Structural, Electrical and Optical Characterization of ZnO:Li Thin Films Prepared by Sol-Gel Spin Coating

Li-doped ZnO thin films prepared by sol-gel spin coating method, have been studied in this research to increase the p-type ZnO layers conductivity. For this purpose, the lithium dopant concentration was changed and structural, electrical, and opti-cal properties of the layers were investigated. For structural analysis, XRD and FESEM were used. Besides, thin films electri-cal properties including resistivity and majority carriers’ type were determined. Eventually, optical properties were studied by UV-Visible and PL spectroscopy. Structural investigations showed that the single phase layers with wurtzite hexagonal structure and 40-50 nm average grain size were formed. For obtaining p-type layers and enhancing their electrical conductiv-ity, there was an optimum in moderate Li concentrations. Furthermore, regarding the optical properties, it was concluded that the band gap energy is sensitive to Li concentration and the refractive index of ZnO layer decreased with Li doping. Fi-nally, the effect of Li doping was further studied by DFT calculation. These calculations propose activation of a self-compensation mechanism by Li doping which can be responsible for decrease of the conductivity at high Li concentra-tions. In the proposed mechanism, Zni donor defect sites, accompanying LiZn sites, cause self-compensation.