IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Tuesday Sessions
       Session SS3-TuP

Paper SS3-TuP24
Halogen Adsorption on Pt(110): A Coverage-dependent Charge Density Wave Transition

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Adsorption/Desorption Poster Session
Presenter: K. Swamy, University of Innsbruck, Austria
Authors: K. Swamy, University of Innsbruck, Austria
C. Deisl, University of Innsbruck, Austria
R. Beer, University of Innsbruck, Austria
A. Menzel, University of Innsbruck, Austria
E. Bertel, University of Innsbruck, Austria
Correspondent: Click to Email
STM and LEED results of halogen (Cl, Br) adsorption on Pt(110) show a sharp, coverage-dependent phase transition into a charge density wave ground state for a coverage of @THETA@ = 0.5 ML. At this coverage Br orders in a c(2x2) and Cl in a (2x1) structure. The (1x2) missing-row reconstruction of clean Pt(110) is lifted. Contrary to our previously published mode,@footnote 1@ LEED-IV data and ab-initio calculations reveal that the halogens are not substitutionally adsorbed, but in every second short-bridge site.@footnote 2@ Both, the Br-c(2x2) and the Cl-(2x1) phase can be transformed into a (3x1) phase by minute amounts of excess halogens (@THETA@ = (0.5 + @delta@) ML), but also of molecular species (CO and NO). The Br-c(2x2) derived (3x1) phase is stable up to T > 500 K, while the Cl-(2x1) derived (3x1) phase is long-ranged ordered only at T < 200 K. Low-temperature ARUPS spectra prove that the Br-(3x1) and the Cl-(3x1) phases have an almost identical electronic structure. We interpret the (3x1) structure as a charge density wave. This is compatible with the ARUPS data, i. e. we find a corresponding nesting vector and a Peierls gap. @FootnoteText@ @footnote 1@ K. Swamy, A. Menzel, R. Beer, and E. Bertel, Phys. Rev. Lett. 86, (2001) 1299. @footnote 2@ K. Swamy, C. Deisl, E. Bertel, V. Blum, L. Hammer, K. Heinz, C. Franchini, and J. Redinger, in prepration.