Visualization of Zero-Dimensional Plasmons in Graphene Quantum Dots with Near-Field Infrared Microscopy

Because of unique plasmonic features, nanostructured graphene such as graphene nanoribbons (CNRs) and quantum dots (GQDs) is attracting much interests. In this work, we investigated real-space characterization of surface plasmon polariton (SPP) in GQDs on SiC substrate by utilizing a scattering-type scanning near-field optical microscope (s-SNOM) in the mid-infrared (MIR) band. Nanoscale near-field images revealed that the SPP in the GQDs was excited at the wavenumber of 929.02 cm(-1), where the SPP in two-dimensional (2D) graphene has not been reported. The present findings provide not only a deeper understanding of the SPP in graphene nanostructures, but also a first step for exploring new plasmonic functionalities impossible with conventional 2D graphene.