Temperature dependence of Raman scattering in amorphous films of In1−xSex alloys

Raman scattering (RS) in amorphous films of In1−xSex with 0.70≥x≥0.38 has been studied in backscattering geometry with the use of a single channel Raman spectrometer at room and 10 K temperatures. The recorded RS spectra reveal dominant vibrational density-of-states character. They exhibit a continuum, spanning the Rayleigh line up to a shoulder at about 250 cm−1, that moves towards lower frequencies as x decreases from 0.70 to 0.38. The bands at about 104, 125 and at 143 and 237 cm−1 are attributed to In–In, Se8 ring molecules and Se-chain oscillations, respectively. The structure of In1−xSex alloys is deduced to be a continuous random network based on InSe4/2 tetrahedral clusters interconnected by Se atoms at the shared corners or local Se-chain fragments or Se8 rings. With growing In content, some Se atoms in such clusters are replaced by In atoms to an extent dependent on In content. The disappearance of the 143 and 237 cm−1 bands in the low temperature spectra taken on the In0.30Se0.70 film is attributed to the contraction of interatomic bonds, making conditions favorable for breaking Se polymer chains and Se8 ring molecule formation.