The effects of surface contamination on the biaxially textured substrate for YBCO thick film deposition

The epitaxial growth of YBa2Cu3O7-x (YBCO) films on biaxially textured subs trates is one of the most promising technique for the fabrication of high c urrent superconducting tapes operating at high temperature. Ni is very attr active as substrate because it easily develops a (100)[001] cubic texture. The low oxidation resistance represents the main drawback of the Ni substra te. In order to better assess the role of oxygen on the Ni substrates, a su rface physics technique as Auger spectroscopy has been used. It has allowed to evaluate the amount of impurities for different Ni processing and expos ure to the air. The results demonstrate that the surface contamination can be efficiently removed by RF sputtering before buffer layer deposition. Thi s procedure allows to obtain CeO2/Pd/Ni architecture by laser ablation with a good epitaxy both of Pd and CeO2 films. On the contrary, when CeO2 is di rectly deposited on Ni a low epitaxy is obtained. The Auger analysis confir ms that the formation of (111) NiO at the Ni-CeO2 interface hampers the epi taxial growth of the ceria film.