Spectrally Resolving Coherent TERS Spectroscopy of Electrically Biased Carbon-Coated Fibers

Abstract

Copyright © 2020 American Chemical Society. Tip-enhanced Raman scattering (TERS) represents an advanced spectroscopic tool that enables probing a specimen on scales far beyond the diffraction limit. An investigation of two-dimensional systems reveals a striking feature of TERS, when the near-field intensity is governed by the 8th and 10th power of the tip-sample distance for the coherent and incoherent scattering cases, respectively. Physically, the coherent TERS response can be observed when the excitation spot size does not exceed the phonon coherence length. In this paper, we demonstrate spectrally resolving capabilities of coherent TERS spectroscopy when studying electrically biased amorphous carbon films. Local electro-annealing at hot spots was found to activate temperature-dependent molecular transformations such as an expansion of the defect-free sp2 domains network at temperatures above 400 °C. Electro-assisted TERS allows one to directly visualize the presence of water-decorated carboxyl/hydroxyl groups at the edge carbon atoms.