Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 14: Organic, polymeric, biomolecular films – also with absorbates I
O 14.7: Talk
Monday, March 23, 2009, 16:30–16:45, SCH A316
In-situ EC-STM studies on the influence of halide anions on structure and reactivity of Dibenzylviologen on Cu(1 0 0) — •Knud Gentz1, Peter Broekmann2, and Klaus Wandelt1 — 1Institute of Physical and Theoretical Chemistry, Bonn University — 2University of Bern
Copper has become a focus of research activities over the last two decades due to its use as interconnect material in microchip design. Nitrogen-containing cationic organic molecules have been studied as additives for the so-called copper damascene process. In the present investigation the structures and reactivity of a Dibenzylviologen (DBV) layer adsorbed on a bromide-modified Cu(1 0 0) surface have been studied by in-situ electrochemical STM and will be compared to the results on the chloride-modified substrate and the related Diphenylviologen (DPV). N,N’-dibenzyl-4,4’-bipyridinium molecules (Dibenzylviologen, DBV) spontaneously adsorb on a halide-modified Cu(1 0 0)-surface, forming distinctive patterns, which have been characterized by in-situ Scanning Tunneling Microscopy. Depending on the adsorption potential a striped phase, a cavitand phase and an amorphous phase have been identified. Cyclic Voltammetry indicates that even more processes take place on the surface, because if the potential is decreased beyond a range of fully reversible processes, an irreversible surface phase formation is observed at -450 mV vs. RHE . This surface phase passivates the surface against adsorption of the dicationic phase, so the charge reversal of the interface in the outer Helmholtz layer seems to be reduced.