Nanopatterning of room-temperature localized excitons in MoS2

We demonstrate a simple approach to pattern a novel localized excitonic state in monolayer MoS2. We raster an electron beam over pristine monolayer MoS2 with a resolution down to 20 nm. In the exposed areas we observe new narrow (1 meV) peaks near 1.72 eV in the photoluminescence (PL) spectrum. We investigate the nature of the state responsible for the peaks using AFM and STEM microscopies, PL spectroscopy, and by examining the response of the state to AFM mechanical cleaning. All these techniques indicate that the state is not associated with structural defects in MoS2, as commonly assumed for irradiation-induced states, and results neither from strain nor from local dielectric screening. Instead, we suggest that this state is a charge transfer exciton associated with the organic substance deposited onto the MoS2 during the e-beam exposure. We show that this new state is well-resolved, easy-to-generate via conventional EBL, and its emission is visible at room temperature. It can be used to study localized excitons, to enable chemical sensing, and to generate new many-body excitonic states.