Diffusion of Li into ZnO from a so-called infinite surface source under oxygen-rich conditions was studied using secondary ion mass spectrometry. The Li concentration versus depth profiles exhibited a distinct and sharp drop, which evolved in position with temperature and time. The sharp drop was associated with an efficient conversion from highly mobile Li-interstitials (Lii) to practically immobile Li-substitutionals (LiZn) via a kick-out mechanism. The characteristic concentration level at which Li drops provides a measure of the active donor concentration in the samples at the processing temperature, and furnished evidence of residual impurities being responsible for the commonly observed “native” n-type conductivity. These donors were suggested to arise from different impurities, with Al and Si as the prevailing ones in hydrothermal and melt grown material. Further, evidence of electric field effects on Li diffusion profiles was obtained, and they were considered as a main reason for the slow diffusivity obtained here (using O-rich conditions) relative to those previously reported in the literature (obtained under Zn-rich conditions).

Diffusion and Configuration of Li in ZnO. Knutsen, K.E., Johansen, K.M., Neuvonen, P.T., Svensson, B.G., Kuznetsov, A.Y.: Journal of Applied Physics, 2013, 113[2], 023702