When scanning tunneling microscopy gets the wrong adsorption site: H on Rh(100)

C. Klein1, A. Eichler2, E.L.D Hebenstreit1, G. Pauer3, R. Koller1, A. Winkler3, M. Schmid1 and P. Varga1

1 Institut für Allgemeine Physik, Technische Universität Wien, A 1040 Wien, Austria
2 Institut für Materialphysik and CMS, Universität Wien, A 1090 Wien, Austria
3 Institut für Festkörperphysik, TU Graz, A 8010 Graz, Austria

Phys. Rev. Lett. 90 (2003) 176101

At low tunneling resistance, scanning tunneling microscopy (STM) images of a Rh(100) surface with adsorbed hydrogen reproducibly show protrusions in all bridge sites of the surface, leading to a naive interpretation of all bridge sites being occupied with H atoms. Using quantitative low-energy electron diffraction (LEED) and temperature programmed desorption we find a much lower H coverage, with most H atoms in fourfold hollow sites. Density functional theory (DFT) calculations show that the STM result is due to the influence of the tip, attracting the mobile H atoms into bridge sites. This demonstrates that STM images of highly mobile adsorbates can be strongly misleading and underlines the importance of additional analysis techniques.

Corresponding author: C. Klein. Reprints also available from M. Schmid (schmid< encoded email address >).

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