Hydrogen mobility under beam impact when using the 1H(15H,αγ) nuclear reaction for material analysis

Systematic or specific mobility of hydrogen atoms at the surface or within the depth of solid samples occurs during the bombardment of high energy heavy ions used for nuclear reaction analysis of hydrogen. Our study, dealing with 15N ions of energy >= 6,4 MeV, points out for the first case that chemical phenomena like adsorption radiolysis and desorption give a coherent picture of the hydrogen evolution. Related coefficients can be extracted from the experimental curves. In-depth mobility has been investigated specifically for (a) Si:H thin films prepared by rf sputtering and contaminated with oxygen. We show that = SIOH or -SIOH2 species are the most susceptible to lead to hydrogen release through dissociation and interaction mechanisms. A phenomenological model is presented. Consequences for hydrogen determination using nuclear reactions are discussed. (orig./HSI)