  Atomic-scale fabrication is an outstanding challenge and overarching goal for
the nanoscience community. The practical implementation of moving and fixing
atoms to a structure is non-trivial considering that one must spatially address
the positioning of single atoms, provide a stabilizing scaffold to hold
structures in place, and understand the details of their chemical bonding.
Free-standing graphene offers a simplified platform for the development of
atomic-scale fabrication and the focused electron beam in a scanning
transmission electron microscope can be used to locally induce defects and
sculpt the graphene. In this scenario, the graphene forms the stabilizing
scaffold and the experimental question is whether a range of dopant atoms can
be attached and incorporated into the lattice using a single technique and,
from a theoretical perspective, we would like to know which dopants will create
technologically interesting properties. Here, we demonstrate that the electron
beam can be used to selectively and precisely insert a variety of transition
metal atoms into graphene with highly localized control over the doping
locations. We use first-principles density functional theory calculations with
direct observation of the created structures to reveal the energetics of
incorporating metal atoms into graphene and their magnetic, electronic, and
quantum topological properties.
