$NO_{2}$ Sensing Properties of Oxide Semiconductor Thick Films

The thick films of oxide semiconductors such as , and ZnO for the detection of sub-ppm range have been prepared and their characteristics were investigated. It is showed that the optimum operating temperatures of the sensors are and for -based and -based thick films, and ZnO-based thick films, respectively. Since the resistance of ZnO-based thick films are extremely high(>), the signal to noise ratio was comparatively low. In order to determine the selectivity, the films are exposed to the interfering gases such as ozone, ammonia, methane and the mixture of carbon monoxide and propane. -ZnO(3 wt.%) and (3 wt.%) thick film sensors show high sensitivity, good selectivity, excellent reproducibility and the linearity of concentration versus sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the detection of in sub-ppm range.