Tip size dependence of passive near-field microscopy

Area of Science:

• Optics
• Materials Science
• Nanotechnology

Background:

• Passive scattering-type scanning near-field optical microscopy (s-SNOM) probes surface waves without external light.
• Understanding tip-sample coupling is crucial for optimizing s-SNOM performance.

Purpose of the Study:

• To improve spatial resolution in passive s-SNOM.
• To investigate the relationship between tip apex curvature and tip-sample coupling.
• To analyze the decay behavior of thermally excited near-field signals.

Main Methods:

• Utilized tungsten tips with varying radii of curvature.
• Studied spatial resolution, signal intensity, and decay behavior of near-field signals.
• Investigated tip size dependence of far-field interference patterns.
• Developed a theoretical model to interpret experimental data.

Main Results:

• Spatial resolution in passive s-SNOM is directly related to tip size.
• Near-field signal decay behavior is independent of tip size.
• Tip-sample coupling strength is not dependent on tip size.
• Experimental data was successfully interpreted by the proposed theoretical model.

Conclusions:

• Passive s-SNOM spatial resolution can be optimized by controlling tip size.
• Tip-sample coupling in passive s-SNOM is robust across different tip sizes.
• The developed theoretical model provides a framework for understanding passive s-SNOM operation.