Letter | Published:

Mapping orbital changes upon electron transfer with tunnelling microscopy on insulators

Naturevolume 566pages245248 (2019) | Download Citation


Electron transfer plays a crucial part in many chemical reactions1,2, including photosynthesis, combustion and corrosion. But even though redox-state transitions change the electronic structure of the molecules involved, mapping these changes at the single-molecule level is challenging. Scanning tunnelling microscopy provides insights into the orbital structure3 of single molecules and their interactions4,5, but requires the use of a conductive substrate that keeps molecules in a given charge state and thereby suppresses redox-state transitions. Atomic force microscopy can be used on insulating substrates to obtain structural6 and electrostatic7,8 information but does not generally access electronic states. Here we show that when synchronizing voltage pulses that steer electron tunnelling between a conductive atomic force microscope tip and a substrate with the oscillation of the tip, we can perform tunnelling experiments on non-conductive substrates and thereby map the orbital structure of isolated molecules as a function of their redox state. This allows us to resolve previously inaccessible electronic transitions in space and energy and to visualize the effects of electron transfer and polaron formation on individual molecular orbitals. We anticipate that our approach will prove useful for the investigation of complex redox reactions and charging-related phenomena with sub-ångström resolution.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Data availability

The data that support the findings of this study are available from the corresponding author on reasonable request.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


  1. 1.

    Marcus, R. A. Electron transfer reactions in chemistry: theory and experiment (Nobel lecture). Angew. Chem. Int. Ed. 32, 1111–1121 (1993).

  2. 2.

    Bauer, A., Westkämper, F., Grimme, S. & Bach, T. Catalytic enantioselective reactions driven by photoinduced electron transfer. Nature 436, 1139–1140 (2005).

  3. 3.

    Repp, J., Meyer, G., Stojković, S. M., Gourdon, A. & Joachim, C. Molecules on insulating films: scanning-tunneling microscopy imaging of individual molecular orbitals. Phys. Rev. Lett. 94, 026803 (2005).

  4. 4.

    Imada, H. et al. Real-space investigation of energy transfer in heterogeneous molecular dimers. Nature 538, 364–367 (2016).

  5. 5.

    Zhang, Y. et al. Visualizing coherent intermolecular dipole-dipole coupling in real space. Nature 531, 623–627 (2016).

  6. 6.

    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).

  7. 7.

    Gross, L. et al. Measuring the charge state of an adatom with noncontact atomic force microscopy. Science 324, 1428–1431 (2009).

  8. 8.

    Steurer, W., Fatayer, S., Gross, L. & Meyer, G. Probe-based measurement of lateral single-electron transfer between individual molecules. Nat. Commun. 6, 8353 (2015).

  9. 9.

    Giessibl, F. J. Atomic resolution on Si(111)-(7×7) by noncontact atomic force microscopy with a force sensor based on a quartz tuning fork. Appl. Phys. Lett. 76, 1470–1472 (2000).

  10. 10.

    Johnson, J. P., Zheng, N. & Williams, C. C. Atomic scale imaging and spectroscopy of individual electron trap states using force detected dynamic tunnelling. Nanotechnology 20, 055701 (2009).

  11. 11.

    Wang, R. & Williams, C. C. Dynamic tunneling force microscopy for characterizing electronic trap states in non-conductive surfaces. Rev. Sci. Instrum. 86, 093708 (2015).

  12. 12.

    Lotze, C., Corso, M., Franke, K. J., von Oppen, F. & Pascual, J. I. Driving a macroscopic oscillator with the stochastic motion of a hydrogen molecule. Science 338, 779–782 (2012).

  13. 13.

    Cockins, L. et al. Energy levels of few-electron quantum dots imaged and characterized by atomic force microscopy. Proc. Natl Acad. Sci. USA 107, 9496–9501 (2010).

  14. 14.

    Steurer, W., Gross, L. & Meyer, G. Local thickness determination of thin insulator films via localized states. Appl. Phys. Lett. 104, 231606 (2014).

  15. 15.

    Fatayer, S. et al. Reorganization energy upon charging a single molecule on an insulator measured by atomic force microscopy. Nat. Nanotechnol. 13, 376–380 (2018).

  16. 16.

    Neese, F. The ORCA program system. WIRES Comput. Mol. Sci. 2, 73–78 (2012).

  17. 17.

    Szabo, A. & Ostlund, N. S. Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory (Courier Corporation, North Chelmsford, 2012).

  18. 18.

    Repp, J., Meyer, G., Olsson, F. E. & Persson, M. Controlling the charge state of individual gold adatoms. Science 305, 493–495 (2004).

  19. 19.

    Schulz, F. et al. Many-body transitions in a single molecule visualized by scanning tunnelling microscopy. Nat. Phys. 11, 229–234 (2015).

  20. 20.

    Wachowiak, A. et al. Visualization of the molecular Jahn-Teller effect in an insulating K4C60 monolayer. Science 310, 468–470 (2005).

