Studying substrate effects on localized surface plasmons in an individual silver nanoparticle using electron...

Area of Science:

• Plasmonics
• Nanophotonics
• Materials Science

Background:

• Localized surface plasmons (LSPs) are crucial for nanoscale optical phenomena.
• Understanding substrate effects on nanoparticle plasmons is essential for device applications.
• Previous studies often used optical methods, limiting detailed spatial analysis.

Purpose of the Study:

• To investigate substrate effects on localized surface plasmons (LSPs) in a single silver nanoparticle (NP).
• To explore LSP excitations using electron energy-loss spectroscopy (EELS) with scanning transmission electron microscopy (STEM).
• To analyze the influence of NP-substrate distance and polarization on LSP resonance.

Main Methods:

• Utilized scanning transmission electron microscopy-electron energy-loss spectroscopy (STEM-EELS).
• Employed an incident electron trajectory parallel to the substrate surface for direct substrate interaction analysis.
• Varied electron trajectories to probe polarization-dependent LSP modes.

Main Results:

• Substrate presence reduced system symmetry, making LSP resonance energies polarization-dependent.
• Observed mode splitting consistent with optical studies, detectable via different electron trajectories.
• STEM-EELS revealed asymmetric LSP intensity distribution, with maximum intensity farthest from the substrate.

Conclusions:

• Substrate-induced electric field modifications are responsible for the asymmetric LSP intensity distribution.
• STEM-EELS provides unique insights into substrate-plasmon interactions beyond optical simulations.
• This study highlights the importance of considering substrate effects in nanoparticle plasmonics.