Desorption of O2 from SiO2 films during irradiation of SiO2 with MeV/a.m.u. heavy ions

Abstract Desorption of O 2 accompanies the electronic sputtering during irradiation of SiO 2 films with ∼1 MeV/a.m.u. heavy ions, but contributes only a few% to the total loss of oxygen. After a small desorption from the entire film at the onset of irradiation, the O 2 molecules appear to originate from the top 5–10 nm of the film. We propose as mechanism that the O 2 molecules are produced along the entire ion track but only are able to escape from the material when they are created in the top few nm. For larger depths they get trapped in the oxide network before they reach the surface, except at the onset of irradiation where the concentration of trapping centers might be insignificant. This irradiation induced mobility of oxygen causes Si 16 O 2 /Si 18 O 2 interfaces to be broadened during irradiation, as we have experimentally verified from desorption sputtering depth profiles and glancing angle RBS measurements.