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arXiv 1802.02501cond-mat.mes-hall
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范德华异质结中的非对称电场屏蔽

Asymmetric Electric Field Screening in van der Waals Heterostructures

Lu Hua Li, Tian Tian, Qiran Cai, Chih-Jen Shih, Elton J. G. Santos

摘要:

电场屏蔽对材料及其器件的物理化学性能有重要影响。在这里,我们使用了一套引人注目的理论和实验技术,包括范德华(vdW)从头算密度泛函理论(DFT)模拟,量子电容为基础的经典模型和电力显微镜(EFM),以阐明由二硫化钼和石墨烯层形成的vdW异质结构(vdWHs)的内在介电屏蔽特性。我们在实验上观察到了在不同方向的外部电场作用下,MoS 2/Graphene vdWHs的非对称电响应。也就是说,当电场朝向石墨烯脱落时,大量的极化电荷屏蔽场,但是当场的符号反转时,存在强的去极化场,并且检测到部分屏蔽。这种效应是厚度依赖性的,特别是在二硫化钼层的数量上;而石墨烯的厚度增加对它们的电学和屏蔽行为的影响很小。我们的研究结果表明,在石墨烯和二硫化钼之间的界面处的不对称偶极贡献的vdWHs中的不寻常的场效应屏蔽的主要原因。这项工作不仅为迄今为止制造的大量异质结的屏蔽特性提供了新的见解,而且还揭示了控制基本特性的巨大潜力,例如屏蔽,用于器件应用。

英文摘要:

Electric field screening plays an important role in the physical and chemical properties of materials and their devices. Here, we use a compelling set of theoretical and experimental techniques involving van der Waals (vdW) ab initio density functional theory (DFT) simulations, quantum capacitance-based classical model and electric force microscopy (EFM) to elucidate the intrinsic dielectric screening properties of vdW heterostructures (vdWHs) formed by MoS2 and graphene layers. We experimentally observed an asymmetric electric response in the MoS2/Graphene vdWHs under different directions of the external electric field. That is, when the electric fields are shed towards graphene, a large amount of polarized charges screen the fields, but as the sign of the field was reversed, a strong depolarization field was present, and a partial screening was detected. This effect is thickness-dependent, in particular on the number of the MoS2 layers; whereas increased thickness of graphene showed a small effect on their electrical and screening behavior. Our results indicate that asymmetric dipolar contributions at the interface between graphene and MoS2 are the main cause to the unusual field-effect screening in the vdWHs. This work not only provides new insights on the screening properties of a vast amount of heterojunction fabricated so far, but also uncovers the great potential of controlling a fundamental property, such as screening, for device applications.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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