Self-organization of an ensemble of Ge nanoclusters upon pulsed irradiation with low-energy ions during heteroepitaxy on Si

Size distribution of Ge islands formed in the course of Ge heteroepitaxy on Si(111) was studied by scanning tunneling microscopy in experiments of two types: (i) conventional molecular beam epitaxy (MBE) and (ii) pulsed ($0.5$ s) irradiation with Ge ions of energy $\simeq 200\,$ eV at instants of time corresponding to a filling degree $>0.5$ for each monolayer. Experiments were performed at a temperature of $350^\circ\,$ C. The pulsed ion-beam irradiation during heteroepitaxy leads to a decrease in the average size of Ge islands, an increase in their concentration, and a decrease in the root-mean-square deviation from the mean, as compared to the analogous values in conventional MBE experiments.