A New Method for Preparing Superconducting MgB₂ Films from Diborane

We report on a new preparation method for magnesium diboride (MgB₂) films by chemical vapor deposition (CVD) from diborane (B₂H₆). It is a two-step ex-situ approach, with the precursor boron films grown by CVD from B₂H₆ at 460°C, and followed by a post-annealing process in magnesium (Mg) vapor at 830°C. The prepared MgB₂ thin films on Al₂O₃ polycrystalline substrates have an onset transition temperature of 35 K and zero-resistance temperature of about 24 K. Well-crystallized MgB₂ grains were clearly observed in the SEM images and confirmed by x-ray diffraction analysis. The advantages of the proposed method are the feasibility to prepare large-area superconducting films and the compatibility with semiconductor technology.