Comparison of CO-gas sensing characteristics between mono- and multi-layer Pt/SnO2 thin films

Sensing characteristics of Pt/SnO2 thin composite films to CO gas were investigated. The composite films were fabricated by rf magnetron sputtering technique. Surface morphology of Pt/SnO2 film was modified to improve its sensitivity to CO gas. The SnO2 films on which Pt was deposited for 12 s showed the maximum sensitivity (Rair/RCO=1.23 to CO gas of 200 ppm) at the sensor operation temperature of 175°C. To increase the sensitivity higher, multi-layer Pt/SnO2 films was suggested in this work. The multi-layer Pt/SnO2 film was prepared by depositing SnO2 and Pt cluster layers again on the mono-layer Pt (12 s)/SnO2 film. Compared with SnO2 films on which only one Pt layer deposited, multi-layer films exhibited remarkable improvement of sensitivity to CO gas (Rair/RCO=1.72 to CO gas of 200 ppm). The increase of the interface area between Pt and SnO2 was reasoned for the superior CO-sensitivity of the multi-layer film.