Bandstructure and Contact Resistance of Carbon Nanotubes Deformed by the Metal Contact

TL;DR

This paper investigates how metal contact-induced deformation of carbon nanotubes affects their electronic properties, showing significant bandgap reduction and increased contact resistance due to structural changes.

Contribution

It provides ab-initio calculations revealing the impact of deformation and collapse on nanotube bandstructure and contact resistance, highlighting the role of symmetry breaking.

Findings

Deformations reduce bandgap by up to 30%

Fully collapsed nanotubes become metallic

Contact resistance increases threefold due to degeneracy lifting

Abstract

Capillary and van der Waals forces cause nanotubes to deform or even collapse under metal contacts. Using ab-initio bandstructure calculations, we find that these deformations reduce the bandgap by as much as 30\%, while fully collapsed nanotubes become metallic. Moreover degeneracy lifting, due to the broken axial symmetry and wavefunctions mismatch between the fully collapsed and the round portions of a CNT, leads to a three times higher contact resistance. The latter we demonstrate by contact resistance calculations within the tight-binding approach.