Raman scattering in In2Se3 and InSe2 amorphous films

Raman scattering (RS) in both In2Se3 and InSe2 amorphous films has been stu died by micro-Raman in backscattering geometry at room temperature. The 40 mu m thick films were prepared by thermal vacuum deposition onto a borosili cate glass substrate. The In2Se3 amorphous film was stripped off from the s ubstrate. The recorded Raman spectra of both amorphous films reveal a gener al phonon density-of-states character, though some contribution of molecula r-like character in the case of In2Se3 amorphous film is observed. The Rama n spectra of In2Se3 film appear to be related to that of the alpha-In2Se3 c rystal, while those of InSe2 seem to be related to the gamma-In2Se3 crystal . The peaks in the frequency range from the Rayleigh line up to about 240 c m(-1) are attributed to the folding of TA-LA and TO-LO crystal related mode s. The strongest feature at 254 cm(-1) and a shoulder at 235 cm(-1) in the Raman spectrum of In2Se3 film are attributed to Se-8 rings and Se-n polymer molecules, while the one at 490 cm(-1) is assigned to a second order contr ibution. The 150 cm(-1) feature in InSe2 a-film is related to the zone cent er mode of the gamma-In2Se3 crystal. The Raman spectra suggest that the str ucture of In2Se3 film is composed of linked InSe4 tetrahedral clusters with locally distributed Se-n polymer and Se-8 ring molecules. For InSe2, the s tructure of the film seems to be composed of InSe4 clusters linked by Se at oms at the corners shared by two vicinal tetrahedra. (C) 2000 Elsevier Scie nce B.V. All rights reserved.