UScholar Works
 
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101 - 125 of 288
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CreatorTitleDescriptionSubjectDate
101 Liu, 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
102 Liu, FengFirst-principles study of strain stabilization of Ge(105) facet on Si(001)Using the first-principles total energy method, we calculate surface energies, surface stresses, and their strain dependence of the Ge-covered Si (001) and (105) surfaces. The surface energy of the Si(105) surface is shown to be higher than that of Si(001), but it can be reduced by the Ge deposition...First-principles calculation; Strain stabilization; Ge(105); Si(001); Strained thin films; Epitaxial growth2005-09
103 Tiwari, AshutoshFormation of self-assembled epitaxial nickel nanostructuresHighly orientated nickel magnetic nanoparticles were obtained by pulsed laser deposition technique on silicon (100) substrate using epitaxial titanium nitride film as the template. These nanoparticles have been characterized by conventional and high-resolution transmission electron microscopy, scann...TiN; Nickel2003
104 Scarpulla, MichaelGa1-xMnxP synthesized by ion implantation and pulsed-laser meltingThe synthesis of single-crystalline epitaxial thin films of the carrier-mediated ferromagnetic phase of Ga1-xMnxP and Ga1-xMnxP-based quaternary alloys using ion implantation and pulsed-laser melting (II-PLM) has allowed for the exploration of the effect of anion substitution on ferromagnetism in Ga...2008
105 Stringfellow, Gerald B.GaInAsSb metastable alloys grown by organometallic vapor phase epitaxyGa1-xlnx As1-ySby alloys have been grown by organometallic vapor phase epitaxy using trimethyl compounds of Ga, In, As, and Sb(TMGa, TMIn, TMAs, and TMSb) plus AsH3 in an atmospheric pressure, horizontal, infrared heated reactor. For the first time, alloys near the center of the region of solid immi...Organometallic; Alloys; Vapor phase epitaxy1986
106 Tiwari, AshutoshGarnet-type Li7La3Zr2O12 electrolyte prepared by a solution-based technique for lithium ion batteryHigh quality garnet-type Li7La3Zr2O12 solid electrolyte was synthesized using a solution-based technique. The electrolyte pellets were sintered at 900 oC, resulting in tetragonal phase, which then transformed to cubic phase after annealing at 1230 oC. The ionic conductivity of both phases was studie...2012-01-01
107 Liu, FengGeometric constant defining shape transitions of carbon nanotubes under pressureWe demonstrate that when a single-walled carbon nanotube is under pressure it undergoes a series of shape transitions, first transforming from a circle to an oval and then from an oval to a peanut. Most remarkably, the ratio of the area of the tube cross sections at the second transition over that ...Geometric constant; Shape transitions; Carbon nanotubes; Pressure2004-03
108 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
109 Scarpulla, MichaelGrain size and texture of Cu2ZnSnS4 thin films synthesized by co-sputtering binary sulfides and annealing: effects of processing conditions and sodiumWe investigate the synthesis of kesterite Cu2ZnSnS4 (CZTS) polycrystalline thin films using cosputtering from binary sulfide targets followed by annealing in sulfur vapor at 500 ?C to 650 ?C. The films are the kesterite CZTS phase as indicated by x-ray diffraction, Raman scattering, and optical abso...2011
110 Tiwari, AshutoshGrowth and characterization of TaN/TiN superlattice structuresEpitaxial B1 NaCl-structured TaN(3 nm)/TiN(2 nm) superlattice structures were grown on Si(100) substrates with a TiN buffer layer, using pulsed-laser deposition. A special target assembly was used to manipulate the thickness of each layer. X-ray diffraction, transmission electron microscopy, and ...Diffusion barriers; Copper diffusion; Tantalum nitride2003
111 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
112 Tiwari, AshutoshGrowth of epitaxial ZnO films on Si(111)Epitaxial ZnO films have been grown on Si(l 11) substrates by employing a A1N buffer layer during a pulsed laser-deposition process. The epitaxial structure of A1N on Si(l 11) substrate provides a template for ZnO growth. The resultant films are evaluated by transmission electron microscopy, x-ray ...Buffer layers; Aluminum nitride; Silicon substrate2002
113 Scarpulla, MichaelHeat flow model for pulsed laser melting and rapid solidification of ion implanted GaAsIn order to further understand the pulsed-laser melting (PLM) of Mn and N implanted GaAs, which we have used to synthesize thin films of the ferromagnetic semiconductor Ga1−xMnxAs and the highly mismatched alloy GaNxAs1−x, we have simulated PLM of amorphous (a-) and crystalline (c-) GaAs. We pre...2010
114 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
115 Stringfellow, Gerald B.Heterostructures in GaInP grown using a change in V/III ratioA natural monolayer 111% superlattice -- the CuPt ordered structure -- is formed spontaneously during organometallic vapor phase epitaxial OMVPE growth of Ga0.52In0.48P. The extent of this ordering process is found to be a strong function of the input partial pressure of the phosphorus precursor dur...Superlattices; Alloys; Atomic ordering; Heterostructures1997-02-24
116 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
117 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
118 Liu, FengImpurity mediated absorption continuum in single-walled carbon nanotubesThe authors demonstrate that in single-walled carbon nanotubes, a weak impurity potential can lead to a strong above-gap absorption continuum. The total absorption is enhanced due to the intraband and indirect transitions, as well as plasmon excitations, which are forbidden in perfect nanotubes. Suc...Carbon nanotubes; SWNT; Defects; Impurities; Above-gap; Absorption continuum2007
119 Stringfellow, Gerald B.InAsSbBi alloys grown by organometallic vapor-phase epitaxyProvides information on a study on the growth of InAsSbBi alloys by organometallic vapor-phase epitaxy. Experiment; Results and discussion; Conclusion.Alloys; Epitaxy; Organometallic Compounds1994
120 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
121 Stringfellow, Gerald B.Influence of Sb, Bi, Tl, and B on the incorporation of N in GaAsGaAs:N is an interesting material for many devices due to its unique compositional variation of band gap. Small amounts of N lead to a strong decrease in band gap energy as well as lattice constant. The further addition of In or Sb leads to quaternary alloys with band gap energies below 1.4 eV latti...Antimony; Gallium Arsenide; Nitrogen2002
122 Stringfellow, Gerald B.Influence of tellurium doping on step bunching of GaAs (001) vicinal surfaces grown by organometallic vapor phase epitaxyAtomic force microscopy has been used to investigate the influence of controlled tellurium Te incorporation on the step structure of GaAs grown by organometallic vapor phase epitaxy on vicinal 001 surfaces. Te doping, using the precursor diethyltelluride, is found to markedly decrease the surface r...Epitaxial growth; Misorientation; Organometallic vapor phase epitaxy1998
123 Bedrov, Dmitro; Smith, Grant D.Integral equation theory for polymer solutions: explicit inclusion of the solvent moleculesSelf-consistent Polymer Reference Interaction Site Model (PRISM) calculations and molecular dynamics (MD) simulations were performed on athermal solutions of linear polymers. Unlike most previous treatments of polymer solutions, we explicitly included the solvent molecules. The polymers were mode...Solvent molecules; Polymer Reference Interaction Site Model; PRISM; Spinodal curve; Intramolecular dimensions; Intermolecular packing; Phase behavior2001
124 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
125 Liu, FengInterplay between quantum size effect and strain effect on growth of nanoscale metal thin filmsWe develop a theoretical framework to investigate the interplay between the quantum size effect (QSE) and strain effect on the stability of metal nanofilms. The QSE and strain effect are shown to be coupled through the concept of quantum electronic stress. First-principles calculations reveal large ...2012-01-01
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