| As a member of the novel semiconductor materials, tungsten oxide has been under an extensive research in recent years for its unique physicochemical properties. It has been widely used in many different applications, such as electrochromic windows, optical devices, fuel cells, gas sensors, and photocatalyst materials, etc. As we known, the morphologies and structures of the material have great influence on its properties. So it is important to study in detail the preparation and physicochemical properties of tungsten oxide-based nano-films.Tungsten oxide film is studied and applied extensively because of its electrochromic property, gasochromic property , photochromic property, electrochemistry,etc. In recent years , some research grouphs have devoted a great deal of their investigation to tungsten oxide for gas sensing application,what has led tungsten oxideto be highly appreciated in the field of MOX(Metal Oxide sensors) gas sensors. In this thesis, The WO3 thin films were deposited on glass substrates by DC- reactive magnectron sputtering technology and then annealed at temperature between 350℃--550℃. The films were characterized with Scanning Electron Microscopy (SEM),X-ray diffraction (XRD),X-ray Photoelectron Spectroscopy ultraviolet visible transmittance spectroscopy (UV-Vis) and step devices. Optical properties,surface microstructure and structual properties of WO3,Ti /WO3 thin films were studied. It is shown that the crystallite phase and the mean grain size varied considerably with the various annealing temperature. As the annealing temperature increased, the general crystallite size considerably increased, and the WO3 thin amorphous films began to crystallize. And finally, the WO3 thin films with hexagonal structure were obtained, which grew preferentially on the direction<001>. The last found the suitble technical condition.It is also investigated that how the O2 pressure and annealing temperature affects the transmissivity, microstructure and other optical properties of WO3 /Ti/WO3 films. The results show that the O2 pressure significantly affects the microstructures of the films. With the increase of O2 pressure,the thickness of thin films increases, were as the mean grain size increases, the interplaner spacing increases gradually and optical band gap decreases. The caculated results demonstrate that the refractive index (n) and extinction coefficients (k) of the WO3 and Ti/WO3 films also increasing of O2 pressure.The reliabilty and repeatability of WO3 and Ti/WO3 sensitive to NO2 were also studied. All the films in various deposited conditions were tested and analysised. At last, the importance factors which affect the properties of the films were analyzed particularly. Firstly, after ananaling the WO3 and Ti/WO3 films were employed for the measurement of gas sensing properties by using nitrogen dioxide and liquefied petroleum gas. Then found the optimal O2 pressure, annealing temperature and other optimal technical parameters. Secondly, the gas sensing properties were evaluated at various operation temperatures from 90℃to 440℃by measuring the changes of resistance of the sensor in air and in NO2 gas, the optimal work temperature was found to be 150℃. Finally, the gas sensitivity mechanism of WO3 and Ti/WO3 films are discussed using surface chemistry and adsorption chemistry in this thesis.
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