The role of proton for the effect of interlayer on ferroelectric behavior of poly(vinylidene fluoride-trifluoroethylene) copolymer ultrathin films

A functional interlayer, poly(3,4-ethylene dioxythioohene)-poly(styrene sulfonic) acid, is introduced as a buffer layer between the metal electrodes of a capacitor composed of ferroelectric poly(vinylidene fluoridetrifluoroethylene) copolymer ultrathin film. The sandwiched structure shows prominent ferroelectric properties even as the thickness of P(VDF-TrFE) film is reduced to 50 nm and the fatigue property is also improved tremendously. We demonstrate that the proton in the PSSH instead of the electron in the PEDOT plays a significant role to improve the ferroelectric properties of P(VDF-TrFE), furthermore, polyvinyl phosphoric acid as well as other polyacid also supplies the proton.