Diffuse x-ray scattering study of the formation of microdefects in heat-treated dislocation-free large-diameter silicon wafers

Diffuse x-ray scattering (DXS) is used to study the formation of microdefects (MDs) in heat-treated dislocation-free large-diameter silicon wafers with vacancies. The DXS method is shown to be efficient for investigating MDs in silicon single crystals. Specific defects, such as impurity clouds, are found to form in the silicon wafers during low-temperature annealing at 450°C. These defects are oxygen-rich regions in the solid solution with diffuse coherent interfaces. In the following stages of decomposition of the supersaturated solid solution, oxide precipitates form inside these regions and the impurity clouds disappear. As a result of the decomposition of the supersaturated solid solution of oxygen, interstitial MDs form in the silicon wafers during multistep heat treatment. These MDs lie in the {110} planes and have nonspherical displacement fields. The volume density and size of MDs forming in the silicon wafers at various stages of the decomposition are determined.     

Native Point Defects and Nonstoichiometry in GaAs (I). Homogeneity Region of Gallium Arsenide

Homogeneity region and the concentration of dominant native point defects along its boundary are calculated by the method of quasichemical reactions with the use of experimental data on the structure type of solid solutions formed by the components in GaAs. The entropy and enthalpy of the formation of dominant native point defects in GaAs are obtained. Temperature ranges of the formation of microdefects-finely dispersed Ga and As precipitates are considered.     

Structure and phase composition studies of partially stabilized zirconia

Zirconia single crystals doped with 2.8, 3.2, 3.7, and 4.0 mol % of Y₂O₃ have been studied. The phase composition and structure have been studied by X-ray diffraction analysis and transmission electron microscopy. It has been established that all investigated samples has two ZrO₂ tetragonal phases with tetragonality c/a = 1.006–1.007 and c/a = 1.014–1.015 independent of the stabilizing impurity content. The former phase is not transformed, whereas the latter is transformed into a monoclinic one. In all cases the samples have a developed twin structure. Twinning hierarchy is observed: there are first-, second-, third-order, etc., twins, each of them containing the next-order twins inside them. Elastic stress relaxation occurs by twinning rather than by generation of dislocations. The stabilizing impurity content affects the structure nonmonotonically; the minimum dimensions of the twin lamellas refer to the Y₂O₃ concentration of 3.2 mol %.     

Inverse problems in underwater acoustics and approximation of the velocity field for signal propagation

A new approach is suggested for solving the inverse problem in underwater acoustics — the determination of the velocity of signal propagation in an inhomogeneous medium. The unknown velocity u(x(t), t) is assumed to be independent of the time t and is sought in the form of a polynomial with respect to the degree of the space coordinate x ₁, x₂, x₃.Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 102–105, 1989.     

Defects and localized states in MBE-grown GaAs1−x N x solid solutions prepared by molecular-beam epitaxy

Defects and localized states have been studied for molecular-beam-epitaxy (MBE)-grown high-resistivity and undoped GaAs_1?x N _x films with a N concentration not exceeding approximately 1.0 at.%. The crystalline quality of the films and hence the defects and localized states were determined by high-resolution X-ray diffraction, photoluminescence spectra, capacitance versus voltage measurements and photoinduced current transient spectra of GaAs and GaAs_1?x N _x layers. It was concluded that incorporation of low concentrations of N into MBE-grown GaAs_1?x N _x films promotes the formation of high densities of deep centres similar to EL2 donors, leading to heavy compensation of the films by some unidentified acceptors. GaAs antisite acceptors were believed to be responsible for the said compensation. A prominent defect band near 1.33-1.38 eV also appeared to be associated with these defects. The most prominent centres in dilute GaAs_1?x N _x films with N content less than 0.35 at.% seem to be the EL2 donors and the hole traps located near E _v +0.3 eV.     

Numerical and analytic investigation of the dynamics of hollow droplet impact onto substrate

A numerical and analytical model is proposed for the impact of a hollow melt droplet onto the surface of a solid polished substrate. The model is based on integral laws of the mass and energy conservation of the colliding droplet, it accounts for capillary and adhesion properties of the melt. The main parameters of the high-velocity deformation of a hollow particle have been computed: the variation of its height, shell thickness, and the contact spot diameter up to the moment of the spreading droplet solidification as well as the pressure variation inside the droplet until the moment of the shell rupture. The critical pressure value at which the rupture occurs is estimated by a formula characterizing the spherical shell strength. Quite a fair agreement of the computed values of the final diameter of the splat of a spread and solidified droplet with the data of physical experiment is shown. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 06-01-00080) as well as within the framework of the Interdisciplinary Integration Project of SB RAS No. 90 for the years 2006–2008 “Scientific Fundamentals of the Creation of Multi-Layer Nano-Structural Coatings and Interfaces in Heterogeneous Materials for Operation in the Fields of Extreme External Effects”.     

Oximes and nitriles of cardenolides

The influence of the oximation of cardenolides and the production of 10-cyanocardenolides on their biological activity has been studied. The prefered conformation of strophanthidin 19-aldoxime has been established; it has chelate fragment as the result of the orientation in the same direction of the nitrogen atom of the oxime group and the hydroxy groups at C-3 and C-5.All-Union Scientific-Research Institute of the Chemistry and Technology of Drugs, Khar'kov. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 608–612, September–October, 1983.