Isotope-induced elastic scattering of optical phonons in individual suspended single-walled carbon nanotubes

Isotope-induced scattering of optical phonons in individual single-walled carbon nanotubes (SWNTs) was investigated by resonance Raman scattering measurements of more than 600 suspended, isotope-mixed SWNTs. The G+ and G− features in the SWNT G-band exhibit broadening of up to 80% and 25%, respectively, indicating a reduced lifetime of the corresponding longitudinal and transverse optical (LO and TO) phonons. We propose that this reduced lifetime is due to a combination of enhanced phonon scattering by isotopic inhomogeneity and overbending in the LO phonon branch, both of which increase the scattering rate.