Electrical and optical characterization of Cd x Zn s thin films deposited by chemical bath deposition in alkaline conditions

Abstract

In this work ternary CdZnS thin films were prepared by chemical bath deposition by doping CdS with different concentrations of Zn ions. The chemical bath comprised of cadmium nitrate [Cd(NO₃)₂], as a source of Cd^2+, zinc nitrate [ZnNO₃)₂]as source of Zn²⁺, thiourea [(NH2)₂CS] as a source of sulphide ions [S^2-]in the presence of ammonia [NH₃] as a complexing agent. The competition mechanisms of Cd²⁺ and Zn⁺² with the complexing agent [NH₃] to form complex ions usually plays a critical role in the formation of Cd_xZn_1-xS thin films and therefore the influence of Zn²⁺ on the formation mechanisms of the Cd_xZn_1-xS was discussed. Optical and electrical properties of these samples were analysed. Parameters like band gap (E_g), extinction coefficient (k), absorption coefficient (α), dielectric constant (ε), refractive index, (n)and resistivity (ρ) were calculated using the data obtained from different measurements. Optical band gap tunability of the deposited films for various Zn²⁺ concentrations was successfully demonstrated by UV-VIS-NIR spectroscopy. Transmittance inCd_xZn_1-xSwas found to be above 80%, optical band gap of 2.47-2.72 eV, refractive index of 2.58 “ 2.39, and sheet resistivity of 1.09“ 1.36 × 10² Ω-cm for x = 1.0 “ 0.6.