UScholar Works
 
Filters: Department: "Materials Science & Engineering" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
176 Liu, FengCritical epinucleation on reconstructured surfaces and first-principle calculation of homonucleation on Si(100)We introduce the concept of ‘‘critical epinucleation'' to distinguish nucleation on surfaces with and without reconstruction. On a reconstructed surface, the critical classical nucleus is stable against dissociation, but may not yet break the underlying surface reconstruction. Consequently, ther...Critical epinucleation; First-principle calculation; Homonucleation; Si(100); Islands2005-09
177 Liu, FengPhysical origin of hydrogen-adsorption-induced metallization of the SiC surface: n-type doping via formation of hydrogen bridge bondWe perform first-principles calculations to explore the physical origin of hydrogen-induced semiconductor surface metallization observed in β-SiC(001)-3 x 2 surface. We show that the surface metallization arises from a novel mechanism of n-type doping of surface band via formation of hydrogen bri...Metallization; Hydrogen adsorption; SiC; n-type doping; Hydrogen bridge bond2005-10
178 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
179 Liu, FengSelf-organization of semiconductor nanocrystals by selective surface facetingThe formation and ordering of Si nanocrystals in dewetting and agglomeration of the thin single crystalline Si layer in silicon-on-insulator has been investigated using low-energy electron microscopy. The evolution of the Si dewetting and agglomeration is captured in real time, revealing the detai...Self-organization; Surface faceting; Silicon nanocrystals; Dewetting2005-12
180 Ostafin, AgnesMonitoring the synthesis and composition analysis of microsilica encapsulated acetylacetonatocarbonyl triphenylphosphinerhodium catalyst by inductively coupled plasma (ICP) techniquesAbstract-A novel technique to monitor the synthesis process of encapsulated acetylacetonatocarbonyl triphenylphosphinerhodium within a microsilica nanoshell has been studied using inductively coupled plasma (ICP) techniques. Nanospheres sized around 50-100 nm were obtained and ICP was used to quanti...2006
181 Liu, FengNature of reactive O2 and slow CO2 evolution kinetics in CO oxidation by TiO2 supported Au clusterRecent experiments on CO oxidation reaction using seven-atom Au clusters deposited on TiO2 surface correlate CO2 formation with oxygen associated with Au clusters. We perform first principles calculations using a seven-atom Au cluster supported on a reduced TiO2 surface to explore potential candidat...Au clusters; TiO2; Kinetic evolution2006
182 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
183 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
184 Liu, FengIntrinsic current-voltage properties of nanowires with four-probe scanning tunneling microscopy: a conductance transition of ZnO nanowireWe report intrinsic current-voltage properties of ZnO nanowire measured by a four-tip scanning tunneling microscopy (F-STM). It is found that after bending the nanowire with the F-STM the conductance is reduced by about five orders of magnitude. The cathodoluminescent spectra indicate that the ZnO n...ZnO nanowire; Four-probe; Four-tip; F-STM; Conductance transition2006
185 Stringfellow, Gerald B.Effects of surfactants Sb and Bi on the incorporation of zinc and carbon in III/V materials grown by organometallic vapor-phase epitaxyThe incorporation of both dopants and background impurities during the organometallic vapor phase epitaxial _x0002_OMVPE_x0003_ growth of GaAs, GaInP, and GaP has been significantly altered by the use of the surfactants Sb and Bi. Sb and Bi are isoelectronic with the group V host elements, and so ...Physical and chemical processes; Surfactants isoelectronic; Electrochemical C-V profilometry2006
186 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
187 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
188 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
189 Liu, FengFabricating artificial nanowells with tunable size and shape by using scanning tunneling microscopyThe authors report a method of precisely fabricating the large-scale nanocrystals with well-defined shape and size. The (111) oriented Pb islands deposited on Si(111)-7x7 substrate were investigated with a manipulation technique based on scanning tunneling microscopy. By applying a series of voltage...Artificial nanowells2006
190 Liu, FengSurface mobility difference between Si and Ge and its effect on growth of SiGe alloy films and islandsBased on first-principles calculations of surface diffusion barriers, we show that on a compressive Ge(001) surface the diffusivity of Ge is 102-103 times higher than that of Si in the temperature range of 300 to 900 K, while on a tensile surface, the two diffusivities are comparable. Consequently, ...Surface mobility; SiGe film; Strained thin films; Surface diffusion barriers2006-01
191 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
192 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
193 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
194 Liu, FengDetermination of the Ehrlich-Schwoebel barrier in epitaxial growth of thin filmsWe demonstrate an approach for determining the "effective" Ehrlich-Schwoebel (ES) step-edge barrier, an important kinetic constant to control the interlayer mass transport in epitaxial growth of thin films. The approach exploits the rate difference between the growth and/or decay of an adatom and a...Ehrlich-Schwoebel barrier; Epitaxial growth; Step-edge barrier; Adatoms2006-11
195 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
196 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
197 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
198 Liu, FengFirst-principles calculation of interaction between interstitial O and As dopant in heavily As-doped SiWe investigate the interaction between interstitial oxygen (Oi) and As dopant in heavily As-doped Si using first-principles total-energy calculations. The interaction between Oi and As (substitutional) is found to be short ranged. The most stable configuration is with As and Oi as second nearest nei...First-principles calculation; Interstitial oxygen; As dopant; As-doped Si; Oxygen diffusion; Oi2007
199 Scarpulla, MichaelMn L3,2 x-ray absorption spectroscopy and magnetic circular dichroism in ferromagnetic Ga1-xMnxPWe have measured the X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) at the Mn i32 edges in ferromagnetic Ga1-xMrixP 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 spectral s...X-ray absorption; Ferromagnetic semiconductors; X-ray magnetic circular dichroism (XMCD); Gallium Manganese Phosphide; Gallium arsenide2007
200 Bedrov, Dmitro; Borodin, Oleg; Smith, Grant D.Comment on "On the accuracy of force fields for predicting the physical properties of dimethylnitramine"Zheng and Thompson have recently reported a comparison of three atomistic force fields for prediction of physical properties of dimethylnitramine (DMNA) from molecular dynamics (MD) simulations.1 Specifically, they compared the rigid molecule force field by Sorescu, Rice, and Thompson (SRT);2 the ge...2007
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