Materials Literature
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In situ Si-TaSi2 composites are studied by synchrotron white beam topography and by double axis diffractometry. These results show that the single crystal Si matrix is of excellent quality: Rocking curve widths are between 40 and 60 s of arc, and the topographs do not exhibit asterism. Diffuse radial streaks in the La…
The scaling relations close to the ideal glass transition point in a self-consistent mode coupling model with realistic structural properties are studied. The behavior of the long time limit of the density autocorrelation function or the nonergodicity parameter over a reasonable density range around the transition poi…
Luminescence spectroscopy of nanocrystals (100 nm) has been used to probe the details of the low-temperature photophysics of AgBr, an indirect-gap semiconductor. Small crystallite size, moderate excitation levels, and radiative decay rates create a situation in which only one electron-hole pair exists in a given nanoc…
Abstract In this paper I review the evidence that shows that the optical and electronic properties of semiconducting diamond can be understood in terms of boron acceptors partially compensated by deep donors. In natural semiconducting diamond, in which the total impurity concentration is less than 1 ppm, there is a lo…
Later-stage spinoidal decomposition (SD) of off-critical mixtures of poly(styrene-ran-butadiene) SBR/polyisoprene or SBR/polybutadiene was investigated by time-resolved light scattering. Changes in the scaled structure factor F(x,t)≡qm(t)3I(x,t) with x≡q/qm(t) were determined as a function of the composition w of the…
The \ensuremath{\pi}-electronic structural changes in a polyene molecule containing seven double bonds, \ensuremath{\alpha},\ensuremath{\omega}-diphenyltetradecaheptaene (DP7), have been studied upon gradually doping with sodium, using x-ray and ultraviolet photoelectron spectroscopies. The spectra are interpreted wit…
We have studied phonon states of Ge small particles by Raman scattering resonating with the ${\mathit{E}}_{1}$\ensuremath{\sim}${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ gaps. Those particles are prepared by evaporation in Ar gas atmosphere and their sizes range from about 2 through 30 nm. Since the elect…
Total electron and total and partial ion yield spectra of Ar clusters (with average size up to 600±200) in the region of Ar 2p excitation have been measured using synchrotron radiation and time-of-flight mass spectrometry. As the average cluster size increases, the x-ray absorption spectrum changes systematically from…
We investigate the optical excitation of visible room-temperature luminescence in electrochemically produced porous silicon and in siloxene obtained from the chemical reaction of calcium disilicide with hydrochloric acid. Luminescence and luminescence excitation spectra (2--5 eV) of different porous silicon and siloxe…
The propagation of acoustic waves in superlattices is investigated within the effective-medium model generalized to the quasiperiodic structure. The effective elastic constants are analytically obtained in closed form for superlattices with hexagonal symmetry. These results are used to interpret the observed low-frequ…
We prepared silica glasses having various concentrations of chlorine, fluorine, hydrogen (SiO2−x), and oxygen (SiO2+x) to examine the precursors of paramagnetic centers induced by γ rays. In the case of glasses sintered under chlorine and hydrogen ambients, the concentration of the E′ center induced by γ-ray irradiati…
Calcium chloride framework alumino-silicate, (Ca 5.88 Mg 0.23 )(Al 4.26 Fe 0.46 )Si 2.00 O 15.68 Cl 2.64 , Al 5 Ca 6 Si 2 Cl 3 O 16 , (ideal), M r =793.9 (ideal), cubic, I43d, a=12.001 (2) A, V=1729 (1) A 3 , Z=4, D m =3.01, D x =3.056 Mg m -3 , λ(Mo kα 1 )=0.70930 A, μ=2.95 mm -1 , F(000)=1565, T=301 K, R=0.062 for 2…
The effect of MeV ion irradiation damage on the luminescence lifetime of erbium-doped silica glass films has been studied. The 10-μm-thick films were first implanted with 3.5 MeV Er at a fluence of 5×1015 cm−2. When optically pumped at 488 nm, the films show a clear photoluminescence spectrum centered around 1.535 μm,…
Melts of the eutectic alloy Ag-39.9 at. %Cu were cooled below the liquidus temperature by the glass flux method. The solidification behavior was followed by measuring the temperature change (recalescence), and the resulting microstructures were investigated by optical and electron microscopy. Up to a certain critical…
The organic crystal 4-nitro-4′-methylbenzylidene aniline (NMBA) was identified as a promising nonlinear material by the powder technique. The material gave a second harmonic intensity 16 times that of urea. Large single crystals of dimensions 5×3×1 cm3 were grown by the temperature lowering of a seeded supersaturated…
Abstract There is considerable interest in growing diamond layers and thin films for a wide range of applications. Some of these thin film requirements can be met already using existing diamond-like carbon coatings. This paper reviews the use of diamond-like carbon films in infra red optical, mechanical, electronic an…
The effect of rf power and substrate temperature Ts on the optical, electrical, and structural properties of a-Si1−xCx:H alloy films deposited in the new hot-plasma-box glow-discharge reactor are reported. The rate of deposition as well as the total fraction x of the carbon incorporated in the alloy films were found t…
Time-of-flight photocurrent measurements of 1,1-bis(di-4-tolylaminophenyl)cyclohexane doped bisphenol-A-polycarbonate show dispersive features at low temperatures. Within the nondispersive regime, transients show anomalously broad tails of universal shape. Their relative width is in quantitative accord with Monte Carl…
Abstract Three‐component emulsion polymer systems constitute an overall four‐component system from a morphological viewpoint. The aqueous phase is always the continuous phase within which 22 distinct and thermodynamically stable particle morphologies may exist. Six uniquely different categories of particles compose th…
Theoretical expressions are presented, at various levels of approximation, for the density of states <ρu(ω)≳ of harmonic modes with imaginary frequencies in liquids; these are also referred to as unstable modes. The relation between the frequency integral of <ρu(ω)≳, which is the fraction of unstable mod…