Scanning tunneling spectroscopy on crossed carbon nanotubes

Crossing nanotubes were investigated using scanning tunneling microscopy (STM) and spectroscopy. From the analysis of the measured mechanical deformation of the nanotubes, the contact force between the nanotubes is estimated to be 1 nN. Spectroscopy measurements showed two effects on the electronic structure: (i) band bending, which we attribute to a position-dependent interaction with the substrate, and (ii) the formation of localized states, as signalled by additional peaks in the density of states at the crossing point. The existence of localized states at the junction represents a much stronger perturbation of the electronic structure than has generally been assumed. The relevance of these STM results for the interpretation of transport measurements is discussed.