Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 39: Poster: Metal Substrates

O 39.4: Poster

Tuesday, March 19, 2024, 18:00–20:00, Poster D

Probing the chemical bond between Ni and a CO-terminated AFM tip — •Maximilian Krüger, Fabian Stilp, Marco Weiss, and Franz J. Giessibl — Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany

AFM with a CO-terminated tip usually images the total charge density of atoms in a sample. Huber et al. [1] discovered exceptions to the chemically inert behaviour of the CO tip. For single Fe adatoms on Cu(111) a subatomic toroidal configuration was found, which maxima are aligned with the threefold symmetry of the underlying Cu lattice. This is resulting from the hybridisation of electronic states of CO and the adatom.

DFT calculations [2] suggest a similar, by 60 degrees rotated signature for Ni adatoms on the Cu(111) surface. Motivated by this, the same AFM measurement processes are used to examine Ni.

It is revealed that the interaction between Ni and CO also transitions from physisorption to chemisorption when approaching. At small tip-sample distances Ni appears as an attractive center with a surrounding repulsive ring as it is the case for Fe, but with different ratios between attractive and repulsive forces. Ultimately the three maxima could not be detected.

[1]: F. Huber, et al. ’Chemical Bond Formation Showing a Transition from Physisorption to Chemisorption’. Science 366, 6462 (2019): 235–238.

[2]: S. Polesya, S. Mankovsky, H. Ebert. unpublished calculations.

Keywords: AFM; atomic force microscopy; chemical bond; CO tip; adatom