Crystallization and diffusion in composite TiO2-SiO2 thin films

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Abstract
The crystallization behavior of evaporated TiO2-SiO2 mixed composition films and its dependence on composition, temperature, time and type of mixing (codeposited or alternating layers) were studied. All codeposited films annealed between 600 and 900 °C with 15%–90% molar TiO2 exhibited crystallization in the anatase phase. Crystallite size increased with Ti content of the film and with temperature. TiO2 in alternating layered films, which had layer thicknesses in the 65–1000 Å range, crystallized in the anatase phase in the 400–600 °C range, with thin layered films requiring higher temperatures for crystallization. For temperatures of 900–1100 °C, codeposited films were transformed into rutile films, whereas alternating layered films remained as anatase. Diffusivity of Ti in the mixed composition film was calculated to be 3×10−14 and 3×10−13 cm2/s from the study of precipitation kinetics at 950 and 1050 °C, respectively. Morphology of intermediate composition analog films (25%–65% atomic TiO2) remained virtually unaltered from its as-deposited state after annealing and crystallization.