Monolithic Metal Dimer-on-Film Structure: New Plasmonic Properties Introduced by the Underlying Metal

Area of Science:

• Plasmonics and Nanophotonics
• Materials Science
• Sensing Technologies

Background:

• Dimers, comprising two closely spaced metallic nanostructures, are fundamental in plasmonics, known for high local field enhancements.
• Fabricating dimers on metallic substrates significantly alters their plasmonic characteristics compared to isolated dimers.

Purpose of the Study:

• To investigate the plasmonic properties of a gold (Au) dimer situated on a gold (Au) substrate.
• To explore the influence of the dielectric environment on the dimer-on-film structure's plasmonic behavior.
• To evaluate the sensing capabilities of these all-metal nanostructures for refractive index sensing.

Main Methods:

• Theoretical examination of a gold dimer on a gold substrate.
• Analysis of plasmonic responses under varying dielectric environments.
• Characterization of localized surface plasmon resonances (LSPR) and collective surface lattice resonances (SLR).

Main Results:

• The Au dimer-on-Au substrate structure supports a screened 'bonding' dimer plasmon and a lower-energy magnetic charge transfer plasmon.
• A diverse range of higher-order hybrid plasmons were observed in the visible spectrum by altering the dielectric environment.
• Both LSPR and SLR exhibited highly sensitive responses to changes in the refractive index.

Conclusions:

• All-metal magnetic-resonant nanostructures, such as the dimer-on-film configuration, demonstrate significant potential for plasmonic sensing.
• These structures offer a promising pathway for developing enhanced localized surface plasmon resonance (LSPR) and surface lattice resonance (SLR) based sensors.
• The observed phenomena highlight the tunability and sensitivity of plasmonic responses in engineered nanostructures.