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1 Liu, Feng(BAl12)Cs: a cluster-assembled solidFirst-principles calculations on the geometry and stability of AlnBm clusters have been carried out to examine the effect of size, composition, and electronic-shell filling on their relative stability. It is shown that although Al and B are both trivalent, a BAl12 cluster is more stable than an Al1...First-principles calculations; (BAl12)Cs; Cluster-assembled; AlnBm clusters1997-06
2 Smith, Grant D.; Borodin, Oleg; Bedrov, Dmitro13C NMR spin-lattice relaxation and conformational dynamics in a 1,4-polybutadiene meltWe have performed molecular dynamics (MD) simulations of a melt of 1,4-polybutadiene (PBD, 1622 Da) over the temperature range 400?273 K. 13C NMR spin?lattice relaxation times (T1) and nuclear Overhauser enhancement (NOE) values have been measured from 357 to 272 K for 12 different resonances. The T...Polybutadiene melt; 13C NMR; Spin-lattice relaxation; Conformational dynamics; Molecular dynamics simulation2001
3 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
4 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
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 Liu, FengAnisotropic strain enhanced hydrogen solubility in bcc metals: the independence on the sign of strainWhen an impurity is doped in a solid, it inevitably induces a local stress, tending to expand or contract the lattice. Consequently, strain can be applied to change the solubility of impurity in a solid. Generally, the solubility responds to strain ‘‘monotonically,'' increasing (decreasing) with...2012-01-01
7 Bedrov, Dmitro; Smith, Grant D.Anomalous pressure dependence of the structure factor in 1,4-polybutadiene melts: a molecular dynamics simulation studyNeutron scattering has shown the first diffraction peak in the structure factor of a 1,4-polybutadiene melt under compression to move to larger q values as expected but to decrease significantly in intensity. Simulations reveal that this behavior does not result from loss of structure in the polymer...Polymer melts; 1, 4-polybutadiene melts; Pressure; Structure factor2004-07
8 Stringfellow, Gerald B.Atomic force microscopy study of ordered GaInPExamines the nature of the steps on the surface of gallium indium phosphide lattice layers matched to gallium arsenide substrates using atomic force microscopy. Temperatures of organometallic vapor phase epitaxy used; Relation of height of steps with misorientation angle; Link of supersteps with the...Surface chemistry; Lattice theory1995
9 Stringfellow, Gerald B.; Williams, Clayton C.Atomic ordering of GaInP studied by Kelvin probe force microscopyThe atomic ordering of GaInP has been established and studied by a variety of methods, including transmission electron microscopy, cathodoluminescence, and photoluminescence. In this work, a Kelvin probe force microscope _x0002_KPFM_x0003_ has been employed to image several GaInP samples previous...Cathodoluminescence; Photoluminescence; Surface morphology1995
10 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
11 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
12 Stringfellow, Gerald B.Bandgap control of GaInP using Sb as a surfactantThe use of surfactants to control specific aspects of the vapor-phase epitaxial growth process is beginning to be studied for both the elemental and III/V semiconductors. To date, most reported surfactant effects for semiconductors relate to the morphology of the growing films. However, semicondu...Band-gap energy; Growth process; Epitaxial growth1999-09-27
13 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
14 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
15 Stringfellow, Gerald B.Bi surfactant control of ordering and surface structure in GaInP grown by organometallic vapor phase epitaxyStudies the effect of the surfactant bismuth on the ordering and surface structure in GaInP layers grown by organometallic vapor phase epitaxy. Disordering caused by the addition of bismuth during growth; Changes in surface structure occurring with the disordering.Thin films, Multilayered; Bismuth2000
