HfO2– and ZrO2–based ferroelectric thin films have emerged as promising candidates for the gate oxides of next‐generation electronic devices. Recent work has experimentally demonstrated that a tetragonal/orthorhombic (t/o‐) phase mixture with partially in‐plane polarization can lead to negative capacitance (NC) stabilization. However, there is a discrepancy between experiments and the theoretical understanding of domain formation and domain wall motion in these multi‐phase, polycrystalline materials. Furthermore, the effect of anisotropic domain wall coupling on NC has not been studied so far. Here, 3D phase field simulations of HfO2– and ZrO2–based mixed‐phase ultra‐thin films on silicon are applied to understand the necessary and beneficial conditions for NC stabilization. It is found that smaller ferroelectric grains and a larger angle of the polar axis with respect to the out‐of‐plane direction enhances the NC effect. Furthermore, it is shown that theoretically predicted negative domain wall coupling even along only one axis prevents NC stabilization. Therefore, it is concluded that topological domain walls play a critical role in experimentally observed NC phenomena in HfO2– and ZrO2–based ferroelectrics.

中文翻译：

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多晶多相氧化铪和氧化锆基超薄膜的 3D 铁电相场模拟


HfO2 和 ZrO2 基铁电薄膜已成为下一代电子器件栅极氧化物的有希望的候选者。最近的工作通过实验证明，具有部分面内极化的四方/斜方（t/o）相混合物可以导致负电容（NC）稳定。然而，对于这些多相、多晶材料中磁畴形成和磁畴壁运动的实验与理论理解之间存在差异。此外，各向异性畴壁耦合对NC的影响迄今尚未研究。在这里，应用硅上 HfO2 和 ZrO2 基混合相超薄膜的 3D 相场模拟来了解 NC 稳定的必要和有利条件。研究发现，较小的铁电晶粒和极轴相对于面外方向的较大角度增强了NC效应。此外，结果表明，理论上预测的负畴壁耦合即使仅沿一个轴也会阻碍 NC 稳定。因此，可以得出结论，拓扑畴壁在实验观察到的 HfO2 和 ZrO2 基铁电体的 NC 现象中起着至关重要的作用。