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 300°C, 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.