The Study On Preparation And Properies Of Ti-doped Tungsten Oxide Films By Co-sputtering

Tungsten oxide is studied and applied extensively because of its electrochromic property, gasochromic property, photochromic property, electrochemistry,etc. In 1990s, 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 metal Oxide gas sensors.Tungsten oxide is metal Oxide semiconductor, its some properties can be improved by doping different metal elements, such as electrochromic property, the sensing behavior and photocatalytic property, et al. Proper doping provided further electron (or hole), enhanced conductance and brought influence to the property of Tungsten oxide film for reaction.In this thesis, The Ti-doped WO3 thin films were deposited on glass substrates by dual target magnetron sputtering system, namely W target(99.95%) and Ti target(99.97%)- reactive magnectron sputtering technology was utilized. During the experimentation, volts d.c and electric current were definite, but the spattering power of titanium was variational. Its power was 100w, 150w, 200w, 250w. The different Ti-doped WO3 thin films were annealed at 450℃and 550℃respectively. The thickness, structual properties and photoelectricity properties of the films were analyzed by step instrument, X-ray diffraction(XRD), ultraviolet visible transmittance spectroscopy (UV-Vis) and the Ecopia HMS-3000 Hall measurement system. The results indicate that the spattering power of titanium increased, the peaks of the transmissivity shift to the short wave. the transmissivity reduced, the absorbed border appeared Einstein shift with the increase of annealing temperature, in addition, the peaks nearby the Einstein shift disappeared nearly. After annealing, the films were monoclinic. The crystal and mean grain size varied considerably. As the spattering power of titanium increased, the diffraction apex of the samples have excuision to the low angle direction. The heat treatment films exhibit n-type at 450℃and p-type at 550℃. On the side, electron(or hole) concentration, hall mobility, resistivity exhibit disciplinarian change with the increase of spattering power.The gas sensing property of Ti-doped WO3 thin films was alse studied. The gas sensing property of the films in various deposited conditions were tested and analysised to C2H5OH gas of 1000ppm and NO2 of 500ppm. The gas sensing property of the sample 2-2(the spattering power was 150w, annealing at 550℃) was better to C2H5OH gas and the sample 3-1(the spattering power was 200w, annealing at 450℃) was better to NO2 at 290℃. Comparing The gas sensing property to C2H5OH with NO2, Because the sample 2-2 is p-type, the C2H5OH is deoxidization gas and NO2 is oxygenation gas. We found the resistance of 2-2 largened to C2H5OH gas and diminished to NO2. Finally, the gas sensitivity mechanism of WO3 and Ti-doped WO3 films are discussed in this thesis.