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Control of carrier density by self-assembled monolayers in organic field-effect transistors

Nature Materials volume 3, pages 317–322 (2004)Cite this article

Abstract

Organic thin-film transistors are attracting a great deal of attention due to the relatively high field-effect mobility in several organic materials. In these organic semiconductors, however, researchers have not established a reliable method of doping at a very low density level, although this has been crucial for the technological development of inorganic semiconductors. In the field-effect device structures, the conduction channel exists at the interface between organic thin films and SiO2 gate insulators. Here, we discuss a new technique that enables us to control the charge density in the channel by using organosilane self-assembled monolayers (SAMs) on SiO2 gate insulators. SAMs with fluorine and amino groups have been shown to accumulate holes and electrons, respectively, in the transistor channel: these properties are understood in terms of the effects of electric dipoles of the SAMs molecules, and weak charge transfer between organic films and SAMs.

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Figure 1: The TFTs structure and related SAMs molecules.
Figure 2: X-ray reflection curves against incident angle for the SAMs-SiO2 (400 nm)-Si substrate systems.
Figure 3: Trans-conductance characteristics of pentacene TFT devices grown on different SAMs.
Figure 4: Trans-conductance characteristics of C60 TFT devices grown on different SAMs.
Figure 5: Summary of the threshold voltage Vth in n-type C60 and p-type pentacene TFT devices for different SiO2 treatments, untreated and with three kinds of SAMs.

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Acknowledgements

This work has been partly supported by a Grant (13440110) from The Ministry of Education, Culture, Sports, Science, and Technology, Japan. The authors thank the staff at the Center for Computational Materials Science at the Insitute for Materials Research, Tohoku University, for computational assistance.

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Authors and Affiliations

  1. Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan

    S. Kobayashi, T. Takenobu, S. Mori, H. Shimotani & Y. Iwasa

  2. CREST, Japan Science and Technology Corporation, Kawaguchi, 333-0012, Japan

    S. Kobayashi, T. Takenobu, H. Shimotani & Y. Iwasa

  3. Technology Platform Research Center, SEIKO EPSON Corporation, Fujimi, Nagano, 399-0293, Japan

    T. Nishikawa & T. Shimoda

  4. Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa, 923-1292, Japan

    T. Nishikawa, T. Shimoda & T. Mitani

  5. Department of Materials Science and Engineering, Iwate University, Ueda, Morioka, 020-8551, Japan

    N. Yoshimoto

  6. Department of Chemical Engineering, Iwate University, Ueda, Morioka, 020-8551, Japan

    S. Ogawa

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  1. S. Kobayashi
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Correspondence to Y. Iwasa.

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Kobayashi, S., Nishikawa, T., Takenobu, T. et al. Control of carrier density by self-assembled monolayers in organic field-effect transistors. Nature Mater 3, 317–322 (2004). https://doi.org/10.1038/nmat1105

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