Minimal Damage and Tunable Fabrication of Atomic‐Scale Ultrathin YBa2Cu3O7‐δ Nanowires with High Uniformity

The growing demand for deep‐space optical communication and remote sensing has highlighted the need for high‐temperature superconducting nanowire single photon detectors (SNSPDs). However, fabricating ultrathin and ultranarrow high‐temperature superconducting nanowires remains significant challenges due to the extreme instability of their films. Herein, an effective approach is presented for fabricating high‐quality YBa 2 Cu 3 O 7 − δ (YBCO) nanowires by utilizing in situ protective layers that shield ultrathin films from environmental and processing‐induced degradation, coupled with low‐temperature etching techniques to achieve precise, and tunable etching while minimizing damage. Thus, YBCO nanowires are successfully fabricated with a minimum width of 68 nm, an atomic‐scale thickness of 5 nm, and lateral damage limited to ≈15 nm. These nanowires exhibit robust I – V hysteresis and a minimum switching current ( I s ) of about 120 μA. The coefficient of variation for the I s less than 6% and for the critical temperature ( T c0 ) is below 1%, confirming the exceptional uniformity of the nanowires. Electrical transport measurements reveal that voltage switching in these nanowires is governed by phase slip and hotspot effects. These advancements open new avenues for YBCO‐based high‐temperature SNSPDs, addressing a key challenge in the broader deployment of high‐temperature superconducting devices, including SNSPDs, superconducting quantum interference devices, and superconducting diodes.