Reversible defect engineering of single-walled carbon nanotubes using scanning tunneling microscopy

The experimental creation and annihilation of defects on single-walled carbon nanotubes (SWCNT) with the tip of a scanning tunneling microscope are reported. The technique used to manipulate the wall structure of a nanotube at the atomic scale consists of a voltage ramp applied at constant tunneling current between the tip and the nanotube adsorbed on a gold substrate. While topographic images show an interference pattern at the defect position, spatially resolved tunneling spectroscopy reveals the presence of localized states in the band gap of the nanotube. Removal of the defect by the same procedure demonstrates the reversibility of the process. Such a precise control in the local modification of the nanotube wall opens up new opportunities to tailor SWCNT electronic properties at will.