Surface topography and tunneling spectroscopy in high-temperature superconducting thin films by scanning tunneling microscopy

Abstract

The surface morphology and tunneling spectroscopies of the YBa2Cu3O7-x (YBCO) and TlBa2Ca2Cu3O9+x (Tl-1223) high-T-c superconducting thin films deposited on LaAlO3(100) substrates were investigated by scanning tunneling microscopy (STM). The preliminary results show that although both systems have a common layer-like surface structure, the grain morphologies are quite different suggesting that they may follow different growth mechanisms probably due to the different preparation methods used. In addition, the tunneling current-voltage characteristics (IVCs) manifested features akin to that of charging effect-induced single electron tunneling in both systems. As a result, the gap-like structure observed in the dI/dV-V curves may not be reflecting the superconducting energy gaps as commonly conceived.