Scanning tunnelling microscopy and atomic force microscopy can be used to study the electronic and structural properties of surfaces, as well as molecules and nanostructures adsorbed on surfaces, with atomic precision1,2,3,4,5,6,7, but they cannot directly probe the distribution of charge in these systems. However, another form of scanning probe microscopy, Kelvin probe force microscopy, can be used to measure the local contact potential difference between the scanning probe tip and the surface, a quantity that is closely related to the charge distribution on the surface8,9,10,11,12. Here, we use a combination of scanning tunnelling microscopy, atomic force microscopy and Kelvin probe force microscopy to examine naphthalocyanine molecules (which have been used as molecular switches13) on a thin insulating layer of NaCl on Cu(111). We show that Kelvin probe force microscopy can map the local contact potential difference of this system with submolecular resolution, and we use density functional theory calculations to verify that these maps reflect the intramolecular distribution of charge. This approach could help to provide fundamental insights into single-molecule switching and bond formation, processes that are usually accompanied by the redistribution of charge within or between molecules14,15,16.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Scientific Reports Open Access 08 March 2022
Nature Communications Open Access 24 September 2021
Communications Physics Open Access 19 March 2020
Subscribe to Journal
Get full journal access for 1 year
only $9.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Piva, P. G. et al. Field regulation of single-molecule conductivity by a charged surface atom. Nature 435, 658–661 (2005).
Sugimoto, Y. et al. Chemical identification of individual surface atoms by atomic force microscopy. Nature 446, 64–67 (2007).
Ashino, M. et al. Atomically resolved mechanical response of individual metallofullerene molecules confined inside carbon nanotubes. Nature Nanotech. 3, 337–341 (2008).
Albers, B. J. et al. Three-dimensional imaging of short-range chemical forces with picometre resolution. Nature Nanotech. 4, 307–310 (2009).
Gross, L., Mohn, F., Moll, N., Liljeroth, P. & Meyer, G. The chemical structure of a molecule resolved by atomic force microscopy. Science 325, 1110–1114 (2009).
Vitali, L. et al. Portrait of the portential barrier at metal–organic nanocontacts. Nature Mater. 9, 320–323 (2010).
Swart, I., Sonnleitner, T. & Repp, J. Charge state control of molecules reveals modification of the tunneling barrier with intramolecular contrast. Nano Lett. 11, 1580–1584 (2011).
Sommerhalter, C., Matthes, T. W., Glatzel, T., Jäger-Waldau, A. & Lux-Steiner, M. C. High-sensitivity quantitative Kelvin probe microscopy by noncontact ultra-high-vacuum atomic force microscopy. Appl. Phys. Lett. 75, 286–288 (1999).
Barth, C. & Henry, C. R. Surface double layer on (001) surfaces of alkali halide crystals: a scanning force microscopy study. Phys. Rev. Lett. 98, 136804 (2007).
Gross, L. et al. Measuring the charge state of an adatom with noncontact atomic force microscopy. Science 324, 1428–1431 (2009).
König, T. et al. Measuring the charge state of point defects on MgO/Ag(001). J. Am. Chem. Soc. 131, 17544–17545 (2009).
Leoni, T. et al. Controlling the charge state of a single redox molecular switch. Phys. Rev. Lett. 106, 216103 (2011).
Liljeroth, P., Repp, J. & Meyer, G. Current-induced hydrogen tautomerization and conductance switching of naphthalocyanine molecules. Science 317, 1203–1206 (2007).
Grill, L. et al. Nano-architectures by covalent assembly of molecular building blocks. Nature Nanotech. 2, 687–691 (2007).
Wang, W. et al. Manipulating localized molecular orbitals by single-atom contacts. Phys. Rev. Lett. 105, 126801 (2010).
Mohn, F. et al. Reversible bond formation in a gold-atom–organic-molecule complex as a molecular switch. Phys. Rev. Lett. 105, 266102 (2010).
Nonnenmacher, M., O'Boyle, M. P. & Wickramasinghe, H. K. Kelvin probe force microscopy. Appl. Phys. Lett. 58, 2921–2923 (1991).
Burke, S. A. et al. Determination of the local contact potential difference of PTCDA on NaCl: a comparison of techniques. Nanotechnology 20, 264012 (2009).
Sadewasser, S. et al. New insights on atomic-resolution frequency-modulation Kelvin-probe force-microscopy imaging of semiconductors. Phys. Rev. Lett. 103, 266103 (2009).
Enevoldsen, G. H., Glatzel, T., Christensen, M. C., Lauritsen, J. V. & Besenbacher, F. Atomic scale Kelvin probe force microscopy studies of the surface potential variations on the TiO2 (110) surface. Phys. Rev. Lett. 100, 236104 (2008).
Bocquet, F., Nony, L., Loppacher, C. & Glatzel, T. Analytical approach to the local contact potential difference on (001) ionic surfaces: implications for Kelvin probe force microscopy. Phys. Rev. B 78, 035410 (2008).
Kawai, S., Glatzel, T., Hug, H-J. & Meyer, E. Atomic contact potential variations of Si(111)-7×7 analysed by Kelvin probe force microscopy. Nanotechnology 21, 245704 (2010).
Masago, A., Tsukada, M. & Shimizu, M. Simulation method of Kelvin probe force microscopy at nanometer range and its application. Phys. Rev. B 82, 195433 (2010).
Repp, J., Meyer, G., Stojkovic, S. M., Gourdon, A. & Joachim, C. Molecules on insulating films: scanning-tunneling microscopy imaging of individual molecular orbitals. Phys. Rev. Lett. 94, 026803 (2005).
Gross, L. et al. High-resolution molecular orbital imaging using a p-wave STM tip. Phys. Rev. Lett. 107, 086101 (2011).
Gross, L. et al. Organic structure determination using atomic-resolution scanning probe microscopy. Nature Chem. 2, 821–825 (2010).
Bartels, L., Meyer, G. & Rieder, K-H. Controlled vertical manipulation of single CO molecules with the scanning tunneling microscope: a route to chemical contrast. Appl. Phys. Lett. 71, 213–215 (1997).
Jäckel, F. et al. Investigating molecular charge transfer complexes with a low temperature scanning tunneling microscope. Phys. Rev. Lett. 100, 126102 (2008).
Tao, C. et al. Spatial resolution of a type II heterojunction in a single bipolar molecule. Nano Lett. 9, 3963–3967 (2009).
Mohn, F., Gross, L. & Meyer, G. Measuring the short-range force field above a single molecule with atomic resolution. Appl. Phys. Lett. 99, 053106 (2011).
CPMD, v.3.15 (copyright IBM Corp. 1990–2011, copyright MPI für Festkörperforschung Stuttgart 1997–2001).
The authors thank J. Repp, R. Allenspach and W. Riess for helpful comments. Financial support from EU projects Herodot and ARTIST, as well as the ERC Advanced Grant CEMAS, is gratefully acknowledged.
The authors declare no competing financial interests.
About this article
Cite this article
Mohn, F., Gross, L., Moll, N. et al. Imaging the charge distribution within a single molecule. Nature Nanotech 7, 227–231 (2012). https://doi.org/10.1038/nnano.2012.20
This article is cited by
Scientific Reports (2022)
Nature Communications (2021)
Communications Physics (2020)
Nature Materials (2019)
Real-space charge-density imaging with sub-ångström resolution by four-dimensional electron microscopy