Placing single atoms in graphene with a scanning transmission electron microscope

We employ the sub-atomically focused beam of a scanning transmission electron microscope ( STEM) to introduce and controllably manipulate individual dopant atoms in a 2D graphene lattice. The electron beam is used to create defects and subsequently sputter adsorbed source materials into the graphene lattice such that individual vacancy defects are controllably passivated by Si substitutional atoms. We further document that Si point defects may be directed through the lattice via ebeam control or modified (as yet, uncontrollably) to form new defects which can incorporate new atoms into the graphene lattice. These studies demonstrate the potential of STEM for atom-byatom nanofabrication and fundamental studies of chemical reactions in 2D materials on the atomic level.