Study On Low-power MEMS Micro-hotplate ZnO Gas Sensors For Coal Mining

Due to the increasing demand for devices to monitor gas pollution sources and quantify emission levels,the research of gas sensors has attracted widespread attention from industry and academia.Metal oxide semiconductor gas sensors are attracting more attention for their excellent response performance.Among them,zinc oxide(ZnO)based gas sensors have become one of the most promising gas sensors because of their advantages of high charge mobility,low cost,non-toxicity and chemical stability.However,when used to detect trace gases,this type of gas sensor also has problems such as poor selectivity,high operating temperature,low sensitivity.(1)Since the response of the sensor to gas is significantly affected by temperature,and the temperature distribution affects the mechanical stability and service life of the sensor.Therefore,firstly,the finite element analysis was carried out using COMSOL software,and a micro-heating plate was designed to prepare a substrate with stable mechanical properties and uniform temperature distribution.The sensitive material is covered with the interdigital electrodes of this substrate by different methods.(2)The ZnO sensitive material was used to make the sensor,and the gas sensing performance of the sensor was improved by morphology optimization,heterostructure construction,precious metal modification.The gas sensing mechanism of the prepared sensor was discussed.Firstly,ZnO membrane materials were prepared by magnetron sputtering or solution coating,and their nanostructures,morphologies and sensing performance were systematically studied,and the gas sensing mechanism was studied based on surface adsorption model.The test results show that the performance of the gas sensor based on magnetron sputtering ZnO is better compared with the common sensor on the market.The100,200 and 300 nm thickness ZnO-based gas sensor prepared by magnetron sputtering method.200 nm ZnO has the best response.The response to methane is highest at the optimal working temperature of 450 ℃,and the response value is as high as 3 to 10000 ppm methane.In addition,the gas sensor has obvious advantages,such as repeatability,response speed,long-term stability and other performance.Secondly,the ZnO film made by the solution coating method has a slightly improved response at low temperatures compared with magnetron sputtering.The structure and morphology of the two devices above were characterized,and the sensing performance of ZnO membranes on methane was systematically analyzed.In addition,the magnetron sputtered ZnO film is doped with gold or alumina on the surface.In summary,the improvement of nano-microstructure,construction of heterostructure and the payload of precious metals can effectively reduce the working temperature,improve the response and selectivity of ZnO-based gas sensors.This work provides a basis for enriching the theoretical basis of ZnO-based gas sensors and promoting practical industrial applications.