16 Stringfellow, Gerald B.; Shurtleff, James KevinBi surfactant effects on ordering in GaInP grown by organometallic vapor-phase epitaxyThe effect of the isoelectronic surfactant Bi on surface structure and ordering has been studied for GaInP semiconductor alloys grown by organometallic vapor-phase epitaxy. A small amount of Bi trimethylbismuth added during growth is found to result in disordering for layers grown using conditions t...Surfactant; Semiconductors; Trimethylbismuth2000
17 Scarpulla, MichaelCarrier concentration dependencies of magnetization & transport in Ga1-xMnxAs1-yTeyWe have investigated the transport and magnetization characteristics of Ga1-xMnxAs intentionally compensated with shallow Te donors. Using ion implantation followed by pulsed-laser melting, we vary the Te compensation and drive the system through a metal-insulator transition (MIT). This MIT is assoc...Gallium arsenide; Ferromagnetic semiconductors; Magnetization; Resistivity2005
18 Tiwari, AshutoshCharacterization of Li7La3Zr2O 12 thin films prepared by pulsed laser depositionA pulsed laser deposition system was employed to fabricate thin films of Li7La3Zr2O12 solid electrolyte. The deposition process was carried out at room-temperature, resulting in amorphous films. These as-deposited films had a large optical band gap of 5.13 eV, and exhibited a lithium-ion conductivit...2012-01-01
19 Stringfellow, Gerald B.;Inglefield, Colin E.;Taylor, P. CraigCharacterization of unicompositional GaInP2 ordering heterostructures grown by variation of V/III ratioPhotoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies are employed to investigate single heterostructures based on two GaInP2 layers that have the same composition but different degrees of order on the cation sublattice. Four sample configurations are studied: two complemen...Heterostructures; Growth parameters; Growth temperature1997
20 Ostafin, AgnesCombined deletion of mouse dematin-headpiece and ß-adducin exerts a novel effect on the spectrin-actin junctions leading to erythrocyte fragility and hemolytic AnemiaDematin and adducin are actin-binding proteins of the erythrocyte "junctional complex." Individually, they exert modest effects on erythrocyte shape and membrane stability, and their homologues are expressed widely in non-erythroid cells. Here we report generation and characterization of double knoc...2007
21 Bedrov, Dmitro; Borodin, Oleg; Smith, Grant D.Comment on "On the accuracy of force fields for predicting the physical properties of dimethylnitramine"Zheng and Thompson have recently reported a comparison of three atomistic force fields for prediction of physical properties of dimethylnitramine (DMNA) from molecular dynamics (MD) simulations.1 Specifically, they compared the rigid molecule force field by Sorescu, Rice, and Thompson (SRT);2 the ge...2007
22 Bedrov, Dmitro; Smith, Grant D.Comparison of self-assembly in lattice and off-lattice model amphiphile solutionsLattice Monte Carlo and off-lattice molecular dynamics simulations of h1t4 and h4t1 (head/tail) amphiphile solutions have been performed as a function of surfactant concentration and temperature. The lattice and off-lattice systems exhibit quite different self-assembly behavior at equivalent ther...Amphiphile solutions; Micellization; Surfactants2002
23 Scarpulla, MichaelCompensation-dependent in-plane magnetization reversal processes in Ga1-xMnxP1-ySyWe report the effect of dilute alloying of the anion sublattice with S on the in-plane uniaxial magnetic anisotropy and magnetization reversal process in Ga1−xMnxP as measured by both ferromagnetic resonance (FMR) spectroscopy and superconducting quantum interference device (SQUID) magnetometry. ...Ferromagnetic semiconductors; Nonmagnetic compensation2008-12
24 Scarpulla, MichaelCompositional tuning of ferromagnetism in Ga1-xMnxPWe report the magnetic and transport properties of Ga1-xMnxP synthesized via ion implantation followed by pulsed laser melting over a range of x, namely 0.018 to 0.042. Like Ga1-xMnxAs, Ga1-xMnxP displays a monotonic increase of the ferromagnetic Curie temperature with x associated with the hole-me...Gallium arsenide; Ferromagnetic semiconductors2006-12
25 Liu, FengComputational designing of carbon nanotube electromechanical pressure sensorsWe investigate electronic transport properties of single-walled carbon nanotubes (SWNT's) under hydrostatic pressure, using first-principles quantum transport calculations aided by molecular-dynamics simulation and continuum mechanics analysis. We demonstrate a pressure-induced metal-to-semiconduc...Carbon nanotubes; Computational designing; Pressure sensors; Electronic transport2004-04
