Temperature-dependent Conductance in Carbon Nanotube Networks

We report a comprehensive experimental and theoretical study on the temperature-dependence of conductance in carbon nanotube networks (CNTNs). Our experimental results demonstrate up to four orders of magnitude change with temperature in electrical conductance. Some of the data can be accounted by the variable range hopping (VRH) mechanism. In particular, we report an analytical formula for the localization length as a function of the Fermi energy and CNT bandstructure, which explains the different families of the observed behavior. The localization length in the zero-gap armchair (6,6) CNT, the localization length is much longer than in other single chirality CNTs. To explain conductance temperature dependence in (6,6) tube, we employ a full-band model within the perturbation theory to account for the phonon-assisted tunneling conductance across the CNTs. The theoretical study shows that while corresponding purely electronic conductance is not-negligible, it does not depend on temperature. On the other hand, phonon-assistant tunneling accounts for the observed temperature dependence in (6,6) CNTNs sample.