Electronic properties of carbon nanotubes partially unzipped by oxygenation or fluorination

• We examine the structural and electronic properties of partially unzipped carbon nanotubes by oxygenation or fluorination.
• Partial oxygenation preserves the metallic but the F-driven partial unzipping results in a bandgap opening.
• For the oxygen-driven nanotubes, the valence band near the Fermi level exhibits many localized states in the open part.
• By contrast, the fluorine-driven nanotubes do not show any localized state in the valence band near the Fermi level.

Unzipping carbon nanotubes has recently attracted interest as a promising route to synthesizing semiconducting graphene nanoribbons. Here, the band structures of O- and F-driven partially unzipped armchair carbon nanotubes (PUCNTs) are computed using the ab initio   pseudopotential method. Although the model structures exhibit a similar pinhole with a length of ∼1nm along the tube axis, the band structures differ distinctly. The O-driven PUCNT has many localized states in the valence band arising mainly from the O 2p   orbitals, and preserves metallic properties. In contrast, the F-driven PUCNT shows properties of a semiconductor with a bandgap of ∼0.15eV, and its localized states occur in the conduction band. When the unzipping process continues further, the O-driven PUCNT also shows the semiconducting behavior.