The Characterization of Zn_1-XCo_xO Thin Films Synthesized by Ultrasonic Spray Deposition with Controlled Visible Light Absorption

This work examines the grown of Zn_1-xCo_xO films at different Co concentrations at 420°C by ultrasonic spray deposition. The effect of Co concentration of Zn_1-xCo_xO films on optical characterization, structure crystallinity and electrical conductivity was studied. Transmission spectra of Zn_1-xCo_xO films presented three edges in the visible region, it was observed in the range of 541 and 656 nm of wavelengths, which related to the d-d transitions of Co²⁺ ion with 3d⁷ high-spin configurations in a tetrahedral crystal field formed by neighboring O²⁻ions. The gap energy was found increases after doping by Co to maximum value of 3.373 eV at x=0.04. The Urbach energy minimum was 0.083eV, it is obtained for x=0.01. The sprayed Zn_1-xCo_xO films exhibit a wurtzite structure with preferred orientation in the (002) direction. The maximum crystallite size of Zn_1-xCo_xO films was 95.61 nm at x=0.06. The maximum electrical conductivity of the Co doped ZnO films was located at x=0.06.