Surface coating of small SiO₂ particles with TiO₂ thin layer by using barrel-sputtering system

Surface coating of small SiO₂ particles with a thin TiO₂ layer was carried out by using a hexagonal barrel-sputtering system. In order to determine suitable sputtering conditions, the TiO₂ layer was deposited on a glass substrate by reactive sputtering under given total pressures, oxygen fractions, and substrate temperatures. The analysis of X-ray diffraction patterns and ultraviolet-visible absorption spectra showed that the preparation of a TiO₂ layer with the rutile phase requires a high total pressure at room temperature whereas that with the anatase phase requires a moderate total pressure at 498 K. The surface coating of SiO₂ particles by TiO₂ layer was performed under the conditions suitable for either the rutile or anatase phase. It was found from scanning electron microscope, energy-dispersion spectrometer, and ultraviolet-visible absorption measurements that the surface of SiO₂ particles was successfully coated with a thin uniform TiO₂ layer with the rutile or anatase phase.