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Free-electron-like dispersion in an organic monolayer film on a metal substrate

Nature volume 444, pages 350–353 (2006)Cite this article

Abstract

Thin films of molecular organic semiconductors are attracting much interest for use in electronic and optoelectronic applications. The electronic properties of these materials and their interfaces are therefore worth investigating intensively1,2,3, particularly the degree of electron delocalization that can be achieved2,4. If the delocalization is appreciable, it should be accompanied by an observable electronic band dispersion. But so far only limited experimental data on the intermolecular dispersion of electronic states in molecular materials is available5,6,7,8, and the mechanism(s) of electron delocalization in molecular materials are also not well understood. Here we report scanning tunnelling spectroscopy observations of an organic monolayer film on a silver substrate, revealing a completely delocalized two-dimensional band state that is characterized by a metal-like parabolic dispersion with an effective mass of m* = 0.47me, where me is the bare electron mass. This dispersion is far stronger than expected for the organic film alone7, and arises as a result of strong substrate-mediated coupling between the molecules within the monolayer.

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Figure 1: Structure and electronic properties of PTCDA/Ag(111).
Figure 2: Free-electron-like two-dimensional band state of PTCDA/Ag(111).
Figure 3: Wavefunctions and energy level scheme of P1 and P2.
Figure 4: Band state in herringbone and square phase islands.

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References

  1. Dimitrakopoulos, C. D. & Malenfant, P. R. L. Organic thin film transistors for large area electronics. Adv. Mater. 14, 99–117 (2002)

    Article  CAS  Google Scholar 

  2. Karl, N. Charge carrier transport in organic semiconductors. Synth. Met. 133–134, 649–657 (2003)

    Article  Google Scholar 

  3. Cahen, D., Kahn, A. & Umbach, E. Energetics of molecular interfaces. Mater. Today 8, 32–41 (2005)

    Article  CAS  Google Scholar 

  4. Sun, Y., Yunqi, L. & Daoben, Z. Advances in organic field-effect transistors. J. Mater. Chem. 15, 53–65 (2005)

    Article  CAS  Google Scholar 

  5. Gensterblum, G. et al. Experimental evidence for 400-meV valence band dispersion in solid C60 . Phys. Rev. B 48, 14756–14759 (1993)

    Article  ADS  CAS  Google Scholar 

  6. Hasegawa, S. et al. Intermolecular energy-band dispersion in oriented thin films of bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole) by angle-resolved photo-emission. J. Chem. Phys. 100, 6969–6973 (1994)

    Article  ADS  CAS  Google Scholar 

  7. Yamane, H. et al. Intermolecular energy-band dispersion in PTCDA multilayers. Phys. Rev. B 68, 033102(4) (2003)

    Article  ADS  Google Scholar 

  8. Koch, N. et al. Evidence for temperature-dependent electron band dispersion in pentacene. Phys. Rev. Lett. 96, 156803(4) (2006)

    ADS  Google Scholar 

  9. Glöckler, K. et al. Highly ordered structures and submolecular scanning tunneling microscopy contrast of PTCDA and DM-PBDCI monolayers on Ag(111) and Ag(110). Surf. Sci. 405, 1–20 (1998)

    Article  ADS  Google Scholar 

  10. Witte, G. & Wöll, C. Growth of aromatic molecules on solid substrates for applications in organic electronics. J. Mater. Res. 19, 1889–1916 (2004)

    Article  ADS  CAS  Google Scholar 

  11. Forrest, S. R. Ultrathin organic films grown by organic molecular beam deposition and related techniques. Chem. Rev. 97, 1793–1896 (1997)

    Article  CAS  PubMed  Google Scholar 

  12. Möbus, M., Karl, N. & Kobayashi, T. Structure of perylene-tetracarboxylic-dianhydride thin films on alkali halide crystal substrates. J. Cryst. Growth 116, 495–504 (1992)

