Nanocrystal growth of single-phase Si1−xGex alloys

•Single-phase FCC structure of Si1−xGex alloy nanocrystals formed.•The average size (2–10 nm) and lattice constant increased with Ge composition.•DFT-GGA calculation demonstrated the replacement of Ge into the Si sites.

We present the formation of single-phase Si1−xGex (x=0.2, 0.4, 0.6, and 0.8) alloy nanocrystals dispersed in a SiO2 matrix. The studied samples were prepared by co-sputtering with excess Si1−xGex in SiO2 of approximately 33 at%. Upon heat treatment, crystallization of Si1−xGex 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 Si1−xGex 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.