Atomic level control of association-dissociation behavior of In impurities in polycrystalline ZnO

In the present work, we have succeeded in controlling association-dissociation process of thermally activated In impurities introduced in polycrystalline ZnO by a multistep doping method. The thermal behavior and eventual residential sites of In ions were monitored on an atomic scale by means of time-differential perturbed angular correlation spectroscopy with the In-111(-> Cd-111) probe. The present doping method of combined heat treatments in air and in vacuum enabled the introduction of a great fraction of 0.5 at.% In donors into defect-free substitutional Zn sites. It was demonstrated that the In-containing ZnO samples show a clear positive correlation between the electrical conductivity and the concentration of In donors at substitutional Zn sites, achieving a conductivity as high as five orders of magnitude compared with undoped ZnO.