| A fundamentally new method for synthesis of thick (200-400 nm) epitaxial films of silicon carbide on single-crystal Al2O3 substrates is proposed. The method develops the previously discovered method of topochemical substitution of atoms during the transformation of Si into SiC. In the proposedmethod, a layer of epitaxial Si of orientation (100) or (111) is being preliminarily deposited on the sapphire via CVD or other technique. Then, using a topochemical reaction between the CO gas and the deposited epitaxial silicon film, a part of Si atoms is being substituted by carbon atoms. As a result, the silicon film transforms into SiC film. As experimental studies have shown, in the process of this transformation a high-quality epitaxial SiC layer can be formed on the sapphire surface under certain synthesis conditions. A detailed investigation of grown SiC layers using the methods of electron diffraction, ellipsometry, Raman spectroscopy, X-ray diffractometry and scanning microscopy is conducted and an analysis of experimental data is given. Formation of both cubic 3C-SiC and hexagonal SiC polytypes during the transformation of Si into SiC was revealed by the XRD method. A detailed analysis of the current state of the problems of growth of epitaxial SiC layers on Al2O3 using various methods is provided. The method developed in this study opens up completely new perspectives not only for synthesis of semiconductors, but also for creation of new classes of composite, heat-resistant and other solid coatings. |
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