Emerging 2D materials, such as atomically thin transition metal dichalcogenides (TMDs) and graphene, have been intensely studied due to their intriguing physical and chemical properties properties. These properties are usually governed by atomic point defects and interfaces in
2D materials, including edges and domain boundaries. Investigation of the defect and interface structures, therefore, is essential for rational
design and optimization of 2D materials. In this talk, I will present our recent scanning tunneling microscopy and spectroscopy studies of
atomic point defects and interfaces in 2D TMDs, focusing on those in few layer PtSe2 and MoS2/WS2 heterostructures. I will further discuss how the defects and interfaces are affected by external stimuli. Particularly, I will show our experimental and theoretical results on the shape evolution of monolayer vacancy islands on TiSe2 surfaces, and the associated growth kinetics, under electrical stressing.