Fabrication And Characterization Of Nano-scare TiO₂/PE Multilayers

In this study, TiO2 thin film and TiO2/ PE nano-scale multilayers were synthesized by chemistry bath deposition (CBD) and layer by layer (LBL) method on silicon single-crystal wafers. Self-assembled monolayers (SAMs) synthesized by LBL method on Si wafers had been used as substrates for the deposition of titanium oxide thin films. The organic surface had been shown to be effective for promoting the growth of films from aqueous solutions. The formation of a titanium complex in the presence of H2O2 was used to be precursors to stabilize precipitating aqueous titanium solution. Uniform titania films had been formed on the SAMs. The films, aqueous titanium solution and SAMs were characterized during deposition process by a variety of techniques. Moreover, mechanical behaviors and optical properties of the films were investigated.Firstly, TiO2 films were deposited on the SAM surfaces from aqueous titanium solution, which included titanium complex in the presence of H2O2, and mixed with hydrochloric acid. The optimum formation condition of the TiO2 films was obtained by considered of a variety of factors, including films thickness, particle radius on and roughness of the films. The films can be synthsized at n(TiCl4):n(H2O2):n (HCl)=1:2: 1 at the temperature of 60℃for two hours. The particles on the surface of the films are uniform. The average size of the particles is ca.30nm and film roughness is ca. 2.76nm.Secondly, aqueous titanium solution was characterized by UV/ Vis for reaction degree. Scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS) was used to characterize TiO2 films and TiO2/ PE multilayered composite surface. Films surface elements were characterized by X-ray photoelectron spectroscopy. A variety of factors were analysed, including temperatures, time, pH and so on. Mechanisms of films formation were study.Finally, the effect of the number of the layers on hardness and fracture toughness were investigated. The hardness of the films varied from 9.85 GPa of the monolayer to 11.04 GPa of the multilayers with increasing layer numbers and the layer thickness. The hardness of the films is enhanced effectively. The fracture toughness increased from 0.8MPa of the monolayer to 1.5 MPa of the multilayers. The optical properties of the TiO2 films were characterized by UV-Vis spectrum. The results shown that the TiO2 film had light transmission at the visible range, but had greatly absorption at the ultraviolet range.