  Focused electron beam induced deposition (FEBID) is a direct write technique
for depositing materials on a support substrate akin to 3D printing with an
electron beam (e-beam). Opportunities exist for merging this existing technique
with aberration-corrected scanning transmission electron microscopy to achieve
molecular- or atomic-level spatial precision. Several demonstrations have been
performed using graphene as the support substrate. A common challenge that
arises during this process is e-beam-induced hydrocarbon deposition, suggesting
greater control over the sample environment is needed. Various strategies exist
for cleaning graphene in situ. One of the most effective methods is to rapidly
heat to high temperatures, e.g., 600 C or higher. While this can produce large
areas of what appears to be atomically clean graphene, mobile hydrocarbons can
still be present on the surfaces. Here, we show that these hydrocarbons are
primarily limited to surface migration and demonstrate an effective method for
interrupting the flow using e-beam deposition to form corralled hydrocarbon
regions. This strategy is effective for maintaining atomically clean graphene
at high temperatures where hydrocarbon mobility can lead to substantial
accumulation of unwanted e-beam deposition.
