Ultrathin SnO2 gas sensors fabricated by spray pyrolysis for the detection of humidity and carbon monoxide

A new gas sensor based on ultrathin SnO2-films with high sensitivity for humidity and carbon monoxide has been developed. The SnO2-sensing films are fabricated by a spray pyrolysis process with a thickness between 50 and 100 nm on oxidized silicon substrates. The SnO2-sensing films are finally processed in arrays of parallel bars to achieve the sensor device. The structure of SnO2-layers has been characterized by SEM, AFM and XPS analysis. The sensors are operated at temperatures of 250–400 °C, show high sensitivity to humidity and are able to detect carbon monoxide down to a concentration of less than 5 ppm. The fabrication process of the gas sensor is fully compatible with silicon process technology. The spray pyrolysis technique is a simple and flexible process and thus is suitable for the cost efficient fabrication of a new gas-sensing device. Strategies to improve sensitivity and selectivity of the sensor toward different gas species are discussed.