Three terminal, non-equilibrium quasiparticle device experiments with submicron tunnel junctions

Abstract

A multilayer film edge technique has been developed for the fabrication of dual small area tunnel junctions on the aligned edges of two overlapping thin films separated by a thin insulating layer, with a common electrode shared by the two junctions. Using this technique with electron beam lithography, junction areas as small as 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> have been produced with separations between the two tunnel barriers of 50-80 nm. Devices of this type have been fabricated with Pb alloy counterelectrodes on Nb edges, using reactive ion beam oxidation to obtain tunnel current densities in the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> range. The potential of this multijunction configuration as a high speed, three terminal Josephson device with current and power gain has been investigated. In addition, the edge junctions have been employed to probe non-equilibrium phenomena in the common electrode.