Atom-Dependent Edge-Enhanced Second-Harmonic Generation on MoS<sub>2</sub> Monolayers.
basic_science · Level V
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- Record sourced from PubMed, PMID 29327927.
- Also identified by DOI 10.1021/acs.nanolett.7b04006.
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Abstract
Edge morphology and lattice orientation of single-crystal molybdenum disulfide (MoS<sub>2</sub>) monolayers, a transition metal dichalcogenide (TMD), possessing a triangular shape with different edges grown by chemical vapor deposition are characterized by atomic force microscopy and transmission electron microscopy. Multiphoton laser scanning microscopy is utilized to study one-dimensional atomic edges of MoS<sub>2</sub> monolayers with localized midgap electronic states, which result in greatly enhanced optical second-harmonic generation (SHG). Microscopic S-zigzag edge and S-Mo Klein edge (bare Mo atoms protruding from a S-zigzag edge) terminations and the edge-atom dependent resonance energies can therefore be deduced based on SHG images. Theoretical calculations based on density functional theory clearly explain the lower energy of the S-zigzag edge states compared to the corresponding S-Mo Klein edge states. Characterization of the atomic-scale variation of edge-enhanced SHG is a step forward in this full-optical and high-yield technique of atomic-layer TMDs.