Extended vacancy-type defects in silicon induced at low temperatures by electron irradiation

We have observed the formation of extended defects in silicon at low temperatures (below 25 K) by means of in-situ high-resolution transmission electron microscopy (HRTEM). The defects are distorted spheres, occasionally truncated by facets, less than 5 nm in diameter. These defects are stable up to 773 K, and they gradually shrink during annealing in the temperature range from 773 to 973 K. From the analysis of HRTEM images of the defects, we have suggested that the defects are voids formed via athermal migration of vacancies under electron irradiation.