A systematic investigation was made of the effects of varying concentrations of randomly distributed multiple defects (single and double vacancies, Stone-Wales defects) on the phonon transport properties of armchair and zig-zag carbon nanotubes with lengths ranging between a few hundred nanometers to several micrometers, using both non-equilibrium molecular dynamics and atomistic Green’s function methods. The results showed that, for both armchair and zig-zag carbon nanotubes, κ converged to nearly the same values for different types of defect, at all the lengths considered here. On the basis of the detailed mean free path analysis, this behavior was explained by the fact that intermediate and high frequency phonons were filtered out by defect scattering, while low-frequency phonons were transmitted quasi-ballistically even for nanotubes that were several micrometers long. An analysis of variations in κ for various defect concentrations indicated that defect scattering at low defect concentrations could be the source of large experimental variations. By taking advantage of the possibility of creating a controlled concentration of defects by electron or ion irradiation, it was possible to standardize κ while minimizing the variance. The results implied the possibility of phonon engineering in nanostructured graphene-based materials by control of the defect concentration.

Phonon Engineering in Carbon Nanotubes by Controlling Defect Concentration. C.Sevik, H.Sevinçli, G.Cuniberti, T.Çan: Nano Letters, 2011, 11[11], 4971-7