Конденсированные среды и межфазные границы (Dec 2022)
Thermodynamics, kinetics, and technology of synthesis of epitaxial layers of silicon carbide on silicon by coordinated substitution of atoms, and its unique properties. A review
Abstract
This review covers studies dedicated to the search for and development of sorbents for the extraction of the caesium-137. The review analyses a new method for growing SiC epitaxial films on Si, which is based on the coordinated substitution of some silicon atoms in the Si crystal lattice with carbon atoms. The main idea and theory of the new method is presented. This method significantly differs from classical growth schemes of thin films. The developed method consists in replacing some Si atoms with C directly inside the silicon matrix and not in depositing atoms on the substrate surface. The method allows us to solve one of the main problems of heteroepitaxy, namely, to synthesise low-defect and unstrained epitaxial films with a large difference between the lattice parameters of the film and the substrate. For the first time in the world, a method of the coordinated substitution of atoms of one sort for atoms of another sort has been implemented right inside the original crystal without destruction of the crystal structure. The method resembles the “genetic synthesis” of protein structures in biology. The structural quality of layers obtained by this method significantly exceeds the quality of silicon carbide films grown on silicon substrates by the world’s leading companies. The method is cheap and technologically advanced. The new growth method is compared with classical thin-film growth methods. The thermodynamic and kinetic analysis of the process of substitution of atoms in the solid phase is presented. Using the example of SiC formation, the mechanisms of a wide class of heterogeneous chemical reactions between the gas phase and a solid are described. The review describes a new method for the synthesis of epitaxial SiC layers on single-crystal sapphire substrates, which is based on the method of coordinated substitution of atoms. It is shown that an interface layer with non-standard optical and electrophysical properties appears at the SiC/Si interface formed by this growth method. The unusual properties are caused by a collapse (shrinkage) of the material at which silicon carbide, as a new phase, separates from the silicon matrix. The silicon is subjected to abnormally strong compression. As a result of such shrinkage, every fifth SiC chemical bond is fully consistent with every fourth Si bond, while the remaining bonds are deformed. The latter leads to a change in the structure of the SiC surface zones adjacent to Si and to a transformation of SiC into a “magnetic semimetal”. The epitaxy of SiC films on Si due to the coordinated substitution of half of the Si atoms by C atoms results in absence of lattice misfit dislocations and thus ensures the high crystalline perfection of the SiC films. A description is given for two quantum effects observed in the SiC/Si structures at room temperature in weak magnetic fields: the Meissner–Ochsenfeld effect and the effect of the generation of the Aharonov-Bohm oscillations in the field ependences of the static magnetic susceptibility. A description is given for a discovered phenomenon of phase transition of charge carriers into a coherent state with the simultaneous appearance of a giant value of diamagnetism of the order of 1/4π in weak magnetic fields, which has been associated with the appearance of a superconducting state.
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