Ambipolar thin-film transistors and an inverter based on pentacene/self-assembled monolayer modified ZnO hybrid structures for balanced hole and electron mobilities

Abstract

We have fabricated high performance ambipolar thin-film transistors (TFTs) and an inverter based on organic–inorganic bilayer structures composed of an upper pentacene layer and a lower atomic-layer-deposited zinc oxide (ZnO) layer. The insertion of a dodecanoic acid (DA) self-assembled monolayer (SAM) into the interface between pentacene and ZnO results in an improvement in the morphology of the pentacene layer and in well-balanced ambipolarity with hole and electron mobilities of 0.34 and 0.38cm2V−1s−1, respectively. The ambipolar TFTs with DA-treated ZnO exhibit a hole to electron mobility ratio of approximately 0.90, which is higher by a factor of ∼2.8 than that of ambipolar TFTs with untreated ZnO. We also tested the introduction of a perfluorooctyltriethoxysilane (PFOTES) SAM; the effects of the permanent dipole fields of the SAMs on the electrical and ambipolar characteristics of the hybrid TFTs were investigated.