Effect of F-doping on structural, electrical, and optical properties of ZnO thin films for optoelectronic application

In this work, Fluorine doped Zinc oxide (FZO) thin films were deposited by the sol-gel spin coating method. Zinc acetate dihydrate, ethanol and mono-ethanolamine were used as precursor, solvent and stabilizer, respectively. The atomic percentages of dopant in solution were [F/Zn]=1%,2%, 4% and 6%. The effect of F doping on the structural, optical and electrical properties of ZnO films were investigated by X-ray diffraction (XRD), Four-Point probe technique and UV-visible spectrophotometery. The results from the X-ray diffraction show that the pure ZnO thin films have polycrystalline structure, hexagonal wurtzite type. All the films have a highly preferential c-axis orientation, and exhibited (002) plane as a preferential growth in all the dopant ratios. Grain sizes of the films were varied in range of 36.5 to 46.2 nm. The optical transmission is decreased with the increase of the dopant concentration. The band gap energy values were determined as 3.252 eV, 3.267 eV, 3.295 eV, 2.299 eV and 3.315 eV, respectively for undoped ZnO, 1, 2, 4 and 6% mole FZO thin films. A minimum resistivity of FZO (2.72 *10
⁻³
) was obtained for the film doped with 29% mol of F. These results make FZO thin films an attractive candidate for transparent and electric material applications.