Proton-Transfer Ferroelectrics with Exceptional Switching Endurance

Abstract

Reliable organic ferroelectrics for memory applications require extreme endurance under repeated electrical switching. Here we demonstrate exceptional fatigue resistance in highly crystalline 2-methylbenzimidazole (MBI) films grown by low-temperature deposition followed by restrained crystallization (LDRC) in a simple Pt/MBI/Pt capacitor geometry. Switching kinetics analyzed using the Kolmogorov-Avrami-Ishibashi (KAI) model reveal characteristic millisecond switching times and quasi-one-dimensional domain growth associated with proton transfer along hydrogen-bond chains. Guided by these kinetics, we implemented a stringent fatigue protocol designed to maximize switching stress, involving bipolar switching at approximately 2Ec with 5 ms pulses, well beyond the characteristic switching time, for continuous operation over approximately 2 weeks. The remanent polarization exhibits only a minor wake-up (+10% within the first 10^4 cycles) and ultimately returns to approximately its initial value after 10^8 cycles, with testing limited by experimental duration rather than device failure. This robust endurance is achieved in an unengineered structure and contrasts with polymer ferroelectrics such as P(VDF-TrFE), where comparable performance typically relies on interfacial engineering. The combination of LDRC-enabled high crystallinity and localized proton-transfer switching, which introduces minimal structural perturbation during polarization reversal, enables this outstanding fatigue tolerance and highlights MBI as a simple, fluorine-free platform for durable organic ferroelectric devices.