[en] The Car-Parrinello method for carrying out molecular dynamics enables the forces between atoms to be calculated by solving Schroedinger's equation for the valence electrons using Density Functional Theory. The method is capable of giving good structural predictions for amorphous network solids by quenching from the melt, even in situations where the bonding changes from one site to another. In amorphous carbon where, depending on its environment, carbon may show sp² or sp³ bonds. The method is applied here to the study of network solids using the example of tetrahedral amorphous carbon

[en] The authors used time resolved fluorescence line narrowing to study optical dephasing and energy transfer among Yb³⁺ ions doped inorganic glasses. They observe for the first time in any rare earth doped glass system a change in the power of the temperature dependence of the homogeneous linewidth of the ²F₅2/(1)-²F₇2/(1) transition of Yb³⁺ as well as an efficient one-phonon assisted energy transfer process occurring among Yb³⁺ ions higher concentration due to a quadrupole-quadrupole coupling of the ions. In this paper, the authors review past studies in rare earth doped glass systems of these topics and compare them to their observations of Yb³⁺ in silicated and phosphate glasses

[en] The authors report a new technique for measuring the density distribution of the D⁰-/ state in a-Si:H before and after light soaking and in a-Si,Ge:H,F alloys. Electron time-of-flight (TOF) measurements as a function of temperature from the basis of their new technique. The deep trapping of electrons controls the mobility-lifetime product (μtau)_n, which is evaluated from the integrated TOF current. The dominant deep trap is the D⁰-/ level. The authors obtain the density of D⁰-/ states in a-Si,Ge:H,F which peak at E_c-(0.40 to 0.45) eV, with maxima in the 10¹⁸ to 10¹⁹ cm^-3eV^-1 range. In a-Si:H, the peak lies at E_c-0.45 eV; they observe its growth with increasing light-soaking time

[en] New spectral emission lines of Ti XXI and Ti XIX have been observed and classified from a laser-produced plasma. The wavelength region for these lines is from 12 to 15 angstrom

[en] The phase diagrams including lanthanide chlorides are available for such ternary systems as DyCl₃-KCl-NaCl (1), PrCl₃-CaCl₂-NaCl (2) and LaCL₃-CaCl₂-NaCl (3). Concerning with GdCl₃, the GdCl₃-NaCl binary system has been studied by Korshunov and Drobot (4), whereas there is no information on the GdCl₃-CaCl₂ system. Here we discuss the GdCl₃-NaCl system in some details and report on the GdCl₃-CaCl₂ system. (author)

[en] Individual, as well as multiple doses of /sup 27/Al/sup +/, /sup 31/P/sup +/, /sup 28/Si/sup +/ and /sup 28/Si/sup +/ plus /sup 12/C/sup +/ were implanted into (100) oriented monocrystaline β-SiC films. A critical energy of ≅ 16 eV/atom required for the amorphization of β-SiC via implantation of Al and P was determined using the TRIM84 computer program for calculation of damage-energy profiles coupled with results of RBS/ion channeling analyses. In order to recrystallize amorphized layers created by the individual implantation of all four ion species, thermal annealing at 1600, 1700, or 1800⁰C was employed. Characterization of the recrystallized layers was performed using XTEM. Examples of SPE regrown layers containing; 1) precipitates and dislocation loops, 2) highly faulted, microtwinned regions, and 3) random crystallites were observed

[en] The authors investigated the incorporation of oxygen into heavily doped silicon during UV excimer laser irradiation. For the case of repetitive laser irradiations in air, the authors observe that the amount of oxygen incorporated into Si depends markedly on the dopant. For As and Sb implanted silicon, there is no anomalous oxygen incorporation. By contrast, increasing amounts of O are incorporated into In implanted silicon as a function of number of laser shots. The incorporation of O is associated with degradation of the optical and structural properties of the surface, and a deep diffusion of the dopant. This behavior is believed to be partly related to specific chemical reactions between oxygen and indium present in the surface at high concentrations as the result of dopant segregation during solidification

[en] It was determined that Zn/sub 1-x/Fe/sub x/Cr₂Se₄ for x ≤ 0.2 are solid solutions of normal spinels, where Fe replaces Zn at the tetrahedral positions. At 4.2 K, as the iron content increases a concentration-induced magnetic phase transition spiral-nonuniform-ferrimagnet occurs near x = 0.1. This transition is accompanied by a decrease in the angle of the magnetic spiral Phi and formation of regions of short-range magnetic order 30-50 A in size

[en] Epitaxial InAs:Sn is grown on semi-insulating GaAs substrates by molecular-beam epitaxy. The large lattice mismatch between these materials (/similar to/7.1%) generates a high density of threading dislocations which propagate into the epitaxial film. Both plan-view and cross-sectional transmission electron microscopy techniques are used to investigate the generation and propagation of these dislocations. For films that exceed the critical thickness, the threading dislocation density is inversely proportional to the epilayer thickness. Epitaxial layers incorporating growth interrupts have lower overall defect densities, yet maintain defect reduction profiles similar to those observed in layers grown without the growth interrupt. Room-temperature mobilities for InAs:Sn epitaxial layers varied from 11 200 to 22 100 cm²/V s for epilayer thicknesses of 0.4 to 4.4 μm, respectively. The thickness dependence on the mobility is attributed to a multiplicity of factors including surface scattering, interfacial strain, surface accumulation, and the high interfacial dislocation density

[en] Consideration is being given to hypothetic transition of a binary condensed system to a new phase state - supplementary solution, which is two-phase for impurity component and single-phase for the basic one. New phase at that must disperse spontaneously, being an integral part of the solution in the form of equilibrium finely dispersed inclusions of system components. Impurity two-phase character of the binary system with single-phase basic component is manifested in formation of additional phase volume for the solvent. Thermodynamic calculations of such supplementary solution, conducted for K-0, Cs-O and Au-Si systems, give satisfactory agreement with experimental data