Tuning selectivity through cobalt doping in spray pyrolysis deposited ZnO thin films

The effect of cobalt (Co) doping on the structural, morphological, electrical, optical and gas sensing properties of nanostructured ZnO thin film was investigated. The undoped and Co-doped ZnO thin films were deposited on glass substrates at 523 K using spray pyrolysis technique. The Co-doping concentration in ZnO was varied from 0.2 to 1 wt%. From the X-ray diffraction pattern the crystallite size was found to be in the range of 19-25 nm for the undoped and Co-doped films. Also the maximum preferential orientation was found to be along (002) plane for all the samples. Scanning electron micrographs for all the films showed uniformly distributed spherical grains with variable grain size. The optical band gap values were found to be decreased with increase in cobalt concentration. The aroma sensing properties of the undoped and Co-doped ZnO thin films were studied. Doping concentration dependent selectivity towards acetaldehyde and ethanol was observed.