Defect trapping of ion-implanted deuterium in copper

Trapping of ion-implanted deuterium (D) by lattice defects in copper has been studied by ion-beam-analysis techniques. The evolving depth distribution of D was monitored by using the nuclear reaction D (3He, p) 4He, and the D lattice location was obtained by means of ion channeling. Linear-ramp annealing following a 15-keV D+ implantation revealed two annealing stages at 250 and 300 K, respectively, corresponding to trap-binding enthalpies of 0.22 and 0.42 eV, referenced to an untrapped solution site. From a comparison of these results with theoretical calculations based on the effective-medium theory, the 0.42-eV trap has been associated with monovacancies and perhaps small vacancy clusters, an assignment supported by previous positron-annihilation experiments, whereas the 0.22-eV trap tentatively is associated with self-interstitials. The channeling data have been analyzed, utilizing an extended multirow continuum model, and it is found that the data for D trapped to vacancies cannot be interpreted in terms of a single lattice site. This is consistent with the theoretical effective-medium results, which show that D trapped at a vacancy is delocalized with maximum probability between the vacancy and the octahedral interstitial site, consistent with the experimental findings.