Emerging NH3 MEMS-Sensing Techniques and Application

Ammonia, a highly toxic and corrosive gas associated with human health, has important application needs in industry, food, agriculture, and other fields. In the past years, the metal-oxide semiconductor (MOS)-based ammonia sensors have gained much attention and few oxides, nitrides, carbides, and their composites have been employed as the sensing materials, however, these sensors have large volume or requirement of high temperature characteristics, which hinder their application in current electronic system, especially in integrated circuits. Developing Micro-Electro-Mechanical System (MEMS)-based ammonia sensors with high integration and low consumption at room temperature become more and more urgent, but is still a challenge. How to compensate the benefit contributing from the high-ratio-of-surface of MOS-sensor in MEMS-sensor. This review briefly introduces and discusses the on-chip ammonic sensing mechanism and the influence factors. Then, most representative chemical resistance sensors in ammonia sensing, as well as diodes and field-effect transistors sensors related to integrated circuits are summarized. The main coupling strategies used to enhance gas sensitivity in recent years are discussed. Finally, the development prospect of high-performance MEMS-based ammonia sensor is discussed.