High vacuum tip-enhanced Raman spectroscope based on a scanning tunneling microscope.

Area of Science:

• Surface science
• Spectroscopy
• Nanotechnology

Background:

• Tip-enhanced Raman spectroscopy (TERS) offers high spatial resolution but is typically limited by atmospheric interference.
• In situ sample preparation and analysis under vacuum are crucial for studying delicate surface phenomena.

Purpose of the Study:

• To construct and validate a novel high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) system.
• To enable in situ sample preparation and nanoscale measurements under ultra-high vacuum conditions.
• To explore novel experimental results and phenomena not observable in atmospheric TERS.

Main Methods:

• Construction of a three-chamber HV-TERS system (analysis, sample preparation, fast loading) operating at 10(-7) Pa.
• Integration of scanning tunneling microscopy (STM) and Raman spectroscopy within the analysis chamber.
• Utilizing molecular beam epitaxy for sample preparation and a gold tip for TERS measurements.

Main Results:

• Demonstrated localized temperature measurement using Stokes and anti-Stokes TERS signals.
• Successfully monitored plasmonic catalysis label-free at the nanoscale.
• Observed simultaneous activation of infrared and Raman modes, Fermi resonance, and non-linear effects unique to HV-TERS.

Conclusions:

• The developed HV-TERS system provides a pure environment for high spatial and spectral resolution surface studies.
• In situ capabilities significantly enhance the study of nanoscale phenomena and surface chemistry.
• HV-TERS opens new avenues for investigating complex molecular interactions and non-linear optical effects on surfaces.