Upper bound for the conductivity of nanotube networks

TL;DR

This paper calculates the theoretical maximum electrical conductivity of nanotube networks considering ideal contacts, showing it depends on nanotube concentration and aspect ratio, and explaining why current conductivities are near this limit.

Contribution

It introduces a theoretical upper bound for nanotube network conductivity using the Kubo formalism, considering ideal ballistic contacts.

Findings

Maximum conductivity depends on nanotube concentration and aspect ratio.

Current measured conductivities are close to the theoretical upper bound.

Further improvements may require alternative nanowire materials.

Abstract

Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. By considering ideal ballistic-like contacts between nanotubes we use the Kubo formalism to calculate the upper bound for the conductivity of such films and show how it depends on the nanotube concentration as well as on their aspect ratio. Highest measured conductivities reported so far are approaching this limiting value, suggesting that further progress lies with nanowires other than nanotubes.