Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 90: Post-Deadline Session

O 90.2: Vortrag

Donnerstag, 3. April 2014, 20:15–20:30, TRE Phy

Quantifying molecular stiffness and interaction with lateral force microscopy — •Alfred J. Weymouth, Thomas Hofmann, and Franz J. Giessibl — University of Regensburg, Regensburg, Germany

One of the most impressive atomic force microscopy (AFM) images was taken by Leo Gross and coworkers at IBM of a molecule showing every carbon-carbon bond within it [1]. A key step was to functionalize the tip with a CO molecule, making the apex of the AFM tip small and chemically inert [2]. However, this comes with a complication: The CO isn't stiff but rather pivots when a horizontal force is applied. Moreover, standard experimental and theoretical approaches have not been able to characterize this torsional spring. We modified our AFM to be sensitive to lateral forces (LFM). As we measure forces along the surface, we are highly sensitive to short-range interactions. We combined both LFM and AFM data of a CO terminated tip probing a CO surface molecule, to determine the parameters of a simple model: two torsional springs interacting via a Morse potential [3].

[1] L. Gross, F. Mohn, N. Moll, P. Liljeroth, G. Meyer, Science 325, 1110 (2009).

[2] L. Bartels, G. Meyer, and K.-H. Rieder, Appl. Phys. Lett. 71, 213 (1997).

[3] A.J. Weymouth, T. Hofmann, F.J. Giessibl, Science, 6 February 2014 (10.1126/science.1249502).