Phonons in epitaxially grown α-Sn1−xGex alloys

We present a Raman scattering study of optical phonons in α-Sn1−xGex alloys (x≤0.08) grown by molecular beam epitaxy on CdTe (100) substrates. The Raman spectra provide strong evidence for the growth of high quality films in the diamond-structure phase. The composition dependence of the Raman modes shows some qualitative differences with results from the isomorphic Ge1−xSix system. We show that these differences can be understood in terms of a simple model that considers confinement and strain effects.