Ni doping effect on electrical conductivity of ZnO nanocrystalline thin films

The electrical conductivity behavior of undoped and Ni-doped ZnO nanocrystalline thin films prepared by spin-coating method was investigated as a function of temperature. The films were found to have polycrystalline structure. Grain size and the conductivity of the films were found to decrease significantly with increase in Ni concentration. This behavior was well explained by the grain boundary conduction model that takes into account electron trapping in surface states. It was observed that by increasing the Ni-doping level the surface trap density increases and implicitly the conductivity decreases.