Specific features of the ion-beam synthesis of Ge nanocrystals in SiO₂ thin films

The systematic features of the formation of Ge nanocrystals in SiO₂ thin films implanted with Ge⁺ ions and then subjected to high-temperature annealing (1130°C) are studied in relation to hydrostatic pressure. It is established that annealing at atmospheric pressure is accompanied by the diffusion of Ge atoms from the implantation region to the Si substrate and does not induce the formation of Ge nanocrystals. An increase in pressure during annealing yields a deceleration in the diffusion of germanium into silicon and is accompanied by the formation of twinned lamellae at the Si/SiO₂ interface (at pressures of ~10³ bar) or by the nucleation and growth of Ge nanocrystals (at pressures of ~10⁴ bar) in the SiO₂ film. The results are discussed on the basis of the concept of a change in the activation volume of the formation and migration of point defects under conditions of compression.