Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Oxides and insulators: Adsorption II

O 45.5: Vortrag

Mittwoch, 16. März 2011, 12:15–12:30, WIL C307

Controlling the charge-state of single molecules — Ingmar Swart, •Tobias Sonnleitner, and Jascha Repp — Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg

The chemical and physical properties of atoms and molecules adsorbed on surfaces are influenced by several factors, such as molecule-substrate and molecule-molecule interactions. In this context, especially the charge state of adsorbates is of great importance, since it governs various properties, such as the spin-state, the interaction with other adsorbates and the substrate. Here, we present an STM study on single molecules adsorbed on an ultrathin NaCl film supported by a Cu surface. The use of an ultrathin insulating NaCl film electronically decouples the molecules from the metallic substrate. The molecules exhibit two states with considerably different conductance, which are associated with two different charge states. This is evidenced by changes in the scattering of the interface state, as well as spectroscopic data. The charge state of a molecule can be controlled by adding or removing a single electron to or from the molecule with the STM tip, analogous to what has previously been shown for individual metal atoms. Most importantly, both states are stable, that is, an additional charge will remain on the molecule until it is removed by a voltage pulse of opposite polarity. We demonstrate how one can generalize the charge state control to other molecules. Furthermore, we demonstrate how the tunneling barrier is modified by the presence of an additional charge with intramolecular resolution.