Morphology-induced spectral modification of self-assembled WS2 pyramids

TL;DR

This study investigates how the nanogeometry of self-assembled WS2 pyramids influences their optical properties, revealing position-dependent spectral features and resonances that could enable tunable nanophotonic devices.

Contribution

It demonstrates the impact of morphology on the optical response of WS2 nanostructures, providing insights into growth-induced effects on their spectral characteristics.

Findings

Hollow WS2 pyramids show reduced photoluminescence compared to monolayers.

Position-dependent spectral features are observed in the pyramids.

Higher-order phononic resonances are excited resonantly in the pyramids.

Abstract

Due to their intriguing optical properties, including stable and chiral excitons, two-dimensional transition metal dichalcogenides (2D-TMDs) hold the promise of applications in nanophotonics. Chemical vapor deposition (CVD) techniques offer a platform to fabricate and design nanostructures with diverse geometries. However, the more exotic the grown nanogeometry, the less is known about its optical response. WS2 nanostructures with geometries ranging from monolayers to hollow pyramids have been created. The hollow pyramids exhibit a strongly reduced photoluminescence with respect to horizontally layered tungsten disulphide, facilitating the study of their clear Raman signal in more detail. Excited resonantly, the hollow pyramids exhibit a great number of higher-order phononic resonances. In contrast to monolayers, the spectral features of the optical response of the pyramids are position dependent. Differences in peak intensity, peak ratio and spectral peak positions reveal local variations in the atomic arrangement of the hollow pyramids crater and sides. The position-dependent optical response of hollow WS2 pyramids is characterized and attributed to growth-induced nanogeometry. Thereby the first steps are taken towards producing tunable nanophotonic devices with applications ranging from opto-electronics to non-linear optics.