Normal-state and superconducting properties of Co-doped BaFe2As2 and MgB2 thin films after focused helium ion beam irradiation

We have investigated the normal-state and superconducting properties of Co-doped BaFe2As2 (Ba122) and MgB2 thin films irradiated at room temperature using a 30 keV focused He+ ion beam with doses between 10(12) and 10(17)cm(2). We show that superconductivity is suppressed and the normal-state resistivity is increased upon irradiation. The critical dose for the complete suppression of superconductivity is similar to 5 x 10(14)cm(-2) for Ba122 and similar to 8 x 10(15)cm(-2) for MgB2. The dependence of the normal-state and superconducting properties on irradiation dose is discussed, taking into account the spatial distribution of ion-induced damage. Hillock formation due to the substrate swelling, arising from the He+ ions stopped in the substrate, is also observed. The findings provide guidelines for exploiting focused He+ ion beam irradiation in fabricating iron pnictide and MgB2 planar Josephson junctions.