MicroRaman scattering from polycrystalline CuInS 2 films: structural analysis

Abstract CuInS 2 thin films co-evaporated with gradual chemical composition have been characterised by MicroRaman scattering measurements. For the Cu rich region, the mode A 1 at about 290 cm −1 corresponding to the chalcopyrite phase is dominant. For the Cu poor region, this mode is accompanied by a strong contribution at about 306 cm −1 . Besides, the mode A 1 is broadened and shifted towards higher frequencies, which suggests an inferior structural quality of the Cu poor region. Decreasing the temperature of deposition leads to a dramatic decrease of structural quality in both In and Cu rich regions. The correlation between the appearance of the 306 cm −1 mode and the spectral features of the mode A 1 suggest the higher frequency mode is not related to the excess In in the layer but to structural effects as lattice disorder. Combined in-depth Auger electron spectroscopy and Raman scattering measurements have also shown the presence of a more complex structure for the Cu poor region of the layers, which presents a significant CuIn 5 S 8 secondary phase contribution in the spectra from the central region of the layers. The correlation of this contribution with the spectral features of the CuInS 2 modes suggests a direct relationship between the presence of this In rich secondary phase and disorder at the CuInS 2 lattice.