Diameter-selective near-field Raman analysis and imaging of isolated carbon nanotube bundles

Tip-enhanced near-field Raman scattering has been utilized to demonstrate the measurement of the distribution of single-walled carbon nanotubes (SWNTs) with a spatial resolution far beyond the diffraction limit of the probing light. This was done by measuring the radial breathing mode (RBM) of SWNTs in the near-field Raman spectra, which corresponded to the diameters of various SWNTs in the immediate vicinity of the tip. Further, near-field Raman imaging of the RBM provided a super-resolved color mapping corresponding to the diameter distribution of SWNTs within a bundle, which is not possible to realize by conventional topographic imaging methods.