Preparation of (002)-oriented ZnO for CO gas sensor

Abstract

In this work, (002) oriented ZnO thin film for carbon monoxide (CO) gas sensing application has been synthesized on the glass substrate using diethanolamine (DEA) as a chelating agent by two-step process. First, the seed layers were formed at a glass substrate using dip coating method, and second, ZnO nanostructure was grown using Chemical Bath Deposition (CBD) at low temperature. The structural and orientation of ZnO films were confirmed using x-ray Diffraction (XRD) while their morphologies and size were analyzed using Scanning Electron Microscopy (SEM). Diffraction pattern showed that the resulting film has wurtzite structure and an extremely sharp (002) peak was found, indicated that the ZnO nanostructure was growth along (002) orientation. The SEM image showed that the (002) oriented ZnO has hexagonal shape nanorods which vertically aligned. It was found that the diameter and length of ZnO nanorods were 71–96 nm and 666 nm, respectively. The gas sensing performance was investigated at various temperatures (160 °C, 200 °C, 250 °C, and 300 °C) and CO gas concentrations (10, 30, 50, 70 and 90 ppm). The results showed that the highest response, 53.25% was obtained at 200 °C toward 90 ppm CO gas. The response and CO gas concentration have a good linearity relationship which indicated that the (002) oriented ZnO has high potential for high sensitive CO gas sensor.