Argon Plasma Induced Phase Transition in Monolayer MoS2

In this work, we report a facile, clean, controllable and scalable phase engineering technique for monolayer MoS2. We found that weak Ar-plasma bombardment can locally induce 2H→1T phase transition in monolayer MoS2 to form mosaic structures. These 2H→1T phase transitions are stabilized by point defects (single S-vacancies) and the sizes of induced 1T domains are typically a few nanometers, as revealed by scanning tunneling microscopy measurements. On the basis of a selected-area phase patterning process, we fabricated MoS2 FETs inducing 1T phase transition within the metal contact areas, which exhibit substantially improved device performances. Our results open up a new route for phase engineering in monolayer MoS2 and other transition metal dichalcogenide (TMD) materials.