High critical current densities in superconducting MgB2 thin films

Superconducting MgB2 thin films were prepared on Al2O3(0001) and MgO(100) substrates. Boron thin films were deposited by the electron-beam evaporation followed by postannealing process with magnesium. Proper postannealing conditions were investigated to grow good superconducting MgB2 thin films. The x-ray diffraction patterns showed randomly oriented growth of MgB2 phase in our thin films. The surface morphology was examined by scanning electron microscope and atomic force microscope. Critical current density (JC) measured by transport method was about 107 A/cm2 at 15 K, and superconducting transition temperature (TC) was ∼39 K in the MgB2 thin films on Al2O3.