    Article  ADS  Google Scholar 

  13. Li, J. T., Schneider, W. D., Berndt, R. & Crampin, S. Electron confinement to nanoscale Ag islands on Ag(111): A quantitative study. Phys. Rev. Lett. 80, 3332–3335 (1998)

    Article  ADS  CAS  Google Scholar 

  14. Kraft, A. et al. Lateral adsorption geometry and site-specific electronic structure of a large organic chemisorbate on a metal surface. Phys. Rev. B 74, 041402(R) (2006)

    Article  ADS  Google Scholar 

  15. Norskov, J. K. Chemisorption on metal surfaces. Rep. Prog. Phys. 53, 1253–1295 (1990)

    Article  ADS  Google Scholar 

  16. Jung, M. et al. The electronic structure of adsorbed aromatic molecules: Perylene and PTCDA on Si(111) and Ag(111). J. Molec. Struct. 293, 239–244 (1993)

    Article  ADS  CAS  Google Scholar 

  17. Zou, Y. et al. Chemical bonding of PTCDA on Ag surfaces and the formation of interface states. Surf. Sci. 600, 1240–1251 (2006)

    Article  ADS  CAS  Google Scholar 

  18. Eremtchenko, M., Schaefer, J. A. & Tautz, F. S. Understanding and tuning the epitaxy of large aromatic adsorbates by molecular design. Nature 425, 602–605 (2003)

    Article  ADS  CAS  PubMed  Google Scholar 

  19. Ando, T., Fowler, A. B. & Stern, F. Electronic properties of two-dimensional systems. Rev. Mod. Phys. 54, 437–672 (1982)

    Article  ADS  CAS  Google Scholar 

  20. Kröger, J. et al. Surface state electron dynamics of clean and adsorbate-covered metal surfaces studied with the scanning tunnelling microscope. Prog. Surf. Sci. 80, 26–48 (2005)

    Article  ADS  Google Scholar 

  21. Hauschild, A. et al. Molecular distortions and chemical bonding of a large π-conjugated molecule on a metal surface. Phys. Rev. Lett. 94, 036106(4) (2005)

    Article  ADS  Google Scholar 

  22. Rurali, R., Lorente, N. & Ordejón, P. Comment on ‘Molecular distortions and chemical bonding of a large π-conjugated molecule on a metal surface’. Phys. Rev. Lett. 95, 209601 (2005)

    Article  ADS  CAS  PubMed  Google Scholar 

  23. Hauschild, A. et al. Reply to “Comment on ‘Molecular distortions and chemical bonding of a large π-conjugated molecule on a metal surface’.”. Phys. Rev. Lett. 95, 209602 (2005)

    Article  ADS  Google Scholar 

  24. Kaufman, D. L., Kosztin, I. & Schulten, K. Expansion method for stationary states of quantum billiards. Am. J. Phys. 67, 133–141 (1999)

    Article  ADS  Google Scholar 

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Acknowledgements

The work was financially supported by the Deutsche Forschungsgemeinschaft. Author Contributions R.T. and S.S. conducted the experiments and prepared the figures. A.L., in the context of her B.Sc. thesis, participated in the analysis of the data on the delocalized state. F.S.T. and R.T. wrote the paper. R.T., S.S. and F.S.T. discussed the experiments, the data analysis, and the manuscript intensively at all stages of the work.

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  1. School of Engineering and Science, International University Bremen, P. O. Box 750561, 28725, Bremen, Germany

    R. Temirov, S. Soubatch, A. Luican & F. S. Tautz

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  1. R. Temirov
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Correspondence to F. S. Tautz.

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Supplementary information

Supplementary Notes

This file contains background information on the structure of the PTCDA/Ag(111) interface (section a), additional data supporting an important conclusion of the main text (section b), and simulated wave functions of two-dimensional confined states for comparison with our data. (PDF 186 kb)

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Temirov, R., Soubatch, S., Luican, A. et al. Free-electron-like dispersion in an organic monolayer film on a metal substrate. Nature 444, 350–353 (2006). https://doi.org/10.1038/nature05270

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