Kinetics of disilane molecule decomposition on the growth surface of silicon in vacuum gas-phase epitaxy reactors

The range of the characteristic decomposition rates of dihydride molecule radicals adsorbed by the silicon surface in the temperature interval 450?C700°C is experimentally found for a number of kinetic models. A relationship between the rate of silicon atom incorporation into a growing crystal and the characteristic rate of disilane molecule pyrolysis on the silicon surface is found. The temperature dependence of the rate of disilane fragment decomposition on the silicon surface is nonmonotonic, and its run depends on temperature conditions. It is shown that the temperature dependence of the molecular decomposition rate on the growth surface is described by a superposition of two activation curves with various activation energies. The activation energies depend on the peculiarity of interaction between the molecular beam and the silicon surface when the filling of surface states with hydrogen is low and high.     

Biphonons in quasicrystals

The spectrum of coupled optical biphonon vibrations in quasicrystals with variation of the atom-atom interaction in accordance with the Fibonacci sequence is investigated. For two-phonon states with strong anharmonicity of the vibrations, a system of recursion equations, which is more complicated than the previously employed system for one-phonon states, is obtained. Calculations using this system made it possible to determine the spectrum of biphonon vibrations in a quasicrystal. It is shown that, on the low-frequency edge of the biphonon band, a scaling-type fine structure of the same form as in biphonon spectra of fractal lattices exists in the density of states. It is found that the energy dependence of the density of states is periodic on a logarithmic scale. The period of this dependence is determined. It is noted that the resonance structure in the density of states is of a nonstandard form in the high-frequency region of the biphonon band. Fiz. Tverd. Tela (St. Petersburg) 39, 163–170 (January 1997)     

Kinetics of the formation of gas bubbles during polarization of copper and graphite electrodes in electrolytic aqueous solutions

The adsorption and kinetic processes of the formation of gas bubbles passivating the surface during polarization of copper and graphite electrodes in 1% aqueous solution of sulfuric acid have been investigated. Three stages of the process related to the recharging of the double electric layer—adsorption accumulation of the gas escaping from the surface, the critical nucleation of the gas bubbles, and their subsequent growth—have been revealed, distinguished, and quantitatively estimated. It has been shown that potential leveling at the steady-state value specified by the Tafel equation is unambiguously associated with achievement of the limiting surface area screened by the gas bubbles for each particular current density. The surface diffusion constants D _H = (1.5–4.4) × 10⁻⁴ and (0.1–3.8) × 10⁻⁵ cm²/s of hydrogen on copper and graphite, respectively, and D _O = (1.8–4.5) × 10⁻⁷ cm²/s of oxygen on graphite during the motion toward the drain (the gas bubbles) have been calculated.     

Magnetic Resonance of Chromium (V) with 2–Hydroxy–2–Ethylbutyrates

A complex of Cr (V) with 2–hydroxy–2–ethylbutyric acid (EHBA) has been studied experimentally by the method of electron spin resonance (ESR). The tensor components of the g–factor, the dependences of the ESR line widths on the concentration of paramagnetic centers, and the SHF power of saturation are determined. It is shown that the main mechanism of dynamic polarization of nuclei in the EHBACr^V complex in a propanediol solution is the mechanism of dynamic cooling with a burnt hole. It has been established that the ESR spectra of the EHBACr^V solutions in deuterated and ordinary propanediol display practically the same behavior, which is indicative of the good solubility of the complex in deuterated alcohols.     

Magnetically simulated variation of dislocation mobility in plastically deformed n-silicon

The acoustic emission method is employed for an experimental investigation of the effect of a magnetic field on the mobility of edge dislocations in a plastically deformed n-silicon sample carrying a current. It is found that the preliminary treatment of a dislocated crystal in a constant magnetic field (B<1 T) changes the intensity of its acoustic response depending on the magnetic induction. The observed effect is associated with spin-dependent magnetosensitive reactions of defects occurring in the vicinity of the dislocation core, which facilitate the detachment of the dislocations from the stoppers and, hence, increase the mobility of dislocations and the acoustic response of the dislocation structure.     

Computer analysis of two-dimensional images in the Zernike phase contrast method for hard X rays

The problems of the numerical simulation of two-dimensional images in the Zernike phase contrast method in hard X rays are analyzed. Calculations are performed for experimental conditions typical of third-generation synchrotron radiation sources (ESRF, APS, Spring-8, etc.). Schemes are considered where the focusing elements are a refracting lens and a zone plate and the phase-shifting element is situated at the point of the source image. It is shown that the refracting lens allows better resolution than the zone plate. A technique similar to ptychography can be successfully applied to improve the quality of the images obtained by the Zernike phase contrast method.     

Peculiarities of the Electron Structure of Pseudobinary Alloys (GeTe)m–(Sb2Te3)n

Crystallography Reports - The electron band structure of GeTe, Sb2Te3, GeSb2Te4, and Ge2Sb2Te5 compounds has been calculated by the electron density functional method using the WIEN2k software...