Ambipolar field-effect transistor on as-grown single-wall carbon nanotubes

We use a simultaneous flow of ethylene and hydrogen gases to grow single-wall carbon nanotubes by chemical vapour deposition. Strong coupling to the gate is inferred from transport measurements for both metallic and semiconducting tubes. At low temperatures, our samples act as single-electron transistors where the transport mechanism is mainly governed by Coulomb blockade. The measurements reveal very rich quantized energy level spectra spanning from the valence to the conduction band. The Coulomb diamonds have similar addition energies on both sides of the semiconducting gap. Signatures of the subband population have been observed at intermediate temperature.