Laser-Induced Sulfur Vacancy Defect Healing by Oxygen in Molybdenum Disulfide Monolayers

The photoluminescence yield of monolayer MoS2 was locally and durably enhanced by prolonged laser exposure, with significant alterations of the spectral weight of its exciton and trion subcomponents. Evidence from Raman and photoluminescence spectroscopy, tip-enhanced photoluminescence, atomic force microscopy, and photoemission spectroscopy allows the phenomenon to be rationalized as a photoinduced oxidation of sulfur vacancies mediated by ambient air. A decrease in the trion emission and a marked blue shift of the A1′ Raman peak suggest p-type counterdoping. Nanoscale spectroscopies reveal that the enhanced photoluminescence emission comes from the very edge of the patterning laser spot, where photoinduced oxidation has occurred.