Abstract The influence of ion implantation of Ar in defect generation in Si SiO 2 structures is examined by the application of an electroluminescence technique. The nature of the electroluminescence spectra is examined and bands at 1.0, 2.7 and 4.3 eV are identified. Each band is related to different intrinsic defects in the oxide. Structural analysis of the irradiated SiO 2 films, performed with i.r. spectroscopy, points to atomic displacements and broken SiO bonds as the origin of the damage induced by the irradiation.