From atoms to grains: Transmission electron microscopy of graphene

Recently, transmission electron microscopy (TEM) and related techniques have brought unique insights to graphene research, demonstrating remarkable flexibility in characterizations ranging from atomic ordering to charge distribution. Such TEM studies have helped advance areas including the understanding of graphene growth and the effects of defects and dopants on the mechanical and electrical properties of graphene. Electron microscopy has proved particularly useful in determining the structure of crystals and grain boundaries across six orders of magnitude'from the shapes, arrangements, and stacking sequences of grains to the atomic arrangements at grain boundaries. Meanwhile, graphene is becoming a promising two-dimensional laboratory bench for electron microscopy, for example, turning graphene into a medium for nanosculpting by transforming buckyballs into graphene and vice versa. Finally, graphene has been used as an ultrathin support membrane for TEM, enabling studies of the motion of single atoms, direct imaging of two-dimensional amorphous materials, and even formation of nano-aquaria for imaging bacteria or nanoparticles in liquid media. Rapid developments in the fields of both electron microscopy and graphene will continue to provide a rich ground for future insights.