Study On Preparation And Characteristics Of Gas Sensing Material Based On MOS

With the rapid development of science technology and industrialization, the flammablegases have not only been widely used, but also bring serious air pollution. Many cities haveemerged haze weather, which seriously damages people’s health. People attach greatimportance to gas detection and make more precise requirements for sensor. Therefore, gassensing characteristics of carbon nanotubes doped metal oxide composites is studied in thispaper, which improve the gas sensing properties of the material. It has important referencevalue to control the current environment pollution.The gas sensing mechanism of metal oxide and carbon nanotubes are described in thispaper. To improve the gas sensing characteristics, we take ZnO as the representative metaloxide and its properties are studied from two methods of preparation and doping. Moreover,the gas sensing properties of CNT/MOS is studied. The gas sensing mechanism of severalcomposites is also explored. The main contents are as follows：(1)The preparation parameters and gas sensing properties of ZnO thin film by RFmagnetron sputtering is studied. These ZnO thin films are prepared in the different sputteringparameters. Through exploring the influence of the substrate temperature, annealingtemperature and oxygen-argon ratio to the crystalline quality, growth structure and resistivityof the thin films, the optimized parameter of preparing ZnO thin film is obtained. The gassensitivity test shows that ZnO thin film has more than70%response at225℃for0.01-1.0%methane and ethanol. It not only reduces the operating temperature of the materialappropriately, but also improves the sensitivity.(2)The influence of doping carbon nanotubes to gas-sensing properties of ZnO is studied.ZnO powder is prepared by sol-gel technology and CNT/ZnO composites is been synthesized.It is found that doping carbon nanotubes can reduce the resistance of the material, and doping 1%carbon nanotubes has not reduce the operating temperature of ZnO from300℃to250℃，but also improve the sensitivity nearly six-fold for100ppm ethanol. This CNT/ZnOcomposites show good selectivity.(3)The gas-sensing properties of the carbon nanotubes doped WO3、SnO2for harmfulgases is studied. The CNT/WO3composite is synthesized with WO3powder usingprecipitation method and CNT. From the experiment, doping carbon nanotubes reduce theresistance of WO3and improve the sensitivity, show good selectivity for ammonia andnitrogen dioxide. Taking SnCl2.2H2O as raw material, SnO2powder is prepared by sol-gelmethod and CNT/SnO2composite is synthesized. From the experiment, doping carbonnanotubes improve the sensitivity and selectivity of SnO2to H2S. In addition, the sensitivityof CNT/WO3/SnO2composite is higher than CNT/ZnO, CNT/WO3and CNT/SnO2, and theresponse up to80%for1ppm NO2. The selectivity is significantly improved. This proves thatmulti-doping is a good method for improving the selectivity of metal oxide.(4)The gas sensing mechanism of CNT/ZnO,CNT/WO3,CNT/SnO2and CNT/WO3/SnO2composites are discussed in the paper.