Interaction of nitrogen with vacancy defects in N+-implanted ZnO studied using a slow positron beam

Abstract

ZnO crystals were implanted with N+, O+, and Al+, and co-implanted with O+∕N+ and Al+∕N+ ions. Positron annihilation measurements indicate introduction of vacancy clusters upon implantation. In the N+-implanted and Al+∕N+ co-implanted samples, these vacancy clusters are only partially annealed at 800°C, as compared with their entire recovery in the O+- and Al+-implanted samples at 800–900°C, suggesting a strong interaction between nitrogen and vacancy clusters. However, in the O+∕N+ co-implanted sample, most vacancy clusters disappear at 800°C. Probably oxygen scavenges nitrogen to enhance the annealing of the vacancy clusters. Upon further annealing at 1000–1100°C, nitrogen also forms stable complexes with thermally generated vacancies. These nitrogen-related vacancy complexes need high-temperature annealing at 1200–1250°C to be fully removed.