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O: Fachverband Oberflächenphysik
O 60: Poster Session IV (Solid/liquid interfaces; Semiconductors; Oxides and insulators; Graphene; Plasmonics and nanooptics; Electronic Structure; Surface chemical reactions; Heterogeneous catalysis)
O 60.76: Poster
Wednesday, March 16, 2011, 17:30–21:00, P4
Low dimensional plasmons in Ag-nanowires grown on Si (557) — •Ulrich Krieg, Christoph Tegenkamp, and Herbert Pfnür — Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany
A quasi 1-dimensional system was prepared by adsorption of about 1 monolayer Ag on Si(557) at 550∘ via self assembly. The morphology and metallicity of these uniaxially grown nanowires were studied by the combination of using low electron energy diffraction and high resolution electron energy loss spectroscopy in one instrument (ELS-LEED) . The clean Si(557) surface consists of a periodic sequence of (111) mini-terraces (3 nm width), separated by (112) facets. After adsorption of Ag LEED reveals the same spot splitting along the [1 12] direction, i.e. the initial alternating facet structure is conserved upon adsorption. A streaky √3 × √3 R30∘ reconstruction suggests further the formation of nanowires along the [110] direction. An alternating contrast seen by STM with spatial separations similar to those seen on Si(557) indeed confirms the growth of separated nanowires. These findings are fully supported by angle resolved EELS measurements. While along the wires a dispersion of a sheet plasmon has been found, across the wires only a non-dispersing state at around 450 meV has been identified. The localized peak, which is apparent also in the direction along the wires, can be reasonably explained assuming metallic wires with finite width of around 2.5 nm. Similar results were obtained recently for DySi22 wires grown on vicinal Si(111) substrates (PRB 81 (2010) 165407)