Effect of self-assembled monolayers on charge injection and transport in poly(3-hexylthiophene)-based field-effect transistors at different channel length scales

K. A. Singh, T. L. Nelson, J. A. Belot, T. M. Young, N. R. Dhumal, T. Kowalewski, R. D. McCullough, P. Nachimuthu, S. Thevuthasan, L. M. Porter

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Charge injection and transport in bottom-contact regioregular-poly(3- hexylthiophene) (rr-P3HT) based field-effect transistors (FETs), wherein the Au source and drain contacts are modified by self-assembled monolayers (SAMs), is reported at different channel length scales. Ultraviolet photoelectron spectroscopy is used to measure the change in metal work function upon treatment with four SAMs consisting of thiol-adsorbates of different chemical composition. Treatment of FETs with electron-poor (electron-rich) SAMs resulted in an increase (decrease) in contact metal work function because of the electron-withdrawing (-donating) tendency of the polar molecules. The change in metal work function affects charge injection and is reflected in the form of the modulation of the contact resistance, R C. For example, R C decreased to 0.18 Mω in the case of the (electron-poor) 3,5-bis-trifluoromethylbenzenethiol treated contacts from the value of 0.61 Mω measured in the case of clean Au-contacts, whereas it increased to 0.97 Mω in the case of the (electron-rich) 3-thiomethylthiophene treated contacts. Field-effect mobility values are observed to be affected in short-channel devices (<20 μm) but not in long-channel devices. This channel-length-dependent behavior of mobility is attributed to grain-boundary limited charge transport at longer channel lengths in these devices.

Original languageEnglish
Pages (from-to)2973-2978
Number of pages6
JournalACS Applied Materials and Interfaces
Volume3
Issue number8
DOIs
Publication statusPublished - 24 Aug 2011
Externally publishedYes

    Fingerprint

Keywords

  • charge mobility
  • organic field effect transistors
  • photoelectron spectroscopy
  • self-assembled monolayers

ASJC Scopus subject areas

  • Materials Science(all)
  • Medicine(all)

Cite this

Singh, K. A., Nelson, T. L., Belot, J. A., Young, T. M., Dhumal, N. R., Kowalewski, T., McCullough, R. D., Nachimuthu, P., Thevuthasan, S., & Porter, L. M. (2011). Effect of self-assembled monolayers on charge injection and transport in poly(3-hexylthiophene)-based field-effect transistors at different channel length scales. ACS Applied Materials and Interfaces, 3(8), 2973-2978. https://doi.org/10.1021/am200449x