Elimination of the Edge Effect in Superconducting Indium and Tin Films

Abstract

Superconducting thin film strips of indium and tin from 3000 to 10 000 Å thick, having sharp, magnetically induced resistive transitions between their superconducting and normal states, have been produced. Usually, the width of such transitions may be as much as 50% to 100% of the critical field because of the relatively high fields required to switch the thinner, tapered edges of the films. This tendency has been counteracted by preferentially depressing the critical temperature near the film edges through the use of an overlapping film of copper or gold, up to several hundred angstroms thick. Transition sharpening equivalent to that observed when the edges of the superconducting films are mechanically removed has thus been achieved. Behavior predicted by analyses of a simplified model has been found to be consistent with experimental observations.