Synthesis and Characterization of ZnO Nanoparticles for Chemiresistive Ammonia Vapor Sensor

Zinc oxide (ZnO) thin films with various concentrations were deposited onto glass substrates by using the spray pyrolysis technique at 230oC substrate temperature. Structural, optical and morphological studies of the samples were characterized using XRD, UV-Vis-NIR spectroscopy, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) respectively. The X-ray diffraction analysis reveals the hexagonal wurtzite structure of the ZnO thin films. An increase in crystal size and roughness with increase in concentration of the precursor solution is observed from the AFM studies. The morphological studies reveal that all samples are polycrystalline in nature. The optical study implies that the absorbance increased with increasing molar concentration. The ZnO films showed high transparency nearly 80% in the visible and NIR regions at lower concentrations and the band gap values are found to be in the range of 3.25 eV to 3.32 eV. A high sensitivity for NH3 was obtained for the ZnO film at 0.1 M. The sensing response of 0.1M ZnO sample towards NH3 vapor has been investigated at different vapor concentrations at 300oC temperature.