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

We demonstrate reliable triple-level cell operation in HfZrO2-based ferroelectric memristors by precisely modulating partial-switching voltages to define eight distinct polarization states. Although stable multi-bit storage is achieved, endurance degradation arising from polarization fatigue remains a major limitation. To mitigate this issue, we introduce a domain-recovery strategy that employs interleaved high-voltage pulses combined with electrically quiescent break intervals. This approach restores polarization states by alleviating domain-wall pinning, enabling endurance exceeding 106 cycles. Notably, we find that spontaneous domain relaxation during short idle periods further contributes to fatigue recovery, whereas excessively long breaks induce domain disorientation. These findings reveal the critical roles of both electrical and time-controlled recovery in stabilizing ferroelectric switching behavior. Our results provide a practical route to enhancing the reliability of high-density ferroelectric memory and yield new physical insights into fatigue dynamics under multi-level operation.