Evolutional photoluminescence property in ultraviolet-ozone-treated monolayer MoS₂

Two-dimensional (2D) semiconductors offer significant advantages for electronic and optoelectronic devices. It is essential to develop the ability to dynamically manipulate and control their physical properties by simple ways for promoting practical applications. Herein, we demonstrate that a simple ultraviolet-ozone (UVO) treatment can bring dynamical properties and additional functions to monolayer MoS₂, as revealed by the time-dependent photoluminescence (PL) behavior. The PL behavior can be flexibly tuned by UVO treatment time, laser irradiation power and storing time in the air, originating from the nonequilibrium adsorption/desorption process of O₂ molecules on the surface of MoS₂. Combined the analysis of material characterizations and theoretical calculations, UVO treatment causes high-density O₂ molecules to physically bond with MoS₂ and thus the direct-indirect bandgap transition, resulting in a strong PL quenching. This metastable O₂ adsorption, which can be easily broken and artificially regulated, further enables an evolutionary, reversible and controllable PL behavior. Moreover, the PL of MoS₂ covered by mask made of patterned 2D materials exhibits graphical evolution and emission switch behavior, offering new possibilities in information storage and security devices.