Temperature-dependant current saturation in double-wall carbon nanotubes*

Current saturation is known to occur at high voltage bias in carbon nanotubes, for single-wall as well as multi-wall configurations. This saturation is generally attributed to the backscattering of carriers by optical phonons. Here we report transport measurements performed on single double-walled carbon nanotubes as a function of temperature between 77K and 400K. The good quality of the contacts between the nanotubes and the electrodes allows to observe a temperature dependence in the I-V curves. At high temperature, the saturation current shows a value around 25$\mu $A, as expected from the energy of optical phonons, but then increases non-linearly with decreasing temperature. The low-bias conductance is also measured to increase with decreasing temperature. Phenomenological models are investigated in order to explain the observed trends.