Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Metal substrates: Solid-liquid interfaces

O 39.6: Vortrag

Mittwoch, 25. März 2009, 16:15–16:30, SCH A315

Anomalous Helmholtz-Capacitance on Stepped Surfaces of Silver and Gold — •Guillermo Beltramo, Harald Ibach, and Margret Giesen — Institute for Bio- und Nano-Systems (IBN), Jülich Forschungszentrum, D-52425 Jülich, Germany

Interest in generation and functionalization of nanoscale structures on solid templates has grown tremendously because of their eminent role in many areas of technology. In vicinal surfaces, the presence of arrays of atomic steps separated by flat terraces creates regions of varying local atomic coordination, which renders unique properties to these surfaces, quite distinct from those of flat surfaces. [1]. We have studied the capacitance of the solid/electrolyte interface on Ag(11n) and Au(11n) surfaces in KClO4 and HClO4 as function of the electrolyte concentration and the step density. We find that the inner layer capacitance (Helmholtz-capacitance) is dramatically reduced on stepped surfaces [2]. Standard theories which describe the Helmholtz-capacitance by properties of the liquid, a hard wall boundary condition and the polarizability of the electron gas at the metal surface fail to describe this behavior. We propose that the different polarizability of water bonded to the surface need be taken into account and attribute the reduced capacitance at steps to the lower polarizability of water molecules bonded to step edges. The results will be discussed. [1] H. Ibach, M. Giesen ann W. Schmickler, J. Electroanal. Chem. 544 (2003) 13. [2] G.L. Beltramo, H. Ibach and M. Giesen, Surf. Sci. 601 (2007) 1876.