The effect of Pb doping on the characteristic properties of spin coated ZnO thin films: Wrinkle structures

Un-doped and lead (Pb) doped ZnO thin films were deposited by sol-gel spin coating technique. Structural, morphological and optical properties of the films were investigated by means of Pb doping, in the range of 1-4% (with 1 at% step). X-ray diffraction results indicated that all films have hexagonal wurtzite crystal structure. (002) Reflection peak has been seen as the most intense peak and the highest texture coefficient value. Grain size values of the films varied from 19.68 nm to 13.37 nm with the increasing Pb incorporation. The top-view and cross sectional scanning electron microscope images demonstrated that the films were made up of wrinkle network structures and the films' thicknesses changed in the range of 400-276 nm. The direct optical band gap was calculated in 3 different functions and a significant harmony was observed among them. Additionally, all results indicated that the direct optical band gap and the Urbach values of the films increase with the increasing Pb doping content. Besides, the effects of Pb content on the photoluminescence properties of ZnO films were evaluated and it was observed that the decrease in the photoluminescence intensity was based on the Pb content. Moreover, the correlation between the optical and structural properties suggested that the optical band gap of Pb doped ZnO films were influenced by the lattice parameters a and c.