Two-dimensional ferroelectricity in a single-element bismuth monolayer.
Two-dimensional ferroelectricity in a single-element bismuth monolayer.
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DOI：
10.1038/s41586-023-05848-5
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发表时间：
2023-05
期刊：
影响因子：
64.8
通讯作者：
Wee, Andrew Thye Shen
中科院分区：
文献类型：
--
作者：
Gou, Jian;Bai, Hua;Zhang, Xuanlin;Huang, Yu Li;Duan, Sisheng;Ariando, A.;Yang, Shengyuan A.;Chen, Lan;Lu, Yunhao;Wee, Andrew Thye Shen
铁电材料因其自发的反转对称性破缺而具有非挥发性的可开关极化而引起人们的关注。然而，在所有常规铁电化合物中，需要至少两种组分离子来支持极化切换。在这里，我们报告了一个单一的元素铁电态的观察在一个黑色的磷类铋层，其中有序的电荷转移和规则的原子畸变的亚晶格之间同时发生。我们发现，在一个黑色的类磷铋单层中，铋原子保持着弱的各向异性的sp轨道杂化，而不是通常发生在基本物质中的均匀轨道构型，从而产生了反转对称性破坏的屈曲结构，伴随着电荷在晶胞中的重新分布。结果，在Bi单层膜中出现面内电极化。利用扫描探针显微镜产生的面内电场，铁电开关进一步可视化实验。由于电荷转移和原子位移之间的共轭锁定，我们还观察到了由电子结构和电极化之间的竞争引起的180°尾对尾畴壁处的反常电势分布。这种单元素铁电性的出现拓宽了铁电体的形成机制，并可能丰富铁电子学的应用。在黑磷铋层中观察到了单元素铁电态，其中有序的电荷转移和亚晶格间规则的原子畸变同时发生，铁电开关在实验上得到了进一步的观察.
Ferroelectric materials are fascinating for their non-volatile switchable electric polarizations induced by the spontaneous inversion-symmetry breaking. However, in all of the conventional ferroelectric compounds, at least two constituent ions are required to support the polarization switching. Here, we report the observation of a single-element ferroelectric state in a black phosphorus-like bismuth layer, in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously. Instead of a homogenous orbital configuration that ordinarily occurs in elementary substances, we found the Bi atoms in a black phosphorous-like Bi monolayer maintain a weak and anisotropic sp orbital hybridization, giving rise to the inversion-symmetry-broken buckled structure accompanied with charge redistribution in the unit cell. As a result, the in-plane electric polarization emerges in the Bi monolayer. Using the in-plane electric field produced by scanning probe microscopy, ferroelectric switching is further visualized experimentally. Owing to the conjugative locking between the charge transfer and atom displacement, we also observe the anomalous electric potential profile at the 180° tail-to-tail domain wall induced by competition between the electronic structure and electric polarization. This emergent single-element ferroelectricity broadens the mechanism of ferroelectrics and may enrich the applications of ferroelectronics in the future. A single-element ferroelectric state is observed in a black phosphorus-like bismuth layer, in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously and ferroelectric switching is further visualized experimentally.
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