Annealing effects on CuInS2 thin films grown on glass substrates by using pulsed laser deposition

Abstract

CuInS2 thin films have been deposited on glass substrates at low temperature by using a self-made ceramic target and the pulsed laser deposition method. Polycrystalline and near-stoichiometric CuInS2 films with a band gap energy of 1.45 eV are obtained by post-annealing/sulfurization at a temperature of 500 °C. X-ray diffraction reveals a highly (112) preferential orientation of the CuInS2 thin films while the Raman spectrum indicates the coexistence of a CuInS2 chalcopyrite phase and CuAu orderings. A polymorphic transformation of metastable CuAu ordering into the equilibrium chalcopyrite structure takes place at a post-annealing temperature of 500 °C with the CuxS phase being segregated at the surface. Further, the morphologies and the chemical states of the films before and after annealing are characterized by atomic force microscopy and X-ray photoelectron spectroscopy, respectively.