Formation of Ge-nanocrystals in SiO2 matrix by magnetron sputtering and post-deposition thermal treatment

The 2D GISAXS patterns, besides giving information on the layered structure, were used to reveal the onset of the synthesis of Ge QDs in SiO2 and to determine the average size and shape of QDs. It has been shown that the insertion of spacer SiO2 layers between (Ge+SiO2) layers transforms the 3D growth of Ge QDs into a preferentially 2D growth, within each 7 nm thick (Ge+SiO2) layer. This resulted in a considerably smaller average size of Ge QDs in the layered films. The synthesis of well crystallized, moderately sized, spherical Ge QDs was achieved by post-deposition annealing in the 700-800 ∘C range.