Physico-chemical characterization of spray-deposited CuInS2 thin films

CuInS2 thin films have been deposited by spray pyrolysis. X-Ray diffraction spectra show that a substrate temperature T-s greater than or equal to 590 K with a ratio of the concentration in the pulverized solution of [Cu]/[In] = 1.1 permits well crystallized thin films with a preferential orientation along the (112) direction to be obtained. Scanning electron micrographs of the cross-sectional and top views of the surface show evidence of the good homogeneity of the films. Microprobe analysis as well as X-ray photoelectron spectroscopy show that an almost stoichiometric composition is obtained. In the best films only 3-8 at.% of oxygen is present, which is very promising for such a simple growth technique. Moreover, the oxygen present in the films segregates at the grain boundaries since there is not any significant variation of the interplanar spacing and the optical band gap with the presence of oxygen. The optical band gap values (1.45 eV) increases slightly with the crystalline state. (C) 2001 Elsevier Science B.V. All rights reserved.