Robust Plasma-Assisted Growth of 2D Janus Transition Metal Dichalcogenides and Their Enhanced Photoluminescent Properties.

Janus transition metal dichalcogenides (TMDs) are a novel class of 2D materials with unique mirror asymmetry. Plasma-assisted synthesis at room temperature is favored for producing Janus TMDs due to its energy efficiency and prevention of alloying. However, current methods require stringent control over growth conditions, risking defects or unintended materials. A robust plasma-assisted (RPA) synthesis strategy is introduced, incorporating a built-in tube with a suitable inner diameter into the plasma-assisted system. This innovation creates a mild, uniform plasma atmosphere, allowing for broader variations in growth parameters without significantly affecting Janus MoSSe's morphology and characteristics. This approach simplifies the synthesis process and enhances the success rate of Janus TMD production. Additionally, methods are explored to enhance the photoluminescence (PL) of Janus MoSSe. Releasing MoSSe from the growth substrate and annealing it removes strain and unintentional doping, improving PL performance. MoSSe on hexagonal boron nitride (h-BN) flakes after annealing shows a 32-fold increase in PL intensity. Bis(trifluoromethane) sulfonimide (TFSI) treatment of MoSSe results in a remarkable 70-fold increase in PL intensity, a 2.5-fold extension in exciton lifetime, and quantum yield (QY) reaching up to ≈31.2%. These findings provide critical insights for optimizing the luminescence properties of 2D Janus materials, advancing Janus optoelectronics.