Superconducting MgB(2) films via precursor post-processing approach

Superconducting MgB(2) films with Tc = 38.6 K were prepared using a precursor-deposition, ex-situ post-processing approach. Precursor films of boron, ~0.5 micrometer thick, were deposited onto Al(2)O(3) (102) substrates by e-beam evaporation; a post-anneal at 890 deg C in the presence of bulk MgB(2) and Mg metal produced highly crystalline MgB(2) films. X-ray diffraction indicated that the films exhibit some degree of c-axis alignment, but are randomly oriented in-plane. Transport current measurements of the superconducting properties show high values of the critical current density and yield an irreversibility line that exceeds that determined by magnetic measurements on bulk polycrystalline materials.