Materials Literature
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Exact eigenstates of a tight-binding model on a two-dimensional Penrose lattice are investigated. Several exact eigenfunctions are found for certain transfer matrices, and a method to obtain more general exact solutions is proposed. The fractal dimension of self-similar non-normalizable eigenfunctions is defined, and…
Distinct antiphase domain structures in GaAs epitaxial layers grown on a Si/SiO2/Si-substrate structure by metalorganic chemical vapor deposition have been revealed by using a silicon etchant (HF/HNO3). The antiphase is characterized by the [011]-oriented etching textures which rotate 90° between adjacent domains. The…
A soft optic phonon which is neither Raman nor infrared active has been directly observed for the first time in the higher-symmetry phase above ${T}_{a}$ (221.5 K) of hexagonal BaTi${\mathrm{O}}_{3}$ by an experiment of hyper-Raman scattering. The underdamped feature of the soft-phonon mode even close to ${T}_{a}$ all…
We have investigated the variation of the structural energy along two transition paths from the layered to the highly condensed phases of BN using the first-principles total-energy pseudopotential method. Along the structural paths considered, the symmetries of the initial layered phases have been maintained, leading…
We have measured the thermal conductivity of two diamond films grown by a chemical vapor deposition process. At room temperature the thermal conductivity is of the order of 10 W cm−1 K−1, i.e., as high as naturally occurring (type Ia) single-crystal diamonds. This value exceeds the thermal conductivity of copper at ro…
We study the long-time self-diffusion coefficient and the zero-frequency effective viscosity for a suspension of spherical Brownian particles. The correction to first order in the volume fraction to the self-diffusion coefficient and the correction to second order in the volume fraction to the effective viscosity are…
A new family of organic molecules, 2-${R}_{1}$-5-${R}_{2}$-DCNQI (with ${R}_{1}$,${R}_{2}$=${\mathrm{CH}}_{3}$, ${\mathrm{CH}}_{3}$O, Cl, or Br; DCNQI=N,N'-dicyanoquinonediimine) works as a ligand as well as an electron acceptor to form highly conducting, charge-transfer and coordination compounds as (2-${R}_{1}$-5-${…
The demagnetizing field and magnetostatic energy of a thin film with surface roughness has been calculated. It is shown that the surface roughness gives rise to an effective perpendicular anisotropy whose order of magnitude is evaluated as a function of the parameters characterizing the roughness. The results are disc…
The effect of pressure on the magnetic phase transition temperature of Hf 1- x Ta x Fe 2 with x =0 and x =0.1 has been studied. The Curie temperature for x =0 decreases with increasing pressure at a rate of -(1.2±1.0) K/kbar, and for x =0.1 it decreases with a pressure coefficient of -7.5 K/kbar up to about 8 kbar and…
Thermochromic VO2−xFx thin films were prepared by reactive rf magnetron sputtering followed by annealing post-treatment. Electrical and optical properties were measured as a function of temperature. The transmittance and reflectance were essentially wavelength independent at 65 °C, i.e., at the metal-insulator transit…
The phonon-drag contribution to the thermoelectric power is calculated at low temperatures in polar semiconductor heterostructures. Carries are assumed to interact with longitudinal acoustic phonons through deformation potential and with both longitudinal and transverse acoustic phonons through piezoelectric field. Th…
We discuss a rate-theory model of polymer crystallization that exhibits many of the morphological and kinetic features observed in the laboratory. The interplay between the growth of the lamellar crystals in directions along the molecular direction and at right angles to it is discussed, together with some of the impl…
Comprehensive (0.05--3-eV) spectroscopic measurements are reported for poly(3-hexylthienylene), P3HT, during photoexcitation (i.e., photoinduced absorption) and after doping with ${\mathrm{NOPF}}_{6}$. A one-to-one correspondence between the photoinduced and doping-induced spectral changes is observed, typical of cond…
The boron carbides are composed of twelve-atom icosahedral clusters which are linked by direct covalent bonds and through three-atom intericosahedral chains. The boron carbides are known to exist as a single phase with carbon concentrations from about 8 to about 20 at. %. This range of carbon concentrations is made po…
Different ratios of boron to carbon ions were implanted into diamond maintained at liquid-nitrogen temperature. After implantation, the diamonds were heated to 500 \ifmmode^\circ\else\textdegree\fi{}C by dropping them onto a platform situated in a vertical tube furnace, and then annealed for 1 h. This was followed by…
We report a picosecond pump–probe study of 55 Å cadmium sulfide microcrystallites embedded in polymer films. Large negative absorbance changes at wavelengths corresponding to energies near the band gap are observed. This absorption bleaching and the associated changes in refractive index are mainly responsible for the…
It is shown that large scale MCSCF linear response (MCLR) calculations can be carried out efficiently using an iterative algorithm where the linear transformations are carried out directly, i.e., without explicitly constructing the MCLR matrices. Calculations are presented on H2O of frequency dependent polarizabilitie…
Injection luminescence in the ultraviolet is observed from a cubic boron nitride pn junction diode made at high pressure. Microscopic observation and spectroscopic studies show that the light emission occurs near the junction region only in the forward-bias condition. The spectra extend from ∼215 nm to the red, having…
Single-particle and collective microscopic dynamics of a classical Yukawa fluid are analysed on the basis of simple memory function and mode-coupling theories. Thermodynamic states for different screening regimes are correlated in terms of an effective hard-sphere packing fraction. The longitudinal current fluctuation…
prednisolone followed by a reducing course of oral prednisolone.She improved clinically and her erythro- cyte sedimentation rate settled to 19 mm in the first hour after 10 days.The tracheostomy tube was removed after 12 days and good movement was seen in both vocal cords.Her recovery was further compli- cated by an e…