Helium-ion-induced release of hydrogen from graphite

The ion-induced release of hydrogen from AXF-5Q graphite was studied for 300- to 500-eV helium ions. The hydrogen was implanted into the graphite with a low energy (≅ 200 eV) and to a high fluence. This achieved a thin (≅ 10 nm),saturated near-surface region. The release of hydrogen was measured as a function of helium fluence. A model that includes ion-induced detrapping, retrapping, and surface recombination was used to analyze the experimental data. The release cross section varied from 1.8x10-16 cm2 at 300 eV to 1.4x10-16 cm2 at 500 eV, while the depletion depth varied from 0.8 nm at 300 eV to 1.2 nm at 500 eV. (orig.)