LONG-RANGE PROXIMITY EFFECT IN ALUMINUM THIN-FILMS WITH SPATIALLY MODULATED TC

We report resistive measurements on a thin-film analog of a modulated-transition-temperature superlattice. The aluminum film was reactive-ion etched in strips perpendicular to the current path, decreasing Tc of the etched sections by 2%, thus spatially modulating the transition temperature. At current densities 600 A/cm2, the resulting structures exhibit a single homogeneous transition for etched lengths up to 50 m, substantially longer than expected from the order-parameter decay length of 0.81 m for the proximity effect in the dirty limit. © 1990 The American Physical Society.