UScholar Works
 
Filters: Department: "Materials Science & Engineering" Collection: "ir_uspace" Type: "Text" Format: "application/pdf"
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CreatorTitleDescriptionSubjectDate
126 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
127 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
128 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
129 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
130 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
131 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
132 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
133 Tiwari, AshutoshEpitaxial growth and properties of Zn1-xVxO diluted magnetic semiconductor thin filmsHere we report systematic studies on the epitaxial growth and properties of Zn1−xVxO[x=0.001-0.2] thin films deposited onto sapphire c-plane single crystals. The thin films were deposited using pulsed laser deposition technique and were found to be epitaxial in nature. X-ray diffraction and high ...ZnO; Vanadium2005
134 Stringfellow, Gerald B.Kinetically controlled order/disorder structure in GaInPA Ga0.52In0.58p order/disorder heterostructure having a band-gap energy difference exceeding 160 meV has been grown by organometallic vapor phase epitaxy. The two layers were grown on a nominally (OOl)-oriented GaAs substrate misoriented by 3° toward the [110] direction in the lattice. The disorder...Indium phosphides; Gallium Phosphides; Heterojunctions1994
135 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
136 Liu, FengLocal strain-mediated chemical potential control of quantum dot self-organization in heteroepitaxyFrom observations of self-assembly of Ge quantum dots directed by substrate morphology, we propose the concept of control of ordering in heteroepitaxy by a local strain-mediated surface chemical potential. Using quite simple lithography, we demonstrate directed quantum dot ordering. The strain part ...Self-organization; Heteroepitaxy; Chemical potential control; Ge quantum dots2004-01
137 Liu, FengMagnetism in nanopatterned graphite filmUsing first-principles calculations, we show that nanopatterned graphite films (NPGFs) can exhibit magnetism in analogy to graphene-based nanostructures (GBNs). In particular, graphite films with patterned nanoscale triangular holes and channels with zigzag edges all have ferromagnetic ground state...Nanopatterned graphite; Graphite films; NPGF2008
138 Liu, FengSimple theory of the electronic structure: clusters to crystalsA simple scheme based upon a cross between the molecular clusters and the tight-binding theory has been developed to calculate the electronic structure of a large class of systems ranging from molecules to solids. The method is applied to study the variations in the magnetic moments of Fe and Ni for...Clusters; Tight-binding theory; Magnetic moment1988-09
139 Liu, FengMagnetism in small vanadium clustersUsing the self-consistent-field molecular-orbital theory and the density-functional approximation, we show that vanadium could become magnetic if its size and dimension were constrained. This is illustrated for vanadium forming clusters with body-centered-cubic (bcc) geometry as well as for linear c...Vanadium clusters; Molecular-orbital theory; Density-functional approximation; Stoner criterion1991-04
140 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
141 Liu, FengPressure-induced hard-to-soft transition of a single carbon nanotubeWe demonstrate a hydrostatic pressure-induced hard-to-soft transition of an isolated single wall carbon nanotube, using classical and ab initio constant-pressure molecular-dynamics simulations and continuum elastic theory analysis. At low pressure, the carbon tube is hard. Above a critical pressur...Carbon nanotubes; Hard-to-soft transition2004-10
142 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
143 Stringfellow, Gerald B.Step structure and ordering in Te-doped GaInPThe step structure and CuPt ordering in GaInP layers grown by organometallic vapor phase epitaxy on singular GaAs substrates have been investigated as a function of Te (DETe) doping using atomic force microscopy, and electrical and optical properties measurements. The degree of order decreases for T...Surfaces; Te doping; Bandgap energy1998
144 Tiwari, AshutoshCharacterization of Li7La3Zr2O 12 thin films prepared by pulsed laser depositionA pulsed laser deposition system was employed to fabricate thin films of Li7La3Zr2O12 solid electrolyte. The deposition process was carried out at room-temperature, resulting in amorphous films. These as-deposited films had a large optical band gap of 5.13 eV, and exhibited a lithium-ion conductivit...2012-01-01
145 Scarpulla, MichaelDetection of ZnS phases in CZTS thin-films by EXAFSCopper zinc tin sulfide (CZTS) is a promising Earthabundant thin-film solar cell material; it has an appropriate band gap of ~1.45 eV and a high absorption coefficient. The most efficient CZTS cells tend to be slightly Zn-rich and Cu-poor. However, growing Zn-rich CZTS films can sometimes result in ...2011-01-01
146 Liu, FengComputational R&D for industrial applicationsRecent advances in high-speed supercomputer and computational algorithms have brought us into a new era of computational materials science. These advances make it possible to investigate many existing materials systems that were previously considered intractable and also predict and design novel mat...Computational materials science2005
147 Liu, FengSuppression of spin polarization in graphene nanoribbon by edge defects and impuritiesWe investigate the effect of edge defects (vacancies) and impurities (substitutional dopants) on the robustness of spin polarization in graphene nanoribbons (GNRs) with zigzag edges by using density-functional-theory calculations. The stability of the spin state and its magnetic moments is found to ...Edge defects; Vacancy; Spin-polarization; Graphene nanoribbon; GNR2008-04
148 Scarpulla, MichaelInvestigating sputtered Cu2Si1-xSnxS3 (CSTS) for earth abundant thin film photovoltaicsThis study investigates the synthesis of chalcopyrite Cu2Si1-xSnxS3 (CSTS) thin films for photovoltaic solar cell absorber layers. Preliminary results indicate that layered sputtering of Cu, Sn, and Si followed by annealing in a sulfur atmosphere at 500⁰C does not provide adequate mixing or sulfu...2010
149 Smith, Grant D.On the non-Gaussianity of chain motion in unentangled polymer meltsWe have investigated chain dynamics of an unentangled polybutadiene melt via molecular dynamics simulations and neutron spin echo experiments. Good short-time statistics allows for the first experimental confirmation of subdiffusive motion of polymer chains for times less than the Rouse time (T R) c...Polymer melts; Chain dynamics; 1,4-polybutadiene melts; Neutron spin echo2001
150 Stringfellow, Gerald B.Effect of growth rate on step structure and ordering in GaInPCuPt ordering is widely observed in GaInP epitaxial layers grown by organometallic vapor phase epitaxy. The formation of this spontaneously ordered structure during epitaxial growth is intimately related to the atomic-scale physical processes occurring on the surface, specifically surface reconst...Atomic force microscopy; Organometallic vapor phase; Crystallographic plane1997
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