NCAFM2023 Programme Booklet

Tuesday 0900 - 0920

LOCAL WORK FUNCTION ON GRAPHENE NANORIBBONS

D. Rothhardt 1 , A. Kimouche, 1 T. Klamroth, 2 and R. Hoffmann-Vogel*

1 Department of Physics and Astronomy, University of Potsdam, 14476 Potsdam 2 Department of Chemistry, University of Potsdam, 14476 Potsdam *Email: hoffmannvogel@uni-potsdam.de

Graphene nanoribbons show special electronic properties due to the local confinement of their charge carriers in the one-dimensional nanoribbon. Additionally, atomic-scale structural details have been resolved using tuning fork scanning force microscopy (SFM) [1]. We have shown that atomic-scale structural details can also be resolved using large-amplitude cantilever SFM using a bimodal oscillation mode with a graphene nanoribbon attached to the tip [2]. We have studied the force as a function of tip-sample distance. The forces are dominated by electrostatic forces. The tip exposes a graphene nanoribbon end to the sample and can be adequately described using a point-charge model. The graphene nanoribbon is well-described using a line-charge model. In addition, we have studied electrostatics of graphene nanoribbons on Au(111) by the Kelvin method. Kelvin prove force microscopy (KPFM) can be used to measure the local contact potential difference (LCPD) between a probe tip and a surface, related to the work function. We have determined the local work function difference between tip and sample. The local work function provides evidence for structural, electronic and chemical variations at surfaces. The LCPD data shows charge transfer between the graphene nanoribbons and the gold substrate. Our results are corroborated with density functional theory calculations. Our results help to understand the role of electron transfer in GNR/metal contacts for future GNR-based electronic devices.

Fig. 1 a) Topography, b) line-cut through topography, c) LCPD, d) line-cut through LCPD, e) calculation, distance: 1A, f) calculation, distance 2 A.

References [1] T. Dienel, S. Kawai, H. Söde, X. Feng, K. Müllen, P. Ruffieux, R. Fasel and O. Gröning, Nano Lett., 2015, 15 , 5185.

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