Sensing characteristics of ZnO-based NOx sensor

Sensing characteristics of ZnO-based sputtered films are studied. The film about 140 nm thick showed high sensitivity to NOx and selectivity against H2 and CO. The sputtering pressure greatly affected the sensitivity, and the sensitivity maximum was observed at 0.67 Pa. The effect of element doping into ZnO on sensitivity and selectivity to NOx was also studied using co-sputtering technique. Rare earth element doping improved sensitivity and selectivity to NO2 against NO. Er-doped ZnO film had good selectivity and fast response time to NO2 above 200°C, and almost linear sensitivity dependence in the sub-ppm concentration range of NO2.