Highly Selective MEMS Gas Sensor to Detect H2 and NH3 With Tunable Discrimination

The emerging advancements in gas sensing technology present an ongoing challenge in achieving the selective detection of hydrogen ( $\text{H}_{{2}}{)}$ and ammonia (NH $_{{3}}{)}$ gases while allowing for adjustable discrimination. Alternative to conventional isothermal sensing methods, we propose a facile pulsed heating modulation (PHM) strategy to decouple surface physisorption and charge exchange processes. As various gases exhibit distinct activation energies governing physisorption and chemisorption, we demonstrate tunable selectivity by modulating the duty ratio ( ${D}{)}$ of heating pulses. When operating under PHM with ${D}$ = 0.33, the sensor exhibits favorable selectivity ( ${S}$ = 2.6) to NH3, while increasing ${D}$ to 0.67 enhances selectivity ( ${S}$ = 4.7) for H2. In contrast to isothermal techniques, the PHM approach offers a new route for manipulating analyte molecule sensing processes, thereby conferring superior response capabilities and the ability to finely tune selectivity for advanced trillion sensors (TSensors) applications.