Band gap control of small bundles of carbon nanotubes using applied electric fields: A density functional theory study

TL;DR

This study uses density functional theory to show how electric fields can modulate the band gaps of small carbon nanotube bundles, enabling control over their electrical conductivity through electrostatic screening effects.

Contribution

It reveals the mechanism of band gap modulation in small CNT bundles under electric fields, highlighting the role of symmetry breaking and electrostatic screening.

Findings

Electric fields close the band gap in semiconducting CNT bundles.

Electric fields open the band gap in metallic CNT bundles.

Electrostatic screening causes symmetry breaking leading to band gap modulation.

Abstract

Electrostatic screening between carbon nanotubes (CNTs) in a small CNT bundle leads to a switching behavior induced by electric field perpendicular to the bundle axis. Using a first-principles method, we investigate the electronic structures of bundles consisting of two or three CNTs and the effects of the electric field applied perpendicular to the bundle axis. The applied field causes band gap closure in semiconducting bundles, while a gap opening occurs in metallic ones, which enables considerable modulation of bundle conductivity. The modulation effect originates from symmetry breaking due to electrostatic screening between the adjacent tube walls.