Fabrication of superconducting MgB2 nanostructures

Electron beam lithography has been used for the fabrication of superconducting magnesium diboride nanofilms (thickness lower than 100 nm), which were then characterized by atomic force microscopy. The analysis reported in this paper demonstrates that these nanofilms have self-affine surfaces with a fractal dimension of ∼2.25. A size-effect on the critical temperature for activating the superconductive state is discussed and fractal scaling laws are consequently proposed. Only a moderate reduction of the critical temperature is imposed by the shrinking of the investigated nanofilms with respect to their bulk counterpart, suggesting that MgB2 nanostructures could play a fundamental role in superconductive nanocircuits.