Enhancement of critical current density in direct-current-sputtered TlBa2Ca2Cu3O9±δ superconducting thin films

Abstract

A multistep postannealing scheme has been developed for preparing nearly single phased, c-axis oriented TlBa2Ca2Cu3Ox (Tl-1223) superconducting thin films fabricated by the direct-current-sputtering process. Films obtained by the present process have shown, for the first time in this system, a critical current density (Jc) above 106 A/cm2 at 77 K with a zero-resistance transition temperature Tc0≊110 K. The order of magnitude enhancement in Jc is attributed to the improvement of film morphology which, in turn, removed most of the weak links encountered previously.

Room-temperature single-electron charging and surface polarization in tunneling spectroscopy of high-Tcsuperconducting thin films

“…Although, it is not clear at present how this would affect the SEC process in a quantitative manner, it should be interesting to make a preliminary comparison with other families of HTS films with more robust surfaces. As has been repeatedly demonstrated, 10 the Tl-based superconducting films should serve as good candidates for such a study.…”

“…9 The Tl-1223 films, on the other hand, were prepared by a two-step ͑i.e., dc-sputtering and postannealing͒ process. 10 These films were having T c 'sϷ108-110 K and J c ͑77 K͒у10 6 A/cm 2 , as well. Nonetheless, the films were even more granular than the YBCO films.…”

Analysis of the fluoride effect on the phase-selective growth of TlBa2Ca2Cu3O9−x thin films: Phase evolution and microstructure development

“…3 Long-length, coated conductors employing Tl-1223 also lie within the realm of possibility, as has been illustrated by (Tl,Bi)-1223 growth on CeO 2 -buffered, single-crystal yttria-stabilized zirconia (YSZ) and on multibuffered rolling-assisted biaxially textured Ni substrates. 6 Such films are epitaxial, display excellent alignment with the (110) LaAlO 3 substrates, and exhibit T c ‫ס‬ 103 K and J c > 10 5 A/cm 2 at 5 K as determined by magnetic measurements in fields up to 4.5 T. Compared with the unsubstituted Tl-1223 thin films of other groups, 7,8 films annealed in the presence of T1F produce Tl-1223 at a considerably lower temperature. Recently, we reported phase-selective nucleation of metal-unsubstituted Tl-1223 thin films from metalorganic chemical vapor deposition (MOCVD) derived BaCaCuO(F) precursor films that were postannealed at 885°C in the presence of TlF as opposed to commonly employed Tl 2 O 3 .…”

Growth of TlBa2Ca2Cu3O9 Epitaxial Thin Films by Two-Step Method in Argon*

“…Particularly, using the traditional two-step method, a coexistent TlBa 2 CaCu 2 O 7 (Tl-1212) or Tl 2 Ba 2 CaCu 2 O 8 (Tl-2212) phase often emerges in Tl-1223 films, which degrades the Tl-1223 film properties. [7,8] To overcome the above challenge, many strategies have been proposed to improve the purity of Tl-1223. For example, by partial substitution of Tl atoms with Bi or Pb and replacing most Ba atoms with Sr, the ratio of the Tl-1212 or Tl-2212 phase in entire Tl-1223 phase crystal can be reduced.…”