Two-dimensional materials under electron irradiation

This article reviews atomic-resolution in situ electron microscopy studies of two-dimensional materials such as graphene, hexagonal boron nitride, and metal dichalcogenides with a focus on defect structures. Electron irradiation allows defect formation and atomic-resolution imaging at the same time by the same electron beam. Two-dimensional hexagonal lattices show unique mechanisms of defect reconstruction that do not appear in other materials. The combination of thermal annealing and irradiation, both adjustable in the electron microscope, sets a balance between equilibrium and nonequilibrium and allows for the generation of new structures and morphologies.