THERMODYNAMIC MODELING OF MOCVD OF THE SUPERCONDUCTING PHASE IN THE Bi-Sr-Ca-Cu-O SYSTEM : INFLUENCE OF METAL PRECURSOR AND OXYGEN SOURCE

Abstract
Chemical vapour deposition (CVD) of the superconducting 2:2:1:2 phase in the Bi-Sr-Ca-Cu-O system from different metalorganic precursors is thermodynamically investigated. Both precursors without fluorine and fluorine-containing precursors were employed. The oxygen source was O₂, H₂O, O₂+H₂O or N₂O. The effect of different deposition parameters on the extension of the region where the 2:2:1:2 phase can be deposited is studied, and the results are presented in calculated CVD stability diagrams. For precursors containing no fluorine, the best conditions were obtained by using N₂O as the oxygen source and by using a low total pressure. For fluorine-containing precursors, the best conditions were obtained using a mixture of O₂ and H₂O as the oxygen source. Moreover, the size of the region where the2:2:1:2 phase can be deposited is reduced compared to when precursors without fluorine are used. The results of the thermodynamic calculations are found to agree well with experimental results.