Desorption of O_2 from SiO_2 films during irradiation of SiO_2 with MeV/a.m.u. heavy ions

摘要

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.