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

Raman scattering (RS) in amorphous films of In1-xSex with 0.70 greater than or equal to x greater than or equal to 0.38 has been studied in backscatte ring geometry with the use of a single channel Raman spectrometer at room a nd 10 K temperatures. The recorded RS spectra reveal dominant vibrational d ensity-of-states character. They exhibit a continuum, spanning the Rayleigh line up to a shoulder at about 250 cm(-1), that moves towards lower freque ncies 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, Se-8 ring molecules and Se-chai n oscillations, respectively. The structure of In1-xSex alloys is deduced t o be a continuous random network based on InSe4/2 tetrahedral clusters inte rconnected by Se atoms at the shared corners or local Se-chain fragments or Ses rings. With growing In content, some Se atoms in such clusters are rep laced by In atoms to an extent dependent on In content. The disappearance o f 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, ma king conditions favorable for breaking Se polymer chains and Se-8 ring mole cule formation. (C) 2001 Elsevier Science Ltd. All rights reserved.