Band structure of boron doped carbon nanotubes

TL;DR

This study investigates how boron doping affects the electronic band structure of semiconducting carbon nanotubes, revealing the formation of acceptor bands and the impact of dopant distribution on electronic properties.

Contribution

It provides ab initio and tight-binding calculations showing the effects of high boron doping levels and dopant distribution on nanotube band structures.

Findings

Periodic boron doping creates acceptor-like bands in the band gap.

Random doping results in hybridized acceptor and carbon states above Fermi level.

Boron doping lowers the Fermi energy into the valence band.

Abstract

We present {\it ab initio} and self-consistent tight-binding calculations on the band structure of single wall semiconducting carbon nanotubes with high degrees (up to 25 %) of boron substitution. Besides a lowering of the Fermi energy into the valence band, a regular, periodic distribution of the p-dopants leads to the formation of a dispersive ``acceptor''-like band in the band gap of the undoped tube. This comes from the superposition of acceptor levels at the boron atoms with the delocalized carbon $\pi$-orbitals. Irregular (random) boron-doping leads to a high concentration of hybrids of acceptor and unoccupied carbon states above the Fermi edge.