CORRELATION BETWEEN THE TL CONCENTRATION DEPTH PROFILES AND THE THALLINATION TIME IN TL-BA-CA-CU-O SUPERCONDUCTING FILMS

The elemental composition and depth profiles of superconducting Tl-Ba- Ca-Cu-O (TBCCO) films deposited on yttrium-stabilized zirconia (YSZ) s ubstrates were studied by IBA techniques such as RES and NRA, The TBCC O films were prepared by annealing in thallium vapour a series of spra y deposited Ba2Ca2Cu3Ox precursor films with crude Tl2Ba2Ca2Cu3Ox pell ets at 850 degrees C for various times of thallination in a single-zon e reaction chamber. Synthesized TBCCO films, 3-4 mu m thick, were char acterized by resistivity and XRD measurements. The zero resistance T-c values ranged from 87 to 97 K, depending on the time of thallination, IBA studies revealed a correlation between the Tl concentration depth profiles and the thallination time. The highest T-c value, 97 K, was obtained after a relatively short thallination time of 5 min, leading also to the best crystallographic orientation. The physical implicatio ns of these results are discussed. (C) 1998 Elsevier Science B.V.