Highly Selective MEMS Gas Sensor to Detect H<sub>2</sub> and NH<sub>3</sub> With Tunable Discrimination
Wenjun Yan, Wenxin Luo, Jianhao Li, Mingjie Li
Abstract
The emerging advancements in gas sensing technology present an ongoing challenge in achieving the selective detection of hydrogen ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{{2}}{)}$ </tex-math></inline-formula> and ammonia (NH <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{3}}{)}$ </tex-math></inline-formula> 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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}{)}$ </tex-math></inline-formula> of heating pulses. When operating under PHM with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula> = 0.33, the sensor exhibits favorable selectivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> = 2.6) to NH3, while increasing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula> to 0.67 enhances selectivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> = 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.