Microroughness and composition of cyanide-treated CuInS2

The effect of KCN etching on morphology and stoichiometry of polycrystalline and single crystalline CuInS2 surfaces was investigated. The changes of the morphology were observed by in situ and ex situ studies using atomic force microscopy (AFM). The in situ investigations of the Cu-rich grown polycrystalline samples were interrupted several times in order to follow the process of CuS dissolution. Quantitative evaluation of the AFM images allowed us to determine the roughness before and after the treatment. While single crystalline samples were strongly attacked by the KCN solution, the polycrystalline CuInS2 was subjected to roughening only after prolonged etching treatments. The composition of the CuInS2 surface was examined by ex situ X-ray photoelectron spectroscopy. By a depth profiling of the copper-to-indium ratio, it was found that the etching process results in an indium-rich composition of the surface. Furthermore, the chemical reactions leading to CuS and CuInS2 dissolution are discussed. (C) 2001 The Electrochemical Society.