26 Liu, FengComputational R&D for industrial applicationsRecent advances in high-speed supercomputer and computational algorithms have brought us into a new era of computational materials science. These advances make it possible to investigate many existing materials systems that were previously considered intractable and also predict and design novel mat...Computational materials science2005
27 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
28 Smith, Grant D.Conformational properties of poly(vinylidene fluoride). A quantum chemistry study of model compoundsThe molecular geometries and conformational energies of model molecules of poly(vinylidene fluoride) (PVDF) have been determined from high-level quantum chemistry calculations and have been used in parametrization of a six-state rotational isomeric state (RIS) model for PVDF. The model molecules inv...Poly(vinylidene fluoride); PVDF; Conformational properties1999
29 Stringfellow, Gerald B.Control and characterization of ordering in GaInPGae,,In,,P layers have been grown by organometallic vapor phase epitaxy on GaAs substrates with [llO]-oriented grooves on the surface that have an important effect on the formation of Cu-Pt ordered structures during growth. In this work, the groove shape is demonstrated to be critically important...Vapor phase epitaxy; Ordered structure; Cathodoluminescence spectroscopy1993-06-28
30 Stringfellow, Gerald B.Control of ordering in Ga0.5In0.5P using growth temperatureThe kinetic processes leading to ordering in Gas,, In o.4P8 have been studied by observing the effects of substrate misorientation (O-9), growth rate (0.1-0.5), and substrate temperature (570- 670 "C) during growth. The ordered structure and degree of ordering are determined using transmission elec...Ordering Structure; Growth Temprature; Growth Rate1994
31 Tiwari, AshutoshCopper diffusion characteristics in single crystal and polycrystalline TaNTaN has become a very promising diffusion barrier material for Cu interconnections, due to the high thermal stability requirement and thickness limitation for next generation ULSI devices. TaN has a variety of phases and Cu diffusion characteristics vary with different phases and microstructures. We...Diffusion barriers; Copper diffusion; Tantalum nitride2003
32 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
33 Stringfellow, Gerald B.Correlation between surface structure and ordering in GaInPGa and In atoms in Ga0.52In0.48P layers spontaneously segregate to form alternating In- and Ga-rich {111} monolayers during organometallic vapor phase epitaxial (OMVPE) growth on (001) oriented GaAs substrates, thus forming the CuPt ordered structure. This ordering phenomenon is believed to be drive...Transformations; Absorbtion spectra; Surface Properties1996
34 Liu, FengCoulomb sink: a novel Coulomb effect on coarsening of metal nanoclusters on semiconductor surfacesWe propose the concept of a ‘‘Coulomb sink'' to elucidate the effect of Coulomb charging on coarsening of metal mesas grown on semiconductor surfaces.We show that a charged mesa, due to its reduced chemical potential, acts as a Coulomb sink and grows at the expense of neighboring neutral mesas. ...Coulomb sink; Coulomb effect; Metal nanoclusters; Semiconductor surface; Pb mesas2004-09
35 Liu, FengCreation of "quantum platelets" via strain-controlled self-organization at stepsWe demonstrate, by both theory and experiment, the strain-induced self-organized formation of "quantum platelets," monolayer-thick islands of finite dimensions. They form at the early stage of heteroepitaxial growth on a substrate with regularly spaced steps, and align along the steps. In the direc...Quantum platelets; Strain-controlled self-organization; Monolayer-thick islands; Heteroepitaxial growth2000-12
36 Liu, FengCritical epinucleation on reconstructured surfaces and first-principle calculation of homonucleation on Si(100)We introduce the concept of ‘‘critical epinucleation'' to distinguish nucleation on surfaces with and without reconstruction. On a reconstructed surface, the critical classical nucleus is stable against dissociation, but may not yet break the underlying surface reconstruction. Consequently, ther...Critical epinucleation; First-principle calculation; Homonucleation; Si(100); Islands2005-09
