A Generic Approach to Boost the Sensitivity of Metal Oxide Sensor by Decoupling the Surface Charge Exchange and Resistance Reading Process.

As one of bottlenecking parameters for practical applications of metal oxide semiconductor based gas sensors, sensitivity enhancement has attracted significant attention in the past few decades. In this work, alternative to conventional strategies of designing sensitive surfaces via morphology/defect/heterojunction control (then operating at an optimized isothermal temperature with a maximal response), a facile enhancement approach by decoupling surface charge exchange and resistance reading process (possessing different temperature-dependent behaviors) through pulsed temperature modulation (PTM) is reported. Substantially magnifying electrical responses of a generic metal oxide (e.g.WO3) MEMS sensor toward diverse analyte molecules is demonstrated. Under the optimal PTM conditions, the response toward 10 ppm NO2 can be boosted from (isothermal) 99.7 to 842.7, the response toward 100 ppm acetone is increased from (isothermal) 2.7 to 425, respectively, which are comparable to or even better than most of the state-of-the-art WO3 based sensors. In comparison to conventional (isothermal) operation, PTM allows to sequentially manipulate the physi/chemisorption of analyte molecules, generation of surface reactive oxygen species (ROS) and sensor resistance reading, and thus provides additional opportunity in boosting electrical response of oxide sensors for advanced health and/or environment monitoring in future.