  Controlled defect creation is a prerequisite for the detailed study of
disorder effects in materials. Here, we irradiate a graphene/Ir(111)-interface
with low-energy Ar+ to study the induced structural changes. Combining computer
simulations and scanning-probe microscopy, we show that the resulting disorder
manifests mainly in the forms of intercalated metal adatoms and vacancy-type
defects in graphene. One prominent feature at higher irradiation energies (from
1 keV up) is the formation of line-like depressions, which consist of
sequential graphene defects created by the ion channeling within the interface
-- much like a stone skipping on water. Lower energies result in simpler
defects, down to 100 eV where more than one defect in every three is a graphene
single vacancy.
