Reducing Leakage Currents in n-Channel Organic Field-Effect Transistors Using Molecular Dipole Monolayers on Nanoscale Oxides

Josué F. Hardigree, Thomas J. Dawidczyk, Robert M. Ireland, Gary L. Johns, Byung-Jun Jung, Mathias Nyman, Ronald Österbacka, Nina Markovic, Howard E. Katz

    Research output: Contribution to journalArticleScientificpeer-review

    19 Citations (Scopus)

    Abstract

    Leakage currents through the gate dielectric of thin film transistors remain a roadblock to the fabrication of organic field-effect transistors (OFETs) on ultrathin dielectrics. We report the first investigation of a self-assembled monolayer (SAM) dipole as an electrostatic barrier to reduce leakage currents in n-channel OFETs fabricated on a minimal, leaky similar to 10 nm SiO2 dielectric on highly doped Si. The electric field associated with 1H,1H,2H,2H-perfluoro-octyltriethoxysilane (FOTS) and octyltriethoxysilane (OTS) dipolar chains affixed to the oxide surface of n-Si gave an order of magnitude decrease in gate leakage current and subthreshold leakage and a two order-of-magnitude increase in ON/OFF ratio for a naphthalenetetracarboxylic diimide (NTCDI) transistor. Identically fabricated devices on p-Si showed similarly reduced leakage and improved performance for oxides treated with the larger dipole FOTS monolayer, while OTS devices showed poorer transfer characteristics than those on bare oxide. Comparison of OFETs on both substrates revealed that relative device performance from OTS and FOTS treatments was dictated primarily by the organosilane chain and not the underlying siloxane-substrate bond. This conclusion is supported by the similar threshold voltages (V-T) extrapolated for SAM-treated devices, which display positive relative V-T shifts for FOTS on either substrate but opposite V-T shifts for OTS treatment on n-Si and p-Si. Our results highlight the potential of dipolar SAMs as performance-enhancing layers for marginal quality dielectrics, broadening the material spectrum for low power, ultrathin organic electronics.
    Original languageUndefined/Unknown
    Pages (from-to)7025–7032
    Number of pages8
    JournalACS Applied Materials and Interfaces
    Volume5
    Issue number15
    DOIs
    Publication statusPublished - 2013
    MoE publication typeA1 Journal article-refereed

    Keywords

    • dielectric
    • interface dipole
    • leakage current
    • monolayer
    • organic field-effect transistor
    • threshold voltage

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