In-situ microscopy study of nanocavity shrinkage in Si under on beam irradiation

We report an in situ transmission electron microscopy (TEM) study of nanocavity evolution in amorphous Si (a-Si) under ion beam irradiation. The size evolution of the nanocavities was monitored during ion irradiation with Si or As at various temperatures between 300 and 600 K. A linear decrease of the nanocavity diameter was found as the ion fluence increased; it was much faster than its counterpart in crystalline Si (c-Si). Here, the shrinkage rate depended on the irradiation-induced atomic displacement rate. No significant temperature dependence was observed, confirming that the irradiation-induced nanocavity shrinkage in a-Si is essentially due to ballistic interactions, i.e., differs radically from that in c-Si.