37 Tiwari, AshutoshCuBO2: a p-type transparent oxideThe authors report the synthesis of CuBO2, a p-type transparent oxide belonging to Cu-delafossite family. High quality thin films of CuBO2 were deposited on c-plane sapphire substrates by pulsed laser deposition technique. Detailed structural, optical, and electrical characterizations on these films...Transparent conducting oxides; Delafossite series; CuBO22007
38 Stringfellow, Gerald B.Deep electron traps in organometallic vapor phase grown AlGaAsDeep electron traps have been studied by means of deep level transient spectrosocopy in type nominally undoped and interntionally te doped Al Ga As epitaxial layers which were grown by vapor phase epitaxy from organometallic compounds (OMVPE). Three main deep electron levels are present in undoped m...Vapor phase epitaxy; Shallow impurity identity; Optoelectronic device performance1980
39 Scarpulla, MichaelDetection of ZnS phases in CZTS thin-films by EXAFSCopper zinc tin sulfide (CZTS) is a promising Earthabundant thin-film solar cell material; it has an appropriate band gap of ~1.45 eV and a high absorption coefficient. The most efficient CZTS cells tend to be slightly Zn-rich and Cu-poor. However, growing Zn-rich CZTS films can sometimes result in ...2011-01-01
40 Liu, FengDetermination of the Ehrlich-Schwoebel barrier in epitaxial growth of thin filmsWe demonstrate an approach for determining the "effective" Ehrlich-Schwoebel (ES) step-edge barrier, an important kinetic constant to control the interlayer mass transport in epitaxial growth of thin films. The approach exploits the rate difference between the growth and/or decay of an adatom and a...Ehrlich-Schwoebel barrier; Epitaxial growth; Step-edge barrier; Adatoms2006-11
41 Scarpulla, MichaelDetermination of the infrared complex magnetoconductivity tensor in itinerant ferromagnets from Faraday and Kerr measurementsWe present measurement and analysis techniques that allow the complete complex magnetoconductivity tensor to be determined from midinfrared (11-1.6 μm; 100-800 meV) measurements of the complex Faraday (θF) and Kerr (θK) angles. Since this approach involves measurement of the geometry (orientati...Magnetoconductivity tensor; Ferromagnets2007-06
42 Liu, FengDetermining the adsorptive and catalytic properties of strained metal surfaces using adsorption-induced stressWe demonstrate a model for determining the adsorptive and catalytic properties of strained metal surfaces based on linear elastic theory, using first-principles calculations of CO adsorption on Au and K surfaces and CO dissociation on Ru surface. The model involves a single calculation of the adsorp...Strained metal surfaces; Adsorption-induced stress; Adsorptive properties; Catalytic properties2004
43 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
44 Stringfellow, Gerald B.Dislocations in GaAs17-xPxDislocations, their origins, and their effects on photoluminescence efficiency have been studied in GaAs1-xPx single crystals grown by vapor phase epitaxy. Dislocations were observed using etch pit, optical-transmission microscopy, and x-ray topography techniques. Two types of dislocations are grown...Photoluminescence efficiency; Growth mechanism; Optical transmission microscopy1969
45 Stringfellow, Gerald B.Doping studies of Ga0.5In0.5P organometallic vapor-phase epitaxyPresents doping studies of gallium[sub0.5] indium[sub0.5] phosphorus organometallic vapor-phase epitaxy. Distribution coefficient of indium; Description of growth conditions; Case of poor growth morphology for gallium[sub0.5] indium[sub0.5] phosphorus.Phosphorus; Gallium; Doping1986
46 Scarpulla, MichaelEffect of film thickness on the incorporation of Mn interstitials in Ga1-xMnxAsWe have investigated the effect of film thickness on the distribution of Mn atoms at various lattice sites in Ga1−xMnxAs thin films. We find that the growth surface acts as a sink facilitating the outdiffusion of Mn interstitials sMnId, and thus reducing its concentration in the film. The outdiffu...Interstitials; Gallium arsenide2005
47 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
48 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
