A NOx gas sensing based on FTO thin film by MEMS technology

• Main Authors: FAN, SHAO-YU, 范邵瑜
• Other Authors: HSU, CHENG-LIANG
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/e9nm79

碩士 === 國立臺南大學 === 電機工程學系碩博士班 === 107 === In this thesis, we prepared the gas sensors based on Fluorine doped Tin Oxide (FTO) films with MEMS micro-electro-mechanical technology and the sensors were used to fabricate the device that can perform gas sensing. The F content is ~10 at%. The sensors illustrate the advance properties of small size, low cost, low power consumption and high reliability. The characteristic of sensing film was analyzed by SEM, XRD, EDX, and infrared thermal imaging. The research theme is roughly divided into three main axes: (1) characteristics of tin dioxide doped fluorine gas sensor; (2) characteristics of tin dioxide and indium tin oxide gas sensor; (3) three different sensing films Comparison of sensing characteristics. The gas response results show that the NOx gas responses of the FTO gas sensor are higher than that of the SnO2 gas sensor and ITO gas sensor. Low gas concentrations of 1 ppm NO and 1 ppm NO2 can be detected with good responses of 85.3% and 75.42%, using the FTO gas sensor at 200 °C and with 1 V applied bias. The magnitude of the sensor response increased with increasing NOx gas concentration. We also repeated responses of the FTO gas sensor to 1 ppm NO at 250 ◦C. The sensor responded quickly when the gas was switched from air to 1 ppm NO, and the response and recovery of the FTO gas sensor were stable and quick. This result demonstrates that the response speed of the fabricated sensor is good. The humidity response results show that the when humidity was increased from 35% to 95%, the sensing current of the device increased. This experimental result that the humidity will change the resistance of sensor.