The indium oxynitride (InON) films were achieved by reactive RF magnetron sputtering indium target which has the purity of 99.999% with a novel reactive gas-timing technique. The structural, optical and electrical properties in a series of polycrystalline InON films affected by gas-timing of reactive N-2 and O-2 gases introduced to the chamber were observed. The X-ray photoelectron spectroscopy revealed that the oxygen content in thin films that compounded to indium and nitrogen, which increased from 10% in indium nitride (InN) to 66% in indiumoxide (In2O3) films. The X-ray diffraction peaks show that the phase of deposited. lms changes from InN to InON and to In2O3 with an increasing oxygen timing. The hexagonal structure of InN. lms with predominant (0 0 2) and (0 0 4) orientation was observed when pure nitrogen is only used as sputtering gas, while InON and In2O3 seem to demonstrate body-center cubic polycrystalline structures depending on gas-timing. The surface morphologies investigated from atomic force microscope of deposited films with varying gas-timing of O2: N2 show indifferent. The numerical algorithm method was used to de. ne the optical bandgap of. lms from transmittance results. The increasing oxygen gas-timing affects extremely to the change of crystallinity phase from InN to InON and to In2O3, the increase of optical bandgap from 1.4 to 3.4 eV and the rise of sheet resistance from 15 Omega/square to insulator. (C) 2008 Elsevier B.V. All rights reserved.