Sub-Coercive Analog Conductance Modulation from Distributed Energy Barriers in Semicrystalline Ferroelectric Polymer...

Ferroelectric switching is understood as a nucleation-limited process, in which polarization domains switch abruptly once the applied electric field exceeds a well-defined coercive field (Ec). However, the macroscopic Ec is an incomplete descriptor in semicrystalline ferroelectric polymers, where continuous polarization evolution can be observed at weak fields far below Ec. Here, we investigate sub-coercive conductance modulation in poly(vinylidene fluoride-trifluoroethylene) ferroelectric transistors and interpret the response using a quasi-continuous energy barrier distribution associated with the heterogeneous semicrystalline morphology. Unlike purely phenomenological distributed-threshold descriptions, this interpretation links the low-field response to structural heterogeneity in semicrystalline ferroelectrics, including crystalline-amorphous interphase-like regions that can provide intermediate local switching barriers. Ferroelectric transistors operating within this regime exhibit near-linear potentiation under repeated fixed-amplitude pulses, reducing reliance on incremental pulse programming or closed-loop control. Furthermore, the transistors operate at nominal externally applied average fields of 130 kV cm-1, below the macroscopic coercive field (Eeff/Ec ≈ 0.24). A mesoscale Landau-Khalatnikov model incorporating a spatially varying barrier hierarchy reproduces the experimentally observed accumulation trend and supports a distributed-barrier interpretation of the sub-coercive conductance modulation consistent with spatially resolved maps obtained from piezoresponse force microscopy. Because structural heterogeneity is inherent to semicrystalline polymers, this interpretation provides a physical basis for low-field analog functionality in ferroelectric polymer neuromorphic and adaptive electronic applications.