Robust Fabrication of Quantum Dots on Few-Layer MoS2 by Soft Hydrogen Plasma and Post-Annealing

Apart from unique properties of layered transition-metal dichalcogenide nanosheets like MoS2, quantum dots (QDs) from these layered materials promise novel science and applications due to their quantum confinement effect. However, the reported fabrication techniques for such QDs all involve the use of liquid organic solvents and the final material extraction from such liquid dispersions. Here a novel and convenient dry method for the synthesis of MoS2 quantum dots interspersed on few-layer MoS2 using soft hydrogen plasma treatment followed by post-annealing is demonstrated. The size of MoS2 nanodots can be well controlled by adjusting the working pressure of hydrogen plasma and post-thermal annealing. This method relies on the cumulative hydrogen ion bombardment effect which can destroy the hexagonal structure of the top MoS2 layer and disintegrate the top layer into MoS2 nanodots and even QDs. Post-thermal annealing can further reduce the size. Such MoS2 quantum dots interspersed on few-layer MoS2 exhibit two new photoluminescence peaks at around 575 nm because of the quantum confinement effect. This dry method is versatile, scalable, and compatible with the semiconductor manufacturing processes, and can be extended to other layered materials for applications in hydrogen evolution reaction, catalysis, and energy devices.