Evolution of surface architectures in sol-gel spin coated multilayered ZnO thin films

Multilayered zinc oxide (ZnO) thin films were successfully deposited by spin coating technique on glass substrates. The number of layers were kept as 5, 10, 15, 20, 25, and 30 and their structural, morphological, elemental, and optical properties were studied. X-ray diffraction (XRD) study confirmed the wurtzite phase. The calculations revealed that the anion-cation bond length increased from 3.79 to 3.91 Å with number of layers. The crystallite size was ∼7–8 nm. Scanning electron microscope (SEM) indicated small cuboidal structure on the surface which led to clustered particles and eventually into a rod-like structures, with the increase in the number of layers. Energy-dispersive X-ray spectroscopy (EDX) revealed information on the elemental composition in which the content of Zn was increased monotonically from 5.5 to 9.9 at.% with increase in layers. Chemical bonds and functional groups were identified using Fourier transform infrared (FTIR) spectroscopy. Additionally, measurements of optical contact angles were performed to evaluate the ZnO thin films' surface wettability which showed that all the thin films were hydrophilic. Comprehensive evolution of properties indicated that spin-coated ZnO thin films can lead to variety of surface architectures, with potential for optical ability.