Adsorption of CO on the Ca₃Ru₂O₇(001) surface

W. Mayr-Schmölzer, D. Halwidl, F. Mittendorfer, M. Schmid, U. Diebold, J. Redinger

Surf. Sci. 680 (2019) 18-23

The adsorption of CO molecules at the Ca₃Ru₂O₇(001) surface was studied using low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT). Ca₃Ru₂O₇ can be easily cleaved along the (001) plane, yielding a smooth, CaO-terminated surface. The STM shows a characteristic pattern with alternating dark and bright stripes, resulting from the tilting of the RuO₆ octahedra. At 78 K, CO adsorbs at an apical surface O at the channel edge with a predicted binding energy of E_ads = -0.85 eV. After annealing at room temperature, the CO forms a strong bond (E_ads = -2.04 eV) with the apical O and the resulting carboxylate takes the place of the former surface O. This carboxylate can be decomposed by scanning the surface with a high sample bias voltage of +2.7 V, restoring the original surface.

Corresponding author: Florian Mittendorfer.

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A preprint is available at arXiv.org.