Role of the orthorhombic phase in endurance degradation of Hf_0.5Zr_0.5O₂ memristors

The development of next-generation memory architectures is essential to overcoming limitations of conventional architectures, notably the von Neumann bottleneck. Among emerging technologies, memristors have attracted considerable attention due to their scalability, low power consumption, and neuromorphic potential. However, limited endurance and retention, as well as process-integration constraints, continue to impede practical deployment. HfO₂-based memristors are promising due to silicon compatibility and thermal stability, yet switching stability remains a key challenge. Here, we systematically investigate the structural role of the orthorhombic phase in Hf_0.5Zr_0.5O₂ (HZO)-based memristors during the degradation process. Using in situ synchrotron X-ray diffraction (XRD) under an applied electric field, we tracked the field-driven structural evolution over repeated SET/RESET cycles. The orthorhombic phase diffraction intensity progressively decreases and peak broadening increases with cycling, while no distinct shift indicative of a macroscopic phase transition is observed within the experimental resolution. This degradation of crystallinity correlates with the rupture of conductive filaments and eventual device breakdown. These findings highlight the critical role of the orthorhombic phase in both switching behavior and device failure, providing insight into phase-engineered stability in memristive devices.