Indium oxide (In2O3) films were grown on (0001) plane sapphire substrates at 600degC by alternate supply of trimethyl-indium (TMIn) and nitrous oxide (N2O). In some cases, a low-temperature (LT) In2O3 buffer layer, 30 nm in thickness, was employed and annealed at elevated temperature before the final growth of In2O3 at 600degC. Based on the X-ray diffraction (XRD) results and the cross-section transmission electron microscopy (XTEM) and high-resolution transmission electron microscopy (HRTEM) analyses, a typical In2O3 film was found to deposit on the sapphire substrate with its (222) plane being in parallel to the (0001) plane of the substrate. However, there are twin structures inside the In2O3 film with the twin boundaries being alone {11-2} planes. Typically, In2O3 films deposited on LT-In2O3 coated substrates (In2O3/LT-In2O3 structures) exhibited an optical transmittance of ~90% in the visible spectrum.