AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA7
H and O promoted Self-Diffusion of Pt(110)

Thursday, November 5, 1998, 4:00 pm, Room 308

Session: Surface Diffusion
Presenter: S. Horch, Aarhus University, Denmark
Authors: S. Horch, Aarhus University, Denmark
S. Helveg, Aarhus University, Denmark
I. Stensgaard, Aarhus University, Denmark
E. Laegsgaard, Aarhus University, Denmark
F. Besenbacher, Aarhus University, Denmark
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The surface self-diffusion of Pt adatoms on the Pt(110)-(1x2) surface is studied using variable-temperature Scanning Tunneling Microscopy. Exposing the surface to Hydrogen or Oxygen leads to an enhancement of the mobility of the adsorbed Pt adatoms. Atomically resolved STM movies provided the first experimental evidence that in the case of H this is due to the existence of H-Pt ad-dimer skyhooks diffusing several orders of magnitude faster than normal Pt adatoms. These movies allow us to analyse the lifetime distribution of these ad-dimers which gives a surprisingly high binding energy of about 0.8 eV. Nevertheless, only a small fraction of all Pt adatoms form these ad-dimers at the same time. A tentative model will be presented to explain these findings and compare them to the case of O.