Vacancy defects in ZnO induced by electron irradiation were characterized by the Doppler broadening of annihilation radiation measurements together with the local density approximation calculations. Zinc vacancies $\left(V_{\mathrm{Zn}}\right)$ are responsible for positron trapping in the as-irradiated state. These are annealed out below $200°\mathrm{C}$. The further annealing at $400°\mathrm{C}$ results in the formation of secondary defects attributed to the complexes composed of zinc vacancies and zinc antisites $(V_{\mathrm{Zn}}-{\mathrm{Zn}}_{\mathrm{O}})$.

• Received 17 February 2008

DOI:https://doi.org/10.1103/PhysRevB.77.113204