49 Liu, FengEffect of size and dimensionality on the magnetic moment of transition metalsThe effect of size and dimensionality on the magnetic moments of Fe, Co, and Ni have been studied theoretically by confining the atoms t o various structural forms such as chains,surfaces, and thin films. The size of these systems is controlled by limiting t h e number of atoms. A new first-princip...Magnetic moment; Dimensionality; Size effects; Fe; Co; Ni1990
50 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
51 Stringfellow, Gerald B.Effect of surfactant Sb on carrier lifetime in GaInP epilayersSamples of Ga0.52In0.48P grown on (001) GaAs with small amounts of surfactant Sb were investigated using time-resolved photoluminescence. All samples show a luminescence that may be fit to a two-stage exponential decay with a fast and a slow lifetime. For growth without Sb (Sb/III(v)(0), the sample ...Semiconductor ternary alloys; Epitaxial layer; Microstructures2002-01-01
52 Stringfellow, Gerald B.; Rieth, Loren W.Effects of Br and Cl on organometallic vapor phase epitaxial growth and ordering in GaInPCuPt ordering in GaInP has significant effects on the electrical and optical properties. In fact, band gap reductions as large as 160 meV are potentially useful for devices. Thus, control of ordering is important. This has led to the investigation of surfactants that affect the surface processes d...Band gap reductions; Surfactants; Surface processes2004
53 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
54 Scarpulla, MichaelEffects of pressure on the band structure of highly mismatched Zn1-yMnyOxTe1-x alloysWe report photomodulation spectroscopy measurements of the pressure dependence of the optical transition in Zn12yMnyOxTe1-x alloys that is associated with the lowest Ѓ conduction band (termed E2 subband). The pressure-induced energy shift of the E2 transition is nonlinear and much weaker as compare...Highly mismatched alloys; Zinc telluride; Anticrossing2004
55 Scarpulla, MichaelEffects of sodium on electrical properties in Cu2ZnSnS4 single crystalWe have studied the effect of sodium on the electrical properties of Cu2ZnSnS4 (CZTS) single crystal by using temperature dependence of Hall effect measurement. The sodium substitution on the cation site in CZTS is observed from the increasing of unit-cell size by powder X-ray diffraction. Sodium in...2014-01-01
56 Stringfellow, Gerald B.Effects of substrate misorientation and growth rate on ordering in GaInPEpitaxial layers of Ga,Tn,_,P with 1=0.52 have been grown by-organometallic vapor-phase apitaxy on GaAs substrates misoriented from the (001) plane in the [ 1 IO] direction by angles 6,) of O", 3", 6", and 9". For each substrate orientation growth rates rg of 1, 2, and 4 pm/h have been used. The ...Transmission electron diffraction; Dark-field imaging; Photoluminescence1994
57 Stringfellow, Gerald B.Effects of surfactants Sb and Bi on the incorporation of zinc and carbon in III/V materials grown by organometallic vapor-phase epitaxyThe incorporation of both dopants and background impurities during the organometallic vapor phase epitaxial _x0002_OMVPE_x0003_ growth of GaAs, GaInP, and GaP has been significantly altered by the use of the surfactants Sb and Bi. Sb and Bi are isoelectronic with the group V host elements, and so ...Physical and chemical processes; Surfactants isoelectronic; Electrochemical C-V profilometry2006
58 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
59 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
60 Stringfellow, Gerald B.Electrical properties of nitrogen doped GaPThe electrical properties namely, electron concentration and mobility, have been investigated in the temperature range from 53 to 400 K for undoped and nitrogen-doped VPE GaP.Electron concentration; Ionization energy; Electron mobility1975
61 Tiwari, AshutoshElectrical properties of transparent and conducting Ga doped ZnOIn this paper, we report on the metal-semiconductor transition behavior observed in transparent and conducting ZnO:Ga films grown by pulsed-laser deposition. The electrical resistivity measurements were carried out on ZnO films with varying Ga concentration in the temperature range of 14 to 300 K. ...Transparent conducting oxides; ZnO; Gallium; Metallic conductivity2006
62 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
