Preparation of stoichiometric CuInS2 surfaces

Thin films of KCN-etched CuInS2 surfaces during an annealing procedure are investigated by photoelectron spectroscopy and scanning electron microscopy, combined with energy dispersive X-ray analysis. A significant deviation from stoichiometric composition and the formation of Cu-poor phases after etching is well known. Because of the ternary system the polycrystalline absorber layer need to be characterised in terms of the CuInS2 monophase, homogeneous elemental distribution or the size of the polycrystalline grains. Here, we present the effect of a heat treatment of samples etched with KCN, a procedure, which leads to surfaces of CuInS2 with almost ideal elemental composition