Influence of annealing temperature on the performance of TiO2/SiO2 nanolaminated films

Different laminated structures of ${\mathrm{TiO}}_2/{\mathrm{SiO}}_2$ composite film were prepared via atomic layer deposition (ALD) on alumina substrates. The effect of the annealing temperature in the air on the surface morphologies, crystal structures, binding energies, and ingredient content of these films was investigated using X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. Results showed that the binding energy of Ti and Si increased with decrease of the Ti content, and the ${\mathrm{TiO}}_2/{\mathrm{SiO}}_2$ nanolaminated films exhibited a complex bonding structure. As the annealing temperature increased, the thickness of the nanolaminated films decreased, and the density and surface roughness increased. An increase in the crystallization temperature was proportional to the ${\mathrm{SiO}}_2$ content in ${\mathrm{TiO}}_2/{\mathrm{SiO}}_2$ composite film. The annealing temperature and thin thickness strongly affected the phase structure of the ALD ${\mathrm{TiO}}_2$ thin film. To be specific, the ${\mathrm{TiO}}_2$ thin film transformed into an anatase phase from an amorphous phase after an increase in the annealing temperature from 400°C to 550°C, and the ${\mathrm{TiO}}_2$ film exhibited an anatase phase until the annealing temperature reached 850°C, owing to its extremely small thickness. The annealing process caused the Al ions in the substrate to diffuse into the films and bond with O.