AFM analysis of MgB2 films and nanostructures

For the fabrication of superconducting devices based on nanostructured thin films, the quality of the starting surface is often of crucial importance. For example, the transport properties of superconducting nanobridges are strongly affected by the geometry and the edge definition of the nanostructures. In this work, we report about AFM characterization of magnesium diboride films and nanobridges fabricated in view of application in superconducting electronics. MgB2 films, obtained by co-deposition method followed by annealing in situ on silicon nitride substrate, have been nanostructured by electron beam lithography and ion milling. The analysis of the AFM images by the height-height correlation function shows that the films have a self-affine smooth textured surface with a RMS roughness of 20 nm. Furthermore, the nanobridges are continuous, with a well-defined geometry and a rounded profile, and the nanostructuration process does not significantly affect the film morphology.