Preparation Of TiO₂ Thin Films And Study On Photocatalytic Properties

With the growth of world population,development of industry and acceleration of urbanization,the global energy consumption is growing continuously,and the environmental problems such as contamination of groundwater,the global warming,and air pollution are becoming more serious.In order to address these issues,extensive researches are being carried out.Since Fujishima and Honda discovered photosensitization effect of TiO₂semiconductor electrode on water electrolysis into H₂ and O₂,TiO₂ has attracted great interest of the scientific fields for its unique physicochemical properties such as nontoxicity,high thermal and chemical stability,and relatively high photocatalytic activity.As one of the multifunctional semiconductor materials TiO₂ is broadly used in many industrial and technical fields including photocatalysis,solar cells,resistive switching,optical switching,self-cleaning,gas sensor,anti-corrosion and photocatalytic antimicrobial applications due to wide band gap,good mechanical properties and thermal stability.But,the defects witch smaller absorption rate and recombination of the electron-hole pairs reduced practical application efficiency of TiO₂.Therefore,researchers in various countries have conducted a large number of studies to improve the efficiency of TiO₂ material.In this study,we used electron beam evaporation method and sol-gel spin coating method to prepare nanostructured TiO₂ films,and annealed at different temperatures.X-ray diffraction spectra?XRD?and Raman spectroscopy were used for investigate the crystal structure of the TiO₂,scanning electron microscopy?SEM?and atomic force microscopy?AFM?were used for investigate the surface morphology of the film,Ultraviolet-visible?Uv-vis?absorption spectroscopy and photocatalysis test system were used to study the optical properties and photocatalytic properties of TiO₂ films.For the electron beam evaporation discuss the effect of evaporation time,substrate temperature and annealing temperature on the structure,morphology and properties of the TiO₂ thin films.For the sol-gel method investigate the effect of different annealing temperatures on the structure,morphology and properties of TiO₂ films.We used electron beam evaporation to prepare TiO₂ thin films on Si/SiO₂ substrates under high vacuum conditions,and discussed the effects of substrate temperature,evaporation time and annealing temperature on the properties of the films.XRD results show that the sample witch annealed at 800?was rutile TiO₂.The results of SEM show that the films prepared by electron beam evaporation are smooth,compact and uniformly covered on the substrate.The photocatalytic efficiency of the sample annealed at 800?under the irradiation of Xenon lamp shows excellent photocatalytic activity.The films prepared by the sol-gel spin coating method on the glass substrate,and annealed at various temperature from400?to 600?.The XRD diffraction spectrum showed that the phase transition occurred when the annealing temperature was increased to500?,the amorphous phase transform into anatase phase,and the anatase phase was transformed into orthorhombic brookite phase when the temperature was 600?.SEM and AFM measurements show that the surface of the films were smooth and uniform.As the annealing temperature increases,the average roughness were increases slightly and the optical band gap was decrease.The results show that the microstructure and optical band gap were highly dependent on the annealing temperature.In addition,the anatase phase TiO₂ film has the best photocatalytic activity compared with the amorphous and brookite TiO₂ thin films.