  21. 21.

    Uhlmann, C., Swart, I. & Repp, J. Controlling the orbital sequence in individual Cu-phthalocyanine molecules. Nano Lett. 13, 777–780 (2013).

  22. 22.

    Setvin, M. et al. Direct view at excess electrons in TiO2 rutile and anatase. Phys. Rev. Lett. 113, 086402 (2014).

  23. 23.

    Esch, F. et al. Electron localization determines defect formation on ceria substrates. Science 309, 752–755 (2005).

  24. 24.

    Stähler, J., Deinert, J. C., Wegkamp, D., Hagen, S. & Wolf, M. Real-time measurement of the vertical binding energy during the birth of a solvated electron. J. Am. Chem. Soc. 137, 3520–3524 (2015).

  25. 25.

    Li, B. et al. Ultrafast interfacial proton-coupled electron transfer. Science 311, 1436–1440 (2006).

  26. 26.

    Miller, A. D. et al. Electron solvation in two dimensions. Science 297, 1163–1166 (2002).

  27. 27.

    O’Driscoll, L. J. et al. Electrochemical control of the single molecule conductance of a conjugated bis(pyrrolo)tetrathiafulvalene based molecular switch. Chem. Sci. 8, 6123–6130 (2017).

  28. 28.

    Holstein, T. Studies of polaron motion: part II. The ‘small’ polaron. Ann. Phys. 8, 343–389 (1959).

  29. 29.

    Toroz, D., Rontani, M. & Corni, S. Proposed alteration of images of molecular orbitals obtained using a scanning tunneling microscope as a probe of electron correlation. Phys. Rev. Lett. 110, 018305 (2013).

  30. 30.

    Wang, R., King, S. W. & Williams, C. C. Atomic scale trap state characterization by dynamic tunneling force microscopy. Appl. Phys. Lett. 105, 052903 (2014).

  31. 31.

    Payne, A., Ambal, K., Boehme, C. & Williams, C. C. Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy. Phys. Rev. B 91, 195433 (2015).

  32. 32.

    Cocker, T. L., Peller, D., Yu, P., Repp, J. & Huber, R. Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging. Nature 539, 263–267 (2016).

Download references


We thank L. Gross, S. Fatayer, F. Giessibl, F. Evers, R. Huber and G. Meyer for discussions. Financial support from the Marie Curie Initial Training Network ‘MOLESCO’ (number 606728) and Deutsche Forschungsgemeinschaft (numbers RE2669/6-1 and GRK 1570) is gratefully acknowledged.

Reviewer information

Nature thanks C. Williams and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information


  1. Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany

    • Laerte L. Patera
    • , Fabian Queck
    • , Philipp Scheuerer
    •  & Jascha Repp


  1. Search for Laerte L. Patera in:

  2. Search for Fabian Queck in:

  3. Search for Philipp Scheuerer in:

  4. Search for Jascha Repp in:


All authors designed and performed the experiments and analysed the data. L.L.P. and J.R. were responsible for DFT calculations and co-wrote the paper. All authors revised the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Laerte L. Patera or Jascha Repp.

Extended data figures and tables

  1. Extended Data Fig. 1 Scheme and detailed shape of a.c.

    voltage pulses.

  2. Extended Data Fig. 2 Orbital confinement upon electron transfer in pentacene.

    a, b, Electronic transitions probed by the same metal tip apex (A = 1 Å): 0→1 (a; Vd.c. = 1.87 V, Va.c. = 1.00 Vpp, Δz = 2 Å); 1→0 (b; Vd.c. = 1.87 V, Va.c. = 1.50 Vpp, Δz = 2 Å). Δz is given with respect to an AFM setpoint of Δf = −3.2 Hz at Vd.c. = 0 V. Scale bar, 5 Å. c, Line profiles taken along the directions indicated in a and b.

  3. Extended Data Fig. 3 Modulus square of calculated orbitals for neutral and negatively charged CuPc.

    a, b, Constant-height cuts of the superposition of degenerate LUMOs (a) and of only one of the degeneracy-lifted LUMOs (b). Scale bar, 5 Å.

  4. Extended Data Fig. 4 Dissipation signal as a function of tip–sample distance.

    Spectrum acquired above the centre of an isolated pentacene molecule (Vd.c. = 1.76 V, Va.c. = 1.00 V, A = 1 Å, 0→1). Δz is given with respect to an AFM setpoint of Δf = −3.2 Hz at Vd.c. = 0 V. Signal saturation is observed at short tip–sample distances because not more than one electron per set pulse can be transferred.

  5. Extended Data Fig. 5 Imaging of electronic transitions in constant-detuning mode.

    a, AFM topography image (Δf = −28.5 Hz, Vd.c. = 1.60 V, Va.c. = 1.00 V, A = 1 Å) of an isolated pentacene molecule on NaCl. b, Simultaneously acquired dissipation channel, corresponding to the 0→1 transition.

About this article

Publication history




Issue Date




By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.