THERMODYNAMIC MODELING OF MOCVD OF YBA2CU3O7-X - INFLUENCE OF METAL PRECURSORS AND OXYGEN SOURCES

Chemical vapour deposition (CVD) of the superconducting YBa2Cu3O7-x phase from different metal chelate 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 YBa2Cu3O7-x phase can be deposited is studied, and the results are presented in calculated CVD phase 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 the YBa2Cu3O7-x 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.