Tuning fulleride electronic structure and molecular ordering via variable layer index


C60 fullerides are uniquely flexible molecular materials that exhibit a rich variety of behaviour1, including superconductivity and magnetism in bulk compounds2,3, novel electronic and orientational phases in thin films4,5,6,7,8,9,10 and quantum transport in a single-C60 transistor11. The complexity of fulleride properties stems from the existence of many competing interactions, such as electron–electron correlations, electron–vibration coupling and intermolecular hopping. The exact role of each interaction is controversial owing to the difficulty of experimentally isolating the effects of a single interaction in the intricate fulleride materials. Here, we report a unique level of control of the material properties of KxC60 ultrathin films through well-controlled atomic layer indexing and accurate doping concentrations. Using scanning tunnelling microscope techniques, we observe a series of electronic and structural phase transitions as the fullerides evolve from two-dimensional monolayers to quasi-three-dimensional multilayers in the early stages of layer-by-layer growth. These results demonstrate the systematic evolution of fulleride electronic structure and molecular ordering with variable KxC60 film layer index, and provide essential information for the development of new molecular structures and devices.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Structure of a representative KxC60 multilayer thin film on Au(111).
Figure 2: Electronic and structural properties of a K3C60 multilayer.
Figure 3: Electronic and structural properties of a K4C60 multilayer.
Figure 4: Electronic and structural properties of a K5C60 multilayer.


  1. 1

    Gunnarsson, O. Alkali-Doped Fullerides: Narrow-Band Solids with Unusual Properties (World Scientific, Singapore, 2004).

    Google Scholar 

  2. 2

    Hebard, A. F. et al. Superconductivity at 18 K in potassium-doped C60 . Nature 350, 600–601 (1991).

    CAS  Article  Google Scholar 

  3. 3

    Allemand, P. M. et al. Organic molecular soft ferromagnetism in a fullerene C60 . Science 253, 301–303 (1991).

    CAS  Article  Google Scholar 

  4. 4

    Tjeng, L. H. et al. Development of the electronic structure in a K-doped C60 monolayer on a Ag(111) surface. Solid State Commun. 103, 31–35 (1997).

    CAS  Article  Google Scholar 

  5. 5

    Hou, J. G. et al. Surface science—Topology of two-dimensional C60 domains. Nature 409, 304–305 (2001).

    CAS  Article  Google Scholar 

  6. 6

    Yang, W. L. et al. Band structure and Fermi surface of electron-doped C60 monolayers. Science 300, 303–307 (2003).

    CAS  Article  Google Scholar 

  7. 7

    Brouet, V. et al. Orientation-dependent C60 electronic structures revealed by photoemission spectroscopy. Phys. Rev. Lett. 93, 197601 (2004).

    CAS  Article  Google Scholar 

  8. 8

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

    CAS  Article  Google Scholar 

  9. 9

    Pai, W. W., Hsu, C. L., Lin, K. C., Sin, L. Y. & Tang, T. B. Characterization and control of molecular ordering on adsorbate-induced reconstructed surfaces. Appl. Surf. Sci. 241, 194–198 (2005).

    CAS  Article  Google Scholar 

  10. 10

    Wang, Y. et al. Novel orientational ordering and reentrant metallicity in KxC60 monolayers for 3<x<5. Phys. Rev. Lett. 99, 086402 (2007).

    Article  Google Scholar 

  11. 11

    Park, H. et al. Nanomechanical oscillations in a single-C60 transistor. Nature 407, 57–60 (2000).

    CAS  Article  Google Scholar 

  12. 12

    Grobis, M., Wachowiak, A., Yamachika, R. & Crommie, M. F. Tuning negative differential resistance in a molecular film. Appl. Phys. Lett. 86, 204102 (2005).

    Article  Google Scholar 

  13. 13

    Schiessling, J. et al. Bulk and surface charge states of K3C60 . Phys. Rev. B 71, 165420 (2005).

    Article  Google Scholar 

  14. 14

    Gunnarsson, O. Superconductivity in fullerides. Rev. Mod. Phys. 69, 575–606 (1997).

    CAS  Article  Google Scholar 

  15. 15

    Yamachika, R., Grobis, M., Wachowiak, A. & Crommie, M. F. Controlled atomic doping of a single C60 molecule. Science 304, 281–284 (2004).

    CAS  Article  Google Scholar 

  16. 16

    Lu, X. H., Grobis, M., Khoo, K. H., Louie, S. G. & Crommie, M. F. Spatially mapping the spectral density of a single C60 molecule. Phys. Rev. Lett. 90, 096802 (2003).

    Article  Google Scholar 

  17. 17

    Chakravarty, S., Gelfand, M. P. & Kivelson, S. Electronic correlation effects and superconductivity in doped fullerenes. Science 254, 970–974 (1991).

