Oxidation process of polycrystalline InN films were investigated using in situ X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS). The films were grown by dc sputter on sapphire (000 1) substrates and were oxidized in air at elevated temperatures. The XRD data showed that the structure of the films changed to the bixbyite In2O3 (a= 10.11 angstrom) above 450 degrees C. Chemical configurations of the sample surfaces were investigated using high-resolution XPS. For the non-intentionally oxidized InN film, XPS analysis on the In 3d peak and the N Is main peak at 396.4 eV suggests that indium, and nitrogen are bound dominantly in the form of InN. An additional peak observed at 397.4 eV in the N Is photoelectrons and the 0 Is peaks indicate that the InN film surface is partly oxidized to have InOxNy, configuration. After oxidation of the InN film at elevated temperature, the 0 Is spectrum is dominated by In,03 peak, which indicates that the structure is stable chemically with In,03 configuration at least within the XPS probing depth of a few tun. (c) 2006 Elsevier B.V. All rights reserved.