Influence of hydrogen on the structural characteristics of sic crystals obtained by the сvd method

Abstract

The results of certification of the structure, crystallomorphology, and phase composition of three varieties of samples in the form of crystals of silicon carbide synthesized from a gas-vapor mixture of the composition (CH₃SiCl₃ + H₂) are considered. Samples were obtained under the same conditions (Т = 1300 °С), but at different concentrations of hydrogen in the mixture flow. The hydrogen flow in the system for the samples of three varieties had the following values (in l / min): I ― 0,2; II ― 0,6; III ― 1,0. Structural studies were performed by transmission electron microscopy in combination with microdiffraction and infrared spectroscopy (IR). General features of samples of all varieties: a) the phase composition of SiC (only cubic modification 3C) and b) the formation in the form of whiskers of cylindrical and triangular sections, the axis of elongation of crystals of the type [111]. In faceted crystals, delamination along the interface of flat faceting surfaces was often revealed. The main range of thread cross sections for the studied three types of samples is 40―120, 50―500, and 20―200 nm, respectively All whiskers were single crystals; they contained a high density of stacking and twin defects along one of the (111) planes or intersecting planes of this type. In a certain part of the crystals, multilayer SiC polytypes were also contained.It has been established that an increase in the concentration of hydrogen in the vapor-gas reaction mixture promotes the formation of whiskers with a core-shell structure: the core consists of cubic modification silicon carbide and the shell is silicon oxide. Microdiffraction studies in combination with IR studies have established that the shell of whiskers has the amorphous SiO_x composition. Full text download