电荷转移机制及其对吸附在单层WS2上的气体分子的费米能级钉扎的影响,The Journal of Chemical Physics

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电荷转移机制及其对吸附在单层WS2上的气体分子的费米能级钉扎的影响
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2015-06-03 13:12:54 , DOI: 10.1063/1.4922049
Changjie Zhou ₁ , Weihuang Yang ₂ , Huili Zhu ₁

Affiliation

进行密度泛函理论计算，以评估吸附各种气体分子（H ₂，O ₂，H ₂ O，NH ₃，NO，NO ₂和CO）后单层WS ₂的几何和电子结构的变化。确定了最稳定的吸附分子构型，吸附能量以及被吸附物与底物之间的电荷转移程度。所有评估的分子均以低电荷转移程度物理吸附在单层WS _2上，并从单层接受电荷，但NH ₃是电荷供体。能带结构计算表明，单层WS的价带和导带₂不显著在吸附H改变₂，H ₂ O，NH ₃和CO，而的O-最低未占分子轨道₂，NO，和NO ₂围绕费米能级钉扎当这些分子被吸附在单分子层WS ₂。根据传统和轨道混合电荷转移理论，讨论了费米能级钉扎现象。对于吸附在单层WS ₂上的气体分子，证实了电荷转移机制对费米能级钉扎的影响。提出的控制费米能级钉扎的机制适用于最近开发的二维材料（例如石墨烯和过渡金属二卤化碳）上的吸附物系统。

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Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS2

Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS₂ upon adsorption of various gas molecules (H₂, O₂, H₂O, NH₃, NO, NO₂, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS₂ with a low degree of charge transfer and accept charge from the monolayer, except for NH₃, which is a charge donor. Band structure calculations showed that the valence and conduction bands of monolayer WS₂ are not significantly altered upon adsorption of H₂, H₂O, NH₃, and CO, whereas the lowest unoccupied molecular orbitals of O₂, NO, and NO₂ are pinned around the Fermi-level when these molecules are adsorbed on monolayer WS₂. The phenomenon of Fermi-level pinning was discussed in light of the traditional and orbital mixing charge transfer theories. The impacts of the charge transfer mechanism on Fermi-level pinning were confirmed for the gas molecules adsorbed on monolayer WS₂. The proposed mechanism governing Fermi-level pinning is applicable to the systems of adsorbates on recently developed two-dimensional materials, such as graphene and transition metal dichalcogenides.

更新日期：2015-06-04

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