Preferential growth of thin rutile TiO₂ films upon thermal oxidation of sputtered Ti films

Thin rutile TiO₂ films with (200) preferred orientation were fabricated by thermal oxidation of sputtered Ti metal films on a fused silica substrate. Experimental results indicate that the preferential crystal growth of (200)-oriented TiO₂ is determined by the competition between surface free energy and strain energy. The highly crystalline Ti film with (002) orientation has a greater tendency to promote the growth of (200)-oriented TiO₂. However, for the amorphous and low crystalline Ti films, orientation of the crystallites evolved in the resulting TiO₂ film tends to be randomly distributed. The extent of preferential crystal growth of TiO₂ (200) plane can be enhanced by decreasing the annealing temperature or the thickness of Ti film.