Secondary ion mass spectrometry and positron annihilation spectroscopy were applied to study impurity migration and open volume defect evolution in Na+ implanted hydrothermally grown ZnO samples. In contrast to most other elements, the presence of Na tended to decrease the concentration of open volume defects upon annealing and, for temperatures above 600C, Na exhibited trap-limited diffusion correlating with the concentration of Li. A dominating trap for the migrating Na atoms was most likely Li residing on Zn site, but a systematic analysis of the data suggested that zinc vacancies also played an important role in the trapping process.

Defect Evolution and Impurity Migration in Na-Implanted ZnO. Neuvonen, P.T., Vines, L., Venkatachalapathy, V., Zubiaga, A., Tuomisto, F., Hallén, A., Svensson, B.G., Kuznetsov, A.Y.: Physical Review B, 2011, 84[20], 205202