Determination of electrical conduction properties of Ni doped ZnO nanocrystalline films

In this work, the electrical conductivity behavior of undoped and Ni-doped ZnO nanocrystalline thin films prepared by spin-coating method was investigated as a function of tempereture. XRD and XPS studies evidenced that Ni entered in ZnO lattice as Ni+2 and also as Ni+3. The films were found to have polycrystalline structure. It was determined that lattice parameters and grain sizes of the films decrease but the defects in lattice increas with the higher percentage of Ni in ZnO. Also, the electrical conductivity of the films decreases with the Ni concentration increases. The observed behavior was well explained by the grain boundary conduction model that takes into account electron trapping in surface sites. It was observed that by increasing the Ni-doping level the surface trap density increases and implicitly the conductivity decreases.