Equivalent interfacial-layer effect on domain switching behaviour in Hf0.5Zr0.5O2 thin-film capacitors

HfO 2 -based ferroelectric materials are promising for the application in CMOS-compatible memory devices. However, achieving nanosecond switching time generally requires extremely high electric fields exceeding ∼9 MV/cm, which could induce dielectric breakdown and reduce endurance cycling number. Here, we identified two distinct domain switching behaviours influenced by the equivalent interfacial layer effect in Hf 0.5 Zr 0.5 O 2 thin-film capacitors. If the interfacial layers including the equivalent contribution of nonpolar phases are thin enough to act as a tunnelling resistor, the coercive voltage increases significantly with shortening of domain switching time. Otherwise, the interfacial layers are insulating to act as an in-series capacitor after thickening during thermal cycling when the coercive voltage is nearly constant irrespective of the applied electric-field frequency. Subsequent structural analysis from transmission electron microscope images confirms the increase in volume fractions of nonpolar monoclinic and tetragonal phases that contributes to equivalent interfacial-layer thickening. These findings offer a pathway to resolve the speed-endurance trade-off, enabling reliable high-speed operations in HfO 2 -based ferroelectric memories.