Yun Yu, Buragohain Pratyush, Li Ming, Ahmadi Zahra, Zhang Yizhi, Li Xin, Wang Haohan, Li Jing, Lu Ping, Tao Lingling, Wang Haiyan, Shield Jeffrey E, Tsymbal Evgeny Y, Gruverman Alexei, Xu Xiaoshan
Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA.
Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA.
Nat Mater. 2022 Aug;21(8):903-909. doi: 10.1038/s41563-022-01282-6. Epub 2022 Jun 27.
Ferroelectric HfO-based materials hold great potential for the widespread integration of ferroelectricity into modern electronics due to their compatibility with existing Si technology. Earlier work indicated that a nanometre grain size was crucial for the stabilization of the ferroelectric phase. This constraint, associated with a high density of structural defects, obscures an insight into the intrinsic ferroelectricity of HfO-based materials. Here we demonstrate that stable and enhanced polarization can be achieved in epitaxial HfO films with a high degree of structural order (crystallinity). An out-of-plane polarization value of 50 μC cm has been observed at room temperature in Y-doped HfO(111) epitaxial thin films, with an estimated full value of intrinsic polarization of 64 μC cm, which is in close agreement with density functional theory calculations. The crystal structure of films reveals the Pca2 orthorhombic phase with small rhombohedral distortion, underlining the role of the structural constraint in stabilizing the ferroelectric phase. Our results suggest that it could be possible to exploit the intrinsic ferroelectricity of HfO-based materials, optimizing their performance in device applications.
基于铪氧化物的铁电材料因其与现有硅技术的兼容性，在将铁电特性广泛集成到现代电子器件方面具有巨大潜力。早期研究表明，纳米级晶粒尺寸对于铁电相的稳定至关重要。这种与高密度结构缺陷相关的限制，阻碍了对基于铪氧化物材料本征铁电性的深入理解。在此，我们证明在具有高度结构有序性（结晶度）的外延铪氧化物薄膜中可以实现稳定且增强的极化。在室温下，于掺钇的铪氧化物（111）外延薄膜中观测到了50 μC/cm的面外极化值，估计本征极化的完整值为64 μC/cm，这与密度泛函理论计算结果高度吻合。薄膜的晶体结构揭示出具有小菱面体畸变的Pca2正交相，突显了结构约束在稳定铁电相中的作用。我们的结果表明，有可能利用基于铪氧化物材料的本征铁电性，优化其在器件应用中的性能。
