Exploration of optical and frequency dependent electrical properties of boron-cobalt co-doped ZnO thin films

In this work, zinc oxide (ZnO) with boron (B) doped and boron-cobalt (Co) co-doped thin films were prepared by the spray pyrolysis technique. The cobalt concentration was varied from 0 to 4 % to investigate the microstructural, morphological, optical, and frequency dependent electrical properties of the deposited films. The Xray diffraction study confirms the polycrystalline hexagonal wurtzite nature of the films. Upon doping cobalt into the boron-zinc oxide lattice, the crystallite size has been reduced. The SEM investigation revealed the nano-fiber network-like surface morphology of the films. The optical transmittance as well as the optical band gap are also greatly affected by the doping of cobalt. However, 2 % of cobalt doped boron-zinc oxide thin films exhibited a high dielectric constant with low loss factor and high impedance at the starting frequency. Electrical ac conductivity also increased with frequency and upon Co addition. Nyquist plots for all of the thin films were drawn to show the response of the grain core, grain boundary, and electrode resistance, which gradually reduced. Thus, the obtained results ensure the enhancement of the opto-electrical properties of cobalt doped boron-zinc oxide thin films.