Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 56: Symposium: The Solid-Liquid Interface: A Challenge for Theoreticians I

O 56.7: Vortrag

Donnerstag, 29. März 2007, 18:45–19:00, H36

Step Bunching Instability on Stepped Au(1 1 17) Electrodes in Sulfuric Acid Solution — •Margret Giesen, Ernesto Pichardo Pedrero, and Guillermo Beltramo — Institute for Bio- and Nanosystems, IBN 4, Research Centre Juelich, D 52425 Juelich, Germany

We present scanning tunneling microscopy data on the stability of stepped Au(1 1 17) electrodes (vicinal to the Au(001) surface) in sulfuric acid solution. We have analyzed the step-step distance probability distribution as a function of the electrode potential. The width of the probability distribution increases with the (absolute) difference between the electrode potential and the potential of zero charge. Our findings are in agreement with a recent theoretical model [1] showing that all electrode surfaces in contact with an electrolyte are instable against step bunching in a certain potential regime with respect to the potential of zero charge. This is the first quantitative experimental confirmation of the step bunching instability model for metal electrodes. Furthermore, we can deduce an estimate for the step-step interaction constant of 120+/-25 meVÅ. This value is more than an order of magnitude larger than typical values for metal surfaces in vacuum. The reason may lie in the specific adsorption of sulfate ions at the step edges. [1] Surf. Sci. 573 (2004) 24