Electronic Density of States of Atomically Resolved Single-Walled Carbon   Nanotubes: Van Hove Singularities and End States
  The electronic density of states of atomically resolved single-walled carbon nanotubes have been investigated using scanning tunneling microscopy. Peaks in the density of states due to the one-dimensional nanotube band structure have been characterized and compared with the results of tight-binding calculations. In addition, tunneling spectroscopy measurements recorded along the axis of an atomically-resolved nanotube exhibit new, low-energy peaks in the density of states near the tube end. Calculations suggest that these features arise from the specific arrangement of carbon atoms that close the nanotube end. 
Philip Kim, Teri W. Odom, Jin-Lin Huang, and Charles M. Lieber   (Harvard University)