Isotope effects in thermal release of H and D implanted into WC layers on graphite

Thermal release of H and D implanted into WC layers graphite with 5 keV H2+ and 5 keV D2+ ions has been measured by means of the elastic recoil detection technique. It has been found that the thermal release on isochronal annealing takes place in three stages: the two stages at the lower temperature take place from the two trapping sites in the WC crystallites, and the last stage at the higher temperature from graphite phase segregated in grain boundaries of the WC layers. The isothermal release from the graphite phase has been measured at different temperatures at 350, 450, and 550°C, for H and 450, 550 and 650°C for D, respectively. The isothermal release data have been analyzed by using the mass balance equations and the rate constants involved have been determined by fitting their solution to the experimental data. The thermal desorption spectrum has been theoretically calculated from the solution of the mass balance equations. It has been also found that the calculated thermal desorption spectrum agrees excellently well with the experimental one obtained by Wang et al. in IPP Garching.