A MEMS-based Benzene Gas Sensor with a Self-heating WO(3) Sensing Layer

In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO(3) sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated WO(3) sensing layer. This causes a change in the electrical conductivity of the WO(3) film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO(3) layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm(−1)), a low detection limit (0.2 ppm) and a rapid response time (35 s).