Abstract
► TiO2–M–TiO2 (M=W and Co) multilayer films with pure anatase phase have been deposited on glass substrates. ► Compared with pure TiO2 film, the crystallization temperature for TiO2–M–TiO2 films decreased significantly to 500°C. ► The optical band gap of TiO2–M–TiO2 films became narrower than that of pure TiO2 film. ► The crystallization of TiO2–M–TiO2 films was attributed to the structural deformation due to the oxidation of metal layers.
TiO2–M–TiO2 (M=W, Co and Ag) multilayer films have been deposited on glass substrates using reactive magnetron sputtering, then annealed in air for 2h at 500°C. The structure, surface morphology and optical properties of the films have been studied using X-ray diffraction, Raman spectroscopy, atomic force microscopy and UV–vis spectroscopy. The TiO2–W–TiO2 and TiO2–Co–TiO2 films showed crystalline phases, whereas the TiO2–Ag–TiO2 films remained in the amorphous state. The crystallization temperature for the TiO2–M–TiO2 films decreased significantly compared with pure TiO2 film deposited on quartz. Detailed analysis of the Raman spectra suggested that the crystallization of TiO2–M–TiO2 films was associated with the large structural deformation imposed by the oxidation of intermediate metal layers. Moreover, the optical band gap of the films narrowed due to the appearance of impurity levels as the metal ions migrated into the TiO2 matrix. These results indicate that the insertion of intermediate metal layers provides a feasible access to improve the structural and optical properties of anatase TiO2 films, leading to promising applications in the field of photocatalysis.