Influence of nano-scale dopants of Pt, CaO and SiO2, on the alcohol sensing of SnO2 thin films

SnO2 thin films were fabricated, by using radio frequency (RF) sputtering techniques, as gas sensors for monitoring alcohol vapors. The effects of dopants of Pt, SiO2 and CaO on the response to alcohol were investigated. The behavior of the SnO2-based sensors was examined, especially with respect to their sensitivities, responses, recovery ability and reproducibility, which were determined in a flow system. The results showed that the presence of Pt could significantly increase the sensitivity, while SiO2 (1 mol%) was able to significantly improve the stability of the films. CaO (1 mol%) when introduced as a dopant shortened the recovery time of the SnO2 film. The synergistic effect obtained by co-deposition of the dopants was also discussed. Various parameters relating to the RF sputtering deposition process, such as sputtering power, substrate temperature, deposition thickness and operating temperature, were also explored. Crystal structure and surface morphology of the deposited films were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally, the gas sensing mechanism of the deposited films was discussed.