STM tunneling spectroscopic studies of YNdxBa2-xCu3O7-delta thin films

We performed tunneling spectroscopy on high quality superconducting YNdxBa2-xCu3O7-delta thin films using a low-temperature scanning tunneling microscope. Superconducting regions show very well-defined gap structures. Disorder introduced by Nd substitution at the Ba site dramatically affects locally the quasiparticle density of states. The measurements show that the impurities induce surface resonant states at energies very close to the Fermi energy, typical of a d-wave superconductor.