Materials Literature
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We report on band-gap luminescence in strain-symmetrized, (Si${)}_{\mathit{m}}$/(Ge${)}_{\mathit{n}}$ superlattices grown on a step-graded, alloy buffer with a reduced dislocation density, using Sb as a surfactant. The luminescence efficiency for a (Si${)}_{9}$/(Ge${)}_{6}$ and (Si${)}_{6}$/(Ge${)}_{4}$ superlattice i…
The unique molecular conductors with p\ensuremath{\pi}-d mixing band structures (${\mathit{R}}_{1}$,${\mathit{R}}_{2\mathrm{\ensuremath{-}}}$N,N'-dicyanoquinonediimine${)}_{2}$Cu [(${\mathit{R}}_{1}$,${\mathit{R}}_{2\mathrm{\ensuremath{-}}}$DCNQI${)}_{2}$Cu] (${\mathit{R}}_{1}$,${\mathit{R}}_{2}$=${\mathrm{CH}}_{3}$,$…
Copper overlayers with thicknesses up to several tens of angstroms have been vapor deposited at various substrate temperatures onto rutile ${\mathrm{TiO}}_{2}$(110) surfaces that have different defect concentrations. The metal films have been studied by means of ${\mathrm{He}}^{+}$ low-energy ion scattering, x-ray pho…
Absorption spectra of Tm3+ ions in yttrium scandium aluminum garnet are reported between 1.9 and 0.25 μm at 4 K. Laser-excited fluorescence was observed at 4 K from Tm3+(4f12) multiplet manifolds 1D2, 1G4, 3F2, and 3H4 to the ground-state manifold 3H6. Emission from 1D2 and 1G4 also includes transitions to Stark level…
I-U characteristics measured in ${\mathrm{TlGaTe}}_{2}$ single crystals consist of two regimes: a linear one at low current densities and a nonlinear one at higher current densities. In the nonlinear part [negative-differential-resistance (NDR) region] of the curves, a considerable increase of the temperature of the s…
The critical behavior of pinned charge-density waves (CDW's) is studied as the threshold for sliding is approached. Using the Fukuyama-Lee-Rice Hamiltonian with relaxational dynamics, the polarization and linear response are calculated numerically. Analytic bounds on the subthreshold motion are used to develop fast nu…
The correlation between free-exciton and bound-exciton recombination has been investigated by cathodoluminescence in high-quality and impurity-controlled chemical-vapor-deposited (CVD) diamond films. The films are formed by [CO(5%)]/[${\mathrm{H}}_{2}$] using microwave-plasma CVD and are doped with ${\mathrm{B}}_{2}$$…
Using a measure of the asymmetry of the valence charge distribution in ${\mathit{A}}^{\mathit{N}}$${\mathit{B}}^{8\mathrm{\ensuremath{-}}\mathit{N}}$ compounds, a mapping to Phillips's ionicity scale is achieved.
We report a systematic study of the first and second hyperpolarizabilities of several small molecules at a consistent level of theory and basis sets. Coupled cluster (CC) methods for correlation, analytical high-order time dependent Hartree–Fock (TDHF) theory for dispersion effects, and polarizability-consistent basis…
The authors report time-resolved photoluminescence spectroscopy of highly porous silicon. Their results show that the luminescence is due to localized quantum-confined excitons in undulating crystalline silicon wires. The resonantly excited photoluminescence spectrum exhibits satellite structure due to momentum-conser…
Abstract The principal chemical mechanisms relevant to the growth of diamond from gaseous hydrogen and hydrocarbon species are presented. The kinetic processes occurring during the activation and transport of the gaseous species to the growing surface are described, with the key processes being the generation and subs…
The spontaneous macroscopic polarization of perovskite ${\mathrm{KNbO}}_{3}$ is calculated as a Berry's phase using the Bloch functions of the tetragonal crystal. The result P=0.35 C/${\mathrm{m}}^{2}$ supports the measured value 0.37 C/${\mathrm{m}}^{2}$ and implies that earlier data from hysteresis loops are too low…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe electrochemical activity of boron-doped polycrystalline diamond thin film electrodesGreg M. Swain and Rajeshuni. RameshamCite this: Anal. Chem. 1993, 65, 4, 345–351Publication Date (Print):February 15, 1993Publication History Published online1 May 2002Published inissue 1…
The parametrization and optical properties such as absorption, photoluminescence (at 300 K and 77 K) and lifetimes of the lasing transition ( 5 D 0 to 7 F 2 ) of the EuF 3 (1 M%)-doped heavy metal fluoride glass (HMFG) systems of: 48ZrF 4 +24BaF 2 +7AlF 3 +20RF where RF=LiF, NaF and KF are studied. These Eu 3+ glasses…
In this review, the present level of infrared spectroscopy at surfaces is described by using hydrogen-terminated silicon surfaces as model systems. The electronic structure of the adsorbate, H, and the large mass difference between H and Si simplify the interpretation of the data and make it possible for the theories…
An electrochemical method for growing macroscopic fibers of electrically conductive poly(3-methylthiophene) is described. Single fibers of uniform diameter (∼0.1 to 0.7 millimeter) and length greater than 10 centimeters are grown in a capillary flow cell by electrochemical oxidation of the monomer, 3-methylthiophene.…
Brushes of liquid crystalline polymers swollen by nematic solvents are described by an extended Alexander model. Long-main-chain LCP with hairpins are considered. For the case of homogeneous anchoring a second-order tilting phase transition is expected as the grafting density is increased. When the grafting density is…
Abstract A number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene‐2,4‐diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n ‐butyl acrylate, ethyl methacrylate, and butyl methacrylate…
Abstract Poly(methyl methacrylate) (PMMA) was photolyzed with monochromatic light of wavelengths 260, 280, 300, 320, 400, and 500 nm in vacuo by the use of the Okazaki Large Spectrograph. UV spectral changes, the quantum yields of main‐chain scission (ϕ cs ), and effects of wavelength were investigated. UV spectral ch…
Abstract The diffusion and permeation coefficients for He, H 2 , D 2 , O 2 , and N 2 in a variety of elastomers were measured by simple manometric methods. The elastomers studied were butyl rubber; Hypalon® 40 and 45; Viton® E60 and GF; Hydrin® 100 and filled Hydrin® 100; Kraton® G, FG, and KG VTEOS; EPDM; epoxidized…