Research On Performance And Key Technology Of CuO And Co₃O₄ Based Heterostructure Gas Sensors

In recent years,sensors have been used in many fields,such as environmental detection,military security,aerospace technology,medical facilities,home security,industrial and agricultural production,and other fields,creating economic benefits for the development of society.And the development of integrated circuits and semiconductor technologies has promoted the research of the sensor.The properties of sensitive materials directly determine the performance of the device.In recent years,metal oxide semiconductor(MOS)sensitive materials have been extensively studied.MOS gas sensors have become research hotspots due to the advantages such as convenient manufacturing,high response,short response/recovery time,high stability,simple operation,and low price.Therefore,this paper takes p-type metal oxide semiconductor CuO and Co₃O₄ as the research object,improves the gas sensor performance by doping and constructing a heterojunction method;studies the sensitivity mechanism of the gas sensors,analyzes and discusses solutions and measures that can improve the performance of gas sensors.The specific research content is as follows:CuO microspheres and Sn and Ce doped CuO microsphere gas sensors were prepared by solvothermal method.The morphology and crystal structure of the samples were tested by various characterization methods.The gas sensitivity to common organic volatile gases was tested.The influence of Sn and Ce doping concentration on the gas-sensing performance of CuO-based microsphere gas sensors is compared and analyzed.The research results showed that the 1mol%Sn-CuO gas sensor had the best response to 100ppm ethanol(S=18.3),which was about 1.4 times higher than the response of pure CuO-based sensor;the response of the 2 mol%Ce-CuO gas sensor to 100 ppm ethanol is 22.2,which is 1.7 times higher than that of pure CuO.Compared with pure CuO microspheres,Sn and Ce doped CuO microspheres have more randomly distributed pores,larger specific surface area and active sites,which increase the effective adsorption and desorption of gas.This has a positive effect on improving gas sensitivity.Therefore,an appropriate amount of metal doping is helpful to improve the gas sensitivity of the CuO microsphere sensor.ZnO nanowire arrays/CuO nanosphere heterostructures and pure CuO nanospheres were prepared on the ITO glass substrate and Al2O3 planar device substrate by low-temperature hydrothermal method.The surface morphology and lattice structure of the samples were characterized.The gas sensitivity to organic volatile gases were systematically studied.The influence of constructing heterogeneous structure on the gas sensitivity of CuO-based gas sensors were analyzed and explored.The response of Zn O/CuO sensor(ZC-2)to 100 ppm ethanol gas at 122?is 55.4,which is 8.8 and3.4 times higher than that of pure CuO nanospheres(R=6.3)and Zn O nanowire arrays(R=16.4),respectively.The response of Zn O/CuO sensor directly grown on the Al2O3planar device to 100 ppm ethanol at 116?is 74.5,which is 11.8 times higher than that of pure CuO nanospheres.The results show that the formation of heterojunction plays an important role in improving the gas sensitivity of CuO microsphere sensors.In addition,the sensitive material is directly grown on the Al2O3 planar device,which makes full contact between the material and the substrate.To a certain extent,the stacking and aggregation of the sensitive material in the film coating process is avoided,which provides more effective active sites for gas adsorption and further improves the gas sensing performance.Flower-like Co₃O₄ microspheres and dandelion flower-like In-doped Co₃O₄microspheres were synthesized by solvothermal method;Sea urchin-like pure Co₃O₄and In2O3/Co₃O₄ composite heterostructures were synthesized by two-step water bath method.Various characterization methods were used to verify the microstructure and chemical composition of the synthesized sensitive materials,and the gas sensitivity of the samples to organic volatile gases was tested.The maximum response of flower-like In-doped Co₃O₄ sensor to 100 ppm ethanol gas at 130?is 15,which is 4.4 times higher than that of pure Co₃O₄ microspheres.The enhanced gas-sensing performance of the In-doped Co₃O₄ microsphere sensor can be attributed to the increase in the specific surface area of the layered flower-shaped microsphere and the increase in adsorption sites,which is beneficial to the gas reaction.The response of In2O3/Co₃O₄heterostructure sensor to 300 ppm ethanol gas at 188?is 19,which is 2.9 times that of single Co₃O₄.The results show that the formation of heterojunction and the change of surface morphology are the main reasons for the enhanced response.