Transition from Coulomb blockade to insulator regime in multiwall carbon nanotubes

An experimental study of electronic transport at very low temperature of multiwall carbon nanotubes is presented. We observed two manifestations of a transition from a Coulomb blockade regime to an insulator regime. The first one is on the temperature dependence of the sample resistance, changing from a power law regime to an activated law at a transition temperature T_C. The second one manifests itself below T_C in the dV/dI(V) profile: at a threshold voltage V_C the resistance changes abruptly from an insulating state to a Coulomb blockade regime characterized by a power law dependence on the voltage. Influence of disorder on Coulomb blockade regime is also enlightened.