Fabrication and characterization of micro-gas sensor for nitrogen oxides gas detection

WO3-based thin film micro-gas sensor was fabricated and the NOx gas sensing as well as electrical properties have been investigated. To obtain the optimal heat distribution, the structure of micro-hot plate was designed from the result of finite element simulation and was prepared by backside etching with KOH solution. The micro-hot plate was made out of N/O/N diaphragm with the thickness of 0.6 nm and area of 1.5 x 1.5 mm(2). The power consumption to maintain the device temperature of 300 degrees C was about 60 mW. WO3, thin film was thermally evaporated on micro-diaphragm. The film exhibited a fast response to NOx gas and the relationship between sensitivity and NO2 concentration showed good linearity in the gas concentration range of 0-30 ppm NO2. The sensitivity of micro-gas sensor to NOx was correlated with the microstructure of the thin film. (C) 2000 Elsevier Science S.A. All rights reserved.