Regensburg 2022 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 9: New Methods and Developments: Scanning Probe Techniques 2 (joint session O/KFM)

KFM 9.1: Talk

Monday, September 5, 2022, 15:00–15:15, S053

The importance of the dipole at the metal tip apex when approaching closer with a CO tip — •Shinjae Nam, Oliver Gretz, Thomas Holzmann, Alfred John Weymouth, and Franz J. Giessible — University of Regensburg, Regensburg, Germany

By functionalizing the tip with a single CO molecule, the resolution of atomic force microscope (AFM) can be drastically increased. The contrast enhancement produced by a CO tip has been explained in terms of strong Pauli repulsion and the associated tilting of the probe molecule. Although these two interactions play a dominant role at very close distances, recent experiments show that other interactions, especially electrostatic forces, are also important to understand the observed contrast. Here, we used Lateral Force Microscope, a variant of frequency modulation atomic force microscopy, to quantify the interaction between a CO tip and a CO on the Cu (111) surface. Interestingly, one more feature appeared in the measurement when we measured closer to the surface at the side of the surface CO. Following the results of other investigations, we include the electrostatic force in our simulations. We modeled our tip as a quadrupole, including a dipole at both the metal tip and on the CO molecules. We found that the dipole of the metal apex of the tip becomes a much greater influence as we approach closer to the surface.