Formation of TiO2(B) nanocrystallites in sol-gel-derived SiO2-TiO2 film

TiO2(B), one of the polymorphs of TiO2, has been formed by annealing a sol-gel-derived SiO2-TiO2 amorphous film on a silicon wafer at 900 degrees C in air. Transmission electron microscopy (TEM) revealed that nanocrystallites with a size of 5-10 nm were dispersed in the amorphous SiO2 matrix in the film. The X-ray diffraction pattern and lattice fringe spacing in high-resolution TEM images corresponded to those of TiO2(B). These TiO2(B) nanocrystallites are probably stable with the presence of surrounding SiO2 in the film at 900 degrees C, because previous works reported that this phase should be converted to anatase at temperatures higher than 550-700 degrees C.