Defect trapping of ion-implanted deuterium in copper

Abstract

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.