Probing isolated bundles of single walled carbon nanotubes using bilayer interference enhanced Raman scattering

We show that the Raman signal from an isolated or a small bundle of single walled carbon nanotubes is significantly enhanced by using the bilayer interference enhancement technique. The square of the normalized electric field of the standing wave formed by the superposition of incident and reflected laser beams from a bilayer of Al and CeO2 is calculated to understand the enhancement of the Raman signal of adsorbents on the top surface of the bilayer. Polarization Raman studies were performed to confirm that the bundles being probed were isolated. The Raman spectra of the isolated metallic nanotubes also show Fano line-shape, revealing a weaker phonon–plasmon coupling as compared to the bulk nanotube bundle, in agreement with theory.