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).
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