Synthesis of the superconducting MgB₂ film on the W-wire by co-evaporation method

We have synthesized the MgB₂/W composite fiber by depositing MgB₂ film on the W-wire with co-evaporation system. Boron was sputtered with the RF-magnetron sputter and magnesium was thermally evaporated simultaneously during deposition. For the uniformity of the deposited layer and the precise stoichiometric compound formation of the MgB₂ film layer, specimen holding unit was rotated at a fixed rate and the sputtered rate of B and evaporated rate of Mg were controlled separately. After post-annealing of the MgB₂/W-wire at 600 °C, we could obtain 100-800 nm MgB ₂ layers with uniform composition. Occasionally un-reacted Mg or second phases such as MgWO₄ were observed depending on the experimental conditions. The phase evolution and the microstructure of the deposited MgB₂ film were investigated with XRD, SEM, and EDS. The superconducting transition temperatures (T_c) and the average critical current density have been measured around ∼33.5 K and 3.7 x 10³ A/cm², respectively using the physical property measurement system (PPMS 9T, Quantum Design).