Ferroelectric Translational Boundaries Separating Antiferroelectric Domains in Y-Doped HfO₂

Domain walls in complex perovskite oxides are known for their unique functional properties and potential in electronic devices. Hafnium oxide (HfO2)-based ferroelectric and antiferroelectric materials, as a simpler transition-metal oxide system compared to perovskite-derived complex oxides, have gained significant interest due to their compatibility with silicon electronics and their lead-free composition, aligning with sustainable development goals. Nevertheless, research into the functionalities and structural characteristics of domain walls in hafnia is still limited, limiting their applications in domain wall electronic devices. In this work, using aberration-corrected scanning transmission electron microscopy high-angle annular dark field and integrated differential phase contrast imaging techniques, we revealed three types of translational boundaries (TBs), two with a phase difference of π and another one with a phase difference of π/2. The π TBs (or antiphase boundaries) show either a ferroelectric phase structure with a 0↑0↑ dipole pattern or a monoclinic phase structure, while the π/2 TB shows a reduced dipole magnitude. The ferroelectric TB is anticipated to enhance residual polarization within the polarization–electric field hysteresis loop. Its reversible switching capability indicates significant potential for implementation in domain wall memory devices, which are projected to be more energy efficient than traditional ferroelectric domain memories.