Enhancement of critical current density in YBa2Cu3O7 films using a semiconductor ion implanter

An up-to-11-fold enhancement was observed in the in-magnetic-field critical current density (Jc) in epitaxial YBa2Cu3O7 films on CeO2-buffered SrTiO3 substrates by irradiation with 200- to 750-keV Si and 200-keV B ions. This enhancement indicates that ion beams in the range of 100 to 1000 keV, which are widely used for modifying the conductive properties of semiconducting materials, can significantly improve the vortex-pinning properties in second-generation superconducting wires. Also observed was a scaling relation between Jc and the density of the vacancies (i.e., of Frenkel pairs) produced by the nuclear collisions between incident ions and target atoms, suggesting that this density is a key parameter in determining the magnitude of the Jc enhancement. Also observed was an additional Jc enhancement by a modification of the depth distribution of the vacancies, thus demonstrating the flexibility in controlling artificial pinning center (APC) properties in physical APC introduction.