Atom-resolved structures of TiO2(001) surface by scanning tunneling microscopy

Surface structures of a TiO2(001) surface are examined in atomic scale by scanning tunneling microscopy (STM). Among two ordered phases which depend on annealing temperature as reported from a low energy electron diffraction (LEED) study, an atomic-scale image of the higher temperature phase, which shows a unique surface reactivity, was successfully visualized. The surface consisted of crossed rows along the [1I¯0] direction and the [I¯10] direction. Each row had a bleacher-like structure which formed stairs at both sides with an average slope identical to the {114} face. An atom-resolved STM image showed that each narrow terrace of the stairs is covered with a unit of three bright spots which are ordered in line perpendicular to the step and arranged with a constant separation of 0.65 nm. It was revealed that the STM image is not consistent with the previously proposed {114}-faceted model.