Tungsten Trioxide Gas Sensening Thin Film Prepared By Magnetron Sputtering

In industrial production and daily life, gas sensors has been widely used to detect toxic gases, flammable gases, and explosive gases to ensure the security of production and life. Therefore the increasingly highly requirements for gas sensors will promote a highly sensitive, reliable, selective gas sensor development. In many gas-sensing materials, WO3 gas comes to the fore because of its excellent gas-sensitivity and highly stability. Tungsten trioxide is one n-type semiconductor material,when it is exposed to the gas which is to be detected (NOx, H2, CO, NH3, C2H5OH, etc.), oxygen adsorbed from the air as an electron acceptor state is in three tungsten oxide material's cut-belt, the reaction of gas on the surface caused that the coverage on some parts of the surface changes, which led to a conductivity change. Currently study of WO3 thin film sensor is just in the ascendant, researchers widely used sol-gel method and vacuum evaporation method to make the gas-sensitive tungsten oxide films.Taking into account that sputtering films have highly purity, good adhesion between film and substrate, uniform-sized particle which constitutes the film, easy realization of nanoparticle films, and that the process is easier to control and so on, in this thesis, facing targets direct current magnetron sputtering method is used to prepare WO3 thin films with highly gas-sensing. Via designing of different experiments, this thesis uses SEM, AFM, XRD and other advanced analytical tools and static gas testing system to analyze the influence of the substrate material, the substrate temperature and sputtering gas ratio, annealing conditions to the microscopic structure, electricity and gas properties of the sample, and found some rules and optimal parameters of some conditions.The sensitivity, operating temperature, selectivity and response time of the superficial modified WO3 thin films have been improved with varying degree. After appending Ti, when the thickness of superficial modified TiO2 layer is 30nm, the microstructure of WO3 thin film has been obviously improved, in the case of operating temperature for 120℃and 15ppm NO2 , the sensitivity achieves 25.2, and WO3 film has the good selectivity and the shorter response time, and is one kind of ideal gas sensor.