Scanning tunneling microscopy and spectroscopy of Y-junction in carbon nanotubes

Scanning tunneling microscopy and spectroscopy were used to observe the variations of electronic structure on the carbon nanotube Y-junction. The electronic structure derived from tunneling conductance maps showed natural metallic–metallic and semiconducting–metallic transitions close to the Y-junction, and the occurrence of metallic character of the whole Y-junction with the presence of additional resonant state at energy of 0.2 eV below the Fermi level. It is suggested that the state originates from heptagons forming the junction.