Observation of Room‐Temperature Dark Exciton Emission in Nanopatch‐Decorated Monolayer WSe 2 on Metal Substrate

• Published in: Advanced optical materials 2021-12, Vol.9 (24)
• Main Authors: Rahaman, Mahfujur, Selyshchev, Oleksandr, Pan, Yang, Schwartz, Rico, Milekhin, Ilya, Sharma, Apoorva, Salvan, Georgeta, Gemming, Sibylle, Korn, Tobias, Zahn, Dietrich R. T.
• Format: Article
• Language: English
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202101801

The presence of strong spin–orbit coupling in the valence band and weak spin‐splitting in the conduction band result in the lowest energy exciton in WX 2 (X = S, Se) being spin forbidden and optically dark. Because of their long lifetimes, dark excitons are highly attractive for quantum optics and optoelectronic applications. To date, studying dark excitonic emissions is limited to cryogenic temperatures or requires very complex experimental configurations to observe them at room temperature (RT). Here, the radiative decay of dark exciton related emission in WSe 2 monolayers is studied using both conventional and tip‐enhanced photoluminescence (TEPL) at RT. Monolayer WSe 2 flakes are sandwiched between noble metal substrates and polydimethylsiloxane nanopatches providing a strong local electrostatic out‐of‐plane dipole moment with respect to the 2D plane resulting in the observation of dark excitonic emission at RT. The spatial distribution of this dark exciton related emission is studied by TEPL with a spatial resolution of