Characterization and estimation of tunnel barrier height in metallic single-wall carbon nanotube quantum dots

A tunnel barrier height has been estimated in quantum dots (QDs) formed in metallic single-wall carbon nanotubes (SWNTs), where QDs can be fabricated simply by depositing metallic contacts on top of the nanotube. Transport measurements have been carried out in a temperature range between 1.5 and 300 K, and revealed single and multi-QD behaviors in different samples at low temperatures. The Arrhenius plot gave an activation energy of ∼6 meV for the barrier formed very likely at the metal-SWNT interface for the single QDs, and two activation energies for seemingly double dots. The latter case comes from the unintentional tunnel barrier due to defects. Discussions on the QD formation and suggestions for a higher temperature operation are given.