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Portrait of the potential barrier at metal–organic nanocontacts

Nature Materials volume 9, pages 320–323 (2010)Cite this article

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Abstract

Electron transport through metal–molecule contacts greatly affects the operation and performance of electronic devices based on organic semiconductors1,2,3,4 and is at the heart of molecular electronics exploiting single-molecule junctions5,6,7,8. Much of our understanding of the charge injection and extraction processes in these systems relies on our knowledge of the potential barrier at the contact. Despite significant experimental and theoretical advances a clear rationale of the contact barrier at the single-molecule level is still missing. Here, we use scanning tunnelling microscopy to probe directly the nanocontact between a single molecule and a metal electrode in unprecedented detail. Our experiments show a significant variation on the submolecular scale. The local barrier modulation across an isolated 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid molecule bound to a copper(111) electrode exceeds 1 eV. The giant modulation reflects the interaction between specific molecular groups and the metal and illustrates the critical processes determining the interface potential. Guided by our results, we introduce a new scheme to locally manipulate the potential barrier of the molecular nanocontacts with atomic precision.

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Figure 1: Potential barrier across the plane of a molecule–metal nanocontact.
Figure 2: Charge-transfer map of deprotonated PVBA absorbed on Cu(111).
Figure 3: Manipulation of the potential barrier by coordination bonding.

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Acknowledgements

We thank Mario Ruben for synthesizing the PVBA. A.D.V. and G.L. acknowledge funding from EPSRC grant EP/G044864/1 and the ESF-EUROCORES SONS Programme.

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Authors and Affiliations

  1. Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany

    Lucia Vitali, Giacomo Levita, Robin Ohmann & Klaus Kern

  2. INFM-DEMOCRITOS National Simulation Center and Center of Excellence for Nanostructured Materials (CENMAT), University of Trieste, via Valerio 6a, 34127 Trieste, Italy

    Giacomo Levita

  3. Physics Department, King’s College London, Strand, London WC2R 2LS, UK

    Alessio Comisso & Alessandro De Vita

  4. Institut de Physique de la Matière Condensée, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

    Klaus Kern

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  1. Lucia Vitali
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All authors contributed extensively to the work.

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Correspondence to Lucia Vitali.

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Vitali, L., Levita, G., Ohmann, R. et al. Portrait of the potential barrier at metal–organic nanocontacts. Nature Mater 9, 320–323 (2010). https://doi.org/10.1038/nmat2625

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