Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 40: Metallic nanowires on the atomic scale (joint session with O)

DS 40.8: Talk

Friday, March 20, 2015, 11:45–12:00, H 2032

Doping Induced 1D Plasmons in Ag Monolayer Stripes on Si(557) — •Timo Lichtenstein, Ulrich Krieg, Christoph Tegenkamp, and Herbert Pfnür — Leibniz Universität Hannover, Institut für Festkörperphysik, 30167 Hannover, Germany

We demonstrate here by testing the plasmonic properties for the system Ag/Si(557) that the interaction between adsorbate layers of transition metal atoms and strongly anisotropic surfaces can lead to various quasi-1D signatures, which, however, are not all necessarily metallic. Using low energy electron diffraction in combination with scanning tunneling microscopy and electron energy loss spectroscopy, we correlate the structure with the properties of low dimensional collective excitations, as measured with momentum and energy resolving electron loss spectroscopy. Semiconducting structures with double periodicity along the chains are formed for Ag coverages below 0.3 ML. At higher coverages, coupled with the onset of √3 × √3 order, metallic wires are formed. This is evident from the appearance of plasmonic losses, which show 1D dispersion only along the wires. This 1D property even persists up to 1 ML, where a densely packed array of metallic √3 × √3 stripes is formed. We show evidence that the metallic property is induced by an extrinsic doping process of excess Ag atoms localized at the step edges, which can be reversibly removed and added. With this system we were able to explicitly show that the 1D plasmon frequency depends on the electron density proportional to √n_e also in the 1D case, and that the confinement of the electrons on the wires is also dependent on doping concentration.