Electronic density of states of atomically resolved single-walled carbon nanotubes: Van hove singularities and end states

The electronic densities 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 tight-binding calculations. In addition, tunneling spectroscopy measurements recorded along the axis of an atomically resolved nanotube were found to 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.