ABSTRACT:Plasmonic gap modes provide the ultimateconfinement of opticalfields. Demanding high spatialresolution, the direct imaging of these modes was onlyrecently achieved by electron energy loss spectroscopy (EELS)in a scanning transmission electron microscope (STEM).However, conventional 2D STEM-EELS is only sensitive tocomponents of the photonic local density of states (LDOS)parallel to the electron trajectory. It is thus insensitive tospecific gap modes, a restriction that was lifted with the introduction of tomographic 3D EELS imaging. Here, we show that by3D EELS tomography the gap mode LDOS of a vertically stacked nanotriangle dimer can be fully imaged. Besides probing thecomplete mode spectrum, we demonstrate that the tomographic approach allows disentangling the signal contributions from thetwo nanotriangles that superimpose in a single measurement with afixed electron trajectory. Generally, vertically couplednanoparticles enable the tailoring of 3D plasmonicfields, and their full characterization will thus aid the development of complexnanophotonic devices.
ASJC Scopus subject areas
- Werkstoffwissenschaften (insg.)
Fields of Expertise
- Advanced Materials Science
Treatment code (Nähere Zuordnung)
- NAWI Graz