3D Imaging of Gap Plasmons in Vertically Coupled Nanoparticles by EELS Tomography

Area of Science:

• Plasmonics
• Nanophotonics
• Electron Microscopy

Background:

• Plasmonic gap modes offer extreme optical field confinement.
• Direct imaging of these modes requires high spatial resolution.
• Conventional 2D STEM-EELS is limited to in-plane photonic local density of states (LDOS).

Purpose of the Study:

• To demonstrate the capability of 3D EELS tomography for imaging plasmonic gap modes.
• To overcome the limitations of 2D STEM-EELS for gap mode characterization.
• To fully map the 3D gap mode LDOS in vertically stacked nanostructures.

Main Methods:

• Utilizing 3D EELS tomography in a scanning transmission electron microscope (STEM).
• Investigating a vertically stacked nanotriangle dimer.
• Analyzing the photonic local density of states (LDOS) with high spatial resolution.

Main Results:

• Achieved full 3D imaging of plasmonic gap mode LDOS.
• Successfully probed the complete mode spectrum of the nanotriangle dimer.
• Demonstrated disentanglement of signal contributions from individual nanoparticles within the dimer.

Conclusions:

• 3D EELS tomography provides comprehensive characterization of 3D plasmonic fields.
• This technique is crucial for understanding and designing vertically coupled plasmonic nanostructures.
• Enables advancement of complex nanophotonic devices through detailed plasmonic field analysis.