  Nickel-doped graphene has been synthesized from propylene on a Ni(111)
surface and studied using scanning tunneling microscopy (STM) and density
functional theory (DFT). It is established that nickel centers are formed
during graphene synthesis on the Ni(111) surface by both chemical vapor
deposition (CVD) and temperature-programmed growth (TPG); apparently, they are
always present in graphene synthesized on Ni(111). The centers are observed in
STM images as single defects or defect chains and identified by DFT
calculations as Ni atoms in carbon bivacancies. These nickel atoms are
positively charged and may be of interest for single-atom catalysis. The
incorporated Ni atoms should remain in graphene after the detachment from the
substrate since they bound more strongly with carbon atoms in graphene than
with substrate nickel atoms.
