The effects of local low-energy irradiation upon the electrical properties of metallic single-walled carbon nanotubes were studied. Defects formed by 20keV electron irradiation, in an electron beam lithography system, converted the room-temperature electrical properties to p-type or ambipolar semiconducting. Coulomb oscillation was also observed at room temperature. The results suggested that electrical measurements were inconclusive for distinguishing whether a nanotube was metallic or semiconducting.

Electric Property Control of Carbon Nanotubes by Defects. S.Suzuki, J.I.Hashimoto, T.Ogino, Y.Kobayashi: Japanese Journal of Applied Physics, 2008, 47[4-2], 3292-5