Vortex arrays and strong proximity coupling in Nb/Au bilayers

Owing to its superconducting properties, niobium (Nb) is an excellent candidate material for superconducting electronics and applications in quantum technology. Here, we perform scanning tunneling microscopy and spectroscopy experiments on Nb films covered by a thin gold (Au) film. We investigate the minigap structure of the proximitized region and provide evidence for a transparent interface between Nb and Au, beneficial for device applications. Imaging of Abrikosov vortices in the presence of a perpendicular magnetic field is reported. Our results show robust and homogeneous superconducting properties of thin Nb films in the presence of a gold capping layer. The Au film not only protects the Nb from surface oxidation but also preserves its excellent superconducting properties.