Defect repairing in two-dimensional transition metal dichalcogenides

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) have stimulated enormous research interest due to rich phase structure, high theoretical carrier mobility and layer-dependent bandgap. In view of the close correlation between defects and properties in 2D TMDCs, more attentions have been paid on the defect engineering in recent years, however the mechanism is still unclear. Herein, we review the critical progress of defect engineering and provide an extensive way to modulate the properties depressed by defects. To insight into the defect engineering, we firstly introduce two common kinds of defects during the growth progress of TMDCs and the possible distribution of energy levels those defects could induce. Then, various methods to improve point defects and grain boundaries during the period of growth are discussed intensively, with the assistance of which more large-area TMDCs films can be obtained. Considering the defects in TMDCs are inevitable regardless of concentration, we also highlight strategies to heal the defects after growth. Through dry methods or wet methods, the chalcogen vacancies can be repaired and thus, the performance of electronic device would be significantly enhanced. Finally, we propose the challenges and prospective for defect engineering in 2D TMDCs materials to support the optimization of device and lead them to wide applied fields.