Magnetotransport in pristine and iodine-doped single-wall carbon nanotubes assembled into transparent films

Measurements of the magnetoresistance and Hall effect on transparent films of single-wall nanotubes before and after their doping with iodine, in the temperature range from 3--5 to 40 K and magnetic fields up to 16 T, are reported. The measured magnetoresistance is fairly well approximated by the sum of two contributions: negative, described in the framework of two-dimensional theory of weak localization (2D-WL), and linear in field positive, unsaturated in strong magnetic fields. The linear temperature dependence of ${L}_{\ensuremath{\phi}}^{\ensuremath{-}2}(T)$ (${L}_{\ensuremath{\phi}}$ is the phase decoherence length) indicates electron-electron scattering as the main mechanism of dephasing, and the coincidence of these linear dependencies for the pristine and doped films suggests that the state of static defects and the nature of electron-electron scattering do not change when doping nanotubes. The values of the two-dimensional density of charge carriers determined from Hall measurements, being, apparently, highly overestimated, increase more than twice after iodine doping. This increase is clearly correlated with the magnetoresistance data processed in 2D-WL theory. The linear in field positive contribution to magnetoresistance is explained by the inhomogeneous distribution of the local density of charge carriers.