A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films
A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films
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DOI：
10.1038/s41563-018-0196-0
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发表时间：
2018-01
期刊：
影响因子：
41.2
通讯作者：
Yingfen Wei;P. Nukala;M. Salverda;S. Matzen;H. Zhao;J. Momand;A. Everhardt;G. Agnus;G. Blake-G.-Bla
中科院分区：
文献类型：
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作者：
Yingfen Wei;P. Nukala;M. Salverda;S. Matzen;H. Zhao;J. Momand;A. Everhardt;G. Agnus;G. Blake-G.-Bla
基于hafnia的薄膜是将强大的铁电性集成到下一代存储器和逻辑器件中的首选候选材料。这是因为随着尺寸的减小，它们的铁电极化变得更加强大，从而暴露出一种机制仍有待了解的铁电性。因此需要提高晶体质量的薄膜。我们报道了hf0.5 zr0.5 o2薄膜在（001）取向La0.7Sr0.3MnO3/ srtio3衬底上的外延生长。该薄膜处于外延压缩应变下，以（111）取向为主，具有高达34 μC cm−2的铁电极化值，且不需要唤醒循环。结构表征显示为菱形相，不同于通常报道的极性正交相。这一发现与密度泛函理论计算相结合，使我们能够提出一个令人信服的铁电相形成模型。此外，这些结果表明，简单氧化物薄膜是一种尚未开发的纳米级铁电体。
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 Hf0.5Zr0.5O2thin films on (001)-oriented La0.7Sr0.3MnO3/SrTiO3substrates. The films, which are under epitaxial compressive strain and predominantly (111)-oriented, display large ferroelectric polarization values up to 34 μC cm−2and 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.