Spatial Resolution of Coherent Cathodoluminescence Super-Resolution Microscopy

Area of Science:

• Nanoscience
• Materials Science
• Spectroscopy

Background:

• Coherent cathodoluminescence (CL) imaging spectroscopy is a powerful technique for nanoscale analysis.
• Understanding the factors limiting CL's spatial resolution is crucial for its application as a deep-subwavelength imaging method.
• Localized surface plasmons in metallic nanoparticles offer unique optical properties exploitable for imaging.

Purpose of the Study:

• To investigate the nanoscale excitation of silver (Ag) nanocubes using CL imaging spectroscopy.
• To determine the factors governing the spatial resolution of CL as a deep-subwavelength imaging technique.
• To analyze the coupling between electron beams and plasmon modes in Ag nanocubes.

Main Methods:

• Utilized coherent cathodoluminescence imaging spectroscopy (CL) with 10-30 keV electron beams.
• Excited localized plasmons in 70 nm Ag nanocubes at 2.4 and 3.1 eV.
• Collected far-field radiation and secondary electron intensity, performing CL line scans.
• Developed a statistical model for electron scattering analysis within Ag nanocubes.

Main Results:

• Observed exponentially decaying CL tails, indicating evanescent coupling of the electron field to plasmon modes.
• Measured CL decay lengths between 8 nm (10 keV) and 12 nm (30 keV), closely matching theoretical calculations (1-3 nm difference).
• Derived Ag nanocube edges from CL line scans with a systematic error below 3 nm.
• Demonstrated that CL probes electron-induced plasmon fields with nanometer accuracy.

Conclusions:

• CL imaging spectroscopy provides deep-subwavelength imaging capabilities with high spatial accuracy.
• The spatial resolution of CL is influenced by electron beam energy and scattering effects within the nanocubes.
• CL is a reliable technique for probing nanoscale plasmonic fields and determining nanostructure dimensions.