[2C01-08] Surface Analysis/Applied Surface Science/Evaluation Technique (ASS)

11:15 AM - 11:30 AM JST(2:15 AM - 2:30 AM UTC)

[2C07] Changes in Raman scattering processes under high spatial resolution in tip-enhanced Raman spectroscopy

*Yuto Fujita¹, Norihiko Hayazawa^2,3, Maria Vanessa Balois-Oguchi^2,4, Takuo Tanaka², Tomoko K. Shimizu¹ (1. Faculty of Science and Technology, Keio University (Japan), 2. RIKEN Center for Advanced Photonics, RIKEN (Japan), 3. RIKEN Pioneering Research Institute, RIKEN (Japan), 4. School of Engineering, Institute of Science Tokyo (Japan))

Tip-enhanced Raman spectroscopy (TERS) now even achieves sub-nanometer resolution, where strong field gradients demand a revised Raman scattering framework. Using carbon nanotubes (CNTs) as a model system with a home-built sub-nanometer TERS setup, we compared far-field and near-field spectra from the same sample. Far-field Raman of metallic CNTs showed only a weak D-band, indicating low defect density, while TERS revealed strong D-band enhancement uniformly along the CNT. We attribute this to non-vertical k-space electronic transitions, forbidden in far-field but allowed near-field since the localized optical field supplies momentum which compensates wavevector mismatch without defect-assisted scattering. Conversely, defects may suppress D-band intensity by reducing intact hexagonal lattice sites within the sub-nanometer excitation volume, opposite to conventional far-field behavior. These results call for reassessing high spatial resolution TERS spectral interpretation.

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