Thermal behavior of In impurities in ZnO

Abstract

Thermally activated association and dissociation behaviors of indium impurities in Zinc oxide (ZnO) were observed on an atomic scale by means of time-differential perturbed angular correlation spectroscopy with the radioactive 111In(→111Cd) probe. We found that In impurities associate in the process of thermal diffusion to form nanoscale clusters in the ZnO matrix under thermal treatment in air, and their structures depend on the concentration of In ions introduced. Heat treatment under vacuum, however, causes dissociation of part of the clusters, suggesting that In ions leave the clusters and migrate into the ZnO matrix. Positron annihilation lifetime spectroscopy performed for the In-doped ZnO also suggests that In ions as impurities migrate into the ZnO matrix by thermal diffusion to settle themselves in Zn vacancies. Dependences of thermal behavior of In impurities on their concentration, treatment temperature, and atmospheric condition are discussed based on the results observed by the nuclear spectroscopic techniques.