Amorphization processes in electron and/or ion-irradiated silicon

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