Fabrication and properties of c-axis Hg-1223 superconducting thin films

摘要

Both undoped and Re-doped c-axis Hg-1223 superconducting chin films are successfully fabricated on SrTiO3 (100) substrates by using the two-step process which comprises pulsed laser deposition of precursor films and subsequent annealing in mercury-vapor atmosphere. The use of HgO/RexBa2Ca2Cu3Oy (x = 0, 0.1) multilayer precursor films capped with an HgO protective layer is found to be effective to obtain more than 75% phase-pure H-1223 films, while the absence of the protective layer leads to appearance of a substantial amount of impurities phases. Re-doped Hg-1223 films exhibit a T-c (zero) as high as 127.5 K and a slightly lower T-c (zero) of 123 K is observed for undoped Hg-1223 films. Re-doped films also show a high J(c) (transport) at 77 K of 1.5 x 10(6) A/cm(2) in a self-field and 1.2 x 10(5) A/cm(2) under a magnetic field of 1 T parallel to the c-axis. It is demonstrated that the Re-doping improves the superconducting properties, as well as the film morphology. Moreover, the irreversibility field above 77 K evaluated from the resistive transitions of the Re-doped Hg-1223 films is found to be substantially higher than those for undoped Hg-1212 and Tl-1223 thin films. (C) 1998 Published by Elsevier Science B.V. All rights reserved. [References: 23]