LOCAL STOICHIOMETRY MEASUREMENT OF Y-BA-CU-O THIN-LAYERS GROWN BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

Y-Ba-Cu-O thin films with different stoichiometry were grown by metal organic chemical vapor deposition on MgO and SrTiO3. The samples showe d superconducting behavior in a wide range of average stoichiometry. H owever, energy dispersive x-ray spectroscopy (EDX) measurements show t hat best results can be obtained only in a small stoichiometry range. Critical temperatures of T(c) > 89 K and critical current densities of j(c) (77 K) > 2 x 10(6) A/cm2 could be obtained with optimized stoich iometry. Spatially resolved EDX measurements show that copper tends to form precipitates on the layers if its average content exceeds 50 mol %, while yttrium is incorporated into the matrix if offered in excess .