Materials Literature
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Trapping of ion-implanted deuterium (D) by irradiation defects and He bubbles in Mo was investigated through nuclear-reaction profiling of the D during linear ramping of temperature. Resulting data were analyzed using transport theory to obtain trap strengths. Nanometer-size He bubbles were found to trap the D with a…
Magnetic anisotropy of R2T14B (R=rare earth and T=transition metals such as Fe and Co) and partly substituted derivatives thereof are studied over a range of temperatures. The salient features are axial anisotropy for Y2Fe14B versus planar anisotropy for Y2Co14B. Only R with negative second-order Stevens’ factor (such…
The self-similarity property of the two-dimensional Penrose lattice is utilized to characterize it in terms of the distribution of different kinds of vertices, the Voronoi cells, and their nearest neighborhoods. Striking similarities are observed between the layer structures of the crystalline \ensuremath{\delta}-${\m…
The electrical conductivity and thermoelectric power of poly(p-phenylene vinylene) films have been studied as a function of heat-treatment temperatures (HTT's) up to 2900 \ifmmode^\circ\else\textdegree\fi{}C. The electrical transport is found to turn from a three-dimensional variable-range-hopping mechanism to metalli…
Photoluminescence studies have been performed on undoped and silicon-doped GaAs crystals, which were annealed between 650 and 1000 °C under different arsenic pressures. Samples were also heat treated with the addition of pure elemental Ga, Mn, or Cu. Spectra were taken in the energy range 1.15–1.55 eV at the surfaces…
Statistical properties of energy spectra in one-dimensional quasiperiodic systems are studied numerically. We find three distinctive level distributions: the Poisson, inverse-power-law (IPL), and cosine-band-like behaviors in the Harper model with an incommensurate potential. These depend on whether the electronic sta…
Magnetic properties of an orthorhombic intermetallic compound Mn 11 Ge 8 , which was formerly referred to as Mn 3 Ge 2 , has been investigated on a single crystal specimen at temperatures between 80 K and 800 K. The compound has features of a non-collinear antiferromagnet below T t = 150 K, and makes a spin-flopping t…
The shape of all major x-ray-excited peaks, including Auger transitions, from Cu, Ag, and Au are studied. The intensity contribution from inelastic (extrinsic) processes are removed. In all cases the primary excitation spectra thus determined are found to consist of a peak and a tail of (intrinsic) electrons which ext…
Initial magnetization and demagnetization data are reported for three forms of rapidly solidified Nd-Fe-B permanent magnet materials: melt-spun ribbons, hot-pressed magnets, and die upset magnets. In all three materials, the results are consistent with domain-wall pinning at Nd2Fe14B grain boundaries as the coercivity…
Simultaneous measurements of electrical conductivity \ensuremath{\sigma} and thermoelectric power Q were performed on a single crystal of ${\mathrm{Ba}}_{0.03}$${\mathrm{Sr}}_{0.97}$${\mathrm{TiO}}_{3}$ over an extensive range of temperature (500--1100?deC) and oxygen partial pressure (${10}^{\mathrm{\ensuremath{-}}18…
We present here a complete set of experimental results, obtained by electron paramagnetic resonance (EPR) and deep-level transient spectroscopy (DLTS), on the so-called EL2 defect in GaAs. It is obtained on semi-insulating materials and specially doped materials grown as semi-insulating ones, which have been submitted…
Unmixing kinetics of quenched critical polymer mixture of polystyrene and poly(vinyl methyl ether) was investigated by time-resolved light scattering technique. In the late stage of spinodal decomposition τ>60, τ being a reduced time, a simple dynamic scaling law was found on the scattering function I(q,t); I(q…
Heterogeneous catalysis in the low-pressure (5 mbar) plasma phase is shown to result from mass and energy exchanges between the plasma and the solid surface. Perturbation of the plasma medium by the solid is interpreted as a catalytic action to the extent that it leads to an increase of chemical reactivity of the syst…
Organic single crystals provide an ideal model for studying the factors that influence chemical processes in structured media. Reaction trajectories are well defined and reveal the influence of spontaneous mechanical stresses equivalent to tens of thousands of atmospheres. Analysis of molecular and crystal structures…
In an axisymmetric approximation the author demonstrates a parity breaking transition to a twisted configuration in tangentially anchored nematic liquid crystal droplets. The twisted phase occurs when K 11 >or=K 22 +0.431K 33 . In a magnetic field there is another transition corresponding to the droplet axis changing…
A mean-field theory is presented for the coarsening of a two-dimensional soap-film network. This theory explains (1) the correlation between area and number of sides of the cells, and (2) the anomalous absence of dynamical scaling laws, which is shown to have its origin in the topological constraint of a space-filling…
A technique of high voltage electron beam lithography and BCl3/Ar reactive ion etching for laterally patterning GaAs/Al0.3Ga0.7As multiple quantum wells is described. The resulting structures were analyzed using scanning electron microscopy and a novel reflection electron microscopy technique, and their geometries are…
Martensitic transformations are shown to be driven by the interplay between two fluctuating strain components. No soft mode is needed, but a central peak occurs representing the dynamics of strain clusters. A two-dimensional magnetic-analog model with the martensitic-transition symmetry is constructed and analyzed by…
Dynamic coarsening of crystal surfaces by formation of macrosteps is explained by an improved model for impurity absorption. It is related to interface propagation in random media. Some unusual recursive equations are encountered. The model is analyzed by various methods and exhibits some universal features. We find c…
Abstract The phase behavior of binary mixtures of copolymers containing varying amounts of styrene and acrylonitrile (SAN) with a large range of aliphatic polyesters was examined. Miscibility was observed over a limited range of AN contents of the SANs, for each polyester, while similarly for each SAN, miscibility was…