Rough FTO electrode interface effect upon ferroelectric switching dynamics in Ag/P(VDF‐HFP)/FTO capacitor structures

Abstract

Rough FTO electrode interface effect upon the characteristic ferroelectric polarization parameters and switching dynamics in Ag/P(VDF‐HFP)/FTO junctions is systematically evaluated by varying electric field amplitude and frequency. Structural and microstructural studies confirm the ferroelectric phase formation of P(VDF‐HFP) on FTO surface. Tilted rectangular P‐E loops have been recorded in the applied fields ranging over 156.25–468.75 MV/m measured between 250 mHz and 5 Hz frequency ranges. Giant saturation of 21.7 μC/cm2 and remnant polarization of 34.9 μC/cm2 has been noted at low frequencies due to the influence of high electric field induced leakage currents. The coercive field, saturation and remnant polarization response with increase in electric field amplitude and frequency of the applied signal are well fitted with classic domain growth model proposed by Kolmogorov‐Avrami‐Ishibashi. A switching time scales of 32.2–693 ms has been observed for forward switching while for backward switching it is noted as 22.1–618.8 ms, when measured at frequencies from 5 Hz to 250 mHz. Furthermore, the tilted P‐E loops are attributed to the excessive leakage currents due to the high surface roughness of FTO bottom electrode.

Microstructures and Ferroelectric Properties of Poly(vinylidene fluoride-ter-trifluoroethylene-ter-vinyl fluoride) Terpolymers

“…The tilted loop can be explained by the inhomogeneous and scattering E c of ferroelectric domains in P­(VDF-TrFE-VF) terpolymers . In addition, polarization from conduction at high field and space charge limited current may also contribute to the tilted loops …”

“…40 In addition, polarization from conduction at high field and space charge limited current may also contribute to the tilted loops. 41 In general, when being introduced as a chain defect, VF plays a very different, and in many ways an opposite role, compared with the bulky chlorinated monomers such as CFE, CDFE, or CTFE in the terpolymers. Previous studies on the composition-dependence of the ferroelectric properties in P(VDF-TrFE-CDFE) and P(VDF-TrFE-CTFE) terpolymers suggest a progressive transition from normal ferroelectric to relaxor ferroelectric behavior as the CDFE or CTFE molar content increases.…”