The effect of intrinsic electric field on electronic structures: The case of polar Janus group-III monochalcogenides and their van der Waals heterostructures
The effect of intrinsic electric field on electronic structures: The case of polar Janus group-III monochalcogenides and their van der Waals heterostructures
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DOI：
10.1063/5.0153060
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发表时间：
2023-06
期刊：
影响因子：
6.1
通讯作者：
Kai Cheng;Jinke Xu;Sihao Wang;Sandong Guo;Yan Su;Jijun Zhao
中科院分区：
文献类型：
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作者：
Kai Cheng;Jinke Xu;Sihao Wang;Sandong Guo;Yan Su;Jijun Zhao
静电控制和范德华积分是二维材料调节其性能的有用方法。在这里，我们构建了九种基于第三族单醇化合物的单层和多层Janus结构，并用第一性原理计算研究了它们的原子和电子结构。通过比较Janus结构在两个表面上的平均真空电子势，我们发现在Janus结构上存在本征电场。仔细的电荷分析表明，单层Janus结构上的电场主要是由于连接负性较弱的III族元素和负性较强的VI族元素的键的偶极所致。当层数(LN)不是很大时，由于各层偶极子的叠加，多层Janus结构上的电场保持不变，当LN足够大时，电场开始减小，并且Janus多层膜的两个表面之间发生了明显的电荷转移。在Janus结构下的电子结构计算表明，在单层情况下，电场几乎不能调制电荷密度布居，而在多层情况下，电场会显著弯曲能带，使价带最大值和导带最小的电荷密度始终位于两个分离面，从而促进电子-空穴的分离。此外，我们还研究了分离的单层原始III族单醇化合物和分离的Janus III族单醇化合物的带对齐，并构建了具有一个原始单层和一个Janus单分子层的van der Waals(VDW)异质结。结果表明，界面处Janus结构的表面终止对VDW异质结的能带偏移和电子结构有显著影响。这些结果不仅可以对单层和多层2D Janus结构的本征电场有一个新的认识，而且对利用静电来调制III族单醇化合物和其他2D材料的性质也有指导意义。
Electrostatic control and van der Waals integration are useful methods for 2D materials to help modulate their properties. Here, we constructed nine types of monolayer and multilayer Janus structures based on group-III monochalcogenides and investigated their atomic and electronic structures from first-principles calculations. We found the existence of an intrinsic electric field at Janus structures by comparing their average vacuum electron potentials at two surfaces. Careful charge analyses reveal that the electric field at monolayer Janus structures is mainly due to the dipole of the bond that connects group-III elements of weaker negativity and group-VI elements of stronger negativity. The E-filed at multilayer Janus structures maintains owing to the superposition of dipole at each layer when layer numbers (LN) are not very large, and the electric field starts to reduce when LN is large enough and obvious charge transfer happens between two surfaces of Janus multilayers. Electronic structure calculations at Janus structures demonstrate that the electric field can hardly modulate the charge density population in the monolayer case, while the electric field will significantly bend the bands in multilayer cases and make the charge density of the valence band maximum and the conduction band minimum always located at two separating surfaces, which promotes electron–hole to separate. Furthermore, we investigated the band alignment of isolated monolayer pristine group-III monochalcogenides and isolated Janus group-III monochalcogenides of monolayer, bilayer, and trilayer, and constructed van der Waals (vdW) heterostructures with one pristine monolayer and one Janus monolayer. The results show that the surface termination of Janus structures at the interface can significantly influence the band offset and electronic structures of vdW heterostructures. These results can not only provide a new understanding of the intrinsic electric field of monolayer and multilayer 2D Janus structures but also give a guide that uses electrostatic to modulate the properties of group-III monochalcogenides and other 2D materials.