In the research, to describe the spinodal decomposition of A 3 B 5 semiconductor solid solutions, in which the substitution of the main components occurs simultaneously in each of the sublattices of the sphalerite crystal structure, the Cahn-Hilliard concepts are extended. The resulting system of differential equations is applied to describe the effect of composition modulation in GaxIn1−xPyAs1−y solid solutions grown on InP substrates. In this case, the elastic deformation energy of a thin layer of GaxIn1−xPyAs1−y solid solution is calculated on the assumption of its coherent conjugation with a massive InP substrate. The excess mixing energy of the components in the solid phase is evaluated in accordance with the simple solution model. The temperature-concentration ranges, in which the conditions for the occurrence of an oscillatory mode of relaxation of the supersaturated metastable state of the solid phase are realized, are found by analyzing phase portraits of the system. The performed analysis shows that the effect of modulation of the material composition is connected with the resonance of total entire excess energy and elastic energy. The parameters of the oscillatory process are compared with data on the effect of composition stabilization, which is experimentally observed in the growth of elastically stressed heterostructures GaxIn1−xPyAs1−y -InP substrate.
The multifractal analysis (MFA) of the spatial microform area formed on the surface of steel C35 and aluminum alloy AA2024 at the face milling was implemented. The input information for the MFA was micro-images of the machined workpiece surface. Multifractal (MF) spectra and their main parameters are calculated for the surface of samples machined at various cutting conditions. Renyi’s numbers and fractal ordering parameters were chosen as the most informative MF parameters describing the surface structure. It is shown that the MF functions of the system correspond to their canonical forms. Quantitative relationships between the parameters of MF spectra for the surface area of microforms formed during machining surfaces of steel and aluminum alloy workpieces and the cutting conditions were obtained. The physical processes that are responsible for the formation of the observed MF spectra on the surface of the workpieces depending on feed and depth of cut at the face milling were discussed. The developed computational technique can be used to describe and analyze the state of spatial fractal structures formed on the surface of other materials.
To obtain epitaxial layers of A2B6 semiconductors with increased structural perfection from their own liquid phase, it has been proposed to use a technological process in which the synthesis temperature varies in such a manner that ensures a constant growth rate of layers during the whole process. The regularities of temperature variation with time for this process have been found on the basis of diffusion crystallization model. The developed model is realized by numerical methods and applied to description of the growth of cadmium telluride layers. Quantitative data on variations of synthesis temperature have been obtained, which can serve as a basis for choosing the temperature-time regimes of growth of cadmium telluride layers with a constant and required rate of solid phase formation.
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