Organometallic chemical vapor deposition routes to high T_c superconducting Tl-Ba-Ca-Cu-O films

Films of the Tl-Ba-Ca-Cu-O high T_c superconductor can be prepared by either of two organometallic chemical vapor deposition routes. Ba-Ca-Cu-O films are first prepared on yttria-stabilized zirconia using the volatile precursors Ba(heptafluorodimethyloctanedionate)_2, Ca(dipivaloylmethanate)2, and Cu(acetylacetonate)_2. Deposition is carried out at 5 Torr pressure with argon as the carrier gas and water vapor as the reactant gas. Thallium is next incorporated in these films either by vapor diffusion using bulk Tl-Ba-Ca-Cu-O as the source, or by organometallic chemical vapor deposition using Tl(cyclopentadienide) as the source. The latter deposition is carried out at atmospheric pressure with an argon carrier and water-saturated oxygen reactant, followed by rapid thermal annealing. Both types of films consist primarily of the TlBa₂Ca₂Cu ₃O_x phase, have preferential orientation of the CuO planes parallel to the substrate surface, and exhibit onset of superconductivity at ∼120 K with zero resistance by 100 K.