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.