Transient Detour and Cooperative Oxygen Exchange in the Polarization Switching of Ferroelectric Hf0.5Zr0.5O2

Abstract

Abstract Hafnium zirconium oxide (HZO) has attracted significant attention as a core material for next-generation non-volatile memories due to its excellent ferroelectricity in the ultra-thin film regime and its CMOS process compatibility. However, the exploration of its polarization switching mechanism has predominantly relied on static energy barrier analyses, leaving the transient bond formation and cooperative dynamic mechanisms under actual electric field driving unresolved. In this study, we performed electric-field-induced MD simulations on a defect-free ideal HZO lattice using a fine-tuned machine learning force field (MACEField). As a result, we successfully reproduced the P-E hysteresis loop dynamically and demonstrated that the polarization switching in HZO is driven not by conventional simple displacement models (S:N/S:T models), but by the dynamic mutual exchange of 3-coordinated oxygen (O3c) and 4-coordinated oxygen (O4c). Analysis of the oxygen atom displacement trajectories revealed that this pathway is accompanied by a unique "detour" behavior originating from transient cation-oxygen bond formation. Furthermore, we identified an "internal local volume compensation behavior" in which the local volumetric expansion and contraction accompanying the coordination number changes partially counteract each other within the cell, thereby suppressing the macroscopic strain during polarization switching. These findings provide, from a dynamic perspective, a microscopic picture of how cooperative O3c/O4c exchange accommodates local structural changes during polarization switching. Such local compensation may contribute to the mechanical robustness of polarization switching under constrained conditions.

The authors' abstract, as published at the source. ACS Applied Electronic Materials, 2026 · DOI ↗