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Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 115: Metallic Nanowires on the Atomic Scale (jointly with DS, O)

TT 115.7: Talk

Friday, March 20, 2015, 11:15–11:30, H 2032

Vibrational properties and optical anisotropy of lead nanowires on Si(557) — •Eugen Speiser1, Arne Baumann1, Sandhya Chandola1, Jochen Räthel1, Daniel Lükermann2, Christoph Tegekamp2, and Norbert Esser11Leibniz-Institut für Analytische Wissenschaften - ISAS - e. V., Department Berlin, Schwarzschildstrasse 8, 12489 Berlin, Germany — 2Institut für Festkörperphysik, Appelstraße 2, 30167 Hannover, Leibniz Universität Hannover, Germany

We use Raman spectroscopy and Reflectance Anisotropy Spectroscopy (RAS) to investigate the vibrational properties and anisotropic optical response of Pb nanowires on Si(557). This model system, which shows quasi-1D conductance below 78 K, consists of 1.31 ML of Pb on the Si(557) surface. The adsorption of Pb induces a refacetting of the surface into evenly stepped (223) facets, decorated by one Pb nanowire each. Above 78 K the 2D coupling between the individual wires increases and allows conductivity perpendicular to them. RAS measurements of the Si(557) surface before and after Pb deposition show that the adsorption of Pb clearly induces a reorganization of the surface. Both phases exhibit a strongly anisotropic optical conductance behavior and anisotropic optical transitions which can be associated with the Pb induced reformation of the surface. The Raman spectra show surface vibrational modes which are only present after Pb deposition. With theoretical calculations it is possible to elucidate the relation of the surface vibrational modes with atomic structure and propose structural models for the high and low temperature phases.

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