Doping Graphene with Substitutional Mn

We report the incorporation of substitutional Mn atoms in high-quality, epitaxial graphene on Cu(111), using ultralow-energy ion implantation. We characterize in detail the atomic structure of substitutional Mn in a single carbon vacancy and quantify its concentration. In particular, we are able to determine the position of substitutional Mn atoms with respect to the Moiré superstructure (i.e., local graphene-Cu stacking symmetry) and to the carbon sublattice; in the out-of-plane direction, substitutional Mn atoms are found to be slightly displaced toward the Cu surface, that is, effectively underneath the graphene layer. Regarding electronic properties, we show that graphene doped with substitutional Mn to a concentration of the order of 0.04%, with negligible structural disorder (other than the Mn substitution), retains the Dirac-like band structure of pristine graphene on Cu(111), making it an ideal system in which to study the interplay between local magnetic moments and Dirac electrons. Our work also establishes that ultralow-energy ion implantation is suited for substitutional magnetic doping of graphene. Given the flexibility, reproducibility, and scalability inherent to ion implantation, our work creates numerous opportunities for research on magnetic functionalization of graphene and other two-dimensional materials.