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.

Thermal activation of nitrogen acceptors in ZnO thin films grown by MOCVD

“…Positron annihilation spectroscopy (PAS) suggested the existence of N O -V Zn complexes in N + -implanted ZnO crystals. This complex was stable even above 1000 °C [22]. Such a complex between N O and V Zn , would agree with the involvement of N O in the transition at ∼3.1 eV, reported by Georgobiani et al [18], as well as the participation of V Zn in the same transition as reported in [20] and [21].…”

Raman investigation of incident N-, Xe-ions induced effects in ZnO thin films

“…Compared to the silicon substrate and the as-deposited ZnO samples, the noteworthy differences are the appearances of new Raman peaks in the ZnO samples after N-or Xe-ions bombardments: It was reported that the Raman mode at about 578 cm À1 may originate from defects related phonon mode [12], O-vacancies related stable complexes [13], or from the disorder-activated B 1 (high) silent mode [14] of w-ZnO. Considering that there are defects could only be introduced in the samples under 308 MeV Xe-ions irradiation, the observed peak at about 578 cm À1 (P 1 ) may originate from the defects or disorder phase produced in the samples.…”

Nitrogen and vacancy clusters in ZnO

“…This is seen in both undoped and Al/Ga-doped thin films 21,[26][27][28] as well as in studies in bulk crystals. [10][11][12]22,25 Clusters of vacancies in ZnO have been observed mainly in implantation studies 4,23,[29][30][31][32][33][34][35][36][37][38] and also after heavy irradiation. 21 These vacancy clusters have been shown to disappear (become unstable) in thermal treatments at temperatures of about 800°C, with a single exception: the N-implantation damage is stable up to at least 1000°C in ZnO.…”