  We assessed the efficiencies of surface plasmon excitation by an
aloof-scattered electron beam on metals and graphene. Graphene is shown to
exhibit high energy transfer efficiencies at very low electron kinetic energy
requirements. We show that the exceptional performance of graphene is due to
its unique plasmon dispersion, low electronic density and thin-film structure.
The potential applications of these aloof-scattered graphene plasmons are
discussed in aspects of coherent radiation.
