Electron transport in carbon nanotube-metal systems: contact effects

TL;DR

This paper investigates how contact effects influence electron transport in carbon nanotube-metal systems, revealing that contact symmetry and channel mixing significantly affect conductance in finite and multi-wall CNTs.

Contribution

It introduces a detailed analysis of contact-induced channel blocking and mixing effects in CNTs using Green function techniques within the Landauer formalism.

Findings

Contact symmetry can block transport channels.

Channel mixing occurs in double-wall CNTs with metallic shells.

Contact effects cause conductance deviations from ideal values.

Abstract

Carbon nanotubes (CNT) have a very large application potential in the rapid developing field of molecular electronics. Infinite single-wall metallic CNTs have theoretically a conductance of 4e2/h because of the two electronic bands crossing the Fermi level. For finite size CNTs experiments have shown that other values are also possible, indicating a very strong influence of the contacts. We study electron transport in single- and double-wall CNTs contacted to metallic electrodes within the Landauer formalism combined with Green function techniques. We show that the symmetry of the contact region may lead to blocking of a transport channel. In the case of double-wall CNTs with both inner and outer shells being metallic, non-diagonal self energy contributions from the electrodes may induce channel mixing, precluding a simple addition of the individual shell conductances.