Slow positrons were used to study ZnO layers grown on a-axis sapphire and irradiated by 2MeV O+ ions to fluences from 1012 to 1017/cm2. At low fluences Zn vacancies were observed, and their introduction rate was estimated to be 2000/cm. At the highest fluences of 1016 to 1017/cm2, vacancy clusters were formed.

Clusterization of Vacancy Defects in ZnO Irradiated with 2MeV O+. Zubiaga, A., Tuomisto, F., Coleman, V.A., Jagadish, C.: Applied Surface Science, 2008, 255[1], 234-6