Effects of Ag-induced acceptor defects on the band gap tuning and conductivity of Li:ZnO films

The effects of Ag-induced acceptor defects on the band gap tuning and conductivity of Li:ZnO film grown by the sol-gel method were investigated. The structural analyses indicate that the Ag-Li:ZnO films possess hexagonal structure with the substitutional Ag defect at the Zn site (Ag-Zn) and the interstitial Li defect (Li-i). The decreased film transmittance and band gap with Ag-Li codoping is mainly due to the incorporation of foreign impurity levels by the Ag-Zn and Li-i defects. The electrical measurements reveal that doping can obviously improve the film conductivity, which could be attributed to the reduction of the grain boundary scattering and the inter-diffusion of the Ag nanoparticles, as well as the decreased ionization energy of the acceptor owing to the Ag-Zn defects. The electronic structures of Ag-Li:ZnO were further studied by the first-principles calculations and the results show that the Ag-Zn defects may lead to p-type conductivity of ZnO. (C) 2013 AIP Publishing LLC.