Resonant electron scattering by defects in single-walled carbon nanotubes.

We report the characterization of defects in individual metallic single-walled carbon nanotubes by transport measurements and scanned gate microscopy. A sizable fraction of metallic nanotubes grown by chemical vapor deposition exhibits strongly gate voltage-dependent resistance at room temperature. Scanned gate measurements reveal that this behavior originates from resonant electron scattering by defects in the nanotube as the Fermi level is varied by the gate voltage. The reflection coefficient at the peak of a scattering resonance was determined to be about 0.5 at room temperature. An intratube quantum dot device formed by two defects is demonstrated by low-temperature transport measurements.