Amorphization processes in electron and/or ion-irradiated silicon

Amorphization has been studied in electron- (e/sup -/) and ion-irradiated Si. Si irradiated at <10 K with 1.0- or 1.5-MeV Kr/sup +/ became amorphous at <0.4 displacement per atom (dpa), whereas Si irradiated at 10 K to a fluence of approx. =14 dpa of 1-MeV e/sup -/ in an electron microscope failed to amorphize. However, Si subjected to a simultaneous e/sup -/ and Kr/sup +/ in situ irradiation, at <10 K, to a Kr/sup +/ fluence of 1.5 dpa retained crystallinity. The critical ratio, at <10 K, of the e/sup -/ to Kr/sup +/ ion displacement rates to maintain a degree of crystallinity is approx. =0.5. Atomistic models for these phenomena are presented.