Nanocrystal growth of single-phase Si 1−x Ge x alloys

We present the formation of single-phase Si 1− x Ge x ( x =0.2, 0.4, 0.6, and 0.8) alloy nanocrystals dispersed in a SiO 2 matrix. The studied samples were prepared by co-sputtering with excess Si 1− x Ge x in SiO 2 of approximately 33 at%. Upon heat treatment, crystallization of Si 1− x Ge x alloys was examined by using X-ray diffraction and high-resolution transmission electron microscopy measurements. Single structure of face-centered cubic nanocrystals in a space group Fd-3m was concluded. The average nanocrystal size (from 2 nm to 10 nm) and the lattice constant a of the single-phase Si 1− x Ge x nanocrystals were found to increase with the Ge composition parameter x . Density functional theory-generalized gradient approximation calculation showed the replacement of Ge into the Si sites and vice versa.