O-O Bonding Stabilized Zinc Vacancy as Origin of p-Type Doping on ..sigma..7 ZnO Grain Boundary: Article No. 045708

Using density functional theory calculations, we investigate different defects on ZnO S7 (1230) grain boundary. We find that on this low energy grain boundary, the formation energy of VZn and Oi are drastically reduced by the formation of O-O bonds and VZn has lower formation energy than Oi. Interaction of defects on grain boundary can form new defect bands, and the calculated impurity band maximum is only 0.1 eV below VZn unoccupied levels. Therefore, we believe that the p-type layers observed in experiments near the ZnO grain boundaries can be attributed to VZn.