Band gap variations in an AFM tip-deformed metallic carbon nanotube

Abstract

The AFM tip-induced deformation effects on the transport properties of metallic carbon nanotubes (CNTs) have been investigated by the π-electron and four-orbital tight-binding (TB) approaches. Three kinds of tips with different diameters are used, showing that the obtained results are insensitive to the tip diameter. The σ – π coupling effect is negligible for the valence band, while plays a role in the conduction band of a tip-deformed CNT. More importantly, it is found that a metal–semiconductor transition occurs under tip deformation for all metallic CNTs except the armchair ones, and the change rate of the band gap versus strain increases as the chiral angle decreases, which is similar to that of the axially-stretched tube, but has a smaller magnitude. Introducing a Stone–Wales defect into the CNTs can further decrease the band gap compared to the case of perfect tube under the same deformation, especially for the smaller strains.