SURFACE CHARACTERIZATION OF CULNS(2) WITH LAMELLAR MORPHOLOGY

Lamellar crystals of CuInS2 grown in a steep temperature gradient have been characterized. Dispersive x-ray analyses show a predominant stoichiometry Cu/In/S = 1/1/2 and inclusions of Cu deficient phases. The cleaved surface is smooth, but after chemical etching a fine structure appears, with a great number of closely packed microcrystals of a dendritic shape. X-ray diffraction spectra of lamellae only show the reflections of the CuInS2 (112) and of the CuIn5S8 (111) lattice planes, indicating a strongly oriented structure. Depth profiles of CuInS2 lamellae investigated with x-ray photoelectron spectroscopy show the presence at the cleaved surface of Cu deficient phases like CuIn5S8, which are a few tens of nanometers thick. The lamellar growth mechanism is discussed on the basis of these findings. X-ray photoelectron spectroscopy and secondary ion mass spectrometry investigations show that the oxidation behavior of the lamellar material resembles that of traditional CuInX(2) phases (X = S, Se).