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

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