Si-rich silicon oxide films with thicknesses of about 1.2 mu m were deposited on p-type Si substrates by the RF magnetron sputtering technique. After annealing at different temperatures in a N-2, atmosphere, the photoluminescence spectra of all samples show two main peaks located at about 710 and 800 nm. After gamma-ray irradiation, these two PL peaks increase 3-5 times in intensity. Moreover, a strong new 580 nm peak emerges from the Pt spectra in all samples. The positions of all three Pt peaks do not show any evident shift when the measurement temperature increases from 10 to 300 K. These experimental results can best be explained by the model that photoemission occurs through the luminescence centers, rather than the nanometer silicon particles, in the Si-rich silicon oxide films.