    CAS  Article  Google Scholar 

  18. 18

    Lu, J. P. Metal–insulator transitions in degenerate Hubbard models and AxC60 . Phys. Rev. B 49, 5687–5690 (1994).

    CAS  Article  Google Scholar 

  19. 19

    Gunnarsson, O., Koch, E. & Martin, R. M. Mott transition in degenerate Hubbard models: Application to doped fullerenes. Phys. Rev. B 54, 11026–11029 (1996).

    Article  Google Scholar 

  20. 20

    Fabrizio, M. & Tosatti, E. Nonmagnetic molecular Jahn–Teller Mott insulators. Phys. Rev. B 55, 13465–13472 (1997).

    CAS  Article  Google Scholar 

  21. 21

    Han, J. E., Gunnarsson, O. & Crespi, V. H. Strong superconductivity with local Jahn–Teller phonons in C60 solids. Phys. Rev. Lett. 90, 167006 (2003).

    CAS  Article  Google Scholar 

  22. 22

    Cox, D. M., Trevor, D. J., Reichmann, K. C. & Kaldor, A. C60La—a deflated soccer ball. J. Am. Chem. Soc. 108, 2457–2458 (1986).

    CAS  Article  Google Scholar 

  23. 23

    Antropov, V. P., Gunnarsson, O. & Jepsen, O. Coulomb integrals and model Hamiltonians for C60 . Phys. Rev. B 46, 13647–13650 (1992).

    CAS  Article  Google Scholar 

  24. 24

    Martin, R. L. & Ritchie, J. P. Coulomb and exchange interactions in C60n. Phys. Rev. B 48, 4845–4849 (1993).

    CAS  Article  Google Scholar 

  25. 25

    Lof, R. W., Vanveenendaal, M. A., Koopmans, B., Jonkman, H. T. & Sawatzky, G. A. Band-gap, excitons, and Coulomb interaction in solid C60 . Phys. Rev. Lett. 68, 3924–3927 (1992).

    CAS  Article  Google Scholar 

  26. 26

    Hesper, R., Tjeng, L. H. & Sawatzky, G. A. Strongly reduced band gap in a correlated insulator in close proximity to a metal. Europhys. Lett. 40, 177–182 (1997).

    CAS  Article  Google Scholar 

  27. 27

    Pederson, M. R. & Quong, A. A. Polarizabilities, charge states, and vibrational modes of isolated fullerene molecules. Phys. Rev. B 46, 13584–13591 (1992).

    CAS  Article  Google Scholar 

  28. 28

    Lammert, P. E., Rokhsar, D. S., Chakravarty, S., Kivelson, S. & Salkola, M. I. Metallic screening and correlation effects in superconducting fullerenes. Phys. Rev. Lett. 74, 996–999 (1995).

    CAS  Article  Google Scholar 

  29. 29

    Meinders, M. B. J., Tjeng, L. H. & Sawatzky, G. A. Comment on “C 1s autoionization study of electron hopping rates in solid C60”. Phys. Rev. Lett. 73, 2937 (1994).

    CAS  Article  Google Scholar 

  30. 30

    Han, J. E., Koch, E. & Gunnarsson, O. Metal–insulator transitions: Influence of lattice structure, Jahn–Teller effect, and Hund’s rule coupling. Phys. Rev. Lett. 84, 1276–1279 (2000).

    CAS  Article  Google Scholar 

  31. 31

    Hebard, A. F., Haddon, R. C., Fleming, R. M. & Kortan, A. R. Deposition and characterization of fullerene films. Appl. Phys. Lett. 59, 2109–2111 (1991).

    CAS  Article  Google Scholar 

  32. 32

    Koch, E., Gunnarsson, O. & Martin, R. M. Filling dependence of the Mott transition in the degenerate Hubbard model. Phys. Rev. B 60, 15714–15720 (1999).

    CAS  Article  Google Scholar 

  33. 33

    Gunnarsson, O., Satpathy, S., Jepsen, O. & Andersen, O. K. Orientation of C60 clusters in solids. Phys. Rev. Lett. 67, 3002–3005 (1991).

    CAS  Article  Google Scholar 

  34. 34

    Ramirez, A. P. Geometrically frustrated matter—Magnets to molecules. Mater. Res. Soc. Bull. 30, 447–451 (2005).

    CAS  Article  Google Scholar 

Download references


This work was supported in part by NSF Grant EIA-0205641 and by the Director, Office of Energy Research, Office of Basic Energy Science, Division of Material Sciences and Engineering, US Department of Energy under contract No. DE-AC03-76SF0098. Y.W. acknowledges a research fellowship from the Miller Institute for Basic Research in Science.

Author information



Corresponding authors

Correspondence to Yayu Wang or Michael F. Crommie.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Wang, Y., Yamachika, R., Wachowiak, A. et al. Tuning fulleride electronic structure and molecular ordering via variable layer index. Nature Mater 7, 194–197 (2008). https://doi.org/10.1038/nmat2100

Download citation

Further reading


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing