Characterization and doping effects study of high hole concentration Li-doped ZnO thin film prepared by sol-gel method

In this study, lithium-doped p-type ZnO thin film was achieved by applying optimized parameters such as surfactant concentration and annealing temperature in sol-gel method. The stable and reproducible Li-doped ZnO film was characterized by Hall-effect measurement, which revealed high hole concentration of 10(19) cm(-3) order. The conductivity of the ZnO film doped with optimized Li ratio (15 at%) changed from n-type to p-type. To study the effect of lithium doping, we characterized the optical, electrical and structural properties in comparison with undoped ZnO thin film fabricated by the same method. The XRD results show Li-doping could strongly improve the crystal quality and c-axis orientation of low temperature annealed ZnO thin film. The SEM observations confirm the XRD results based on size reduction. The UV-visible spectra of films show high transparency over 95 % in visible region. The PL-spectra obviously revealed that Li dopants substitute in Zn vacancies. And most deep level defects could disappear with Li doping.