Low-temperature-operated sensitive NO2 gas sensors based on p-type SnO thin-film and thin-film transistors

We demonstrated a p-type MOS-based thin-film transistor (TFT) nitrogen dioxide (NO₂) gas sensor that uses tin monoxide (SnO) for both the channel and sensing layers. The fabricated SnO TFT showed a maximum response value of 19.4-10 ppm NO₂ at room temperature (RT) when operated in the subthreshold region, which was significantly higher than the maximum response value of 2.8-10 ppm NO₂ obtained with a SnO thin-film chemiresistor at RT. In addition, the SnO TFT gas sensor showed significantly higher sensitivity to NO₂ gas than to other target gases such as NH3, H₂S, CO₂, and CO at RT. To our knowledge, this is the first report on a p-type MOS-based field-effect transistor-type gas sensor. Our experimental results demonstrate that the p-type SnO TFT is a promising gas sensor that can operate at RT with high sensitivity and selectivity to NO₂ gas.