63 Tiwari, AshutoshElectrical transport in ultrathin NdNiO3 filmsElectrical transport properties in ultrathin NdNiO3 films grown on single crystal LaAlO3 (001) substrate were characterized. Films with thicknesses ranging from 0.6 nm to 12 nm were grown using a pulsed laser technique. Four probe resistivity as a function of temperature measurements indicated a str...2012-01-01
64 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
65 Liu, FengElectrochemical measurements on cells, I: Simulation of potential distribution with an embedded probeMeasurements of electric potential in electrochemical devices such as solid oxide fuel cells (SOFC) or solid oxide electrolyzer cells (SOEC) are often made by placing a reference electrode on the surface. Measurement of electric potential with embedded electrodes (probes) has also been reported [1]....2013-01-01
66 Scarpulla, MichaelElectron backscatter diffraction and photoluminescence of sputtered CdTe thin filmsElectron backscatter diffraction (EBSD) has been used to characterize the grain size, grain boundary structure, and texture of sputtered CdTe at varying deposition pressures before and after CdCl2 treatment in order to correlate performance with film microstructure. It is known that twin boundaries ...2011-01-01
67 Stringfellow, Gerald B.Electron mobility in AlxGa1-xAshe electron mobility in AlxGa1-xAs grown by several techniques has been studied to determine whether VPE layers are more highly compensated than comparable LPE layers. The techniques used to grow layers included (1) organometallic VPE using Al(CH3)3, AsH3, and Ga(C2H5)3 or Ga(CH3)3, (2) ''hybrid'' o...Alloys; Organometallics1979-06
68 Stringfellow, Gerald B.Electron mobility in compensated GaAs and AlGaAsThe dependence of electron mobility on temperature in GaAs and Al Ga As indicates that for cimpensated material a term having causes a significant reduction in the mobility measured at high temperatures. The magnitude of the term in mobility, denoted is found to be linearly proportional to the compe...Unspecified mobility; Reduced mobility; Space charge regions1980
69 Tiwari, AshutoshElectron tunneling experiments on La0.7A0.3MnO3 (A=Ca, Sr, Ba)Tunneling conductance measurements of the electronic density of states of perovskite manganates, La0.7A0.3MnO3 are reported. Tunneling data of all the samples show a zero-bias anomaly with a minimum in the density of states at the Fermi level. This behavior is interpreted as arising from strong elec...Perovskite manganates; Tunneling conductance1999-10
70 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
71 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
72 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
73 Liu, FengEnhanced growth instability of a strained film on wavy substrateWe demonstrate that the growth of a strained film is inherently less stable on a wavy substrate than on a flat substrate. For small surface undulation, the lowest strain energy state is for the film surface to adopt the same wavelength as the substrate surface in an antiphase configuration at the ea...Growth instability; Strained film; Wavy substrate; Strain induced self-assembly2008
74 Scarpulla, MichaelEnhanced light absorption in thin-film silicon solar cells by scattering from Embedded Dielectric NanoparticlesWe investigate the light-trapping effects of dielectric nanoparticles embedded within the active semiconductor layer of a thin-film solar cell. The baseline model consists of a 1.0 μm slab of crystalline silicon on an aluminum back contact topped with a 75 nm Si3N4 anti-reflective coating. Using fi...2011-01-01
75 Scarpulla, MichaelEnhanced nitrogen incorporation by pulsed laser annealing of GaNxAs1-x formed by N ion implantationWe demonstrate that pulsed laser annealing followed by rapid thermal annealing greatly enhances incorporation of substitutional N in N1-implanted GaAs. Films implanted to 1.8% N exhibit a fundamental band gap of 1.26 eV (a band gap reduction of 160 meV), corresponding to an N activation efficiency ...Highly mismatched alloys; Gallium arsenide2002
76 Tiwari, AshutoshEpitaxial growth and properties of MoOx(2We report the growth of epitaxial molybdenum oxide (MoOx,2<x<2.75) films on c plane of sapphire substrate using pulsed laser deposition in oxygen environment. The structure was characterized using x-ray diffraction, high resolution transmission electron microscopy and x-ray photoelectron spectroscop...Epitaxy; MoO2005
