Spatially resolved Raman spectra of individual pristine suspended carbon nanotubes are observed under electrical heating. The Raman $G_{+}$ and $G_{-}$ bands show unequal temperature profiles. The preferential heating is more pronounced in short nanotubes ($2\mu \mathrm{m}$) than in long nanotubes ($5\mu \mathrm{m}$). These results are understood in terms of the decay and thermalization of nonequilibrium phonons, revealing the mechanism of thermal transport in these devices. The measurements also enable a direct estimate of thermal contact resistances and the spatial variation of thermal conductivity.

• Received 17 December 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.105501