d.c. sputtering elaboration of thin films of the high-Tc superconductor YBa2Cu3O7-x: evidence for strong film-substrate interactions

Abstract
Superconducting thin films of YBa2Cu3O7- x have been prepared by d.c. sputtering deposition followed by a suitable thermal treatment. The deposition parameters were optimized in order to obtain ideal 1: 2 : 3 composition of the films. A wide variety of substrates were tested, most of them giving evidence for a strong chemical interaction with the film when annealed. To better determine the contamination effects of potential substrates on the properties of YBa2Cu 3O7-x, a number of foreign elements were diluted in sintered samples of the superconducting matrix. Their influence was evaluated from a.c. susceptibility or magnetization (SQUID) measurements. Superconducting films were thus obtained, mainly on zirconia, BaZrO3 or YSZ (yttrium stabilized zirconia) sintered plates, with the onset of superconducting transition occurring near 90 K. The width of the transition strongly depends on the crystalline state of the film, which is connected to the applied thermal treatment