Scalable Synthesis of SnO2 Nanosheet Arrays on Chips for Ultralow Concentration NO2 Detection*

This work reports a chemiresistive type of NO<inf>2</inf> sensor based on patterned SnO<inf>2</inf> nanosheet arrays (NSAs), which are in-situ synthesized on MEMS chips via a scalable one-step homogeneous precipitation approach. Dry etching of SnO<inf>2</inf> NSAs is studied by using an inductively couple plasma (ICP) process. As-grown SnO<inf>2</inf> nanosheets demonstrate ultrathin thickness with cross-linked networks. The SnO<inf>2</inf> NSAs based sensor exhibits ultrasensitive (150.9, at 10 ppm) to NO<inf>2</inf> gas at 150°C with a wide concentration range from 30 ppb to 50 ppm. Especially, this sensor also shows liner relationships between sensor response and NO<inf>2</inf> concentration within the range of 30–1000 ppb and 2–50 ppm, respectively, indicating a promising route for detection of ultralow concentration of NO<inf>2</inf>. Our results provide a new strategy toward in-situ wafer-level fabrication of SnO<inf>2</inf> NSAs based micro gas sensing devices.

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