Journal
MATERIALS TODAY NANO
Volume 18, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.mtnano.2022.100183
Keywords
Scanning transmission electron microscopy; Tungsten disul fide; Two-dimensional materials; Growth kinetics; Hydrogen evolution reaction
Funding
- China Postdoctoral Science Foundation [2021M692172]
- Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (Eugene P. Wigner Fellowship)
- Office of Science of the U.S. Department of Energy [DE-AC05-00OR22725]
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The atomic structure of 2D transition metal dichalcogenides with faceted edges, grown using chemical vapor deposition, was investigated using aberration-corrected annular dark-field scanning transmission electron microscopy. Triangular edge structures with zigzag terminations were observed, exhibiting near-atomic sharpness. DFT calculations suggested that the atomic-scale sharpness at these edges remained stable, even under different growth conditions.
Chemical vapor deposition (CVD)-grown 2D transition metal dichalcogenides can adopt faceted edges. To investigate how sharp these sites can be, we utilize aberration-corrected annular dark-field scanning transmission electron microscopy (ADF-STEM) to resolve the atomic structure of two-dimensional (2D) WS2 domains that show jagged edges. Nanoscale triangular edge structures with S zigzag terminations are observed. Both the peak and valley regions exhibit near-atomic sharpness. The peaks are as sharp as two atoms in width. Highly ordered valley sites display a minimum width of three atoms, and prospective single-atom valleys appear as two-atom-wide sites in the ADF-STEM contrast. Regarding the kinetics, density-functional theory (DFT) calculations indicate that the 2-W-atom peak would not evolve into a single-W-atom peak even though the latter configuration is also stable with a high enough binding energy under the growth conditions. These results help deepen our understanding of the possible structuring at the nanoscale and the atomic-scale limits of peaks and valleys formed via intersection of two zigzag edges. The enriched edge sites lead to higher catalytic activities for the hydrogen evolution reaction (HER).
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