Study of defects in Li-doped ZnO thin films

Li-doped ZnO films were deposited on glass substrate by sol-gel spin coating technique. In order to investigate the effect of Li doping on ZnO thin films properties, we have varied the Li doping ratio in the range of 0-10%. The structural and optical properties of samples have been investigated by X-ray diffraction and UV-Vis spectroscopy. XRD analysis reveals that doped and undoped films have an hexagonal Wurtzite structure. The optical measurements indicate that Li doping causes the red shift of the absorption edge. Films photoluminescence spectra do not contain any defects peak related to Li atoms. Being too close to the valence band, the Li defect level is buried in the band tail width states; this explains the difficulty of its detection. However, the effect of Li doping, manifests through its oxygen vacancy defects promotion to the detriment of oxygen interstitial oxygen defect.