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CreatorTitleDescriptionSubjectDate
126 Liu, FengOrigin of intergranular embrittlement of Al alloys induced by Na and Ca segregation: grain boundary weakeningUsing a first-principles computational tensile test, we show that the ideal tensile strength of an Al grain boundary (GB) is reduced with both Na and Ca GB segregation. We demonstrate that the fracture occurs in the GB interface, dominated by the break of the interfacial bonds. Experimentally, we f...Intergranular embrittlement; Grain boundary; Intergranular fracture2006-06
127 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
128 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
129 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
130 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
131 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
132 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
133 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
134 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
135 Liu, FengSelf-organized quantum-wire lattice via step flow growth of a short-period superlatticeWe develop a theoretical model for step flow growth of multilayer films, taking into account the interlayer step-step interaction induced by misfit strain.We apply the model to simulate the growth of strain-compensated short-period superlattices. Step-bunch ordering improves in successive layers, le...Quantum-wire lattice; Short-period superlattice; Step flow growth2004-06
136 Liu, FengPressure-induced transition in magnetoresistance of single-walled carbon nanotubesWe applied hydrostatic pressure (up to 10 GPa) to single-walled carbon nanotube bundles at low temperature (down to 2 K) to measure their magnetoresistance (MR) in a field up to 12 T. We found a pressure-induced transition in MR from positive to negative in the high-field regime. The onset of the tr...Single-walled carbon nanotubes; Pressure-induced2006-07
137 Bedrov, 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
138 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
139 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
140 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
141 Scarpulla, MichaelNear-infrared absorption and semimetal-semiconductor transition in 2 nm ErAs nanoparticles embedded in GaAs and AlAsWe report strong near-infrared absorption peaks in epitaxial films of GaAs and AlAs containing approximately 0.5-5% of the semimetal ErAs. The energy of the resonant absorption peak can be changed from 0.62 to 1.0 eV (2.2-1.4 μm) by variation of the ErAs volume fraction and the substrate temperatu...Near-infrared absorption; Semimetal-semiconductor transition; GaAs; AlAs; ErAs; Gallium arsenide; Aluminum arsenide2008
142 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
143 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
144 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
145 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
146 Stringfellow, Gerald B.Step structure and ordering in Zn-doped GaInPPresents the results of a study of Zinc dopant effects on both step structure and ordering in GaInP in an effort to further clarify the disordering mechanism. Comparison of the results obtained for Zinc with those reported for tellurium; Experiment; Results; Discussion; Conclusion.Gallium Compounds; Zinc; Ordering1999
147 Tiwari, AshutoshMetallic conductivity and metal-semiconductor transition in Ga-doped ZnOThis letter reports the metallic conductivity in Ga:ZnO system at room temperature and a metal-semiconductor transition (MST) behavior at low temperatures. Zn0.95Ga0.05O films, deposited by pulsed laser deposition in the pressure range of ~10−2 Torr of oxygen, were found to be crystalline and exhi...Transparent conducting oxides; ZnO; Gallium; Metallic conductivity2006
148 Liu, FengPattern formation on silicon-on-insulatorThe strain driven self-assembly of faceted Ge nanocrystals during epitaxy on Si(001) to form quantum dots (QDs) is by now well known. We have also recently provided an understanding of the thermodynamic driving force for directed assembly of QDs on bulk Si (extendable to other QD systems) based on ...Pattern formation; Silicon-on-insulator; Strain driven; Faceted Ge nanocrystals; Si(001); Directed assembly2005
149 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
150 Scarpulla, MichaelSuppression of hole-mediated ferromagnetism in Ga1-xMnxP by hydrogenWe report the passivation of the Mn acceptors in Ga1−xMnxP upon exposure to a hydrogen plasma. The as-grown films are nonmetallic and ferromagnetic with a Curie temperature of TC=55 K. After hydrogenation the sample resistivity increases by approximately three orders of magnitude at room tempera...Ferromagnetic semiconductors; Hydrogenation2008
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