Crystal-face dependences of surface band edges and hole reactivity, revealed by preparation of essentially atomically smooth and stable (110) and (100) n-TiO2 (rutile) surfaces

Essentially atomically smooth (100) and (110) n-TiO2 (rutile) surfaces were prepared by immersion of commercially available single-crystal wafers in 20% HF, followed by annealing at 600 degreesC in air. The obtained surfaces were stable in aqueous solutions of pH 1-13, showing no change in the surface morphology on an atomic level, contrary to atomically flat surfaces prepared by ion sputtering and annealing under UHV. The success in preparation of the atomically smooth and stable n-TiO2 surfaces enabled us to reveal clear crystal-face dependences of the surface band edges and hole reactivity in aqueous solutions.