Effect of anionic fluorine incorporation on structural, optical and electrical properties of ZnO nanocrystalline films

Abstract

ZnO and ZnO:F (fluorine doped Zinc oxide) films have been deposited on glass substrates at 325 ± 5 °C through ultrasonic spray pyrolysis method (USP). X-ray diffractometer (XRD) has been utilized to determine the crystal structural and some structural parameters such as lattice constants, texture coefficients TC (hkl), crystallite size and dislocation densities of all the ZnO films. The XRD results have revealed that all the ZnO films have the hexagonal wurtzite structure and F incorporation shows no significant effect on the crystal structure. X-ray photoelectron spectroscopy (XPS) measurements have confirmed the presence of fluorine atoms in the ZnO lattice and also the existence of Zn–F bonding states. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements have been carried out to investigate the effect of F doping on the surface morphology of the ZnO films. The optical properties of the films have been analyzed by utilizing transmittance, absorbance and reflectance measurements. Some optical parameters such as extinction coefficient (k), refractive index (n) and optical conductivity have been determined depending on the change in F incorporation. Increasing the F doping initially led to a decrease in the optical band gap, but later increased. Electrical resistivity and carrier concentration values of the deposited films have been determined with Hall effect measurement system and it has been detected that 6% F-doped ZnO film has the minimum resistivity and maximum carrier concentration.