Electronic structure of carbon nanotubes studied by photoelectron spectromicroscopy

The electronic structure of multiwalled carbon nanotubes aligned perpendicularly on a Si substrate was studied by means of photoelectron spectromicroscopy. The valence band and the C 1s spectra, measured systematically from spatially selected regions along the tube axes, were the fingerprint for lateral variations in the electron density of states and in the band bending, respectively. It was found that the tips have a larger density of states near the Fermi level than the sidewalls, whereas band bending, which would explain such a spectral difference, was not observed. It is suggested that the different density of states near the Fermi level is due to a larger dangling bond density at the tips.