Modification of high-Tc superconducting thin films by light-ion irradiation

Irradiation of high-temperature superconducting (HTS) YBa2Cu3O7 (Y-123) thin films by light ions of low energy modifies the electrical and superconducting properties of layers without destroying the lattice structure of the HTS material. In situ electrical measurements reveal a strong and non-linear increase of film resistance with employed Helium ion dose (ion energy 75 keV) and a relaxation of resistance after irradiation is stopped. The resistance increase during irradiation is described by a simple resistor network model. Ex situ measurements show a substantial decrease of critical temperature Tc with increasing applied dose and a relaxation of Tc and normal state resistivity that continues for several weeks after the ion irradiation. The modification of defect density and charge carrier density of Y-123 films by light-ion irradiation is discussed. Masked ion irradiation enables to pattern Y-123 films into high-Tc superconducting and non-superconducting regions and to produce tracks of high critical current density (3 MA/cm2 at 77 K) without removal of HTS material.