Photoluminescence Quenching in Single-Layer MoS$_{2}$ via Oxygen Plasma Treatment

Ultrathin two-dimensional (2D) layered transition dichalcogenides (TMDs) families have emerged as a new class of semiconducting candidates due to its intrinsic bandgap. The ability to control the properties of 2D TMDs will become a key in the development of future electronic and optoelectronic applications; however, altering the properties via creating and manipulating defects through external control is not fully investigated yet. In this work, we studied tunable optical properties of single-layer (SL) MoS$_{2}$ by applying time-dependent oxygen plasma exposure. As the exposure time increased, the strong photoluminescence (PL) of SL MoS$_{2}$ changed to complete quenching accompanied by clear changes in Raman spectra with gradual reduction of MoS$_{2}$ peaks as well as an appearance of oxidization-induced peak of Mo-O bonds formation. Using band structure calculations, we found that the creation of MoO$_{3}$ disordered-domains led to plasma-induced direct-to-indirect bandgap transition in defected SL MoS$_{2}$, resulting in PL quenching with lattice distortion. Our results suggest new opportunities of tailoring and understanding the properties of 2D TMDs.