Preferential amorphization at extended defects of self-ion-irradiated silicon

Nucleation of an amorphous Si layer is shown to occur preferentially at a t hin band of dislocations during self-ion-irradiation of silicon at elevated temperatures. This process occurs even when the defect band is well separa ted from the peak of the ion damage distribution. Without such a nucleation site, amorphization does not occur under identical bombardment conditions. These results suggest that amorphization can be nucleation limited under c onditions where significant defect annealing occurs during irradiation. Thi s process can be understood if mobile, implantation-induced defects are tra pped at preexisting damage and raise the local free energy above that of th e amorphous phase.