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

Films of the Tl-Ba-Ca-Cu-O high-Tc superconductor can be prepared by either of two organometallic chemical vapor deposition (CVD) 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 CVD 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 TlBa2Ca2Cu3O(x) phase, have preferential orientation of the CuO planes parallel to the substrate surface, and exhibit onset of superconductivity at about 120 K with zero resistance by 100 K. (Author)