Identifying high-order plasmon modes in silver nanoparticle-over-mirror configuration

Area of Science:

• Plasmonics and Nanophotonics
• Materials Science
• Spectroscopy

Background:

• Metallic nanoparticle-over-mirror (NPOM) configurations are crucial for surface-enhanced spectroscopy, sensing, and light-emitting metasurfaces.
• Experimental identification of high-order localized surface plasmon modes in NPOMs, particularly with silver, is challenging due to low scattering cross-sections and poor reproducibility.
• Existing NPOM fabrication methods using colloidal nanoparticles or polycrystalline films lead to spectral fluctuations and hinder mode identification.

Purpose of the Study:

• To develop a method for reliably identifying high-order localized surface plasmon modes in silver NPOM structures.
• To achieve reproducible single-particle absorption spectra for advanced plasmonic applications.
• To overcome the limitations of current NPOM fabrication techniques that affect spectral quality and reproducibility.

Main Methods:

• Utilized differential reflection spectroscopy to probe plasmonic properties.
• Constructed uniform NPOMs using silver nanospheres, single-crystallized silver microplates, and a self-assembled monolayer of 1,10-decanedithiol.
• Compared spectral reproducibility of NPOMs fabricated with single-crystal components versus those made from polycrystalline silver films.

Main Results:

• Achieved reproducible single-particle absorption spectra by employing uniform NPOMs with specifically chosen silver components and a self-assembled monolayer.
• Demonstrated significant spectral fluctuations in silver NPOMs fabricated from typical polycrystalline films, even with template stripping.
• Successfully identified high-order localized surface plasmon modes in the engineered silver NPOM configuration.

Conclusions:

• The developed method allows for the identification of high-order plasmon modes in silver NPOMs, overcoming previous reproducibility issues.
• Uniform NPOMs constructed with single-crystal silver components are essential for obtaining stable and reproducible plasmonic spectra.
• This approach provides a pathway to high-quality plasmonic substrates for applications including colloidal metasurfaces, surface-enhanced Raman spectroscopy, and fluorescence.