论文标题
菱形HFO $ _2 $中对铁电的有限尺寸影响
Finite-size effects on the ferroelectricity in rhombohedral HfO$_2$
论文作者
论文摘要
在这项工作中，我们分析了对hfo $ _2 $的菱形相位的结构特性的有限尺寸影响以及对双轴压缩应变的极化。我们展示了表面电荷的存在如何影响极化，从而导致其大量值的大幅减少。这种还原可以归因于两种机制：压缩应变与相变顺序参数之间的耦合；铁电扭曲的变化。我们对这种现象提供了两种替代解释：从原子观的角度来看，分析键长的演变，以及从对称分析的角度来看，考虑到对称性失真的幅度的变化，当考虑到平板构型时。这些结果在被考虑的范围内独立于平板厚度，这表明缺乏HFO $ _2 $的铁电性的临界厚度，这与拟议的Hafnia ferroelectricity的不当性质一致。
In this work we analyze the finite-size effects on the structural properties and on the polarization of the rhombohedral phase of HfO$_2$ subjected to a biaxial compressive strain. We show how the presence of surface charges affects the polarization, leading to a strong reduction with respect to its bulk value. This reduction can be ascribed to two mechanisms: the coupling between compressive strain and the phase-transition order parameter; the changes in the ferroelectric distortion. We give two alternative explanations of this phenomenon: from an atomistic point of view, analyzing the evolution of the bond lengths, and from a symmetry-analysis point of view, considering the changes in the amplitude of the symmetry-allowed distortions, when a slab configuration is considered. These results are independent on the slab-thickness in the considered range, suggesting the absence of a critical thickness for ferroelectricity in HfO$_2$, in agreement with the proposed improper nature of hafnia ferroelectricity.