77 Tiwari, AshutoshEpitaxial growth and properties of Zn1-xVxO diluted magnetic semiconductor thin filmsHere we report systematic studies on the epitaxial growth and properties of Zn1−xVxO[x=0.001-0.2] thin films deposited onto sapphire c-plane single crystals. The thin films were deposited using pulsed laser deposition technique and were found to be epitaxial in nature. X-ray diffraction and high ...ZnO; Vanadium2005
78 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
79 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
80 Tiwari, AshutoshEpitaxial growth of TaN films on Si(100) and Si(111) using a TiN buffer layerWe have deposited high-quality epitaxial B1 NaCl-structured TaN films on Si(100) and Si(111) substrates with TiN as the buffer layer, using pulsed laser deposition. Our method exploits the concept of lattice-matching epitaxy between TiN and TaN and domain-matching epitaxy between TiN and silicon. X...Diffusion barriers; Buffer layers; Tantalum nitride; Silicon substrate2002
81 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
82 Bedrov, Dmitro; Smith, Grant D.Equilibrium sampling of self-associating polymer solutions: a parallel selective tempering approachWe present a novel simulation algorithm based on tempering a fraction of relaxation-limiting interactions to accelerate the process of obtaining uncorrelated equilibrium configurations of self-associating polymer solutions. This approach consists of tempering (turning off) the attractive interactio...Equilibrium sampling; Self-associating systems; Parallel selective tempering2005
83 Liu, FengEquilibrium shape of two-dimensional islands under stressWe show that the equilibrium shape anisotropy of two-dimensional islands in heteroepitaxial growth depends on island size, a consequence of the presence of strain. Even in homoepitaxy, in which the island shape has conventionally been equated with the ratio of step energies, a substrate surface str...Two-dimensional islands; Equilibrium shape; Heteroepitaxial growth; Homoepitaxy2000-08
84 Scarpulla, MichaelExact field solution to guided wave progagation in lossy thin filmsWave guidance is an important aspect of light trapping in thin film photovoltaics making it important to properly model the effects of loss on the field profiles. This paper derives the full-field solution for electromagnetic wave propagation in a symmetric dielectric slab with finite absorption. ...2011
85 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
86 Liu, FengExotic electronic states in the world of flat bands: from theory to materialIt has long been noticed that special lattices contain single-electron at bands (FB) without any dispersion. Since the kinetic energy of electrons is quenched in the FB, this highly degenerate energy level becomes an ideal platform to achieve strongly correlated electronic states, such as magnetism,...2014-01-01
87 Tiwari, AshutoshExperiments along coexistence near tricriticality in 3He-4He mixturesThe tricritical point in the phase diagram of 3He-4He mixtures offers unique opportunities to test our understanding of critical phenomena. Because D = 3 is the marginal spatial dimension for tricriticality, the associated critical exponents are exact integer fractions. In addition, one expects to f...Tricriticality; Tricritical point; 3He-4He mixtures2000
88 Bedrov, Dmitro; Smith, Grant D.Exploration of conformational phase space in polymer melts: a comparison of parallel tempering and conventional molecular dynamics simulationsParallel tempering molecular dynamics simulations have been performed for 1,4-polybutadiene polymer melts in the 323 K-473 K temperature domain at atmospheric pressure. The parallel tempering approach provides a vast improvement in the equilibration and sampling of conformational phase space for ...Polymer melts; 1,4-polybutadiene; Conformational phase space; Parallel tempering2001
89 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
90 Tiwari, AshutoshFabrication and characterization of Li7La3Zr 2O12 thin films for lithium ion batteryThin films of Li7La3Zr2O12 were deposited on SrTiO3 (100) and Sapphire (0001) substrates at room-temperature using a pulsed-laser-deposition technique. Detailed structural, compositional, optical, and electrochemical characterizations of the films were performed. The films deposited at room-temperat...2012-01-01
