Materials Literature
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Hexagonal lattice parameters a and c of the NiAs-type NiS 1- y Se y expand with increasing y below the solubility limit y L =0.20. The first-order transition temperature T t ( y ) [between the antiferromagnetic less-conductive and the Pauli-paramagnetic high-conductive states] decreases with increasing y , and is supp…
The band structure of ${\mathrm{C}}_{8}$K is investigated both experimentally and theoretically. For this purpose we have used low-energy electron-energy-loss spectroscopy (LEELS) on ${\mathrm{C}}_{8}$K and also calculated the density of states using the band structure of Ohno, Nakao, and Kamimura (ONK) and the charge…
The polarization of the x-ray-induced blue luminescence from synthetic quartz has been measured between 80 and 225 K. Two overlapping bands having different polarizations are observed; one peaks at 2.48 eV and is almost completely polarized perpendicular to the $c$ axis, while the other peaks at 2.74 eV and is polariz…
A theory is presented which explains recurrent precipitation bands (‘‘Liesegang rings’’) as dissolution patterns in a previously produced essentially homogeneous and continuous colloid. This picture is consistent with recent experimental evidence that the formation of Liesegang bands is a postnucleation phenomenon. Ma…
The temperature dependence of chromium photoluminescence spectra and lifetimes have been measured in ordered perovskite (${\mathrm{Cs}}_{2}$${\mathrm{NaYCl}}_{6}$, ${\mathrm{K}}_{2}$${\mathrm{NaScF}}_{6}$, and ${\mathrm{K}}_{2}$${\mathrm{NaGaF}}_{6}$) host crystals. Analysis of lifetime data yields thermal-quenching a…
Nematic cyanobiphenyl molecules are aligned normal to a glass electrode by a polymerized DMOAP silane coating. Under the action of a normal electric field, oriented toward the bulk nematic, a weak diffuse surface splay bend is observed, above a field threshold ∼ 0.1 V/μm. This polar instability can be attributed to th…
We have measured by spectroellipsometry the dielectric function \ensuremath{\epsilon} of pure and ultraheavily doped germanium from the near-infrared (\ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\simeq}1.6 eV) to the near-ultraviolet (\ensuremath{\Elzxh}\ensuremath{\omega}\ensuremath{\simeq}5.6 eV) regions. The…
Using diagrammatic valence-bond calculations, we have investigated the interplay between neutral-ionic (N-I) and regular-dimerized stack interfaces in mixed-stack organic charge-transfer (CT) crystals. The interactions relevant to the above two interfaces, that is, the intersite Coulomb and the electron-lattice phonon…
The magnetic properties of the 4:1, 6:1, 9:1, and 19:1 mixed crystals of galvinoxyl (4-[[3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadien-1-ylidene]methyl]-2,6 -bis(1,1-dimethylethyl) phenoxy) radical and its precursory closed shell compound, hydrogalvinoxyl, have been studied. From the measurements of the temperatu…
Ultraviolet-sensitive photodiodes have been made using the Schottky barrier formed in the contact layer between a thin sputtered layer of ZnO and Au. The sputtering parameters for the ZnO layer were optimized. The IV characteristics and the sensitivity spectra of the ZnO–Au photodiodes were investigated.
Step structure models for hydrogenated and clean Si(110) surfaces are proposed by kinematical analysis of low-energy electron diffraction patterns. The step structures are described as periodically up and down sequence of terraces with [1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{} 2]…
The EPR data for strained ruby have been reanalyzed using a model in which the mixing of five excited multiplets into the ground state are considered. Consistent crystal-field superposition-model parameters were obtained. Tables of the necessary superposition-model ``projection'' coefficients for both trigonally and t…
We analyse the integro-differential equation giving the shape of steady dendrites growing from a weakly undercooled melt in two spatial dimensions. A generalized WKB method shows that solutions at small velocities can exist with anisotropic surface tension only, a result completely out of reach of regular perturbation…
We study the acoustic and electronic properties of one-dimensional quasicrystals. Both numerical (nonperturbative) and analytical (perturbative) results are shown. The phonon and electronic spectra exhibit a self-similar hierarchy of gaps and many localized states in the gaps. We study quasiperiodic structures with an…
The theoretical formalism of Ritchie et al. is used to characterize the electromagnetic properties of plasma oscillations in two-dimensional electron-gas disks, such as those produced lithographically in the GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As semiconductor heterojun…
The anharmonic interaction (third-order elastic Hamiltonian) between fractons (short-length-scale vibrational excitations) and phonons (long-length-scale vibrational excitations) is introduced. The relationship between phonon-fracton scattering rates and the thermal conductivity \ensuremath{\kappa} is developed. Two r…
Metal selenide clusters have been made and characterized, using the arrested precipitation colloidal technique. A comparison of sulfide and selenide spectra enables observation of the effect of changes in the highest occupied molecular orbitals upon cluster electronic properties. The first and second excited electroni…
Measurements have been made of the current pulses observed in a negative point-to-plane corona discharge in oxygen. The apparatus was constructed to ultra-high vacuum standards to ensure controllable conditions on the gas purity and the state of the electrode surfaces. The effects of cathode voltage, tip diameter and…
The possibility of roughening in low-angle grain boundaries is investigated. By exhibiting an analogy between grain-boundary steps which do not have long-range strain and steps on solid surfaces, I argue that a grain-boundary roughening transition, of the same type as for solid surfaces, is possible. It is found that,…
By means of quasielastic neutron scattering we show that the H-diffusion mechanism in ${\mathrm{Pd}}_{85}$${\mathrm{Si}}_{15}$${\mathrm{H}}_{7.5}$ is characterized by two well-separated regimes of jump rates, in clear contradiction to present ideas on diffusion in amorphous substances. A semiquantitative interpretatio…