Crystal Growth in Mesoporous TiO2 Optical Thin Films

Abstract

Synthesizing mesoporous TiO2 films with tunable crystallized content, using rapid and facile hydrolytic sol–gel routes, is of interest for developing optical and photocatalytic applications on different substrates. Here, the crystallinity and the porosity of TiO2 is fine-tuned, starting from low annealing temperatures. We further investigate the role of crystal seeds in temperature-induced crystalline phase changes in mesoporous TiO2 thin films by Raman spectroscopy, which is interpreted in the framework of a phonon quantum confinement model. The presence of crystal seeds in the films and the high atomic diffusion in the porous structure lead to the lower activation energy of crystal growth and stabilization of the anatase phase above 700 °C. The film nanostructural and optical properties emphasize the role of complexation by acetylacetone in the formation of nanocrystals and pores. Such fine-tuned optical thin films with varying crystallite and porosity content offer promising perspectives of application...