  Direct-write processes enable the alteration or deposition of materials in a
continuous, directable, sequential fashion. In this work we demonstrate an
electron beam direct-write process in an aberration-corrected scanning
transmission electron microscope. This process has several fundamental
differences from conventional electron beam induced deposition techniques,
where the electron beam dissociates precursor gases into chemically reactive
products that bond to a substrate. Here, we use elemental tin (Sn) as a
precursor and employ a different mechanism to facilitate deposition. The
atomic-sized electron beam is used to generate chemically reactive point
defects at desired locations in a graphene substrate. Temperature control of
the sample is used to enable the precursor atoms to migrate across the surface
and bond to the defect sites thereby enabling atom-by-atom direct-writing.
