Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 11: Metal substrates: Adsorption of organic / bio molecules II

O 11.4: Talk

Monday, March 23, 2009, 15:45–16:00, SCH A118

Reversible breaking and forming of a metal-ligand bond by STM: PVBA and Cu adatoms on Cu(111) — •Robin Ohmann, Lucia Vitali, and Klaus Kern — Max-Planck-Institute for Solid State Research, Stuttgart, Germany

Controlling functional properties at the atomic scale is interesting for fundamental research and is a key for creating smaller operational units for computational devices. Recently, strong attention is focused on surface-adsorbed atoms and molecules, which undergo reversible positional or conformational changes. Here, we used 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) molecules, which were deposited in ultra high vacuum (UHV) via molecular beam epitaxy on a Cu(111) surface and measured with a scanning tunneling microscope operating at low temperature (6 K). Single PVBA molecules and self-assembled dimers, which are bond together by a Cu atom in the center, are predominantly observed. Although the single molecules show a stable configuration, for the dimers we found that the tunneling current oscillates between two values above a threshold voltage. This random telegraph noise has been investigated as a function of tip-sample distance, applied voltage and lateral position of the tip. By measuring the topography at well defined conditions, we were able to image both states of the dimer and ascribe their origin to a ligand in contact with and detached from the central metal atom.