Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 12: Postersitzung (Struktur und Dynamik reiner Oberfl
ächen, Grenzfl
äche fest-flüssig, Nanostrukturen, Teilchen und Cluster, Halbleiteroberfl
ächen und Grenzfl
ächen, Zeitaufgelöste Spektroskopie, Rastersondentechniken, Methodisches)

O 12.38: Poster

Montag, 24. März 2003, 18:00–21:00, P1

Theoretical models for the transfer of image-state electrons through Ar spacer layers — •W. Berthold¹, U. Höfer¹, P. Feulner², C. Marinica³, A. Borisov³, J.-P. Gauyacq³, M. Machado⁴, E. Chulkov⁴, and P. Echenique⁴ — ¹Fachbereich Physik, Philipps-Universtät, D-35032 Marburg — ²Physik-Department E20, Technische Universtät München, D-85748 Garching — ³Laboratoire des Collisions Atomiques et Moléculaires, Université Paris-Sud, 91405 Orsay Cedex, France — ⁴Donostia International Physics Center, 20018 San Sebastián, Spain

We have investigated the image-potential states of Cu(100) in the presence of Ar spacer layers as prototype for electron transfer processes through thin, insulating dielectric layers. We demonstrate that a detailed quantitative comparison of experimental results is possible for this well-defined, simple system. Our time-resolved two-photon photoemission (2PPE) experiments show that films with thicknesses of only a few monolayers decouple the image-potential states efficiently from the metal surface and result in lifetime increases of up to three orders of magnitude. A parameterized one-dimensional atomic potential results in a bulk penetration of the image-state wavefunction as a function of layer thickness that scales like the measured lifetimes. Absolute lifetimes are reproduced by GW many-body calculations using this potential. Finally, a three-dimensional parameter-free treatment of the Ar layers is considered. The results of wave-packet propagation methods are compared with the measured lifetime and dispersion of the states.