Low-voltage organic ferroelectric field effect transistors using Langmuir-Schaefer films of poly(vinylidene fluoride-trifluororethylene)

Langmuir-Schaefer transfer was used to fabricate ultrathin films of ferroelectric copolymer, poly(vinylidene fluoride-trifluoroethylene) (70-30 mol%), for non-volatile memory application at low operating voltage. Increasing the number of transferred monolayers up to 10 led to improved film crystallinity in the "in-plane" direction, which reduced surface roughness of the semicrystalline film. Treatment of the substrate surface by plasma results in different film coverage which was subsequently found to be governed by interaction of the deposited film and surface condition. Localized ferroelectric switching was substantially attained using piezo-force tip at 10 V on 10-monolayer films. Integrating this film as a dielectric layer into organic capacitor and field effect transistor yields a reasonably good leakage current (<10^-7 A/cm²) with hysteresis in capacitance and drain current with ON/OFF ratio of 10³ for organic ferroelectric memory application at significantly reduced operating voltage of |15| V.