Role of contact bonding on electronic transport in metal-carbon nanotube-metal systems

TL;DR

This study explores how the atomic arrangement at the contact interface influences electronic transport in metal-carbon nanotube-metal systems, revealing complex behaviors dependent on nanotube helicity and interface geometry.

Contribution

It provides a detailed analysis of the effects of contact bonding and interface geometry on electron transport, comparing modeling approaches and highlighting the importance of chemical bond accuracy.

Findings

Contact-nanotube distance significantly affects conduction.

Nanotube helicity influences transmission spectra.

Tight Binding model is less accurate for chemical bonds.

Abstract

We have investigated the effects of the interfacial bond arrangement on the electronic transport features of metal-nanotube-metal systems. The transport properties of finite, defect-free armchair and zigzag single-walled carbon nanotubes attached to Au(111) metallic contacts have been calculated by means of the non-equilibrium Green functional formalism with the Tight-Binding and the Extended Huckel Hamiltonians. Our calculations show that the electrode material is not the only factor which rules contact transparency. Indeed, for the same electrode, but changing nanotube helicities, we have observed an overall complex behaviour of the transmission spectra due to band mixing and interference. The comparison of the two models shows that the Tight Binding approach fails to give a satisfactory representation of the transmission function when a more accurate description of the C-C and Au-C chemical bonds has to be considered. We have furthermore examined the effect of interface geometry variance on conduction and found that contact-nanotube distance has a significant impact, while contact-nanotube symmetry plays a marginal, yet evident role.