Investigation of the Doping and Withdrawal Speed Effect on the Properties of sol–gel Dip-coated Cu-Doped ZnO Thin Films

Cu-doped ZnO nanofilms were prepared by sol–gel process using zinc acetate dihydrate, Copper (II) chloride dihydrate as a precursor and ethanol as solvent. The influence of Cu-doping concentration (2 wt%, 5 wt% and 7 wt%) and withdrawal speed of the dip coating process (20, 50 and 100 mm/min) on the structural, morphological and optical properties of the nanofilms have been investigated. The prepared films were characterized by x-ray diffraction (XRD), atomic force microscopy, scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS), and UV–visible. The XRD patterns show the typical hexagonal ZnO in the (002) plane, and the crystallite size of the doped film increases with the doping concentration and withdrawal speed. The SEM images show that the morphological surface of the films was affected by Cu doping. The successful doping of ZnO films with Cu was confirmed by the EDS analysis. The transmittance considerably decreases accompanying increase in the Cu concentration, and increases as the withdrawal speed increases from 20 to 100 mm/min. The optical band gap of pure and Cu-doped ZnO was found to decrease from 3.25 to 3.18 eV as the withdrawal speed increased.