Ferroelectric domain relaxation enables reliable multi-bit storage in hafnia-based memristors

We report reliable triple-level cell (TLC) operation in HfZrO2-based ferroelectric memristors by precisely modulating partial switching voltages to define eight polarization states. Despite achieving stable multi-bit storage, endurance degradation due to polarization fatigue emerged as a limiting factor. To address this, we introduced a domain recovery strategy based on interleaved high-voltage pulses and electrically quiescent break time intervals. Our approach restored polarization states by mitigating domain wall pinning, with endurance exceeding 106 cycles. Notably, we found that spontaneous domain relaxation during short idle periods also contributed to fatigue recovery, whereas excessively long breaks induced domain disorientation. These findings unveil the critical role of both electrical and time-controlled recovery in stabilizing ferroelectric switching behavior. Our results offer a practical route to enhance the reliability of high-density ferroelectric memory and provide new physical insights into fatigue dynamics under multi-level operation.