Gate-dependent transport in single-walled carbon nanotubes with mesoscopic Co electrodes

We studied the gate-dependent transport properties of two different single-walled carbon nanotubes with Co electrodes. One nanotube showed a metallic gate response and the other showed a semiconducting behavior. In the metallic sample, multiple Coulomb oscillations and peak splitting, depending on the temperature, were observed. Our observations could be explained by the formation of quantum dots in the CNT created by two metal contacts and defects. Inter-dot coupling was modulated by a gate bias voltage. In the semiconducting sample, an ambi-polar gate response was observed with a gap structure near 0.5 V. A magnetoresistance study for the semiconducting sample showed a hysteretic behavior in the range of H = ±100 mT, which depended on the gate voltage. This behavior might be explained by assuming that the spin polarization of the nanotube played a role in the spin-dependent transport with the spin-aligned Co electrode in a magnetic field.