CuInS2 and CuGaS2 thin films grown by modulated flux deposition with various Cu contents

Copper indium sulphide and copper gallium sulphide thin films have been prepared using a novel modulated flux deposition process from elemental evaporation sources that were adjusted to give different cation (Cu/In or Cu/Ga) ratios ranging from 0.6 to 1.4. The crystalline structure and optical properties of the samples, as determined by X-ray diffraction and spectrophotometry, have been analysed as a function of the overall composition. Also, the atomic distribution in the film depth has been obtained by combining X-ray photoelectron spectroscopy and Ar+ sputter etching. An increase in copper content leads to an increase of the average crystallite size and a decrease of the structural stress, and an increase of the absorption coefficient at low energies. These effects are more pronounced for the copper gallium sulphide than for the copper indium sulphide samples for the preparation conditions used. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.