ELECTRON-IRRADIATION-INDUCED CRYSTALLINE-TO-AMORPHOUS TRANSITION IN BETA-SIC SINGLE-CRYSTALS

An electron-irradiation-induced crystalline-to-amorphous (C-A) transition in beta-SiC single crystals has been studied as a function of irradiation temperature, by means of ultra-high-voltage electron microscopy. The C-A transition can be induced at temperatures below 340 K. The dose of electrons required for the C-A transition is essentially constant at temperatures below 250 K, while at temperatures above 250 K the electron dose increases quickly with temperature until no amorphization can be induced any more at the critical temperature T(c) of 340 K. At temperatures below T(c), chemical disordering occurs in every case and always precedes a complete C-A transition, while at temperatures above T(c) the degree of chemical disordering is greatly reduced and there is no amorphization. Based on the results obtained, the role of chemical disordering in the C-A transition is discussed in terms of the energy increases due to the production of anti-site defects. The thermal stability of the irradiation-produced amorphous SiC has been also studied and it is revealed that the amorphous SiC crystallizes into fine-grained polycrystalline beta-SiC at temperatures above 1298 +/- 25 K.