High-temperature post-annealing to improve Jc-B-T properties of MgB2 thin film synthesized via hybrid deposition combining thermal evaporation of magnesium and sputtering of boron

A new in-situ process for depositing MgB2 film is being developed in the present study as a candidate method to facilitate the mass production of MgB2-thin-film superconducting tapes. Here, a MgB2 film was synthesized on a heated copper substrate via “hybrid deposition,” comprising thermal evaporation of magnesium and sputtering of boron. High-temperature post-annealing was performed to increase the critical current density (Jc) of the MgB2 thin films obtained via hybrid deposition. The Jc of the MgB2 film deposited at 360°C by hybrid deposition and post-annealed at 430°C was drastically improved to 1,100 A/mm2 at 20 K under 4 T, 79,000 A/mm2 at 15 K under 3 T, and 59,000 A/mm2 at 10 K under 5 T under a magnetic field parallel to the film. It was expected that the incorporation of hybrid deposition in processing using a reel-to-reel machine would facilitate the synthesis of high-Jc, long MgB2-thin-film superconducting wires.