We employ tip-enhanced infrared near-field microscopy to study the plasmonic properties of
epitaxial quasi-free-standing monolayer graphene on silicon carbide. The near-field images
reveal propagating graphene plasmons, as well as a strong plasmon reflection at gaps in
the graphene layer, which appear at the steps between the SiC terraces. When the step
height is around 1.5 nm, which is two orders of magnitude smaller than the plasmon
wavelength, the reflection signal reaches 20% of its value at graphene edges, and it …

Tip-enhanced infrared near-field microscopy is used to study propagating plasmons in
epitaxial quasi-free-standing monolayer graphene on silicon carbide. We observe that
plasmons are strongly reflected at graphene gaps at the steps between the substrate
terraces. For the step height of only 1.5 nm, which is two orders of magnitude smaller than
the plasmon wavelength, the reflection signal reaches 20 percent of its value at graphene
edges, and it approaches 0.5 for steps of 5 nm. We support this observation with extensive …