Critical Considerations in Polymer Thin-Film Transistor (TFT) Dielectrics


We present a study of aqueous and plasma anodised aluminium oxide (Al2O3) and its performance in thin film transistors (TFTs). The current through the oxide was measured with aluminium electrodes and with one of the electrode replaced by poly(3-hexylthiophene)(P3HT). The current increased by up to 2 orders of magnitude with P3HT. The current increased further when the polymer was doped with different percentages of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). It was also found to be dependent on the thickness of the polymer film. Surprisingly, the oxide current fell to its initial value when the polymer film was removed. Two mechanisms may explain the behaviour in these devices: charge injection and/or displacement. C-V plots were obtained from the MOS capacitors and were frequency dependent. They also showed substantial hysteresis, with a lateral shift along the voltage axis. This indicates the presence of a mobile species that increases with the concentration of dopant. We deduce that much of the increased gate current is associated with displacement currents induced by ion motion.

This is a preview of subscription content, access via your institution.


  1. 1.

    G. Lloyd, M. Raja, I. Sellers, N. Sedghi, R. Di Lucrezia, S. J. Higgins and W. Eccleston Microelectronic Engineering 59, 323 (2001).

    CAS  Article  Google Scholar 

  2. 2.

    R. D. McCullough, S. P. Williams, S. Tristram-Nagle, M. Jayaraman, P. C. Ewbank and L. Miller, Synthetic Metals 69, 279 (1995).

    CAS  Article  Google Scholar 

  3. 3.

    M. Traznadel, A. Pron, M. Zagorska, R. Chrzaszcz and J. Pielichowski Macromolecules 31, 5051 (1998).

    Article  Google Scholar 

  4. 4.

    M. Raja, G. Lloyd, N. Sedghi, R. Di Lucrezia, S. J. Higgins and W. Eccleston MRS Meeting Fall Meeting 2001.

    Google Scholar 

  5. 5.

    H. Sirringhaus, P. J. Brown, R. H. Friend, M. M. Nielsen, K. Bechgaard, B. M. W. Langeveld-Voss, A. J. H. Spiering, R. A. J. Jansen, E. W. Meijer, P. Herwig and D. M. de Leeuw, Nature 401, 685 (1999).

    CAS  Article  Google Scholar 

  6. 6.

    N. Sedghi, G. Lloyd, M. Raja, R. Di Lucrezia, S. J. Higgins and W. Eccleston Mat. Res. Soc. Symp. Proc. 708, BB10.57 (2002).

  7. 7.

    O. Buiu, G. P. Kennedy, M. Gartner and S. Taylor IEEE Trans. on Plasma Science 26 (6), 1700 (1998).

    CAS  Article  Google Scholar 

  8. 8.

    I. Musa, D. A. I. Munindrasdasa, G. A. J. Amaratunga and W. Eccleston Nature 395, 362 (1998).

    CAS  Article  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Munira Raja.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Raja, M., Lloyd, G., Sedghi, N. et al. Critical Considerations in Polymer Thin-Film Transistor (TFT) Dielectrics. MRS Online Proceedings Library 725, 65 (2002).

Download citation