200-keVHe+-ion irradiation effects on the properties of pulsed-laser-depositedYBa2Cu3O7−xthin films

We report the effects of 200-keV ${\mathrm{He}}^{+}$-ion irradiation on the properties of high-quality ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ thin films made in situ by pulsed-laser deposition. There is no significant change in ${\mathit{T}}_{\mathit{c}}$ or the normal-state resistivity for fluences up to 1×${10}^{14}$ ${\mathrm{He}}^{+}$/${\mathrm{cm}}^2$. There is only a small increase in the critical current density ${\mathit{J}}_{\mathit{c}}$ measured at 60 K for fluences up to 3×${10}^{13}$ ${\mathrm{He}}^{+}$/${\mathrm{cm}}^2$ and in nonzero magnetic fields. At fluences above 1×${10}^{14}$ ${\mathrm{He}}^{+}$/${\mathrm{cm}}^2$, the induced changes are more rapid and have a deleterious effect on the superconducting properties.