A Chemo-mechanical Approach to Modifying Single Photon Emission in Monolayer WSe2

Monolayer WSe2 is an important member of the 2D layered materials family due to its valley physics and excitonic properties with potential application in quantum optoelectronics. Sites of sufficiently localized excitons in this material have been shown to host single photon emitters (SPEs). However, this emission is part of a broader, strain-induced defect emission spectrum and therefore the desired SPEs are not spectrally isolated. In this work, a combined approach of localized mechanical strain and chemical functionalization was used to create and isolate single photon emitters in monolayer WSe2. Treatment of the monolayer with an aqueous solution of nitrobenzenediazonium (4-NBD) tetrafluoroborate quenched broader defect emission on sites strained with prefabricated nanopillars, leaving behind stable, spectrically isolated SPEs of high photon purity. In particular, photoluminescence measurements taken at cryogenic temperatures show a near complete quenching of exciton fine structures beyond the neutral exciton. Overall, these results show that diazonium-based chemical functionalization is an effective method to modify the optical properties of WSe2 and can be utilized to improve SPE integrity.