Scanning probe microscopy by localized surface plasmon resonance at fiber taper tips.

Area of Science:

• Nanotechnology
• Optical Microscopy
• Materials Science

Background:

• Localized surface plasmon resonance (LSPR) is a highly sensitive method for detecting nanoscale electrical permittivity changes.
• Integrating LSPR probes with atomic force microscopy (AFM) is challenging due to overwhelming scattering from the AFM tip.

Purpose of the Study:

• To develop a method for extracting clean LSPR spectra from plasmonic antenna probes attached to AFM tips.
• To achieve high-quality nanoscale imaging by mapping LSPR wavelength shifts.

Main Methods:

• Combined evanescent coupling, polarization and spatial filtering, confocal spectroscopy, and numerical methods.
• Utilized a gold nanosphere-antenna probe attached to a fiber taper mounted on a custom quartz-tuning-fork SPM.
• Mapped LSPR wavelength shifts for imaging.

Main Results:

• Successfully extracted clean LSPR spectra, overcoming AFM tip scattering.
• Achieved high-quality, nanometer-scale imaging of gold nanospheres on glass slides.
• Demonstrated LSPR wavelength shift enhancement with more complex probe designs, indicating potential for higher sensitivity.

Conclusions:

• The developed optical system and spectral processing method effectively enable LSPR scanning microscopy.
• This work provides a solution for the long-standing challenge of integrating LSPR with scanning probe microscopy.
• The findings pave the way for higher-sensitivity nanoscale imaging and sensing applications.