Three effects have been observed in wet-thermally grown structures under bombardement with energetic 15N ions: (1) Out-diffusion of H from the SiO2/Si system through the surface, (2) Accumulation of H at the SiO2/Si interface, (3) Changes in the optical fingerprint spectra of Ψ and Δ in dependence on λ (wavelength) obtained by ellipsometric measurements.