SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE Co-DOPED ZnO THIN FILMS PREPARED BY CHEMICAL SPRAY PYROLYSIS FOR OPTOELECTRONIC APPLICATIONS

ZnO:Co thin films were synthesized by the chemical spray pyrolysis (CSP) on glass substrates. Then, investigated the impact of Co doping concentration on its physical properties. XRD analyses show that all films have a polycrystalline structure of hexagonal ZnO. The crystallite size increased from 18nm to 25nm with Co doping concentrations. Furthermore, the unit cell volume increased from 47.485Å to 47.831Å, and the Zn–O bond length expanded from 1.97588Å to 1.98071Å. SEM observations reveal the formation of fiber-like nanostructures in the Co-doped thin films. The diameter of nanofibers increased with Co doping concentration from 260nm to 700nm. The optical characteristics were studied by the UV-Visible spectrophotometer and manifest the optical transparency vary with Co doping. In addition, the band gap decreases from 3.27eV to 2.73eV with increasing Co doping concentrations. The conductivity varied from 3.35S⋅m−1 to 19.88S⋅m−1 with Co doping concentrations. Empirical models were proposed to evaluate the correlated variables with excellent accuracy with the experimental data. The best result was accomplished in ZnO:Co1% films, where good transparency and high conductivity were achieved.