Effect of zinc acetate concentration on the structural and optical properties of ZnO thin films deposited by Sol-Gel method

Abstract

The transparent Zinc Oxide (ZnO) thin films were deposited by multi-step sol-gel method and the effect of sol concentration on structural, morphological and optical properties were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize structures and morphologies of the as-deposited films. The crystallographic orientation of the ZnO films shows the preferred orientation of (002) that is along c-axis direction and the films were uniform and well adherent to the substrates. The grain size is in the range of 15.3~19.7 nm and the thickness in the range of 266~295 nm, both increase with zinc acetate concentration. It is found that the transmittance of the films is enhanced from 83 to 95% in the visible near- IR region in the range from 400 to 800 nm by increasing the concentration. The optical band gap energy attenuates from 3.307 to 3.227 eV and whereas the Urbach energies of the films increase from 68.2 to 82.4 meV with increasing the concentration from 0.35 M to 0.65 M. Key words: Sol-Gel method, spin coating, structural properties, optical properties.