Effect of Spinrate on the Structural, Optical and Surface Properties of the Sol-Gel Spin Coated Zinc Oxide Thin Films

Abstract

Zinc Oxide thin films have been deposited on glass substrates at different spin rate by sol-gel spin coating method. XRD measurement of the ZnO films confirms the Wurtzite hexagonal phase with the preferred orientation along the C-axis (002) plane. The other characteristic orientations (100) and (101) have also been observed. The average crystallite size evaluated from the XRD data lies between 5 nm and 20 nm. The crystallographic parameters viz., lattice constants, mean crystalline size, dislocation density, texture coefficient and standard deviation have been calculated from the XRD data. The estimated texture coefficient indicates the oriented overgrowth of (002) plane for the ZnO films spin coated up to the spin rate 3500 rpm. ZnO thinfilm spin coated at 4000 rpm and 3500 rpm shows maximum transmittance of 87.5% and 88.5 % respectively at 850 nm. The measured direct band gap energy of the ZnO films coated at different spin rates varies between 3 eV and 3.3 eV. The grain size observed from the microstructure of AFM is around 50 nm and this indicates the aggregation of nanosize cryatallites. The effect of spin rate on the structural, optical and surface properties of the spin coated ZnO thinfilms have been investigated and reported.