Gas Sensing Performance of Hydrothermally Produced ZnO Nanostructures Based on Dip-Coated Seed Layers with Different Dipping Cycles

Abstract

It is admitted that synthesis methods and their relative parameters have a crucial effect on the size of the produced nanoparticles, surface area/volume ratio, porosity as well as defects in the film which in turn affect the morphology and thus the ultimate performance of the fabricated gas sensor. In this study, ZnO films were synthesized for gas sensing applications using a hydrothermal technique based on dip-coated seed layers with different number of dipping cycles. The effect of the number of dipping cycles in seed layers on the structural, morphological and gas sensing properties of the hydrothermally synthesized ZnO films was investigated respectively using X-ray diffraction patterns, scanning electron microscope images and gas sensing measurements. The increase in the number of dipping cycles deteriorated the crystal quality of the subsequent hydrothermal growth and adversely affected the gas sensing performance of the produced films. Actually, the increment in the number of dipping cycles caused a decrease in the sensitivity of the sensors at all investigated operating temperatures and for all investigated gas concentrations. The structural and morphological variations that happened due to the number of dipping cycles in the seed layers were correlated with the gas sensing properties of the produced films for a better comprehensive understanding.