Studies of structural and optical properties of Cu-In-O thin films

We report in this paper the preparation and characterization of Cu–In–O films. The samples were prepared by an annealing at 200 °C for 2 h in vacuum followed by an annealing at 400 °C for 3 h in air atmosphere (sample A) and directly by an annealing at 400 °C for 3 h in air atmosphere (sample B). The films were characterized for their structural, surface morphological, compositional, electrical and optical properties by using X‐ray diffraction (XRD), scanning electron microscopy, electrical conductivity and optical measurement techniques (transmittance and reflectance). The XRD patterns revealed the presence of CuO and In2O3 phases. The absorption coefficients of Cu–In–O thin films in both cases are in the range (104–105) cm–1 and the direct optical band gaps are 3 eV and 3.55 eV for the samples B and A, respectively. The electrical measurements show a conversion from a metallic phase to a semiconductor phase. n‐type conductivity was found for the sample B, whereas the sample A was highly resistive. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)