Materials Literature
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Elastic scattering of polarized electrons from unpolarized Hg, Tl, and Pb atoms has been studied at energies ranging from 0.3 to 2.0 eV and scattering angles ranging from 30' to 125'. The experimental data of the Sherman function S are compared with two calculations in which the target configuration is accounted for i…
The optical absorption, site selective excitation and luminescence spectra of the trivalent praseodymium ion in three rare earth gallium garnet matrices, RE 3 Ga 5 O 12 (REGG; RE=Y, Gd, and Pr) were detected at 4, 77 and 300 K. The 4f 2 energy level schemes comprising 56 to 68 crystal field (CF) sublevels were simulat…
Ultrathin films of vanadyl phthalocyanine (VOPc) have been grown on hydrogen-terminated Si(111) surfaces by molecular beam epitaxy. Epitaxial growth was examined on the two types of substrates. Reflection high energy electron diffraction studies have revealed that VOPc molecules form commensurate lattices [−3[3 1]4],…
A sudden shift from a bidimensional to a three-dimensional growth mode is observed when InAs is deposited by molecular-beam epitaxy on a pseudomorphic buffer layer grown on GaAs. The critical thickness for this shift is merely sensitive to the indium composition of the surface monolayer prior to growth. This property…
We relate anharmonic equilibrium thermal fluctuations of smectics A to fluctuations of the Kardar-Parisi-Zhang (KPZ) dynamical model for a growing interface. The KPZ model in 1+1 dimensions is one to one related to a 2D smectic elastic model whose scaling behavior is then obtained exactly. The KPZ model in 2+1 dimensi…
Temperature dependences of the dark conductivity and the photoconductivity for amorphous thin films of Ga 30 Se 70-x In x in the temperature range 298-328 K have been reported. The dark conductivity and the photoconductivity increase at all temperatures as the concentration of In (x=0, 5, 10, 15 and 20) increases. The…
Weak, low frequency disorder induced Raman scattering is observed in nanocrystalline, ‘‘glassy’’ carbon having an in-plane correlation length La≂30 Å. Similar, relatively more intense low frequency scattering is observed after the annealing of amorphous carbon films to 600 °C, suggesting the formation of quite small n…
Thin films of BaTiO3 were deposited on platinum coated silicon substrates by excimer laser (248 nm) ablation at 600 °C or ex situ crystallized at about the same annealing temperature. Films deposited at 600 °C showed good crystallinity and were characterized for ferroelectricity, dielectric constant, dielectric loss,…
Visible photoluminescence has been observed in crystallized a-Si:H/a-SiNx:H multiquantum-well structures at room temperature. The MQW heterostructures consisting of 72 layers were formed by computer controlled plasma-enhanced chemical-vapor deposition method and then crystallized by Ar+ laser annealing technique. The…
Siloxene (${\mathrm{Si}}_{6}$${\mathrm{O}}_{3}$${\mathrm{H}}_{6}$) and its derivatives show strong visible luminescence. By applying semiempirical quantum chemical calculations to the siloxene structure, we demonstrate that the presence of oxygen in a planar array of silicon atoms results in molecular orbitals confine…
We present carbon K emission spectra of diamond excited with high-resolution undulator radiation. The valence-band emission spectra are shown to be strongly dependent on the excitation energy, up to 20--30 eV above the C K edge. It is proposed that the dependence is indicative of the resonant inelastic scattering desc…
Abstract This paper presents a proprietary process developed to manufacture polyurethane (PU) pultruded composites. The blocked isocyanate (NCO)‐terminated PU prepolymer synthesized in this study was prepared from ε‐caprolactam blocked blends of toluene diisocyanate (TDI) and branched polyester. The processability and…
Abstract The photograftings of methacrylic acid (MAA), acrylic acid (AA), methacrylamide (MAAm), and acrylamide (AAm) as hydrophilic monomers onto polyethylene (PE) plates were carried out in the liquid phase. The contact‐angle measurement and the surface analysis by ESCA reveal that the grafted amount at which the PE…
The authors show that the phenomenological renormalization-group analysis based on the finite-size scaling hypothesis is very effective in analysing the critical properties of the localization-delocalization transition (LDT) of the wavefunctions in quasiperiodic systems. They have applied it successfully to the LDT of…
A neutron powder diffraction refinement of the structure parameters of five samples of magnesium cobalt oxide spinels Mg x Co 3-x O 4 (0<x<1) has been carried out. It was found that all spinels under study are inverse and there is a limit to the occupancy of the tetrahedral sites by Mg.
The photoluminescence of intentionally vanadium-doped ZnSe crystals displays at low temperatures (T approximately=4 K) the emission of the V 3+ (d 2 ), V 2+ (d 3 ) and V + (d 4 ) ions with different no-phonon structures at 5440, 4740 and 3640 cm -1 , respectively. The excitation spectra of the V 3+ and V 2+ luminescen…
It was demonstrated that the MgIn2O4 spinel is a very promising material as a transparent electronic conductor. By the measurements of diffuse reflectance spectra, the optical band gap of MgIn2O4 (∼3.4 eV) was found to be wider than that of ITO (indium tin oxide). Electrical conductivity of the sintered sample of MgIn…
We theoretically investigate excitonic effects on the optical properties of silicon quantum wires, based on ab initio electronic structure calculations. The Si wires have a direct, allowed band gap in the visible energy range and exhibit a strong optical anisotropy. Taking into account the electron-hole Coulomb intera…
We have performed photoluminescence studies on porous, p-type as well as n-type silicon wafers which have been prepared in air or in a dry nitrogen atmosphere, utilizing a spark-erosion technique. This sample preparation, which does not involve aqueous solutions or fluorine contaminants, yields similar photoluminescen…
We have calculated the electronic structure of spherical silicon crystallites containing up to 2058 Si atoms. We predict a variation of the optical band gap with respect to the size of the crystallites in very good agreement with available experimental results. We also calculate the electron-hole recombination time wh…