As-Grown Superconducting<tex>$rm MgB_2$</tex>Films Prepared by Electron Beam Deposition

Abstract

As-grown superconducting MgB/sub 2/ thin films were prepared on Al/sub 2/O/sub 3/ [001] single crystals by electron beam deposition technique by changing the substrate temperature, the flux rate ratio of Mg/B and the basal pressure before the deposition starting. Higher Mg deposition rate and lower basal pressure gave a lower normal state resistivity of the MgB/sub 2/ thin films and gave a higher critical temperature. Magnetic hysteresis of the MgB/sub 2/ film prepared under lower basal pressure was smaller than that of the film prepared under higher basal pressure. Although the critical temperature of the MgB/sub 2/ film prepared under higher basal pressure became lower, the critical current density was enhanced. Higher basal pressure introduced some pinning centers in to MgB/sub 2/ films. These results suggest that precision control of the atmosphere during the MgB/sub 2/ deposition is very important for obtaining the high critical current density.