Observation of rapid decay and optical properties of micro-pyramidically grown molybdenum diselenide MoSe2 crystal

In two-dimensional transition metal dichalcogenides (2D-TMDs), the existence of excitons and trions promises their fascinating optical properties for applications in nanophotonic. The more exotic the nanostructure geometry, the less explored its optical responses. The chemical vapor deposition (CVD) technique enables the synthesis of nanostructures with different geometries ranging from monolayers to pyramids driven by a screw-dislocation mechanism. Here we report the CVD synthesis of micro-pyramids with a curious optical response exotic geometry like pyramid. The photoluminescence of as-grown micro-pyramids is significantly diminished compared to their flat-layered structures. In contrast, nanostructured micro-pyramids exhibit a large number of higher-order phononic resonances when excited resonantly by the Raman signal, allowing a more detailed exploration of exciton dynamics. The spectral peak position, intensity, and ratio of the spectral peak reveal local variations in the atomic arrangement of the center and sides of the micro-pyramid. We have investigated the optical response of MoSe2 micro-pyramids and correlated them with their growth-induced nano geometry. In this study, we have taken into account the first step towards producing tunable nanophotonic devices with applications ranging from optoelectronics to nonlinear optics.