Temperature-tuned reversal of gas response polarity in the detection of C 2 H 2 gas by DC-sputtered WO 3 thin films

Abstract In order to detect toxic gases in application scenarios, there is a requirement for an efficient gas sensor with ultra-sensitive capabilities. This work presents a method that achieves reversible phase transitions in tungsten trioxide by adjusting the operating temperature. This enables n-type tungsten trioxide to exhibit pseudo-p-type gas-sensing responses at low temperatures, which effectively solves the problem of detecting specific gases in gas mixtures. The deposition of WO 3 thin films on ceramic electrode sheets by the DC magnetron sputtering method was the foundation for the gas sensitivity tests conducted at varying operating temperatures. The tests were conducted with a fixed acetylene (C 2 H 2 ) gas concentration of 2 ppm, and the results indicated that the WO 3 thin films exhibited anomalous p-type-like behavior up to 200 °C and n-type behavior above 200 °C for C 2 H 2 gas. The tunable switching of the sensing behavior from p-type-like to n-type allows the WO 3 sensor to accurately identify a specific gas, C 2 H 2 , independent of the relative strength of the response between the target and interfering gases. Furthermore, the sensing behavior of the sensor for C 2 H 2 undergoes a transition from n-type to p-type-like when the operating temperature is reduced from a high to a low temperature. It has been demonstrated that this phenomenon stems from the differing phase transitions of tungsten trioxide at various operating temperatures and the distinct forms of adsorbed oxygen ions on its surface. In this work, the prepared WO 3 thin films have the potential to be applied for the identification and detection of specific gases in a mixture of gases based on a single sensor, which is expected to provide an effective reference for the application of the magnetron sputtering method in gas sensors.