Scanning tunneling microscopy observation of circular electronic superstructures on multiwalled carbon nanotubes functionalised by nitric acid

We have performed STM measurements on nitric acid treated, functionalised multiwalled carbon nanotubes. Atomic resolution STM images around defects created by the acid treatment show circular √3 × √3 R30° type superstructures. We have used a simple scattering model to reproduce the experimentally observed STM images and show that such superstructures can be obtained by considering only the contribution of β site carbon atoms, known to dominate the STM image of graphite and multiwalled carbon nanotubes (MWCNTs).