Thin Film Fractal Morphology and the Enhancement of Superconducting Critical Parameters

In superconducting films, it is known that the use of artificial defects can enhance a films' superconducting critical parameters. In particular, it has recently been reported that regular arrays of sub-micron sized holes produced by means of lithographic techniques can substantially increase the critical temperature for all fields. [1] We report here our observations that careful control of Pb film deposition conditions can result in film texture that has naturally occurring ``holes'' and enhanced critical parameters reminiscent of the artificially structured films. We characterize the texture of these films via their fractal dimension, and find that it is a useful approach for characterizing a films superconducting critical parameters. This work was funded by NSF and AFOSR. \newline \newline [1] A.V. Silhanek et al., PRB \textbf{72}, 014507 (2005)