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

Nucleation of an amorphous Si layer is shown to occur preferentially at a thin band of dislocations during self-ion-irradiation of silicon at elevated temperatures. This process occurs even when the defect band is well separated 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 conditions where significant defect annealing occurs during irradiation. This process can be understood if mobile, implantation-induced defects are trapped at preexisting damage and raise the local free energy above that of the amorphous phase.