AMS depth profiling of humidity in silica

Depth profiling measurements of light elements have been performed at the Forschungszentrum Rossendorf using an AMS facility at the 3 MV Tandetron. This facility is equipped with a simple arrangement for mechanical scanning of the sample inside a commercial sputter source and with a conventional detection system. After measurements of depth profiles of tritium in carbon samples from fusion experiments this AMS facility has been applied to depth profiling of humidity penetrated into as-implanted SiO2 layers. For this aim, Ge+ and Si+ ion implanted SiO2 layers (1014-1016 cm-2) were exposed to an artificial atmosphere with H218O humidity. AMS allows the discrimination of isobar atomic and molecular ions, thus depth profiles of 18O- and (18OH)- molecular ions could be investigated. By measuring 18O4+ or H+ species of these ions, the process of humidity penetration in as-implanted SiO2 has been studied