Research On Process Optimization And Performance Of SnO₂ Based Gas Sensor

35 years after the discovery of SnO₂ gas sensor,the SnO₂ based gas sensor has been widely used in many fields,such as air monitoring,process scene monitoring and indoor air detection,and so on.But,because of the high operating temperature and large power consumption,it's still difficult to use the sensor based on SnO₂ on low power wide area network system in the Internet of things.If the working temperature couldn't be effectively reduced,the gas sensor based on SnO₂ will encounter obstacles in the trend of continuous,automatic and intelligent components.The sensitivity of the gas sensor based on SnO₂ is still limited.In the detecting of extremely low concentration gas,the fabricated SnO₂ sensor has a poor performance at the current signal intensity,which limits the application of the sensor in the low threshold toxic gas monitoring scenario.In addition,the gas sensor based on SnO₂,as one of the resistive semiconductor sensors,the SnO₂ based sensor was also caught in the problems to be selective to different gas.Based on this research background,we have done three major works by the depth of literature research and experiment:1)Through the literature review,we have summarized the main current optimization methods for hydrothermal synthesis of metal oxide semiconductor gas sensor performance,and which could be divided into structure optimization,composition optimization and process optimization.?1?The structure optimization is mainly to fabricate the special structure of higher specific surface area and surface reactivity;?2?composition optimization is to change the properties of the crystals and increase the gas-solid reaction,control grain size,increase the Schottky barrier and build more active reaction sites through doping,noble metal loading and construct heterojunction way.?3?The process optimization is mainly to control the temperature and time of hydrothermal reaction.2)By synthesizing Zn doped SnO₂ crystals,we have confirmed that one-dimensional SnO₂ crystals based sensor was poor in spite of high electron mobility.The key point was the poor surface gas adsorption capacity of one-dimensional SnO₂ crystals.However,with the compounding of Au particle and CuO,the surface of one-dimensional SnO₂ crystals'gas adsorption capacity would be improved significantly,which could achieve a high response value and low response time.3)Through the Cu-Zn two elements doped SnO₂ crystal,we have achieved the best coordination of the three atmospheric sensitivity optimization methods:?1?structure,?2?composition and?3?process method.In our work,the?221?high energy surface closed octahedron single crystal particles of 50 nm has been prepared successfully.The response of the gas sensor based on the synthesized material to 50 ppm is as high as 210,which is significantly higher than that reported in the literatures.At the same time,the response time is as low as 4s,the working temperature is reduced to110?.