Effect of Precursor Concentration on Structural, Morphological, and Optical Properties of ZnO Thin-Filmed Sensor for Ethanol Detection

Abstract

Zinc Oxide (ZnO) nanostructured thin films with precursor concentration variation of 0.025 M (1Z), 0.075 M (2Z), and 0.125 M (3Z) were fabricated on fluorine-doped tin oxide glass substrates using a simple hydrothermal technique. X-ray diffraction confirmed Wurtzite hexagonal structure of ZnO. Changes in the lattice constant in accordance with the variation in precursor concentrations were observed. It was manifested by bond length, unit cell volume, micro strain, and dislocation density. Optical band gap, diameter, and photoluminance peak intensity ratios of each sensor were determined. The field emitting scanning electron microscope image of 1Z, 2Z, and 3Z sensors revealed massive changes in the morphology of the nanostructures grown on the substrate. The ethanol sensing behavior of ZnO thin-film sensors toward different ethanol concentration under varied operating temperatures were experimented and recorded. The results demonstrated highest sensitivity of 58.5% by 1Z sensor with response and recovery time of 40 and 45 s, respectively. Particularly, 2Z sensor outperformed other two sensors with a fast response time and quick recovery time of 25 and 15 s, respectively, with moderate sensitivity.