Enhanced superconducting performance in solution-derived YBa₂Cu₃O_7−δ films using parallel ion-beam structure modification method

Surface modification of superconductors has been extensively researched. However, such modification usually degrades the superconducting properties by creating rough surface morphologies and non-superconducting phase impurities, with the exception of the antidot method modification. Here, a new parallel ion-beam structure modification (PISM) method proves extraordinarily effective in improving the superconductivity of solution-derived YBa₂Cu₃O_7−δ (YBCO) films. Experimental results demonstrate that the surface morphologies of the treated YBCO films become smoother than the pristine samples, and large-sized pores, needle-like a-axis grains, and/or secondary-phase impurities are almost completely removed. Treatment by the PISM method affords remarkable increase ratios ΔJ_c of the critical current density by 128.9% or more, where greater improvements are achieved by increasing the Ar⁺ ion bombardment time. The current-carrying capacity is improved by newly generated impurities, i.e., Ba‒Cu‒O phases acting as Δl volume pinning centers, and drastic shortening of Cu‒O bonds derived from the non-uniform compressive strain.