The Interplay between Curvature Effect and Atomic Vacancy Defects in the Electronic Properties of Semi-Metallic Carbon Nanotubes

TL;DR

This study explores how various vacancy defects influence the electronic properties of semi-metallic (12,0) carbon nanotubes, revealing complex interactions between defect states and curvature effects that alter conductance.

Contribution

It provides a detailed analysis of defect-induced modifications in electronic structure and conductance in semi-metallic carbon nanotubes using first-principles calculations.

Findings

Defect states hybridize with nanotube states, modifying the band edge.

Conductance varies non-monotonically with defect size and geometry.

Hexa-vacancy nanotubes exhibit higher conductance than di-vacancy ones due to mid-gap states.

Abstract

We investigate the electronic properties of semi-metallic (12,0) carbon nanotubes in the presence of a variety of mono-, di- and hexa-vacancy defects, by using first principle DFT combined with non-equilibrium Green's function technique. We show that defect states related to the vacancies hybridize with the extended states of the nanotubes to modify the band edge, and change the energy gap, resulting from the curvature effect. As a consequence, the nanotube conductance is not a monotonic function of the defect size and geometry. Paradoxically, hexa-vacancy nanotubes have higher conductance than di-vacancy nanotubes, which is due to the presence of mid-gap states originating from the defect, thereby enhancing the conductance.