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 me- tallic-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. 2002 Elsevier Science B.V. All rights reserved.