UScholar Works
 
Filters: Department: "Materials Science & Engineering" School Or College: "College of Engineering" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
26 Liu, FengGiant room-temperature spin caloritronics in spin-semiconducting graphene nanoribbonsSpin caloritronics refers to generating spin current by thermal gradient. Here we report a theoretical study demonstrating giant spin caloritronic effects in a new class of materials, called spin semiconductors, which are characterized with a "spin gap," the energy gap between spin-up and -down chan...2014-01-01
27 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
28 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
29 Scarpulla, MichaelInvestigation of combinatorial coevaporated thin film Cu 2ZnSnS4. I. Temperature effect, crystalline phases, morphology, and photoluminescenceCu2ZnSnS4 is a promising low-cost, nontoxic, earth-abundant absorber material for thin-film solar cell applications. In this study, combinatorial coevaporation was used to synthesize individual thin-film samples spanning a wide range of compositions at low (325 C) and high (475 C) temperatures. Film...2014-01-01
30 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
31 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
32 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
33 Bedrov, Dmitro; Smith, Grant D.Thermodynamic, transport and viscoelastic properties of PBX-9501 binder: a molecular dynamics simulation studyAtomistic molecular dynamics simulations were performed on a low molecular weight nitroplasticized Estane® mixture representative of the binder used in PBX-9501. Pressurevolume-temperature (PVT) behavior over a wide range of pressure and temperatures above the order-disorder temperature (ODT) of Es...PBX-9501 binder; Estane; Viscosity; Shear stress relaxation modulus2008-04-04
34 Liu, FengSimple generic method for predicting the effect of strain on surface diffusionWe show, by first-principles calculations, that the effect of external strain on surface diffusion is inherently correlated with the intrinsic surface stress induced by the adatom along its diffusion pathways. We demonstrate a simple generic method for a priori predicting quantitatively how an ext...Surface diffusion; First-principles calculations; Adatoms2001-11
35 Stringfellow, Gerald B.; Shurtleff, James KevinHeterostructures in GaInP grown using a change in Te dopingIn organometallic vapor phase epitaxy, changes in growth conditions can be used to modulate the extent of CuPt ordering and, hence, the band gap energy of GaInP. One method is to add Te during growth. An increase in the band gap energy of 0.1 eV due to a decrease in ordering has been obtained by ...Heterostructures; Alloys2000
36 Tiwari, AshutoshZn0.9Co0.1O-based diluted magnetic semiconducting thin filmsHere we report a systematic study of structural, optical, and magnetic measurements on epitaxial Zn0.9Co0.1O films grown on c-plane sapphire single crystal, at various temperatures (500-650°C), using pulsed-laser deposition. The main emphasis in this work has been on the correlation of microstructu...ZnO; Cobalt2004
37 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
38 Liu, FengMagnetization on rough ferromagnetic surfacesUsing Ising-model Monte Carlo simulations, we show a strong dependence of surface magnetization on surface roughness. On ferromagnetic surfaces with spin-exchange coupling larger than that of the bulk, the surface magnetic ordering temperature decreases toward the bulk Curie temperature with incre...Ferromagnetic surfaces; Surface magnetization2000-11
39 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
40 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
41 Smith, Grant D.; Bedrov, Dmitro; Borodin, OlegStructural relaxation and dynamic hetrogeneity in a polymer melt at attractive surfacesMolecular dynamics simulations of polymer melts at flat and structured surfaces reveal that, for the former, slow dynamics and increased dynamic heterogeneity for an adsorbed polymer is due to densification of the polymer in a surface layer, while, for the latter, the energy topography of the sur...Polymer melts; Structural relaxation; Dynamic heterogeneity; Attractive surfaces; Surface energy topography; Polymer densification2003-06
42 Liu, FengHydrogen induced Si surface segregation on Ge-covered Si(001)Using Fourier transform infrared-attenuated total reflectance spectroscopy in conjunction with hydrogen adsorption to probe surface layer composition, we observe a reversible place exchange between Ge and Si on Ge-covered Si(001) when the surface is dosed with atomic H at elevated temperatures. F...Si surface segregation; Ge-covered; Si(001)1998-10
43 Bedrov, Dmitro; Smith, Grant D.Molecular dynamics simulations of HMX crystal polymorphs using a flexible molecule force fieldMolecular dynamics simulations using a recently developed quantum chemistry-based atomistic force field [J. Phys. Chem. B 103 (1999) 3570] were performed in order to obtain unit cell parameters, coefficients of thermal expansion, and heats of sublimation for the three pure crystal polymorphs of octa...HMX; Crystal polymorphs; Force field; Coefficients of thermal expansion; Heat of sublimation; Cell parameters2002
44 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
45 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
46 Smith, Grant D.; Borodin, OlegMolecular-dynamics simulation study of dielectric relaxation in a 1,4-polybutadiene meltWe have carried out atomistic molecular dynamics simulations of a melt of 1,4-poly(butadiene) from temperatures well above the experimentally observed merging of the primary a process and secondary b process down to temperatures approaching the experimentally observed bifurcation temperature. The re...Polymer melts; 1,4-polybutadiene; Chain dynamics; Conformational dynamics2002
47 Stringfellow, Gerald B.Miscibility gaps and spinodal decomposition in III/V quaternary alloys of the type AxByC1−x−yDThermodynamic concepts have been developed for the calculation of solid-phase miscibility gaps and spinodal decomposition in quaternary alloys of the type AxByC1−x−yD. These concepts have been applied to the analysis of III/V quaternary alloys using the delta-lattice-parameter (DLP) solution mod...Thermodynamics; Quartenary alloys; Coherent decomposition1983-01
48 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
49 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
50 Liu, FengLiu et al. replyIn our paper we were alluding to a structural phase transition rather than an order-disorder one. We agree with Blaschko2 that more work needs to be done regarding the statistical mechanics of the hydrogen ordering. This was already acknowledged in our paper when we stated that the model of nonint...Structural phase transition; Hydrogen ordering; Ising lattice-gas models; Proton glass1990
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