investigate the mechanical stability of ultrathin Ge/Si film grown on or bonded to SiO2, using imperfect interface elements between Si and SiO2 to model Si/SiO2 interfacial slippage. We demonstrate that the overall composite film i...Ultrathin films; Si/SiO2 interface; Mechanical stability2005
15 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
16 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
17 Scarpulla, MichaelThe importance of Se partial pressure in the laser annealing of CuInSe2 electrodeposited precursorsOne method for producing CuInSe2 (CISe) absorber layers is electrodeposition followed by annealing. Replacing the commonly used furnace annealing step with a laser can reduce annealing times by 2-3 orders of magnitude: from 30 minutes to 1 s. However, laser processing has, to date, not resulted in a...2014-01-01
18 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
19 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
20 Tiwari, AshutoshEpitaxial growth of ZnO films on Si(111)In this paper, we report the growth of ZnO films on silicon substrates using a pulsed laser deposition technique. These films were deposited on Si(111) directly as well as by using thin buffer layers of AlN and GaN. All the films were found to have c-axis-preferred orientation aligned with normal to...Buffer layers; Aluminum nitride; Silicon substrate; Biaxial strain2002
21 Stringfellow, Gerald B.; Williams, Clayton C.Spatial mapping of ordered and disordered domains of GaInP by near-field scanning optical microscopy and scanning capacitance microscopyImaging of topography, locally induced photoluminescence and Fermi-level pinning in adjacent ordered and disordered domains on a cleaved GaInP sample is performed using a near-field scanning optical microscope and scanning capacitance microscope at room temperature in air. Highly localized photolumi...Gallium Phosphides; Surface Structure; Photoluminescence1996-04-13
22 Stringfellow, Gerald B.Effect of step structure on ordering in GaInPExamines the effect of step structure on ordering in gallium indium phosphite (GaInP) using atomic force microscopy. Coverage of the surface by islands several monolayers in height with elongated direction; Formation of the edges of the islands; Role of the observations in explaining the nature of t...Gallium indium phosphite (GaInP); Twin boundaries1995-11-12
23 Liu, FengKinetics of mesa overlayer growth: climbing of adatoms onto the mesa topWe have calculated the energy barriers for an adatom climbing up onto a Pb mesa top either over a facet-facet edge or through a facet-step joint, using a modified embedded atom method. We found that the second process is not only thermodynamically more favorable than the first one but also much fast...Mesa overlayer growth; Adatoms; Epitaxial growth2008
24 Scarpulla, MichaelMn L3,2 x-ray absorption and magnetic circular dichroism in ferromagnetic Ga1-xMnxPWe have measured the x-ray absorption and x-ray magnetic circular dichroism (XMCD) at the Mn L3,2 edges in ferromagnetic Ga1−xMnxP films for 0.018≤x≤0.042. Large XMCD asymmetries at the L3 edge indicate significant spin polarization of the density of states at the Fermi energy. The temperatur...X-ray absorption; Gallium Arsenide; Ferromagnetic semiconductors2006
25 Liu, FengEpitaxial growth of large-gap quantum spin Hall insulator on semiconductor surface : The substrate orbital filtering effectFormation of topological quantum phase on conventional semiconductor surface is of both scientific and technological interest. Here, we demonstrate epitaxial growth of 2D topological insulator, i.e. quantum spin Hall (QSH) state, on Si(111) surface with a large energy gap, based on first-principles ...2014-01-01
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