High-quality Superconducting MgB2 Thin Film Preparation on Plastic Substrates

We have synthesized as-grown superconducting MgB2 thin films on polyimide film substrates, making use of a low substrate temperature growth of MgB2 thin films, and found that Tc's above 30 K were obtained on polyimide films, like on Al2O3-C substrates. For highquality MgB2 thin film fabrication on substrates completely out of lattice-matching with MgB2 lattice, we have examined Ti/Ag double-layered buffers on glass substrates, and clarified that a double-layered buffer composed of Ag bottom layer 50 nm thick and Ti upper layer 50 nm thick prepared at an ambient temperature is effective for this purpose.