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CreatorTitleDescriptionSubjectDate
51 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
52 Stringfellow, Gerald B.;Inglefield, Colin E.;Taylor, P. CraigCharacterization of unicompositional GaInP2 ordering heterostructures grown by variation of V/III ratioPhotoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies are employed to investigate single heterostructures based on two GaInP2 layers that have the same composition but different degrees of order on the cation sublattice. Four sample configurations are studied: two complemen...Heterostructures; Growth parameters; Growth temperature1997
53 Liu, FengMagnetization on vicinal ferromagnetic surfacesUsing Ising model Monte Carlo simulations, we show a strong dependence of surface magnetization on surface miscut angle. For ferromagnetic surfaces, when surface spin exchange coupling is larger than that of the bulk, the surface magnetic ordering temperature decreases, toward the bulk Curie tempera...Vicinal ferromagnetic surfaces; Surface magnetization; Surface miscut angle1997
54 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
55 Liu, Feng(BAl12)Cs: a cluster-assembled solidFirst-principles calculations on the geometry and stability of AlnBm clusters have been carried out to examine the effect of size, composition, and electronic-shell filling on their relative stability. It is shown that although Al and B are both trivalent, a BAl12 cluster is more stable than an Al1...First-principles calculations; (BAl12)Cs; Cluster-assembled; AlnBm clusters1997-06
56 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
57 Stringfellow, Gerald B.Step structure and ordering in GaInPPresents information from an experiment on the step structure and ordering in GalnP. Information on the step spacing and degree of order in the epitaxial layers; Details on the experiment; Results from the experiment.Physics; Ordering; Steps1998
58 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
59 Liu, FengSelf-organization of steps in growth of strained films on vicinal substratesComputer simulations show that if stress is present, steps on a vicinal surface can self-organize into a regular array of step bunches. Such self-organization can provide templates for subsequent fabrication of "quantum wire" nanostructures. The size and spacing of the bunches can be controlled inde...Self-organization; Strained films; Growth; Vicinal substrates; Step bunches1998-02
60 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
61 Liu, FengModification of Si(001) substrate bonding by adsorbed Ge or Si dimer islandsHigh-resolution scanning tunneling microscopy studies of the Si(100)-(2 X 1) surface show a heretofore unrecognized distortion of the substrate structure when islands form during the initial stage of growth of either Si or Ge. The distortion, reflecting the influence of strain, extends at least thre...Si(001); Adsorbed Ge; Adsorbed Si; Dimer islands; Substrate bonding; Distortion1998-09
62 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
63 Stringfellow, Gerald B.; Inglefield, Colin E.; Taylor, P. CraigQuantum wells due to ordering in GaInPCuPt ordering results in a reduction of the band-gap energy of GaInP. Thus, heterostructures and quantum wells can be produced by simply varying the order parameter, without changing the solid composition. Changes in the order parameter can be induced by changes in growth conditions. The disorder...Band-gap energy; Growth temperature; Quantum wells1998-12-28
64 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
65 Smith, Grant D.Conformational properties of poly(vinylidene fluoride). A quantum chemistry study of model compoundsThe molecular geometries and conformational energies of model molecules of poly(vinylidene fluoride) (PVDF) have been determined from high-level quantum chemistry calculations and have been used in parametrization of a six-state rotational isomeric state (RIS) model for PVDF. The model molecules inv...Poly(vinylidene fluoride); PVDF; Conformational properties1999
66 Smith, Grant D.; Bedrov, DmitroQuantum-chemistry-based force field for simulations of dimethylnitramineThe molecular geometries and conformational energies of nitramide and dimethylnitramine (DMNA), determined from high-level quantum chemistry calculations, have been used in parametrization of a classical potential function suitable for simulations of DMNA. A thorough investigation of basis set size ...Dimethylnitramine simulations; DMNA; Nitramide; Force field; Molecular dynamics simulations1999
67 Smith, Grant D.Quantum chemistry based force field for simulations of HMXThe molecular geometries and conformational energies of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 1,3-dimethyl-1,3-dinitro methyldiamine (DDMD) and have been determined from high-level quantum chemistry calculations and have been used in parametrizing a classical potential function ...HMX simulations; Molecular geometries; Conformational energies; DDMD1999
68 Smith, Grant D.Molecular dynamics of a 1,4-polybutadiene melt. Comparison of experiment and simulationWe have made detailed comparison of the local and chain dynamics of a melt of 1,4-polybutadiene (PBD) as determined from experiment and molecular dynamics simulation at 353 K. The PBD was found to have a random microstructure consisting of 40% cis, 50% trans, and 10% 1,2-vinyl units with a number-av...Polybutadiene melt; Molecular dynamics1999
69 Tiwari, AshutoshMetal-insulator transition in La0.7Sr0.3Mn1-xFexO3We report the effect of Fe doping at the Mn site in La0.7Sr0.3MnO3 oxides. We find that the doping of Fe does not cause any structural change, but the electrical transport in the system is strongly affected. The parent compound La0.7Sr0.3MnO3 shows a resistivity peak at T=Tp (365 K) and behaves as ...Tunneling conductance; Perovskite manganates; Iron doping; Fe doping1999
70 Liu, FengStep-induced optical anisotropy of vicinal Si(001)It is demonstrated, using reflectance difference spectroscopy, scanning tunneling microscopy, and low-energy electron diffraction, combined with deliberate straining of the surface, that the presence of atomic steps dramatically changes the optical anisotropy of the Si(001) surface. The step-induce...Step-induced; Optical anisotropy; Vicinal Si(001); Electron diffraction; Atomic steps1999-01
71 Liu, FengSelf-organized replication of 3D coherent island size and shape in multilayer heteroepitaxial filmsA model is proposed to elucidate the evolution of the morphology of strained 3D islands in multilayer heteroepitaxial films. The model explains the experimental observation that islands grown in successive layers not only replicate, forming individual island columns, but self-organize to reach a com...Coherent island size; Island shape; Heteroepitaxial films; Strained 3D islands; Heteroepitaxial films1999-03
72 Stringfellow, Gerald B.Te doping of GaInP: ordering and step structureThe donor Te has been added to GaInP during organometallic vapor phase epitaxial growth using the precursor diethyltelluride. In agreement with previous studies, the addition of high Te concentrations leads to the elimination of the CuPt ordering observed in undoped layers. The degree of order is es...Epitaxial growth; Heterostructures; Growth parameters1999-04-01
73 Stringfellow, Gerald B.Bandgap control of GaInP using Sb as a surfactantThe use of surfactants to control specific aspects of the vapor-phase epitaxial growth process is beginning to be studied for both the elemental and III/V semiconductors. To date, most reported surfactant effects for semiconductors relate to the morphology of the growing films. However, semicondu...Band-gap energy; Growth process; Epitaxial growth1999-09-27
74 Tiwari, AshutoshElectron tunneling experiments on La0.7A0.3MnO3 (A=Ca, Sr, Ba)Tunneling conductance measurements of the electronic density of states of perovskite manganates, La0.7A0.3MnO3 are reported. Tunneling data of all the samples show a zero-bias anomaly with a minimum in the density of states at the Fermi level. This behavior is interpreted as arising from strong elec...Perovskite manganates; Tunneling conductance1999-10
75 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
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