Ultrathin self-assembled organophosphonic acid monolayers/metal oxides hybrid dielectrics for low-voltage field-effect transistors

By using organophosphonic acid self-assembled monolayers (SAMs) on metal oxides (MOs) such as AlO_x and HfO₂ as ultrathin gate dielectrics and templates, we have realized low-voltage organic field-effect transistors (OFETs) with low leakage currents and small subthreshold slopes. In the demonstrated OFETs, the following device characteristics has been achieved: 1) low leakage current density - down to few nA/cm²; 3) large capacitance density - up to 760 nF/cm²; 2) low operating voltage (<2 V); 3) small subthreshold slope - down to 85 mV/decade. This is achieved by: a) modification of MO dielectric surface with SAM to decrease charge carrier traps; b) tailoring of the surface energy of MO dielectric to control the molecular orientation and morphology of subsequently deposited semiconductor layer; c) well-packed and dense organophosphonic acid SAMs (<4 nm) on metal oxides (<4 nm) as ultrathin dielectrics.