Morphology-induced spectral modification of self-assembled WS₂ pyramids

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional transition metal dichalcogenides (2D-TMDs) possess unique optical properties, including chiral excitons, making them promising for nanophotonics.
• Chemical vapor deposition (CVD) enables the fabrication of diverse 2D-TMD nanostructures, but their optical responses are not fully understood, especially for complex geometries.

Purpose of the Study:

• To investigate the optical response of WS2 nanostructures, specifically hollow pyramids, created using CVD.
• To characterize the position-dependent optical features and relate them to the nanogeometry and atomic arrangement.

Main Methods:

• Fabrication of WS2 nanostructures, including monolayers and hollow pyramids, via CVD.
• Resonant excitation and detailed analysis of photoluminescence and Raman spectroscopy to study phononic resonances.
• Characterization of spectral features, including peak intensity, ratio, and position, to identify local variations.

Main Results:

• Hollow WS2 pyramids exhibit significantly reduced photoluminescence compared to layered WS2, facilitating clearer Raman signal analysis.
• Resonant excitation reveals numerous higher-order phononic resonances in the hollow pyramids.
• Optical response spectra are position-dependent, with variations in peak characteristics indicating local differences in atomic structure within the pyramids.

Conclusions:

• The position-dependent optical response of hollow WS2 pyramids is directly linked to growth-induced nanogeometry and local atomic variations.
• This research lays the groundwork for developing tunable nanophotonic devices for applications in opto-electronics and non-linear optics.