Reproducibility evaluation and Al doping of sol–gel-derived single- and multi-layer zinc oxide thin films

Both single- and multi-layer thin films of sol–gel-derived undoped and Al-doped zinc oxide material systems were fabricated for potential use in transparent conducting oxide modules. Functional properties of the resultant films were characterised comparatively. High degree of reproducibility was demonstrated for the characterised properties, with the exception of the electrical conductivity. Influences of Al doping on the characterised properties were also investigated. Al doping reduced the average crystallite size, and led to a denser and less porous morphology, and also caused an increase in transparency in the UV region. Moreover, it was shown that the electrical conductivity of this thin film system could be improved upon either the application of a forming gas process, or Al doping.