Work

Tailoring the properties of YBa 2 Cu 3 O 7 − δ thin films by 30-keV He + irradiation: An enabling route to superconducting-device nanopatterning

Year: 2026

Type: article

Abstract: Focused helium ion beam (He-FIB) irradiation with 30-keV ions is a key tool for nanoscale patterning and defect engineering in high-transition temperature ( T c ) cuprate superconducting devices, yet its usable fluence window is constrained by the competing requirements of reliable superconductivity suppression and minimal structural degradation. In this work, we provide a comprehensive dataset on the effects of large-area 30-keV He + ion exposure on the electric transport and superconducting properties of epitaxial YBa 2 Cu 3 O 7 − δ (YBCO) thin films. X-ray diffraction shows a fluence-driven loss of crystalline order accompanied by an out-of-plane lattice expansion and an orthorhombic-to-tetragonal transition, culminating in predominant amorphization at the highest fluence of 1 × 10 16 cm − 2 . Raman spectra exhibit increasing disorder while lacking signatures of oxygen depletion, indicating that irradiation mainly generates oxygen-related Frenkel defects rather than changing the carrier concentration. Consistently, with increasing fluence, the normal-state resistivity ρ N ( T ) at temperature T above T c increases strongly, while ∂ ρ N / ∂ T remains nearly unchanged at moderate fluence. The suppression of T c is accurately described by Abrikosov–Gor’kov pair breaking and reaches complete quenching of superconductivity at 4.5 × 10 15 cm − 2 . The anisotropic upper critical fields decrease approximately exponentially with increasing fluence; the vortex activation energy is reduced, and the anisotropy drops, in contrast to oxygen-depleted YBCO. Hall-angle analysis confirms a nearly constant carrier density but a systematic increase in defect scattering and reduced mobility, consistent with a crossover toward the dirty limit at high fluence. These results establish quantitative fluence thresholds and a practical operational window for He-FIB nanopatterning of YBCO quantum circuits.

Source: Physical Review Applied

DOI: 10.1103/7dhm-9tvs