The preparation of high-quality superconducting MgB2 thin films on plastic film substrates

The preparation of MgB2 thin films, which can grow with fairly good superconducting properties at temperatures below 300degC, was examined on heat-resistant plastic substrates such as polyimide film, making use of this low-temperature growth characteristic. To obtain high-quality MgB2 films even at low temperatures, the idea of epitaxial growth is essential, and a metallic buffer with a hexagonal crystal structure of the same lattice parameter as that of MgB2 was previously proved to be effective for this purpose. Here, we have examined a double-layered metallic buffer Ti/Ag for growing MgB2 with good crystallinity. We then clarified that this buffer, each layer being 50 nm-thick and fabricated at an ambient temperature, is useful for polyimide film substrates. Preliminary results on the deformation properties of MgB2/polyimide films are also described. (author)