Stress-induced nanoislands nucleation during growth of Ge/Si heterostructures under low-energy ion irradiation

Stress-induced nucleation of nanoislands under pulsed low-energy ion-beam assisted growth of Si/Ge heterostructures is studied by molecular dynamics and Monte-Carlo calculations. It is shown that cluster of interstitials is produced in Si bulk by an ion impact. Stresses induced at the surface by clusters of interstitials affect migration ability, stimulating nucleation and growth of Ge nanoislands. The main effects of ion-beam action observed in experiments, e.g. increase in islands density, decrease in islands average size and nonmonotonous dependence of islands density upon degree of molecular beam ionization, are interpreted in terms of stress-induced mechanism.