  Chemical, mechanical, thermal and/or electronic properties of bulk or
low-dimensional materials can be engineered by introducing structural defects
to form novel functionalities. When using particles irradiation, these defects
can be spatially arranged to create complex structures, like sensing circuits,
where the spatial resolution of the defective areas plays a fundamental role.
Here, we show that structural defects can be patterned by low-energy electrons
in monolayer graphene sheets with spatial resolution strongly defined by the
surface of the supporting substrate. Indeed, two-dimensional micro-Raman
mapping revealed that the surroundings of irradiated areas contain
unintentional defects of the graphene lattice, whose density depends on the
methods exploited to clean the supporting surface. By combining Monte Carlo
simulations with the analysis of the graphene Raman modes, we attributed these
structural modifications mainly to the action of back-scattered electrons and
back-scattered electrons-created secondaries. The latter create reactive
radicals at the interface between graphene and the supporting surface that
affect the spatial resolution of the defective areas. Hence, defects pattern
can be produced with high spatial resolution by removing any organic
contaminants from the supporting surface and by reducing the thickness of the
substrate, in order to minimize the number of back-scattered and secondary
electrons.
