Effects of B–N co-doping into the ultra-small diameter zigzag single-walled carbon nanotubes: A density functional theory study

• Simulation research of B–N co-doping ultra-small diameter zigzag carbon nanotubes.
• B–N co-doping converts ultra-small diameter CNTs from metallic to semiconducting.
• B–N co-doping ultra-small diameter CNTs are more stable than pristine CNTs.
• B–N co-doping into ultra-small diameter CNTs is a realizable exothermic process.
• Discussion of reasons that changed the electronic properties of ultra-small CNTs.

The boron(B)–nitrogen(N) co-doping ultra-small diameter (5,0) and (4,0) single-walled carbon nanotubes (SWCNTs) have been investigated by using the first-principles pseudopotential plane wave method. The results show that B–N pairs are easy to dope into ultra-small diameter zigzag nanotubes, which have numbers of differences with other large diameter nanotubes, and the B–N co-doping configurations are the energetically stable structures. Furthermore, by introducing B–N pairs, the (5,0) and (4,0) SWCNTs both transform from metal to semiconductor. These ultra-small diameter nanotubes have potential to be applied in semiconductor integrated circuit of extremely small size.