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 regio n, 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 c ontribution at about 306 cm(-1). Besides, the mode A(1) is broadened and sh ifted towards higher frequencies, which suggests an inferior structural qua lity of the: Cu poor region. Decreasing the temperature of deposition leads to a dramatic decrease of structural quality in both In and Cu rich region s. The correlation between the appearance of the 306 cm(-1) mode and the sp ectral features of the mode A(1) suggest the higher frequency mode is not r elated to the excess In in the layer but to structural effects as lattice d isorder. 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 seco ndary phase contribution in the spectra from the central region of the laye rs. 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.