Evolution of ion induced point defects in silicon

Problems of the dose rate dependence of the defect production by ion beam irradiation are addressed. Damage accumulation effects are studied for sequential and overlapping cascades induced by 1 keV recoils in silicon crystals. The defect generation and evolution is simulated by a molecular dynamics method using the Stillinger–Weber three body potential. It is shown that the damage produced by temporally and spatially overlapping cascades at room temperature can be both smaller and larger than the total damage induced by the individual recoils each starting in perfect crystalline silicon. The different damage levels are related to the characteristics of the defect structure shortly before and after initiating the subsequent cascades.