Preparation of atomically smooth TiO₂ single crystal surfaces and their photochemical property

Atomically smooth rutile TiO₂(110), (100), (001), (111) and (101) surfaces were obtained for the first time by an appropriate cleaning and subsequent thermal treatment of commercially available single crystals. The annealing temperature for obtaining the ultra-smooth surface varied between 400 and 900°C depending on the crystallographic planes. The key point to the successful preparation of the regularly stepped TiO₂ surface was an HF treatment for the removal of surface impurities. By using these well-defined TiO₂ surfaces, the photochemical property was found to depend on the surface orientation; the photo-reduction of Ag⁺ to Ag metal from an aqueous solution proceeded in the order of (101) > (100) > (001) > (111) > (110) on the TiO₂ surfaces.