Bias dependent NO2 sensitivity of SnO2 thin films at room temperature

Amorphous granular SnO2 thin films were investigated from a standpoint of an NO2 gas sensor working at room temperature. The films were deposited using pulsed laser deposition method with substrate at room temperature and ∼90 nm thick SnO2 films with amorphous structure were obtained as a result. SnO2 films deposited on Pt electrode substrates formed a sensor structure that showed response Iair/Igas to 4 ppm NO2 up to ∼8000. I–V characteristics of the sensor structure were described by the power law dependence, whereas the power indexes were different for measurements in pure air and in the presence of NO2. As a result, the sensor response was highly dependent on bias voltage between the sensor electrodes. It was demonstrated that the nonlinear electrical characteristics and bias dependent gas sensitivity were the inherent properties of thin films and the contacts were ohmic.