Raman spectroscopy of amorphous Ge/SiOx superlattices

Raman spectroscopic studies have been performed on a series of vacuum evaporated amorphous Ge/SiOx superlattice films with germanium layer thicknesses between 8 and 200 Å and silicon oxide layer thicknesses between 12 and 300 Å. The results show the presence of a Gey (SiOx )1−y interface alloy of thickness (0.7±0.2) nm and average composition of y∼0.35. This alloy region is identified as the residence of the observed germanium bond angle disorder, leaving the pure germanium layers in the superlattices essentially undistorted from the bulk a-Ge structure.