UScholar Works
 
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201 - 225 of 275
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CreatorTitleDescriptionSubjectDate
201 Stringfellow, 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
202 Liu, FengModified Timoshenko formula for bending of ultrathin strained bilayer filmsMechanical bending of nanoscale thin films can be quite different from that of macroscopic thick films. However, current understanding of mechanical bending of nanoscale thin strained bilayer films is often limited within the Timoshenko model [Timoshenko, J. Opt. Soc. Am. 11, 233 (1925)], which was ...Timoshenko formula; Bending theory; Ultrathin films; Strained nanoscale thin films; Nanofilms2008
203 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
204 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
205 Liu, FengQuantum size effect on the magnetism of finite systemsThe magnetic moments of the ferromagnetic transition metals Fe, Co, and Ni confined to one-dimensional chains are found to fluctuate with increasing chain length before converging to the infinite limit. This quantum size effect is derived from a simple first-principles theory that we have developed...Quantum size; Finite systems; Ferromagnetic transition metals; Magnetic moments; Fe; Co; Ni; Molecular-orbital approach1990-07
206 Liu, FengStability of doubly charged transition-metal dimersThe spatial dependence of the interaction potentials in doubly charged dimers of transition-metal atoms has been calculated by use of both the tight-binding and the self-consistent-field linear combination of atomic orbitals-molecular orbitals methods. The study reveals an interesting correlation be...Doubly charged; Transition metal dimers; Spatial dependence; Interaction potentials; Metastability1987-11
207 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
208 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
209 Scarpulla, MichaelSynthesis and optical properties of II-O-VI highly mismatched alloysWe have synthesized ternary and quaternary diluted II-VI oxides using the combination of O ion implantation and pulsed laser melting. CdOxTe12x thin films with x up to 0.015, and the energy gap reduced by 150 meV were formed by O1-implantation in CdTe followed by pulsed laser melting. Quaternary Cd0...Highly mismatched alloys; Cadmium telluride; Zinc telluride; Thermal annealing; Anticrossing; Photomodulation spectroscopy2004
210 Stringfellow, Gerald B.Surface photoabsorption study of the effect of V/III ratio on ordering in GaInPCu-Pt ordering is widely observed in Ga0.5In0.5P layers grown by organometallic vapor phase epitaxy. The degree of order is a strong function of the input partial pressure of the phosphorus precursor, i.e., the V/III ratio, during growth. By observing the surface structure using in situ surface p...Degree of order; Photoluminescence; Transmission electron microscopy1996
211 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
212 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
213 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
214 Stringfellow, Gerald B.; Williams, Clayton C.Spatial mapping of ordered and disordered domains of GaInP by near-field scanning optical microscopy and scanning capacitance microscopyImaging of topography, locally induced photoluminescence and Fermi-level pinning in adjacent ordered and disordered domains on a cleaved GaInP sample is performed using a near-field scanning optical microscope and scanning capacitance microscope at room temperature in air. Highly localized photolumi...Gallium Phosphides; Surface Structure; Photoluminescence1996-04-13
215 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
216 Liu, FengKinetics of mesa overlayer growth: climbing of adatoms onto the mesa topWe have calculated the energy barriers for an adatom climbing up onto a Pb mesa top either over a facet-facet edge or through a facet-step joint, using a modified embedded atom method. We found that the second process is not only thermodynamically more favorable than the first one but also much fast...Mesa overlayer growth; Adatoms; Epitaxial growth2008
217 Scarpulla, MichaelMn L3,2 x-ray absorption and magnetic circular dichroism in ferromagnetic Ga1-xMnxPWe have measured the x-ray absorption and x-ray magnetic circular dichroism (XMCD) at the Mn L3,2 edges in ferromagnetic Ga1−xMnxP films for 0.018≤x≤0.042. Large XMCD asymmetries at the L3 edge indicate significant spin polarization of the density of states at the Fermi energy. The temperatur...X-ray absorption; Gallium Arsenide; Ferromagnetic semiconductors2006
218 Stringfellow, Gerald B.Surface photoabsorption transients and ordering in GaInPHeterostructures and quantum wells can be produced in GaInP without changing the solid composition by simply varying the order parameter. Since CuPt ordering reduces the band-gap energy, changes in the order parameter induced by changes in growth conditions result in heterostructures with band-ga...Order parameters; Quantum wells; P-dimers1998-03-15
219 Scarpulla, MichaelMagnetocrystalline anisotropy and magnetization reversal in Ga1-xMnxP synthesized by ion implantation and pulsed-laser meltingWe report the observation of ferromagnetic resonance (FMR) and the determination of the magnetocrystalline anisotropy in (100)-oriented single-crystalline thin film samples of Ga1−xMnxP with x=0.042. The contributions to the magnetic anisotropy were determined by measuring the angular and the te...Magnetocrystalline anisotropy; GaMnAs; Gallium arsenide2007-06
220 Tiwari, AshutoshMethods of forming three-dimensional nanodot arrays in a matrixNanostructures and methods of making nanostructures having self-assembled nanodot arrays wherein nanodots are self-assembled in a matrix material due to the free energies of the nanodot material and/or differences in the Gibb's free energy of the nanodot materials and matrix materials.Nanodots2006
221 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
222 Scarpulla, MichaelNonmagnetic compensation in ferromagnetic Ga1-xMnxAs and Ga1-xMnxP synthesized by ion implantation and pulsed-laser meltingThe electronic and magnetic effects of intentional compensation with nonmagnetic donors are investigated in the ferromagnetic semiconductors Ga1−xMnxAs and Ga1−xMnxP synthesized using ion implantation and pulsed-laser melting. It is demonstrated that compensation with nonmagnetic donors and MnI ...Ferromagnetic semiconductors2008
223 Tiwari, AshutoshSynthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrixSingle domain magnetic nickel nanocrystals were embedded in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out at the atomic level using scanning transmission electron microscopy with atomic number contrast (STEM-Z) in conjunction with electron energy ...Nanophase magnetic materials; Alumina2002
224 Liu, FengSeeing the atomic orbital: first-principles study of the effect of tip termination on atomic force microscopyWe perform extensive first-principles calculations to simulate the topographical atomic-force-microscope image of an adatom on the Si(111)-(7 X 7) surface, demonstrating the feasibility of imaging not only the atoms but also the atomic orbitals. Our comparative study of tip terminations shows that ...First-principles; Tip termination; Adatoms2003-06
225 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
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