91 Scarpulla, MichaelFabrication of GaNxAs1-x quantum structures by focused ion beam patterningA novel approach to the fabrication of GaNxAs1-x quantum dots and wires via ion beam patterning is presented. Photomodulated reflectance spectra confirm that N can be released from the As sublattice of an MBE-grown GaNxAs1-x film by amorphization through ion implantation followed by regrowth upon r...Gallium arsenide; Quantum dots; Quantum wires; Thermal annealing2005
92 Scarpulla, MichaelFerromagnetic Ga1-xMnxAs produced by ion implantation and pulsed-laser meltingWe demonstrate the formation of ferromagnetic Ga1-xMnxAs films by Mn ion implantation into GaAs followed by pulsed-laser melting. Irradiation with a single excimer laser pulse results in the epitaxial regrowth of the implanted layer with Mn substitutional fraction up to 80% and effective Curie tempe...Gallium arsenide; Ferromagnetic semiconductors; Remanent magnetization2003
93 Scarpulla, MichaelFerromagnetic resonance investigation of magnetic anisotropy in Ga1-xMnxAs synthesized by ion implantation and pulsed laser meltingA systematic investigation of ferromagnetic resonance (FMR) was carried out on Ga1−xMnxAs layers synthesized by Mn ion implantation into GaAs followed by pulsed laser melting. Angular and temperature dependences of FMR were measured on layers prepared on GaAs (001), (110), and (311) surfaces. The ...Magnetic anisotropy; Ga1−xMnxAs; Gallium manganese arsenide2009-12
94 Tiwari, AshutoshFerromagnetism in Co doped CeO2: observation of giant magnetic moment with a high Curie temperatureWe report room temperature ferromagnetism in single crystal Ce1−xCoxO2−δ (x≤0.05) films deposited on a LaAlO3(001) substrate. Films were grown by a pulsed laser deposition technique and were thoroughly characterized using x-ray diffraction, high-resolution transmission electron microscopy cou...CeO2; Cobalt2006
95 Tiwari, AshutoshFerromagnetism in Cu-doped ZnO films: role of charge carriersWe report the observation of room temperature ferromagnetism in Cu-doped (5%) ZnO films grown on c-plane sapphire substrates. Films were prepared by pulsed laser deposition technique and were thoroughly characterized using several state-of-the-art characterization techniques. Hall measurements sho...Charge carriers2008
96 Scarpulla, MichaelFerromagnetism in Ga1-xMnxP: evidence for inter-Mn exchange mediated by localized holes within a detached impurity bandWe report an energy gap for hole photoexcitation in ferromagnetic Ga1-xMnxP that is tunable by Mn concentration (x ≤ 0:06) and by compensation with Te donors. For x ~ 0:06, electrical transport is dominated by excitation across this gap above the Curie temperature (TC) of 60 K and by thermally a...Gallium Phosphide; Ferromagnetism; Mn impurity band2005-11
97 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
98 Liu, FengFirst-principles studies on structural properties of β-cristobaliteThe structure of β-cristobalite has been studied through a first-principles total-energy minimization in the local-density approximation using a Car-Parrinello-type algorithm combined with the Vanderbilt ultrasoft pseudopotential scheme. It was found that the hypothetical ordered structure propose...First-principles; Car-Parrinello-type algorithm1993-05
99 Liu, FengFirst-principles study of crystalline silicaWe have investigated the structural properties of five different crystalline forms of Si02 using a first-principles approach. An ultrasoft Vanderbilt pseudopotential is generated for oxygen which enables us to use a small plane-wave cutoff of 25 Ry. The relative stability, the equation of state, an...First-principles; Crystalline silica; Ultrasoft Vanderbilt pseudopotential1994-05
100 Liu, FengFirst-principles study of electronic properties of biaxially strained silicon: effects on charge carrier mobilityUsing first-principles method, we calculate the electronic band structure of biaxially strained silicon, from which we analyze the change in electron and hole effective mass as a function of strain and determine the mobility of electrons and holes in the biaxially strained silicon based on Boltzmann...Biaxially strained silicon; Boltzmann transport theory2008-12
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