It was demonstrated that ozone exposure of individual multi-walled carbon nanotubes resulted in an up to threefold increase in carbon nanotube conductivity and a 50% decrease in carrier transport activation energy. Ozone exposure induced bond-breaking in the individual shells, and promoted cross-shell bridging via sp3 bond formation. Inter-shell bridging facilitated charge carrier hopping to inner shells which could serve as additional charge carrier transport pathways, off-setting the effect of defect-scattering-induced conductivity decrease. The carbon nanotube etch-rate systematically increased with decreasing initial outer diameter and decreased with incremental ozone exposure. This offered a means for tailoring the carbon nanotube conductance controllably. The results suggested that controlled defect creation could be an attractive strategy for inducing electrical conductivity increases in multi-walled carbon nanotubes.

Defect-Induced Electrical Conductivity Increase in Individual Multiwalled Carbon Nanotubes. S.Agrawal, M.S.Raghuveer, H.Li, G.Ramanath: Applied Physics Letters, 2007, 90[19], 193104