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O: Oberflächenphysik

O 42: Symposium Electron transfer processes II

O 42.3: Fachvortrag

Donnerstag, 30. März 2006, 16:00–16:30, WIL C207

Dynamics of surface-localised electronic excitations studied with the scanning tunnelling microscope — •J. Kröger — Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany

The dynamics of surface-localised electronic states can be influenced by confinement, by the presence of single adsorbed atoms, and, in the case of superstructures, by Brillouin zone backfolding.

On Ag(111) monatomically deep vacancy islands were fabricated to confine the electronic surface state. Depending upon the size of the vacancy island the dominant lifetime-limiting process can be lossy scattering of the electron waves at the vacancy boundary. An analytic expression is derived to take this effect into account. Further, a corrected analysis of the spatial decay of electron interference patterns is presented, which leads to a more consistent description of the Ag(111) surface state lifetime.

Single adsorbed Ag, Cu, and Co atoms on Ag(111) and Cu(111) induce an electronic resonance, which is split off from the bottom of the surface state band. Whereas Ag atoms on Ag(111) and Cu atoms on Cu(111) decrease the surface state lifetime, the impact of Co atoms on the surface state dynamics is found to be negligible.

The role of elastic scattering in the dynamics of quantum well states on Cu(111)-p(2x2)Cs is addressed. We find that elastic scattering is enhanced by Brillouin zone backfolding and contributes appreciably to the observed quantum well state linewidth: Calculations show that 50% of the linewidth are due to the backfolding mechanism.