Mapping VIS-terahertz (≤17 THz) surface plasmons sustained on native and chemically functionalized percolated gold...

Area of Science:

• Plasmonics
• Surface Science
• Spectroscopy

Background:

• Investigating molecule-surface interactions is crucial for understanding nanoscale optical phenomena.
• Nano-corrugated metallic surfaces offer unique platforms for plasmonic applications.
• Electron energy loss spectroscopy (EELS) is a powerful tool for characterizing nanoscale materials.

Purpose of the Study:

• To investigate heterogeneous assemblies of Rhodamine B molecules on a nano-corrugated gold (Au) surface using STEM-EELS.
• To analyze the plasmonic response of the metallic substrate and its interplay with molecular vibrations and electronic excitations.
• To provide a foundation for rationalizing optical measurements of molecule-plasmon interactions.

Main Methods:

• Scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS).
• Characterization of a percolated gold thin film with nanostructures (≤10 nm thickness).
• Acquisition and analysis of EELS spectrum images before and after Rhodamine B deposition.

Main Results:

• Observed a rich, nanometrically varying plasmonic response from the gold substrate across the VIS-terahertz region.
• Detected multiple localized plasmons and simultaneous resonances at different locations within the film.
• Identified spectral variations in hybrid molecular-metallic constructs, indicating simultaneous detection of plasmons, molecular vibrations, and electronic excitations.

Conclusions:

• STEM-EELS effectively probes the interplay between plasmons and molecules on nanostructured surfaces.
• The study provides detailed spectral characterization of Rhodamine B on gold nanostructures.
• Findings can inform and rationalize optical microscopic and spectroscopic measurements leveraging molecule-plasmon coupling.