Vibrational properties of Si/Ge and α-Sn/Ge superlattices with intermixed interfaces

It is found that Raman spectra of Si/Ge and {α}-Sn/Ge[001] superlattices are drastically modified by the introduction of interface intermixing. Some new peaks appear due to intermixing. The calculations clearly show that the peaks around 400 cm^-1 in Si/Ge and 230 cm^-1 in {α}-Sn/Ge superlattices observed in Raman experiments originate from the alloyed layers formed at the interface. It is suggested that relative frequencies and relative intensities of some Raman peaks could be used as a measurement of the composition profiles and the degree of interface perfectness.