Epitaxial growth of YbBa2Cu3O7−δ films on (100)-oriented MgO and SrTiO3 substrates by oxidation of a liquid alloy precursor

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Abstract
Textured superconducting films of YbBa2Cu3O7−δ were grown on single crystals of MgO (100) and SrTiO3 (100) by oxidation of a liquid alloy precursor. The substrates were coated by dipping them in molten YbBa2Cu3 (m.p. ~870 °C). After removal from the melt, the liquid layers on the substrates were oxidized in pure oxygen to form the tetragonal oxide phase, i.e., YbBa2Cu3O7−δ, then annealed at 500 °C to obtain the superconducting orthorhombic phase of the same compound. The microstructure of the films obtained in this way was found to be related to the nature of the substrate as well as to processing variables that included oxidation temperature and oxidation time. Films grown on MgO (100) showed c-axis texture as well as a random growth structure. Films prepared on SrTiO3 (100) showed either a c-axis texture or a mixture of c-axis and a-axis texture. The superconducting properties of the as-prepared films and the effects of key process parameters on film quality and microstructure are presented and discussed.