Ion beam irradiation of high-temperature superconductors: From nano-size defects to the fabrication of nanodevices

Ion-beam irradiation of high-temperature superconductors creates different types of defects depending on ion mass, energy and dose. Computer simulations reveal the diversity of the ion-target interactions with YBa₂Cu₃O₇ and are compared to previous experimental results from transmission electron microscopy and electrical transport properties. While protons have a very low efficiency to create defects in YBa₂Cu₃O₇, significantly heavier ions produce defect clusters and inhomogeneous damage in the target material. On the other hand, He⁺ ions with energy of about 75 keV do not implant into 100-nm thick films of YBa₂Cu₃O₇ but primarily create point defects by displacement of the oxygen atoms. Such defects are very small and distributed homogeneously in YBa₂Cu₃O₇. The small lateral straggle of the collision cascades allow for the patterning of nanostructures by directing a low divergence beam of He⁺ ions onto a thin film of YBa₂Cu₃O₇ through a mask. Features with about 60 nm size have been produced and observed by transmission electron microscopy.