Fluorescence Spectroscopy of Monolayer MoS₂ under Low-Energy Electron Irradiation

We present the development of a single-photon scanning confocal microscope and the application of the system for characterizing monolayer molybdenum disulfide (MoS₂). MoS₂ semiconductors are the new generation of two-dimensional materials that possess several advantages compared to graphene due to their tunable bandgap and high electron mobility. Several approaches have been used to modify their physical properties for optical device applications. Here, we report a facile and non-destructive surface modifcation method for monolayer MoS₂ via electron irradiation at a low accelerating voltage. Raman and photoluminescence spectroscopy confirmed that the structure remains unchanged after irradiation. However, when the surface was illuminated with a 532 nm laser for a prolonged period, PL quenching can occur. We showed that the quenching is reversible depending on the ambient environment, providing another means for using the MoS₂ for optical gas sensing applications.