Gas sensing performance of the spray deposited Cd-ZnO thin films

Abstract A simple and cost-effective spray pyrolysis technique was employed to deposit undoped and cadmium doped zinc oxide (Cd-ZnO) thin films onto the glass substrates and the deposited films were characterized for their structural, morphological and optical properties. The doping concentration was varied from 1 to 5 at.%. All the films showed the preferred orientation along (0 0 2) plane. However, the (0 0 2) plane was shifted towards the lower 2 θ values after Cd doping. The lattice parameters and texture coefficients were obtained by analyzing the XRD patterns. The band gap energies of the films were decreased with increase in Cd concentration. Moreover, the gas sensing properties of the Cd-ZnO films were investigated towards the reducing gases such as Liquefied petroleum gas (LPG), acetone, ethanol and ammonia. The cadmium dopant plays a vital role in fine tuning the physico-chemical properties and consequently gas sensitivity of the ZnO thin films. The sample with 2 at.% Cd doped ZnO (CZO2) showed the maximum gas sensitivity (87%) towards acetone at 325 °C with faster response and recovery time periods of 6 s and 23 s, respectively.