CO and NO2 response of tin oxide silicon doped thin films

Research trends of gas sensors based on silicon doped tin oxide semiconducting thin films are presented. The films, deposited by DC and RF sputtering from targets of Sn and Si, are investigated by the volt-amperometric technique for electrical and gas-sensing properties. The layers are capable of sensing CO and NO2, no evidence of surface poisoning is detected, and recovery of the resistance is complete. The response of the sensors is stable and reproducible at all operating temperatures tested (200–500°C). The layers are capable of detecting concentrations as low as 15 ppm of CO and 200 ppb of NO2 with a response time of approximately 2–5 min.