Hafnia-based thin films are a favoured candidate for the integration of robust ferroelectricity at the nanoscale into next-generation memory and logic devices. This is because their ferroelectric polarization becomes more robust as the size is reduced, exposing a type of ferroelectricity whose mechanism still remains to be understood. Thin films with increased crystal quality are therefore needed. We report the epitaxial growth of Hf_0.5Zr_0.5O₂ thin films on (001)-oriented La_0.7Sr_0.3MnO₃/SrTiO₃ substrates. The films, which are under epitaxial compressive strain and predominantly (111)-oriented, display large ferroelectric polarization values up to 34 μC cm⁻² and do not need wake-up cycling. Structural characterization reveals a rhombohedral phase, different from the commonly reported polar orthorhombic phase. This finding, in conjunction with density functional theory calculations, allows us to propose a compelling model for the formation of the ferroelectric phase. In addition, these results point towards thin films of simple oxides as a vastly unexplored class of nanoscale ferroelectrics.

基于Hafnia的薄膜是将强大的铁电纳米级集成到下一代存储器和逻辑器件中的首选候选人。这是因为随着尺寸的减小，它们的铁电极化变得更加牢固，从而暴露了一种类型的铁电，其机理还有待理解。因此需要具有提高的晶体质量的薄膜。我们报道了在（001）取向的La _0.7 Sr _0.3 MnO ₃ / SrTiO ₃衬底上Hf _0.5 Zr _0.5 O ₂薄膜的外延生长。受到外延压缩应变且主要（111）取向的薄膜显示出高达34μCcm的大铁电极化值⁻²，不需要唤醒循环。结构表征揭示了菱面体相，不同于通常报道的极性正交斜相。这一发现与密度泛函理论计算相结合，使我们能够为铁电相的形成提出令人信服的模型。此外，这些结果表明，简单氧化物薄膜是一类未经广泛研究的纳米铁电体。