Nanoscale Optical Characterization of Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDs) are layered semiconductors whose atomically thin nature gives rise to pronounced excitonic and quantum phenomena. Nanoscale optical characterisation techniques, including tip-enhanced Raman spectroscopy (TERS), tip-enhanced photoluminescence (TEPL) and scattering-type scanning near-field optical microscopy (s-SNOM), circumvent the diffraction limit to resolve features down to tens of nanometres. These approaches enable direct mapping of vibrational modes, exciton recombination pathways and local band structure variations induced by defects, edges, strain and heterointerfaces. By correlating optical contrasts with structural and compositional heterogeneities, researchers have uncovered how grain boundaries and edge terminations modulate electron–phonon coupling, exciton lifetimes and charge-transfer excitations. Such insights are driving defect engineering, strain tuning and heterostructure assembly for applications in photodetectors, light-emitting diodes and valleytronic devices, where precise control over local optoelectronic properties is essential for performance and scalability.

Research from Nature Portfolio

Recent studies have used TERS to probe the distinct Raman signatures of armchair and zigzag edge defects in monolayer MoS2, revealing an edge-activated double-resonance peak that visualises local band bending and electron–phonon interactions with sub-15 nm resolution. Complementary near-field optical imaging has mapped excitonic relaxation at disordered edges and grain boundaries, distinguishing an energetically disordered edge region from a locally ordered interior quantum well. By quantifying exciton quenching at sulphur-deficient grain boundaries, this work established critical structure–property relationships that guide defect management in two-dimensional optoelectronic devices.

Nanoscale Optical Characterization of Transition Metal Dichalcogenides publication trend

The graph below shows the total number of articles in nanoscale optical characterization of transition metal dichalcogenides across all publications each year (not limited to Nature Index journals).

Technical terms

Transition Metal Dichalcogenides (TMDs): Two-dimensional semiconductors of the form MX2 (M = transition metal, X = chalcogen) with thickness-dependent electronic and optical properties.

Tip-Enhanced Raman Spectroscopy (TERS): A near-field technique using a plasmonic probe to amplify and localise Raman scattering below the diffraction limit.

Tip-Enhanced Photoluminescence (TEPL): A method coupling a metallic tip with photoluminescence detection to achieve nanoscale optical emission maps.

Exciton: A bound electron–hole pair whose recombination governs light emission in low-dimensional semiconductors.

Grain Boundary: The interface between crystalline domains in a two-dimensional material, often hosting defect states and altered optoelectronic responses.

Heterostructure: A junction of two or more distinct two-dimensional materials, enabling unique interfacial phenomena such as charge-transfer excitons and strain-modulated band alignment.

References

1. Tip-enhanced photoluminescence of monolayer MoS2 increased and spectrally shifted by injection of electrons. Nanophotonics (2023).
2. Probing the edge-related properties of atomically thin MoS2 at nanoscale. Nature Communications (2019).
3. Visualizing nanoscale excitonic relaxation properties of disordered edges and grain boundaries in monolayer molybdenum disulfide. Nature Communications (2015).
4. Near-field optical imaging and spectroscopy of 2D-TMDs. Nanophotonics (2021).
5. Investigating heterogeneous defects in single-crystalline WS2 via tip-enhanced Raman spectroscopy. npj 2D Materials and Applications (2022).
6. Probing the multi-disordered nanoscale alloy at the interface of lateral heterostructure of MoS2–WS2. Nanophotonics (2024).