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7 September 1999 Optical properties of mixed TiO2-SiO2 films, from infrared to ultraviolet
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Mixed oxides are useful for obtaining the intermediate refractive indices needed in the realization of graded-index thin films. Co-evaporated TiO2-SiO2 mixtures are studied for a large range of concentrations via UV-VIS, IR ellipsometry and XPS. An understanding of the nature of these mixtures and their air exposure stability is important for further applications. At low TiO2 concentrations, Ti4+ ions are inserted into the silica tetrahedral network, as shown by the IR peak at 945 cm-1. At higher concentrations, an evolution from TiO4 tetrahedra to TiO6 octahedra is presumed. The behavior of the O1s core level peak indicates that a least two phases coexist. Comparison between concentration determined using XPS and RBS shows a deficit in TiO2 at the surface of the films, especially at high TiO2 concentrations. The evolution of the mixtures optical constants will be presented in a large wavelength range, going from IR to UV. Particular attention will be paid to the variations with respect to the frequency of the vibration modes in the IR range, to the refractive index in the transparency region, and to the extinction coefficient at he absorption threshold. In addition, AFM measurements show the variation of the grain size as a function of the TiO2 concentration.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Brunet-Bruneau, S. Fisson, Bruno Gallas, G. Vuye, and Josette Rivory "Optical properties of mixed TiO2-SiO2 films, from infrared to ultraviolet", Proc. SPIE 3738, Advances in Optical Interference Coatings, (7 September 1999);

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