Raman scattering in In 2Se 3 and InSe 2 amorphous films

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Raman scattering (RS) in both In 2Se 3 and InSe 2 amorphous films has been studied by micro-Raman in backscattering geometry at room temperature. The 40 μm thick films were prepared by thermal vacuum deposition onto a borosilicate glass substrate. The In 2Se 3 amorphous film was stripped off from the substrate. The recorded Raman spectra of both amorphous films reveal a general phonon density-of-states character, though some contribution of molecular-like character in the case of In 2Se 3 amorphous film is observed. The Raman spectra of In 2Se 3 film appear to be related to that of the α-In 2Se 3 crystal, while those of InSe 2 seem to be related to the γ-In 2Se 3 crystal. The peaks in the frequency range from the Rayleigh line up to about 240 cm −1 are attributed to the folding of TA–LA and TO–LO crystal related modes. The strongest feature at 254 cm −1 and a shoulder at 235 cm −1 in the Raman spectrum of In 2Se 3 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 contribution. The 150 cm −1 feature in InSe 2 a-film is related to the zone center mode of the γ-In 2Se 3 crystal. The Raman spectra suggest that the structure of In 2Se 3 film is composed of linked InSe 4 tetrahedral clusters with locally distributed Se n polymer and Se 8 ring molecules. For InSe 2, the structure of the film seems to be composed of InSe 4 clusters linked by Se atoms at the corners shared by two vicinal tetrahedra.