Oxygen diffusion in pure and doped ZnO

Oxygen diffusion coefficients in pure and doped ZnO polycrystals were determined by means of the gas-solid isotope exchange method using the isotope 18O as oxygen tracer. The diffusion experiments were performed from 900 to 1000 C, under an oxygen pressure of 10 exp(5) Pa. After annealing, the 18O diffusion profiles were determined by SIMS. The results of the experiments show that oxygen diffusion in Li-doped ZnO is similar to that in pure ZnO, while in Al-doped ZnO it is enhanced in relation to that observed in pure ZnO, under the same experimental conditions. Based on these results, an interstitial mechanism for oxygen diffusion in ZnO is proposed. Moreover, it was found that oxygen grain boundary diffusion is about 3 to 4 orders of magnitude greater than oxygen volume diffusion in pure and doped ZnO, which means that the grain boundary is a fast path for oxygen diffusion in ZnO. 13 refs.