Enhancement of critical current density in direct-current-sputtered TlBa_2Ca_2Cu_3O_(9±δ) superconducting thin films

摘要

A multistep postannealing scheme has been developed for preparing nearly single phased, c-axis oriented TlBa_2Ca_2Cu_3O_x (Tl-1223) superconducting thin films fabricated by the direct-current-sputtering process. Films obtained by the present process have shown, for the first time in this system, a critical current density (J_c) above 10~6 A/cm~2 at 77 K with a zero-resistance transition temperature T_(c0) ≈ 110 K. The order of magnitude enhancement in J_c is attributed to the improvement of film morphology which, in turn, removed most of the weak links encountered previously.