From Growth to Devices: Oxygen-Controlled Superconductivity in BSCCO Thin Films

Realizing device-compatible high-Tc superconductors requires simultaneous control of oxygen stoichiometry and tolerance to nanofabrication. Here, we investigate sputtered Bi₂Sr₂Caₙ₋₁CuₙO2n+4+δ (BSCCO) thin films and establish a direct link between annealing conditions, oxygen incorporation, and superconducting transport. By independently varying the annealing temperature and duration, we identify an optimal annealing condition of 860\,∘C for 3\,h, which yields the highest superconducting transition temperature and the narrowest transition among the investigated samples. X-ray diffraction, electron microscopy, and X-ray photoemission spectroscopy reveal a non-monotonic evolution of lattice oxygen, which governs hole doping in the CuO₂ planes and produces the characteristic dome-like dependence of Tc on doping concentration. We further translate these optimized films into micro-devices to assess fabrication-induced effects, via micro-bridges as well as a planar Josephson junction. We demonstrate devices fabricated via both lift-off and focused ion beam (FIB) patterning methods -- proving the fabrication compatibility of these films. Importantly, we demonstrate their air-stability for extended periods of time (2 months). The combined insights offer practical guidelines for integrating cuprate thin films into superconducting electronics and quantum device architectures.