P(VDF-TeFE)/Organic Semiconductor Structure Ferroelectric-Gate FETs

Abstract

Organic ferroelectric-gate field-effect transistor (FET) memories were fabricated using pentacene and rubrene thin films as the semiconductors and a poly(vinylidene fluoride-tetrafluoroethylene) [P(VDF-TeFE)] thin film as the ferroelectric gate. The P(VDF-TeFE) film was prepared by spin coating and annealing at 170 °C for 2.5 h, and the pentacene was prepared by vacuum evaporation. In contrast, the rubrene thin film sheet was grown by physical vapor transport and placed onto a spin-coated P(VDF-TeFE) thin film layer. The polarization-electric field hysteresis of the P(VDF-TeFE) thin film was observed, and the obtained remanent polarization of 3.9 μC/cm2 was sufficient for controlling the surface potential of pentacene or rubrene. A hysteresis loop was clearly observed in the drain current-gate voltage behavior of the ferroelectric-gate FET. In the case of the ferroelectric-gate FET with P(VDF-TeFE)/pentacene, the ON/OFF ratio of drain current was 830, and the carrier mobility was 0.11 cm2/Vs. On the other hand, the maximum drain current of the FET with P(VDF-TeFE)/rubrene was 1.6 × 10−6 A, which is about two orders of magnitude larger than that of the P(VDF-TeFE)-gate FET using the pentacene thin film. The mobility of the organic ferroelectric-gate FET using the rubrene thin film was 0.71 cm2/Vs, which is 6.5 times larger than that of the FET with pentacene thin film.