Abstract
We performed a series of distance tunnelling characteristics measurements for the system Au(111)/0.05 M H2SO4 + 1 mM Cu2+ to understand, if it is possible to map the liquid part of the double layer perpendicular to the electrode surface. We found that we probed the double layer in a distance range where we do not penetrate into the inner Helmholtz layer. Nevertheless, the tip is sufficiently close to the metal surface to address adlayer features showing sensitivity toward long-range ordered structures. The bias between the STM tip and the sample drops in the inner Helmholtz layer, and electronic overlap exists between the adsorbed layer and the metal surface. Molecular contributions to the electronic structure of ordered adlayers appear to be detectable. At larger distances from the surface the average barrier height was found to be about 1 eV, practically independent on the electrode potential.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
