Superconducting properties of MgB2 thin films prepared on flexible plastic substrates

Abstract

Superconducting MgB2 thin films were prepared on 50-μm-thick, flexible polyamide Kapton-E foils by vacuum co-deposition of Mg and B precursors with nominal thickness of about 100 nm and a subsequent ex situ rapid annealing process in an Ar or vacuum atmosphere. In the optimal annealing process, the Mg–B films were heated to approximately 600 °C, but, at the same time, the backside of the structures was attached to a water-cooled radiator to avoid overheating of the plastic substrate. The resulting MgB2 films were amorphous with the onset of the superconducting transition at Tc,on≈29 K and a transition width of approximately 3 K. The critical current density was >7×105 A/cm2 at 4.2 K, and its temperature dependence indicated a granular film composition with a network of intergranular weak links. The films could be deposited on large-area foils (up to 400 cm2) and, after processing, cut into any shape (e.g., strips) with scissors, or bent multiple times, without any observed degradation of their superconducting properties.