The influence of dopants in ZnO films on defects was investigated by slow positron annihilation technique. The results showed S that parameters meet SAl > Sun > SAg for Al-doped ZnO films, undoped and Ag-doped ZnO films. Zinc vacancies were found in all ZnO films with different dopants. According to S parameter and the same defect type, it could be deduced that the zinc vacancy concentration was the highest in the Al-doped ZnO film, and it was the least in the Ag-doped ZnO film. When Al atoms were doped in the ZnO films grown on silicon substrates, Zn vacancies increase as compared to the undoped and Ag-doped ZnO films. The dopant concentration could determine the position of Fermi level in materials, while defect formation energy of zinc vacancy strongly depended upon the position of Fermi level, so its concentration varies with dopant element and dopant concentration.

Influence of Dopants in ZnO Films on Defects. Peng, C.X., Weng, H.M., Zhang, Y., Ma, X.P., Ye, B.J.: Chinese Physics Letters, 2008, 25[12], 4442-5