Three effects have been observed in wet-thermally grown SiO 2 Si structures under bombardement with energetic 15N ions: 1. (1) Out-diffusion of H from the SiO 2 Si system through the surface, 2. (2) Accumulation of H at the SiO 2 Si interface, 3. (3) Changes in the optical fingerprint spectra of Ψ and Δ in dependence on λ (wavelength) obtained by ellipsometric measurements.