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Tunable Fröhlich polarons in organic single-crystal transistors

Nature Materials volume 5, pages 982–986 (2006)Cite this article

Abstract

In organic field-effect transistors (FETs), charges move near the surface of an organic semiconductor, at the interface with a dielectric. In the past, the nature of the microscopic motion of charge carriers—which determines the device performance—has been related to the quality of the organic semiconductor. Recently, it was discovered that the nearby dielectric also has an unexpectedly strong influence. The mechanisms responsible for this influence are not understood. To investigate these mechanisms, we have studied transport through organic single-crystal FETs with different gate insulators. We find that the temperature dependence of the mobility evolves from metallic-like to insulating-like with increasing dielectric constant of the insulator. The phenomenon is accounted for by a two-dimensional Fröhlich polaron model that quantitatively describes our observations and shows that increasing the dielectric polarizability results in a crossover from the weak to the strong polaronic coupling regime. This represents a considerable step forward in our understanding of transport through organic transistors, and identifies a microscopic physical process with a large influence on device performance.

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Figure 1: High-quality organic single-crystal transistors.
Figure 2: Gate-voltage dependence of the carrier mobility.
Figure 3: Temperature dependence of the carrier mobility.
Figure 4: Dependence of the threshold charge on temperature and dielectric constant of the gate insulator.
Figure 5: Comparison between experimental data and theory.

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Acknowledgements

We gratefully acknowledge V. Podzorov for discussions and for letting us use his temperature-dependent measurements on FETs with a parylene gate dielectric. We thank R. W. I. de Boer and A. F. Stassen for contributing to the initial part of this work. Useful discussions with J. van den Brink are also acknowledged. This work was supported by FOM and by NWO through the Vernieuwingsimpuls 2000 program.

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Authors and Affiliations

  1. Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands

    I. N. Hulea, H. Xie, C. L. Mulder, N. N. Iossad & A. F. Morpurgo

  2. Laboratoire d’Etudes des Propriétés Electroniques des Solides, CNRS, BP 166-25, Avenue des Martyrs, F-38042, Grenoble, Cedex 9, France

    S. Fratini & G. Rastelli

  3. INFM-CNR SMC and Dipartimento di Fisica, Università dell’Aquila, via Vetoio, I-67010, Coppito-L’Aquila, Italy

    G. Rastelli & S. Ciuchi

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  1. I. N. Hulea
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Correspondence to A. F. Morpurgo.

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Hulea, I., Fratini, S., Xie, H. et al. Tunable Fröhlich polarons in organic single-crystal transistors. Nature Mater 5, 982–986 (2006). https://doi.org/10.1038/nmat1774

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