Fabrication of transparent conductive zinc oxide films by chemical bath deposition using solutions containing Zn²⁺ and Al³⁺ ions

Abstract

Transparent ZnO films were fabricated on glass substrates by a chemical bath deposition method using zinc acetate solutions also containing AlCl₃. A predominant effect of the Al³⁺ addition seemed to be suppression of the growth of ZnO crystals and change of the crystallographic orientation of ZnO films. The c-axis and the a-axis of the ZnO films came to stand parallel and vertical to the substrate, respectively, by increasing the Al³⁺ concentration. A post ultraviolet irradiation to the films led to a decrease in the sheet resistance from the order of 10⁶ to 10⁴ Ω·sq.⁻¹ without changing the morphology or the crystallinity. This might be related to the photocatalytic effect of ZnO to decompose residual organics in the films and increase the number of carriers. The ZnO film obtained from the solution with 1.0 mol % AlCl₃ showed the lowest sheet resistance of 2.5 × 10⁴ Ω·sq.⁻¹.