Non-volatile Organic Ferroelectric Field-Effect Transistors Fabricated on Al Foil and Polyimide Substrates

The flexible organic non-volatile ferroelectric field-effect transistors (FeFETs) with poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] was fabricated on polyimide and aluminum foil substrates. Al foil has merit of flexibility because of ultraflexible and ultrathin properties. It can be bent with small bend radius and even folded. It serves as bottom gate electrode in itself as well. Thus, an expensive fabrication step, evaporation of bottom gate, can be removed. In spite of these merits of Al foil, it is difficult to fabricate FeFETs on it owing to difficulty in handling: Al foil wrinkles easily and cannot be flattened during fabrication. The regioregular poly(3-hexylthiophene) [P3HT] film was formed as an active layer by the sol–gel method at low temperature. In case of the fabricated FeFETs on polyimide substrates, the field-effect mobility was ~0.28 cm²/Vs, the on/off ratio was approximately 5.6 × 10³, and the memory window (threshold voltage shift) was approximately 7 V. It has ~10³ of current on/off ratio and about 7–8 V of memory window for the Al foil substrates.