Optical, structural and surface analysis of ZnO thin films prepared by SILAR method

Abstract

ZnO t is a hexagonal wurtzite semi conducting material, which finds numerous applications in the modern world. In thin film form ZnO shows unique properties such as high surface to volume ratio, piezo electric properties etc. Due to these mentioned properties ZnO thin films are considered as one of the most important material base for sensor applications. The unique property of ZnO thin films as the change in resistance and conductivity of the films on exposure to gases and bio materials are employed in thin film sensors. The performance of the sensing materials will depend up on the method of synthesis, crystal structure and morphology of the samples. So structural and morphological identifications of the samples are essential before any sensor application. Hence the current work was done with two stages. In the first stage ZnO thin films were synthesized from 0.05M and 0.1M precursor medium using 50 dip cycles of SILAR method. Thus prepared samples were annealed for 350°C for two hours. Obtained films were investigated with UV-Visible, XRD and SEM analysis. Transmittance and absorption spectrum of samples were compared. The transmittance for 0.05M sample was found to be more, where as absorbance of 0.1M sample was more. Comparing with standard data XRD peaks were identified for each samples. From the comparative intensity study of XRD peaks, 0.1M sample was observed to be more crystalline. From the observed h,k,l values lattice parameters of each samples were determined and were reported. Values were found to be comparable with literature values which confirm the hexagonal structure of ZnO. Crystallite sizes were determined using Scherer formula and it was found to be comparable for each samples. The SEM images revealed the morphology of the samples. It infers that surface roughness was more for 0.1M sample. It reveals a direct dependence of absorbance and surface morphology of the samples analysed.