Microstructure and superconducting properties of MgB ₂ films prepared by solid state reaction of multilayer precursors of the elements

Surface morphology and superconducting properties of MgB ₂ superconducting thin films prepared by ex-situ annealing of multilayer Mg/B precursors in Mg vapor are studied. Depending on the precursor structure different physical and microstructural properties of the superconductor evolve. Structure and composition of the films are analyzed by scanning electron microscopy and wavelength dispersive x-ray spectroscopy. It is found that certain precursor structures can lead to high quality superconducting films, however, in specific precursor structures mechanical stress leads to the formation of wrinkles strongly affecting the superconducting homogeneity of the films. A correlation between microstructure and superconducting properties, such as pinning or critical current density, can be provided via magneto-optical Faraday microscopy.