Conduction carriers in multi-walled carbon nanotubes

ESR spectra of MWNTs have been studied with isochronal annealing and temperature dependence down to View the MathML source. Two closely spaced peaks are observed in the ESR signals. The higher-field signal disappears after thermal annealing at 500°C and can be related to the presence of contaminations and /or defects in the MWNTs. However, the lower-field signal is thought to be associated with free carriers in the carbon nanotube and the transport relaxation time can be expected to decrease roughly by one-third after annealing. This suggests an associated enhancement of the spin-relaxation rate of conduction electrons due to an increase of carrier scatterings in the metallic system, consistent with Elliotʹs spin relaxation mechanism.