Ion beam induced depth profile modification of H, D and He implanted in Be, C and Si

A study has been made of modification induced by ion beam irradiation (350 KeV He, 2.5 MeV He and 2.54 MeV N) on depth profiles of H, D and He implanted in beryllium, Highly Oriented Pyrolytic Graphite (HOPG) glassy carbon and silicon. Desorption rates have been measured as a function of depth. These rates can be related to models predicting activated (detrapped) atom profiles based on local molecular recombination. It is found that molecular recombination between activated atoms is a dominant mechanism for H and D implanted in carbon and beryllium with one important exception. In this case, of high concentration of H implanted in Be, stronger H and D trapping is observed in the vacancy profile. A higher desorption is also found to occur near the surface of crystalline samples. Finally, measured values of detrapping cross sections due to He and N beam bombardment are found to agree with a model which assumes that detrapping is induced by the primary recoils. (C) 1997 Elsevier Science B.V.