Preparation And Characterization Of TiO₂-based Composite Thin Films

As a typical n-type semiconductor with wide band gap,titanium dioxide(TiO₂) has good chemical stability,no toxicity and good photo-catalytic property.While TiO₂ thin film materials not only have these advantages,but also have a special property that is superhydrophility.Now TiO₂ thin films have been widely used in the fields such as sewage treatment,anti-bacterial disinfectant,antifogging and self-cleaning and solar cells etc.In this paper,three series of uniform and transparent nano-TiO₂ thin films deposited on glass were prepared by sol-gel dip-coating technology, including SiO₂-TiO₂,CeO₂-TiO₂ and CeO₂-SiO₂-TiO₂ thin films.The as-synthsized samples were characterized by X-ray diffraction(XRD), Atomic force microscopy(AFM),X-ray photoelectron spectroscopy (XPS).Ultraviolet visible(UV-vis) spectra and water contact angle measurement were used to analyze the optical and hydrophilic properties. The effects of CeO₂ and SiO₂ additives on the structure,morphology,and chemical element,optical and hydrophilic properties of TiO₂ thin films were investigated and the related mechanisms were discussed.SiO₂-TiO₂ thin film was composed of smaller particles because SiO₂ inhibited the growth of TiO₂ grain during thermal treatment,and the surface was smoother and the root mean square roughness and peak to peak for the film was smaller than those of TiO₂ thin film.Optical absorption edges of the films showed blue shift due to quantum size effect.The hydrophilicity of SiO₂-TiO₂ thin films was greatly improved compared with TiO₂ thin film.After UV irradiation for 30min,water contact angles of films with Si/Ti=20%and 33.3%were 1°and 3°,which reached superhydrophilicity.CeO₂-TiO₂ thin film was composed of smaller spherical particles and the surface was smooth.Absorption edges of the films with Ce/Ti=5%and 10%showed red shift.Water contact angles of the films decreased with increasing Ce/Ti molar ratio,which demonstrated that hydrophilicity of the films was improved by adding CeO₂.CeO₂-SiO₂-TiO₂ thin film was also composed of smaller particles and the surface was smoother.Absorption edges of the films with Si/Ti=10%had red shift.Hydrophilicity of all the films were improved and after UV irradiation for 30min,water contact angles of the films with Si/Ti=20%were 5°,4°and 3°,which reached superhydrophilicity.