Toward Two-Dimensional MoS2 Electrets with Modulated Fluorescence

We show how spatially controlled sulfur vacancy engineering enables monolayer MoS2 to act as an electret, storing quasi-permanent electrostatic charge within a single atomic layer and modulating its emission properties. Sulfur vacancies are created by stamp-assisted, electrode-free electrochemical nanolithography, yielding tunable defect densities from 1010 to 1013 cm-2. The vacancy domains act as electron traps, resulting in surface charge density up to 1 μC cm-2, with charge retention exceeding 300 days under ambient conditions. Kelvin probe and electric force microscopies reveal electrostatic patterns replicating the lithographic motif. These domains also define a colocalized exciton-quenching regions in fluorescence microimages. They modulate the exciton fluorescence lifetime recorded at room temperature from tens of nanoseconds to a few hundred picoseconds by enhanced nonradiative exciton deactivation and induce a different balancing between excitons and trion emission via free electron draining from the untreated zones of the crystal.