  The direct manipulation of individual atoms in materials using scanning probe
microscopy has been a seminal achievement of nanotechnology. Recent advances in
imaging resolution and sample stability have made scanning transmission
electron microscopy a promising alternative for single-atom manipulation of
covalently bound materials. Pioneering experiments using an atomically focused
electron beam have demonstrated the directed movement of silicon atoms over a
handful of sites within the graphene lattice. Here, we achieve a much greater
degree of control, allowing us to precisely move silicon impurities along an
extended path, circulating a single hexagon, or back and forth between the two
graphene sublattices. Even with manual operation, our manipulation rate is
already comparable to the state-of-the-art in any atomically precise technique.
We further explore the influence of electron energy on the manipulation rate,
supported by improved theoretical modeling taking into account the vibrations
of atoms near the impurities, and implement feedback to detect manipulation
events in real time. In addition to atomic-level engineering of its structure
and properties, graphene also provides an excellent platform for refining the
accuracy of quantitative models and for the development of automated
manipulation.
