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

Paper SS2-WeA9
Bridging the Pressure Gap at the Atomic Level

Wednesday, October 31, 2001, 4:40 pm, Room 121

Session: Adsorption on Metal Surfaces
Presenter: P. Thostrup, University of Aarhus, Denmark
Authors: P. Thostrup, University of Aarhus, Denmark
L Österlund, University of Aarhus, Denmark
I. Stensgaard, University of Aarhus, Denmark
E. Laegsgaard, University of Aarhus, Denmark
F. Besenbacher, University of Aarhus, Denmark
Correspondent: Click to Email
Surface science studies conducted under ultrahigh vacuum (UHV) conditions have contributed immensely to our current knowledge about catalytic processes. A fundamental question is however still, whether UHV data are in general applicable at technologically relevant pressures magnitudes higher than those obtainable in UHV studies. We have developed a novel high-pressure scanning tunneling microscope (HP-STM)@footnote 1@ in order to compare eg. the UHV and HP response of the H/Cu(110) and CO/Pt(110) systems. The H/Cu(110) system is a classic model system for activated dissociation. We find that hydrogen reconstructs the surface both at UHV and high pressures. Through a detailed comparison we even find quantitative agreement between HP and UHV data,@footnote 2@ thus providing support for the surface science approach to heterogeneous catalysis. The CO/Pt(110) system has attracted widespread attention since CO displays an unusually strong dependence upon the coordination number of the Pt atom to which it binds. This property makes the open Pt(110) surface ideal for HP experiments since high pressures of CO are expected to induce massive roughening of the surface. Notwithstanding, already in UHV this interesting property reveals itself:@footnote 3@ We find the equilibrium structure at intermediate coverages to be extremely rough to an extent where almost all top-layer Pt atoms are at steps. Interestingly, we have been able to reproduce this behavior quantitatively in Monte Carlo simulations where all energies involved are taken from ab initio density functional calculations. Preliminary experiments indicate that the roughening behavior described above is also present at high pressures, but in this case to an even more extensive degree. @FootnoteText@ @footnote 1@ E. Laegsgaard, P. Thostup et al., submitted to Rev. Sci. Instr. @footnote 2@ L. Österlund, P. Thostrup et al., Phys. Rev. Lett. 86, 460 (2001). @footnote 3@ P. Thostrup et al., submitted to Phys. Rev. Lett.