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O: Fachverband Oberflächenphysik

O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory

O 36.29: Poster

Dienstag, 1. April 2014, 18:30–22:00, P1

STM/STS investigation of ionic liquids adsorbed at metal surfaces — •Thomas Groß, Matthias Stocker, and Berndt Koslowski — Institut für Festkörperphysik, Universität Ulm, D-89081 Ulm

In the last years, ionic liquids (ILs) gained more and more interest in the fields of, e.g., catalysis, electrolytes, liquid crystals, electro-elasticity etc. We employ scanning tunneling microscopy and spectroscopy (STM and STS) at low temperature to investigate the properties of such ILs being adsorbed at metal surfaces. We therefore deposited 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)-imide (BMP-TFSA) and 1-ethyl-3-methylimidazoliumtrifluoromethanesulfonate (EMIM-TFSA) on Ag(111) in the sub-monolayer range. Preliminary results are reported as follows: The ILs form stable islands frequently bound by steps in the substrate. The resolution within the islands depends strongly on the state of the tunneling tip. Enhanced resolution is achieved with an IL molecule adsorbed at the tip. The surface state of Ag(111) prevails underneath the IL monolayer and shifts by about +100 meV towards the unoccupied states. We derive the charge state of the adsorbed molecules by determining the differential barrier height thus discriminating the anions and kations at the surface.