Nanoscale-resolved subsurface imaging by scattering-type near-field optical microscopy.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Subsurface imaging is crucial for analyzing buried nanostructures and defects.
• Traditional optical microscopy is limited by diffraction, hindering nanoscale subsurface resolution.
• Near-field optical microscopy offers enhanced resolution beyond the diffraction limit.

Purpose of the Study:

• To demonstrate the capability of scattering-type scanning near-field optical microscopy (s-SNOM) for subsurface imaging.
• To achieve nanoscale-resolved imaging of objects located below transparent surface layers.
• To explore subsurface imaging at both visible and mid-infrared wavelengths.

Main Methods:

• Utilized scattering-type scanning near-field optical microscopy (s-SNOM).
• Performed imaging at visible (633 nm) and mid-infrared (10.7 microm) wavelengths.
• Investigated subsurface gold islands buried in a polymer and varied oxide layer thicknesses.

Main Results:

• Achieved topography-free subsurface imaging at 633 nm.
• Resolved buried gold islands (50 nm depth) with < 120 nm lateral resolution (lambda/90) at 10.7 microm.
• Provided experimental evidence of mid-infrared near-field probing at depths exceeding 80 nm.

Conclusions:

• s-SNOM is a powerful tool for nanoscale subsurface imaging across different wavelengths.
• The technique offers significant resolution improvements for buried nanostructures.
• Demonstrated the potential for non-destructive analysis of materials with buried features.