Helium-ion-induced release of hydrogen from graphite

The ion-induced release of hydrogen from AXF-5Q graphite was studied for 350-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. A value of (1.65 +- 0.2) x 10-16 cm2 was obtained for the detrapping cross section, and a value of (0.5--4) x 10-14 cm4 s was obtained for the recombination coefficient