Identifying and Visualizing the Edge Terminations of Single-Layer MoSe<sub>2</sub> Island Epitaxially Grown on Au(111).

Lu, Jianchen; Bao, De-Liang; Qian, Kai; Zhang, Shuai; Chen, Hui; Lin, Xiao; Du, Shi-Xuan; Gao, Hong-Jun · ACS Nano · 2017

basic_science · Level V

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Abstract

Recently, single-layer transition-metal dichalcogenides have drawn significant attention due to their remarkable physical properties in the monolayer as well as at the edges. Here, we constructed high-quality, single-layer MoSe<sub>2</sub> islands on the Au(111) surfaces in ultrahigh vacuum by molecular beam epitaxy. All of the islands have hexagonal or triangular shapes with two kinds of well-defined edges. Scanning tunneling spectroscopy (STS) curves show notable differences in positive sample bias for the two types of edges. Density functional theory calculations for several edge configurations of MoSe<sub>2</sub> confirm that the STS differences are attributed to the coupling between the p<sub>z</sub> orbital of Se atoms and the d<sub>xz</sub> orbital of Mo atoms, and the two types of observed edge terminations are the bare Se edge and selenium-saturated Mo edge.