Modeling of hydrogen implantation into graphite

Abstract

A new theoretical framework has been developed which is applicable to the implantation and ion-induced release of hydrogen isotopes in graphite. It provides a physical basis and a refinement of the predictions of the simple model of local saturation and mixing. The model treats the trapping at defects and a local release of trapped atoms by nuclear knock-on. Ion deposition and damage functions are taken from trim simulations. The detrapped atoms may become retrapped or recombine to molecules, which then are transported to the surface by fast molecular diffusion, and subsequently released. By the choice of suitable rate constants in the model calculations, different experimental findings for the implantation and high-fluence self-reemission of deuterons in graphite may be explained consistently. Examples cover the saturation as a function of temperature and energy, depth profiles, gas reemission, thermal desorption, and effects of predamage.