Resonant Raman scattering of isolated single wall carbon nanotubes: Structural (n,m) determination and resonant window

Abstract

We studied the resonant Raman spectra of isolated single wall carbon nanotubes (SWNTs). The isolated SWNTs were prepared by a chemical vapor deposition method on a Si/SiO2 substrate containing nanometer size iron particles. By using a tunable laser, we measured the resonant Raman window for the radial breathing mode of one isolated SWNT, in both the Stokes and anti-Stokes processes. We show that resonant confocal micro Raman spectroscopy of an (n,m) individual SWNT makes it possible to assign its chirality uniquely by measurement of one radial breathing mode frequency (ωRBM) and using the theory of resonant interband transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter dt, using the nearest neighbor overlap energy γ0=2.9 eV and the relation ωRBM=248/dt.