Atomically Resolved Scanning Tunneling Microscopy and Spectroscopy of Carbon Nanotubes

摘要

We report on recent structural investigation of carbon nanotubes, prepared by arc discharge methode, using scanning tunneling microscope operated in ambient conditions. A true atomically resolved images show the details of the nanotube lattice structure, namely the nanotube diameters, chirality, defects, stacking nature (in case of multiwall carbon nanotubes) nanotube junctions and tips. From these images and scanning tunneling Spectroscopy measurements we have found a strong correlation between the electronic structure and the geometrical parameters (diameters and chiralities) in which NT span the semiconducting metallic regime. Standing wave pattern of the charge density is observed at the tube cap which is formed due to constructive interference between the electronic states and its reflection on the nanotube tips. Atomically resolved images show asymmetry in the charge density that decay out within 6 nm away from the cap. These distinctive tip states do not exist elsewhere on the tube and are related to the presence of topological defects at tube ends.