Reversible and Irreversible Polarization Degradation of Hf0.5Zr0.5O₂ Capacitors with Coherent Structural Transition at Elevated Temperatures

In this study, we investigated the reversible and irreversible polarization degradation of hafnia-based ferroelectric capacitors (FeCAPs) using the state-of-the-art spherical aberration corrected transmission electron microscope (Cs-TEM) with realtime temperature changes. The key observations are as follows: (1) Rapid thermal annealing (RTA) results in incomplete formation of the orthorhombic (o-) phase in the ferroelectric (FE) material, leading to a coherent phase boundary (CPB) between o- and tetragonal (t-) structures. (2) The movement of the o-/t-CPB with temperature corresponds to reversible changes in polarization of hafnia-based FeCAPs. (3) Irreversible degradation in polarization occurs due to migration of the o-/monoclinic (m-) CPB with temperature. These findings provide a new perspective for evaluating the stability of the o-phase in fluorite-type FE materials and offer guidance for optimizing their properties through regulation strategies.