Effect of ZnO film thickness on its optical and structural properties

In this study, we report the effect of ZnO film thickness on its optical and structural properties. The sol solution was synthesized by sol-gel method and deposited on silicon substrates by spin coating technique. The ZnO films thickness was varied from 60 to 180 nm. The ZnO films obtained showed a highly preferred orientation along the (002) plane. It was also observed that the crystallite size was not affected by increasing thickness. Transmittance measurements indicated that the ZnO films have a high transparency in the visible range (∼90 %), which remained constant with thickness. Morphological evolution measurements confirmed that the thinner ZnO film consist mostly of a porous layer which became homogeneous and compact to increase the thickness. Photoluminescence measurements exhibit a strong ultraviolet (UV) emission, and the emission intensity was improved with thickness due to crystallinity enhancement.