title: Strong plasmon reflection at nanometer-size gaps in monolayer graphene on SiC.
abstract: 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 approaches 50% for step heights as small as 5 nm. This intriguing observation is corroborated by numerical simulations and explained by the accumulation of a line charge at the graphene termination. The associated electromagnetic fields at the graphene termination decay within a few nanometers, thus preventing efficient plasmon transmission across nanoscale gaps. Our work suggests that plasmon propagation in graphene-based circuits can be tailored using extremely compact nanostructures, such as ultranarrow gaps. It also demonstrates that tip-enhanced near-field microscopy is a powerful contactless tool to examine nanoscale defects in graphene.
authors.affiliation: CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.
authors.forename: Jianing
authors.initials: J
authors.lastname: Chen
authors.forename: Maxim L
authors.initials: ML
authors.lastname: Nesterov
authors.forename: Alexey Yu
authors.initials: AY
authors.lastname: Nikitin
authors.forename: Sukosin
authors.initials: S
authors.lastname: Thongrattanasiri
authors.forename: Pablo
authors.initials: P
authors.lastname: Alonso-González
authors.forename: Tetiana M
authors.initials: TM
authors.lastname: Slipchenko
authors.forename: Florian
authors.initials: F
authors.lastname: Speck
authors.forename: Markus
authors.initials: M
authors.lastname: Ostler
authors.forename: Thomas
authors.initials: T
authors.lastname: Seyller
authors.forename: Iris
authors.initials: I
authors.lastname: Crassee
authors.forename: Frank H L
authors.initials: FH
authors.lastname: Koppens
authors.forename: Luis
authors.initials: L
authors.lastname: Martin-Moreno
authors.forename: F Javier
authors.initials: FJ
authors.lastname: García de Abajo
authors.forename: Alexey B
authors.initials: AB
authors.lastname: Kuzmenko
authors.forename: Rainer
authors.initials: R
authors.lastname: Hillenbrand
mesh_terms: D017554:Carbon Compounds, Inorganic / Q000737:chemistry*; D004574:Electromagnetic Fields; D006108:Graphite / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D020349:Surface Plasmon Resonance; D013499:Surface Properties
chemical_list: D017554:Carbon Compounds, Inorganic; D017655:Silicon Compounds; D006108:Graphite; C022088:silicon carbide