Ge-nanocrystal-embedded SiO2 films were fabricated by Ge+ implantation into SiO2 films thermally grown on crystalline Si wafers, and were examined by Fourier transform infrared absorption spectroscopy, Raman spectroscopy, and X-ray photoemission spectroscopy. Due to Ge+ ion implantation, the SiO2 film moved off stoichiometry, and there were Ge oxides formed in it. The precipitation and growth of Ge nanocrystals (nc-Ge) were found to be related to some thermodynamical reductions of the Ge oxides during annealing. The average size of nc-Ge increases from similar to 3 nm to similar to 6 nm when the annealing temperature increase's from 400 degrees C to 1100 degrees C.