Ion-beam modification of high-temperature superconductor thin films for the fabrication of superconductive nanodevices

Unconventional critical state in YBa2Cu3O7−δthin films with a vortex-pin lattice fabricated by masked He+ion beam irradiation

“…On one hand, n fluxons can be trapped in the normal-conducting core of a CD. At the used irradiation fluence, the material inside a CD is converted to a normal-conducting, defect-rich metal with an almost temperature-independent resistivity of about 1 mΩ cm [5]. Acting as a cylindrical antidot in the superconducting film it can accommodate many fluxons [34,35] due to the large ratio of the diameter of the CD to the in-plane coherence length D/ξ ab (0)∼130, where ξ ab (0)∼1.4 nm [36].…”

“…An array of columnar defect cylinders is created in the YBCO film by masked ion beam irradiation (MIBS). The method is based on our previous observation [5] that irradiation of YBCO with 75 keV He + ions leads to a reduction of the critical temperature T c . At the applied fluence of 3×10 15 cm −2 superconductivity is suppressed, leaving the irradiated regions normal conducting with a resistivity of ρ∼1 mΩ cm that is almost temperature independent between 20 and 310 K. This effect is due to the sensitivity of YBCO to displacements of the weakly-bound chain oxygen atoms [24], while the skeleton of YBCO's crystalline structure still remains intact.…”

“…Since higher ion energies result in larger penetration depths but also in a reduced scattering cross section, a tradeoff between the possible thickness of the sample and a feasible ion fluence has to be found. Several studies [4,5] have revealed that He + ion irradiation of moderate energy is well suitable to tailor the superconducting properties of YBa 2 Cu 3 O 7−δ (YBCO) thin films by displacing mainly oxygen atoms, leading to a systematic reduction of T c .…”