MicroRaman scattering from polycrystalline CuInS2 films:: structural analysis

CuInS2 thin films co-evaporated with gradual chemical composition have been characterised by MicroRaman scattering measurements. Fur the Cu rich region, the mode Al 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 CuIn5S8 secondary phase contribution in the spectra from the central region of the layers. The correlation of this contribution with the spectral features of the CuInS2 modes suggests a direct relationship between the presence of this In rich secondary phase and disorder at the CuInS2 lattice. (C) 2000 Elsevier Science S.A. All rights reserved.