Approaching theoretical polarization limit in HfZrO2/HfLaO2 multilayers

Hafnia-based ferroelectric materials have garnered considerable attention due to robust ferroelectricity in ultrathin films and excellent compatibility with silicon-based technology. Theoretical predictions of the polarization along [001] direction of ferroelectric HfO₂ are 50 μC/cm² and 70 μC/cm², respectively, depending on the switching mechanism. However, most experimental observations of the intrinsic polarization are much lower than these predictions. Here, we report that an intrinsic remnant polarization up to 40 μC/cm² is achieved in epitaxially grown (111)-oriented Hf_0.5Zr_0.5O₂/Hf_0.9La_0.1O₂ multilayer film, corresponding to 69.3 μC/cm² along [001], approaching the theoretical limit. Structural analyses reveal a rhombohedral-distorted orthorhombic phase in the Hf_0.5Zr_0.5O₂/Hf_0.9La_0.1O₂ multilayers, stabilized by an in-plane compressive strain. Density functional theory calculations demonstrate that La doping in Hf_0.5Zr_0.5O₂/Hf_0.9La_0.1O₂ promotes an unconventional switching pathway and contributes to the high intrinsic polarization. These findings provide a compelling strategy for achieving high intrinsic polarization and establish a design paradigm for high-performance hafnia-based ferroelectric devices.