Multi-Gas Sensor by Infrared Spectrometer

Abstract

AbstractIn order to detect many types of gases (CO2, NOx, SOx, C2H5OH) in the automotive cabin by infrared absorption sensor, we developed a novel micro electro mechanical systems (MEMS) based Fabry–Perot spectrometer with an ultra wide wavelength range (3.20–8.40 μm) compared to previously reported spectrometers (typically 2.80–5.80 μm). The wavelength range of a Fabry–Perot spectrometer is known to increase by increasing the ratio of the refractive indices of the multilayer mirrors. Thus, a novel mirror structure was proposed replacing the low refractive index layer of SiO2 (nL = 1.44) with “air (nL = 1.00)” for a wider wavelength range. To fabricate the proposed structure, the internal stress of the four ultra-thin polycrystalline silicon films (ca. 320 nm) was controlled tensile by the deposition temperature. A gas sensor was fabricated using our developed spectrometer. It was found that the sensor detected CO2 and C2H5OH successfully.KeywordsInfrared absorption sensorGas sensorFabry–Perot spectrometerMEMS