UScholar Works
 
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CreatorTitleDescriptionSubjectDate
1Stringfellow, 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
2Stringfellow, 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
3Stringfellow, 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
4Tiwari, 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
5Stringfellow, 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
6Smith, Grant D.Prediction of the linear viscoelastic shear modulus of an entangled polybutadiene melt from simulation and theoryWhile accurate quantum chemistry based potentials,1 improved simulation algorithms, and faster computers have made accurate calculation of chain dynamics in unentangled polymer melts from molecular dynamics simulations possible,2-5 direct calculation of the viscoelastic properties of entangled polym...Polybutadiene melt; Viscoelastic shear; Chain dynamics; Entangled polymers2000
7Smith, Grant D.Quantum chemistry based force field for simulations of poly(vinylidene fluoride)A classical potential function for simulations of poly(vinylidene fluoride) (PVDF) based upon quantum chemistry calculations on PVDF oligomers has been developed. Quantum chemistry analysis of the geometries and conformational energies of 1,1,1,3,3-pentafluorobutane (PFB), 1,1,1,3,3,5,5,5-octofluoro...Poly(vinylidene fluoride) simulations; PVDF2000
8Stringfellow, Gerald B.Surfactant controlled growth of GaInP by organometallic vapor phase epitaxyThe effect of the surfactant Sb has been studied for GaInP semiconductor alloys grown by organometallic vapor phase epitaxy. Dramatic changes in the optical and electrical properties of GaInP with CuPt ordering have been observed. A small concentration of triethylantimony TESb in the vapor is fou...Semiconductors; Surface active agents2000
9Bedrov, Dmitro; Smith, Grant D.Temperature dependent shear viscosity coefficient of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX ): a molecular dynamics simulation studyEquilibrium molecular dynamics methods were used in conjunction with linear response theory and a recently published potential-energy surface [J. Phys. Chem. B 103, 3570 (1999)] to compute the liquid shear viscosity and self-diffusion coefficient of the high explosive HMX (octahydro-1,3,5,7-tetran...Polymer melts; HMX; Shear viscosity coefficient; Plastic-bonded explosives2000
10Bedrov, Dmitro; Smith, Grant D.Thermal conductivity of molecular fluids from molecular dynamics simulations: application of a new imposed-flux methodWe have applied a new nonequilibrium molecular dynamics (NEMD) method [F. Müller-Plathe, J. Chem. Phys. 106, 6082 (1997)] previously applied to monatomic Lennard-Jones fluids in the determination of the thermal conductivity of molecular fluids. The method was modified in order to be applicable to...Thermal conductivity; Molecular fluids; Heat flux; Imposed-flux NEMD method2000
11Liu, 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
12Liu, 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
13Liu, FengFirst-principles study of impurity segregation in edge dislocations in SiUsing ab initio calculations, the segregation of As, Ga, and Ge atoms in the core regions of perfect edge dislocations in Si is examined. When all nearest neighbors of an impurity are Si atoms, As favors the core site at maximum compression and has a segregation energy of 0.25 eV/atom. Ga and Ge im...First-principles; Impurity segregation; Edge dislocations2000-01
14Liu, 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
15Scarpulla, MichaelNew methodologies for measuring film thickness, coverage, and topographyWe describe how the techniques of X-ray reflectivity (XRR), electron spectroscopy for chemical analysis (ESCA), and atomic force microscopy (AFM) can be used to obtain the structural parameters-thickness, coverage, and topography-of thin films used on magnetic recording disks. We focus on ultra-thi...Atomic force microscopy; Electron spectroscopy for chemical analysis; X-ray reflectivity2000-01
16Liu, FengThermal roughening of a thin film: a new type of roughening transitionThe equilibrium thermal roughening of thin Ge layers (one and two monolayers) deposited on Si(001) has been investigated with low-energy electron microscopy. A Ge-coverage-dependent roughening is observed. For two monolayers, the temperature at which imaging contrast is lost due to surface roughness...Thermal roughening; Roughening transition; Heteroepitaxial growth2000-09
17Liu, FengUnique dynamic appearance of a Ge-Si Ad-dimer on Si(001)We carry out a comparative study of the energetics and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a ...Ge-Si Ad-dimer; Si(001); First-principles calculations; Energetics2000-12
18Stringfellow, Gerald B.; Shurtleff, James KevinUse of surfactant Sb to induce triple period ordering in GaInPA surfactant is used to induce an ordered structure in an epitaxial layer. The addition of small amounts of triethylantimony during the organometallic vapor phase epitaxy growth of GaInP on 001 GaAs substrates is shown to remove CuPt ordering with a resultant increase in band gap energy. Increasi...Organometallic; Thermodynamics; Surfactant2000-03-13
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