Construction Of Metal Oxide Semiconductor Sensors And Research On Sensing Signal Processing

Gas sensors act as an important environment detection device,which are extensively used in industrial and agricultural production,daily life and many other fields.But there are still many defects and shortcomings in gas sensors,such as high working temperature,slow response speed,low sensitivity,and poor stability and so on.In this study,the microstructure,morphology and specific surface area were carefully investigated by doping bismuth or iron element,especially,into the traditional oxide materials.accordingly,the gas sensing properties of the composites were significantly enhanced;The sensitive mechanism and advantages of the method are analyzed by various detection methods;At the same time,an electronic system for sensor signal acquisition and processing is designed.The research work of this paper can be summarized as follows:(1)A new cauliflower like Bi₂O₃/ZnO nanocomposite with excellent ethanol sensing properties was synthesized.It includes high gas response,low operating temperature of175?,wide concentration detection range of 1-500 ppm,excellent selectivity,and long-term stability,fast response time and recovery time,which is better than pure zinc oxide sensor or other bismuth oxide and zinc oxide nanocomposites.The excellent sensing properties can be attributed to the formation of p-Bi₂O₃/n-ZnO heterostructure?-Bi2O3 is tetragonal phase.The Bi₂O₃/ZnO nanocomposites with low cost and high stability will become one of the promising sensing materials in the field of ethanol detection.(2)The hierarchical structure of the?-Fe₂O₃/SnO₂ nanospheres were prepared.Compared with pure SnO₂,Fe₂O₃(2%)/SnO₂ and Fe₂O₃(6%)/SnO₂,Fe₂O₃(4%)/SnO₂ are more sensitive to acetone.Specifically,Fe₂O₃(4%)/SnO₂ sensor has good selectivity,low working temperature of 200?,wide concentration detection range(500 ppb-500 ppm),response/recovery time of 3 seconds and 4 seconds respectively.The device can operate effectively at 80%relative humidity.This work provides a novel Fe₂O₃/SnO₂nanocomposite for the development of miniaturized,low-cost and high-performance acetone gas sensor.(3)An electronic system for sensor signal acquisition is designed.One is an intelligent detection system based on STM32,the other is a PPM modulation and demodulation system based on FPGA,which is used to complete the transmission and processing of sensor signals.The electronic system obviously improved the portability and flexibility of the sensor detection system.