Oxygen ion-induced detrapping of hydrogen retained in graphite

The ion-induced re-emission of hydrogen isotopes (H and D) from graphite has been studied at room temperature with high energies of 2.0-4.8 MeV oxygen ions (O+) which penetrate through the H and D implanted region. The concentrations of H and D remaining in graphite during the ion bombardment were measured by an elastic recoil detection (ERD) technique using O+ ions. The re-emission rates of H and D from graphite increase with increasing the incident energy of the O+ ion bombardment. The re-emission rate of H at low O+ ion fluence is larger than that of D. The O+ ion-induced detrapping cross-sections evaluated from mass balance equations for H and D are independent of the incident energy and have no isotope effect. The results indicate that the electron excitation by the O+ ion bombardment in the incident energy range of MeV plays an important roll for the detrapping of H and D. (C) 2003 Elsevier B.V. All rights reserved.