X-ray and neutron scattering study of Si-rich Si-Ge single crystals

The local atomic environments of homogeneous Si-rich Si-Ge single crystals were studied using x-ray and neutron diffuse scattering. No evidence of either chemical short-range order or clustering was observed. Static atomic displacements, however, were clearly present and are consistent with an expansion of the lattice in the vicinity of the Ge atoms. The dispersion of the acoustic phonons was also measured using inelastic neutron scattering. The acoustic modes of the Si-Ge alloy were found to lie nearer those of pure Si than expected from the homologous relationship found between pure Si and pure Ge.