Formation of germanium nanocrystals in GeO[SiO$_{2}$] and GeO[SiO] films

Films of nonstoichiometric germanosilicate glasses GeO$_{0.5}$[SiO$_{2}$]$_{0.5}$ and GeO$_{0.5}$[SiO]$_{0.5}$ were obtained by co-evaporation of GeO$_2$ and SiO$_2$ or GeO$_2$ and SiO powders, respectively, and by deposition on cold Si (100) and fused quartz substrates in a high vacuum. Then the films were annealed at temperatures up to 900$\circ$C. The presence and phase composition of germanium nanoclusters in the films was investigated using Raman spectroscopy technique. The transformation after annealing of the GeSixOy matrix surrounding the nanoclusters was investigated using Fourier transform infrared spectroscopy. Analysis of the Raman spectra showed that annealing at a temperature of 800$^\circ$C led to the formation of germanium nanocrystals (NC-Ge), but the content of the amorphous germanium phase remains up to half of the volume. Annealing at a temperature of 900$^\circ$C led to almost complete crystallization of amorphous nanoclusters in all films. The sizes of the NC-Ge depended on the annealing temperature, the composition of the films, and on the substrate; in this case, the formation of Ge-Si nanocrystals was not observed.