Effects of hydrothermal annealing on characteristics of CuInS2 thin films by SILAR method

CuInS2 thin films have been deposited by successive ionic layer absorption and reaction (SILAR) method, then annealed in a Na2S solution (denoted as hydrothermal annealing) at 200 °C for different time. The effect of hydrothermal annealing on the properties of the films was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and optical absorption spectroscopy. The XRD, TEM and SEM results indicate that well-crystallized CuInS2 films could be obtained after annealing in 0.1 mol/L Na2S solution for 1.5 h. The annealed CuInS2 films were slightly S-rich and the direct band gap varied from 1.32 to 1.58 eV as the annealing time increased from 0.5 h to 2 h.