Research Project Highlight

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

monolayer leakage 1Leakage 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 monolayer dipole as an electrostatic barrier to reduce leakage currents in OFETs fabricated on a minimal, leaky ~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 silicon wafers gave an order of magnitude decrease in gate leakage current, and a two order-of magnitude increase in on/off ratio for a naphthalenetetracarboxylic diimide (NTCDI) OFET.  Relative device performance from OTS and FOTS treatments was dictated primarily by the organosilane chain and not the underlying siloxane-substrate bond. 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.

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