Effect of irradiation on the formation of Si nanoclusters from a-SiOx films and their luminescence properties are investigated. 1 mum thick SiOx films with Si content ranging from 33 to 50 at.% and were deposited by electron cyclotron resonance enhanced chemical vapor deposition of SiH4 and O-2. Prior to anneal, some samples were implanted with 380 keV Si to a dose. ranging from 5.74 x 10(14) cm(-2) to 5.74 x 10(16) cm(-2). All films were rapid thermal annealed under flowing Ar environment, and hydrogenated after anneals to passivate defects. For films with Si content less than 40 at.% ion irradiation slightly reduces the PL intensity and induces a. slight blueshift of the luminescence. For films with Si cotent greater than 40 at.%, ion irradiation greatly increases the PL intensity. Based on the effect of the irradiation dose and the ion specie, we rule out chemical effects due to the implanted ions, and propose that irradiation damage greatly accelerates nucleation of small Si clusters from the a-SiOx matrix.