Abstract
The study presents a micro carbon monoxide (CO) sensor integrated with a readout circuit-on-a-chip manufactured by the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The sensing film of the sensor is a composite cobalt oxide nanosheet and carbon nanotube (CoOOH/CNT) film that is prepared by a precipitation-oxidation method. The structure of the CO sensor is composed of a polysilicon resistor and a sensing film. The sensor, which is of a resistive type, changes its resistance when the sensing film adsorbs or desorbs CO gas. The readout circuit is used to convert the sensor resistance into the voltage output. The post-processing of the sensor includes etching the sacrificial layers and coating the sensing film. The advantages of the sensor include room temperature operation, short response/recovery times and easy post-processing. Experimental results show that the sensitivity of the CO sensor is about 0.19 mV/ppm, and the response and recovery times are 23 s and 34 s for 200 ppm CO, respectively.
Highlights
Carbon monoxide sensors are widely applied in industrial and environmental monitoring
The results revealed that the resistance of the carbon monoxide (CO) sensor increased as the concentration of CO
A micro carbon monoxide sensor integrated with a readout circuit-on-a-chip has successfully been implemented using a commercial complementary metal oxide semiconductor (CMOS) process and a post-process
Summary
Carbon monoxide sensors are widely applied in industrial and environmental monitoring. Micro gas sensors fabricated by MEMS technology have the advantages of small size, high performance, low cost and easy mass-production. Many studies have used MEMS technology to develop micro carbon monoxide sensors. Thereby, in this work a carbon monoxide sensor integrated with a readout circuit-on-a-chip was developed. Micro devices made by the CMOS-MEMS technique usually need a post-process to coat the functional films [17] or to release the suspended structures [18]. The CMOS-MEMS technique was employed to fabricate a micro carbon monoxide sensor integrated with a readout circuit-on-a-chip. The carbon monoxide sensor needs post-processing to coat the sensing film. The resistance of the sensor was converted by the readout circuit into the voltage output
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