In2O3 thin films were prepared by the thermal oxidation of amorphous In Se films in air atmosphere. The structure, morphology and composition of the thermal annealed products were characterized by X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive spectroscopy, respectively. The XRD patterns indicate that the as-deposited In Se films were amorphous and they fully transformed into polycrystalline In2O3 films with a cubic crystal structure in the preferential (222) orientation at a temperature around 600 degrees C. The optical energy gap of 3.66 eV was determined at room temperature by transmittance and reflectance measurements using UV-vis-NIR spectroscopy. A preliminary characterization shows that these films have a promising response towards NO2 gas at a working temperature around 180 degrees C. (C) 2011 Elsevier B.V. All rights reserved.