期刊
ACS NANO
卷 15, 期 2, 页码 2858-2868出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c08835
关键词
MoS2; transition-metal dichalcogenides; defects; grain boundaries; moire patterns; scanning transmission electron microscope; pulsed laser deposition
类别
资金
- Independent Research Fund Denmark, Sapere Aude grant [804900095B]
- Center for Nanostructured Graphene (CNG) under the Danish National Research Foundation [DNRF103]
- European Research Council (ERC) under the European Union [773122]
- U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division
- European Research Council (ERC) [773122] Funding Source: European Research Council (ERC)
Pulsed laser deposition is a powerful method for growing 2D transition-metal dichalcogenides, but defects in these materials remain largely unknown. Sulfur vacancies and MoS antisites are the predominant defects in 2D MoS2 grown by PLD. The atomic structure of monolayer MoS2 and the role of grain boundaries on the growth of bilayer MoS2 are detailed, with results showing various structural symmetries in bilayer MoS2 and experimental demonstrations of stacking orientation transitions.
Pulsed laser deposition (PLD) can be considered a powerful method for the growth of two-dimensional (2D) transition-metal dichalcogenides (TMDs) into van der Waals heterostructures. However, despite significant progress, the defects in 2D TMDs grown by PLD remain largely unknown and yet to be explored. Here, we combine atomic resolution images and first-principles calculations to reveal the atomic structure of defects, grains, and grain boundaries in mono- and bilayer MoS2 grown by PLD. We find that sulfur vacancies and MoS antisites are the predominant point defects in 2D MoS2. We predict that the aforementioned point defects are thermodynamically favorable under a Mo-rich/S-poor environment. The MoS2 monolayers are polycrystal-line and feature nanometer size grains connected by a high density of grain boundaries. In particular, the coalescence of nanometer grains results in the formation of 180 degrees mirror twin boundaries consisting of distinct 4- and 8-membered rings. We show that PLD synthesis of bilayer MoS2 results in various structural symmetries, including AA ' and AB, but also turbostratic with characteristic moire patterns. Moreover, we report on the experimental demonstration of an electron beam-driven transition between the AB and AA' stacking orientations in bilayer MoS2. These results provide a detailed insight into the atomic structure of monolayer MoS2 and the role of the grain boundaries on the growth of bilayer MoS2, which has importance for future applications in optoelectronics.
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