Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore.
Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore.
Nano Lett. 2016 Jun 8;16(6):3682-8. doi: 10.1021/acs.nanolett.6b00888. Epub 2016 May 9.
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have revealed many novel properties of interest to future device applications. In particular, the presence of grain boundaries (GBs) can significantly influence the material properties of 2D TMDs. However, direct characterization of the electronic properties of the GB defects at the atomic scale remains extremely challenging. In this study, we employ scanning tunneling microscopy and spectroscopy to investigate the atomic and electronic structure of low-angle GBs of monolayer tungsten diselenide (WSe2) with misorientation angles of 3-6°. Butterfly features are observed along the GBs, with the periodicity depending on the misorientation angle. Density functional theory calculations show that these butterfly features correspond to gap states that arise in tetragonal dislocation cores and extend to distorted six-membered rings around the dislocation core. Understanding the nature of GB defects and their influence on transport and other device properties highlights the importance of defect engineering in future 2D device fabrication.
二维（2D）过渡金属二卤族化合物（TMD）具有许多未来器件应用感兴趣的新颖性质。特别是，晶界（GB）的存在会显著影响 2D TMD 的材料性质。然而，在原子尺度上直接表征 GB 缺陷的电子性质仍然极具挑战性。在这项研究中，我们采用扫描隧道显微镜和光谱学来研究具有 3-6°取向角的单层二硒化钨（WSe2）的低角度 GB 的原子和电子结构。在 GB 沿线观察到蝶形特征，其周期性取决于取向角。密度泛函理论计算表明，这些蝶形特征对应于在四方位错核中产生的带隙态，并扩展到位错核周围的扭曲六元环。了解 GB 缺陷的性质及其对传输和其他器件性能的影响，突出了在未来 2D 器件制造中进行缺陷工程的重要性。
