IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoP

Paper SS2-MoP6
Metastable Crossed Row Structure and Nano-structural Change on TiO@sub 2@(001) Studied by STM

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Surfaces and Interfaces Poster Session
Presenter: R. Tero, The University of Tokyo, Japan
Authors: R. Tero, The University of Tokyo, Japan
K. Fukui, The University of Tokyo, Japan
Y. Iwasawa, The University of Tokyo, Japan
Correspondent: Click to Email
Atom-resolved structures on a rutile TiO@sub 2@(001) surface were visualized by scanning tunneling microscopy (STM). We have found that a flat ordered structure, which consists of crossed rows along the [110] and the [11-0] directions, can be prepared by annealing an Ar ion-sputtered TiO@sub 2@(001) surface at 850-1050 K under UHV with heating and cooling rates at 7-10 K s@super -1@. Its LEED pattern was identical to that for a {114}-faceted structure proposed in previous studies. The rows 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 units of three bright spots, which were lined perpendicular to the steps, were arranged by 0.65 nm on each narrow step. The crossed row structure was metastable and its stability depended on the degree of the bulk reduction. Structural transformation occurred at much lower temperatures than that for preparing the crossed row structure. Particles with nm scale appeared on the crossed row structure by reannealing the surface under UHV at 400-490 K. The surface was covered up with the particles of 0.9-6 nm in diameter. Adsorption of formic acid on the crossed row structure before reannealing drastically modified the structural transformation. The particle size was distributed to 2-8 nm in diameter after the formic acid-covered crossed row structure was reannealed at 710 K. The stability of the crossed row structures and the mechanism of the particle growth, which depended on the degree of bulk reduction and reaction of adsorbates, will be discussed.