铁电的180°极化翻转：不同路径的机制
本帖最后由 hdy 于 2025-6-3 01:05 编辑近年被发现的HfO2基铁电材料，具有与硅基半导体工艺兼容的特点，并且在纳米尺度上能保持良好的铁电性。因此，这类铁电材料被认为是用于非易失性存储器及相关电子设备的重要候选材料。然而，除了HfO2的铁电亚稳相稳定机制外，其极化翻转机制也是困扰人们的重要问题，从而给HfO2基铁电材料的可控设计及其存储器可靠性与工艺稳定性的提升带来了困难。
来自湘潭大学材料科学与工程学院的铁电薄膜与存储器团队，基于第一性原理弹性带方法，在块体和Ni/HfO2/Ni异质结中研究了HfO2的180°一致极化翻转和电畴演化。研究结果较为系统地揭示了不同翻转路径的结构和能量演化规律，对HfO2基材料铁电性的理解具有重要意义。他们首先研究了正交HfO2铁电体的一致极化翻转，发现在8种可能极化翻转路径中，O原子不跨Hf平面的极化翻转模式(N路径)具有最低的块体翻转势垒；而在Ni/HfO2/Ni异质结中，由于表面终断的引入，即使伴随着界面Ni-O键的形成和断裂，O跨Hf平面的极化翻转(T路径)势垒也被极大地抑制。
随后他们研究了HfO2铁电的电畴演化，发现由于引入高能的畴壁，N路径的极化翻转具有较高的形核势垒和很低的畴壁迁移势垒，而T路径则具有较低的形核势垒和较高的畴壁迁移势垒；而在上述异质结中，T路径的畴壁迁移势垒被降低到与N路径的相当。作者的这些研究结果表明，在HfO2中，N和T路径的极化翻转在适当的条件下都有可能发生，从而导致HfO2铁电体极化翻转性质的复杂性。相关论文近期发布于npj Computational Materials 11, 126 (2025)。手机阅读原文，请点击本文底部左下角“阅读原文”，进入后亦可下载全文PDF文件。
Editorial SummaryThe 180° polarization switching of ferroelectric: Mechanism of different switching pathways!Recently discovered HfO2-based ferroelectric materials exhibit compatibility with silicon-based semiconductor processes and retain robust ferroelectricity at the nanoscale, making them promising candidates for non-volatile memory and related electronic devices. However, besides the stabilization mechanism of the metastable ferroelectric phase of HfO2, its polarization switching mechanism remains a critical issue has not been well understood yet, thereby bring significant obstacles to the controllable design of HfO2-based ferroelectric materials and the enhancement of memory device reliability and process stability.The Ferroelectric Thin Films and Memory Devices Team from Xiangtan University investigated 180° uniform polarization switching and domain evolution in bulk HfO2 and Ni/HfO2/Ni heterostructures using first-principles nudged elastic band calculations. Their findings systematically reveal structural and energetic evolution of different switching pathways, significantly advancing the understanding of HfO2-based ferroelectrics. The uniform polarization switching in orthorhombic HfO2is first studied. Among eight possible polarization switching pathways, the pathway with O atoms not shifting through the Hf atomic planes (N pathway) exhibits the lowest bulk switching energy barrier. However, in the Ni/HfO2/Ni heterostructures, surface termination effects drastically suppress the energy barrier of pathway with O shifting through Hf atomic planes (T pathway), even with accompanied formation and breaking of interfacial Ni-O bonds. Then, the domain evolution of HfO2 ferroelectric is studied. It is found that, the N pathway has high nucleation energy barrier but low domain wall migration barrier due to the introduction of high-energy domain wall, while the T pathway does the opposite. However, in the heterostructure, domain wall migration energy barrier for T pathway is reduced to be comparable to that of N pathway. These results indicate that both N and T pathways may be possible in HfO2 ferroelectric under appropriate conditions, leading to the complexity of its ferroelectric switching behavior. Thisarticle was recently published in npj Computational Materials 11:126 (2025).原文Abstract及其翻译Polarization switching of HfO2 ferroelectric in bulk and electrode/ferroelectric/electrode heterostructure (氧化铪铁电体的极化翻转：在块体和电极/铁电/电极异质结中) Xinpeng Mu, Yao Wu, Binjian Zeng, Jie Jiang, Yichun Zhou, Lu Yin*, Min Liao*, & Qiong Yang*Abstract HfO2-based ferroelectric films are of great potential for the application of non-volatile information storage. In this paper, to understand the polarization switching properties of ferroelectric HfO2, the 180° polarization switching of HfO2film in the uniform polarization reversal and domain evolution are studied in both bulk form and Ni/HfO2/Ni heterostructure based on the climbing image nudged elastic band (CI-NEB) simulation. It is found that the polarization reversal pathway with O atoms not shifting through the Hf-atomic planes has higher domain nucleation energy barrier due to the induced high energy domain wall (DW) but lower DW migration energy barrier, which is contrary to the pathway with O atoms shifting through the Hf-atomic planes. However, the interface effect of heterostructure considerably lower the energy barrier for the latter pathway in both uniform polarization reversal and DW migration. This indicates that both types of pathways may be possible and synergistically determine the polarization switching mechanism of HfO2ferroelectric.摘要 HfO2基铁电薄膜在非易失性信息存储应用中具有巨大潜力。为了深入理解HfO2铁电的极化翻转性质，本文采用爬坡弹性带(CI-NEB)方法，分别基于一致极化翻转和电畴演化机制，在块体和Ni/HfO2/Ni异质结中研究了HfO2薄膜的180°极化翻转。研究表明，由于形成的高能畴壁，O原子不跨Hf平面的极化翻转模式具有较高的形核势垒，但是其畴壁迁移势垒较低。而O原子跨过Hf平面的极化翻转模式刚好相反。然而，异质结构的界面效应显著降低了后一种翻转模式在一致极化翻转和畴壁迁移过程中的能垒。这表明两种路径都可能存在，共同决定了HfO2铁电材料的极化翻转机制。
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