Recovery of original superconducting properties in ion-irradiated Y 1Ba2Cu3O7-x thin films

The changes in the superconducting properties of in situ pulsed laser deposited Y1Ba2Cu3O7-x thin films caused by irradiation with 200 keV He+ ions are due to both oxygen loss as well as oxygen and cationic displacements induced by the irradiation. This is demonstrated by a study of the recovery of these defects by plasma oxidation and relatively low temperature (∼600°C) annealing in oxygen. Plasma oxidation of films irradiated to low fluences enables the replacement of oxygen atoms in the lattice, leading to a substantial recovery of Tc0, Jc, and normal state resistivity. Irradiation-induced oxygen and cationic displacements and other microscopic defects can be further annealed out at relatively low temperatures leading to an almost full recovery of Tc0, Jc, and normal state resistivity. A transmission electron microscope study of irradiated films shows evidence that they are structurally disordered.