Enhanced suppression of superconductivity in amorphous films with nano-scale patterning

We have measured the thickness dependence of the superconducting critical temperature, Tc(dBi), in amorphous Bi/Sb films patterned with a regular array of holes as well as nanoscale thickness variations. We find that the mean field Tc is suppressed relative to simultaneously produced unstructured films of the same thickness. Surprisingly, however, the functional form for Tc(dBi), remains unaffected. The role of the thickness variations in suppressing Tc is compared to the role of the holes, through parameterization of the surface, as measured through AFM/SEM and a proximity effect calculation. These results suggest that these two nanoscale modifications suppress Tc about equally and are consistent with Tc being determined on a microscopic length scale.