A Closer Look at Corrugated Au Tips

Area of Science:

• Plasmonics
• Nanophotonics
• Spectroscopy

Background:

• Metallic tips are crucial for plasmonic field enhancement.
• Tip structure dictates optical resonances and plasmonic fields.
• Nanoscale details influence tip-enhanced Raman (TER) spectra.

Purpose of the Study:

• To investigate the properties of corrugated metallic tips using optical and electron microscopies.
• To understand how tip morphology affects plasmonic resonances and TER spectra.
• To analyze molecular behavior under tip-tip TER geometry.

Main Methods:

• Combined optical and electron microscopy techniques.
• Tip-enhanced Raman nanospectroscopy (TERS) with 4-thiobenzonitrile (TBN) as a molecular reporter.
• Analysis of spatially resolved TER spectra.

Main Results:

• Tip shape determines optical resonances and plasmonic enhancement.
• Nanometric details govern TER spectra and images.
• Optical rectification and molecular charging observed in tip-tip TER geometry.
• Surface corrugation causes localized resonances, complicating spectral assignments.
• Tip-tip geometry sustains unique junction plasmons.

Conclusions:

• Nanoscale corrugations on metallic tips introduce complex plasmonic effects.
• TERS is sensitive to structural details, enabling the study of optical rectification and molecular charging.
• Understanding these nanoscale phenomena is crucial for accurate spectral interpretation in TERS.