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Superconducting properties of magnetron sputtered high T/sub c/ thin films containing oxide compounds of yttrium, bismuth, or thallium

Conference ·
OSTI ID:6643164

We have used multiple source magnetron sputtering to prepare thin films of Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and Tl-Ca-Ba-Cu-O on (100) SrTiO/sub 3/, (100) MgO, and ZrO-9%Y/sub 2/O/sub 3/ substrates. Y-Ba-Cu-O films grow best on SrTiO/sub 3/ with mostly an a-axis orientation. Stoichiometry, particularly the Ba/Cu ratio must be within 2% of the correct value to obtain narrow ..delta..T/sub c/ transitions. Conversely, the 80K phase of Bi-Ca-Sr-Cu-O films grows best on MgO substrates and has a predominant c-axis orientation. The requirements on composition are less stringent, however, the annealing temperature must be held within a narrow range around 865/degree/C to obtain the best films. The best films of Tl-Ca-Ba-Cu-O compounds are grown on (100) oriented and polycrystalline ZrO/sub 2/ substrates. The highest transition temperature, T/sub c0/, where the resistance goes zero is about 114K in the Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase and 100--105K in Tl/sub 2/Ba/sub 2/Ca/sub 1/Cu/sub 2/O/sub x/ and Tl/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ phase samples. The upper critical field measurements show high anisotropies in the critical field slopes (greater than or equal to70 for Tl-Ba-Ca-Cu-O compounds and approx.15 for Bi-Sr-Ca-Cu-O compounds), as might be expected from highly oriented materials. We will compare the preparation conditions and superconducting properties, including T/sub c/, ..delta..T/sub c/, dB/sub c2//dT (parallel and perpendicular to film surface), of all three compounds. 17 refs., 6 figs.

Research Organization:
Argonne National Lab., IL (USA)
DOE Contract Number:
W-31109-ENG-38
OSTI ID:
6643164
Report Number(s):
CONF-880812-26; ON: DE89003621
Country of Publication:
United States
Language:
English