Field-independent voltage jump transitions in quasi-single-crystal YBCO films synthesized by gradient-cooling TFA-MOD

In this study, Yba 2 Cu 3 O 7- δ (YBCO) superconducting thin films with quasi-single-crystal characteristics were fabricated on single-crystal LaAlO 3 substrates via the trifluoroacetate metal-organic deposition (TFA-MOD) method combined with gradient-cooling crystallization. Structural and performance analysis reveals that samples obtained through a slow cooling process (800°C→790°C for 90 min) exhibit a single crystal-like structure with preferred (00 l ) orientation, exhibiting a dense and uniform surface. The lattice arrangement demonstrates remarkable consistency and is devoid of grain boundary defects or heterogeneous inclusions. Under self-field conditions at 77 K, the YBCO microbridge exhibits pronounced voltage jump characteristics. The critical current density Jc, measured by the four-lead method at the instant voltage jump, attains 1.2 MA/cm 2 , achieved with a 0.2 mm wide microbridge and a 250 nm film thickness. The process of losing superconductivity displays abrupt transition characteristics with a voltage jump amplitude exceeding 12 V. Notably, the current value at the voltage jump instant remains unaffected by the magnetic field, aligning with the Larkin-Ovchinnikov. This work establishes a non-vacuum pathway for manufacturing large-area superconducting components that require sudden switching behavior.