Controlled synthesis of large-area monolayer Janus MoSSe nanostructures based on interface strain-induced strategy

Janus transition metal dichalcogenides (TMDCs) exhibit exceptional potential for advancing applications in the fields of optoelectronics, spintronics, and valleytronics, owing to their broken structural symmetry and unique properties. However, the controlled synthesis of large-area, homogeneous monolayer Janus MoSSe remains a significant challenge due to the high activation energy barriers of chalcogen atom substitution and the complexity of conventional fabrication methods. Here, we demonstrate a one-step, two-stage chemical vapor deposition strategy enabling precise synthesis of large-area monolayer Janus MoSSe nanostructures. The preparation of Janus MoSSe in our system proceeds through the top-layer S–Se substitution mechanism, while the interfacial strain introduced by softened soda-lime glass weakens Mo–S bonds and lowers the activation barrier, thereby enabling this substitution to occur without plasma assistance. First-principles calculations reveal that increasing interfacial strain monotonically reduces the formation energy of Janus MoSSe, highlighting its critical role in directing the selective chalcogen exchange. Our work presents a scalable and controllable technique for synthesizing Janus TMDCs, which is a critical step toward practical implementation in photodetectors, solar cells, and spintronic devices.