THE EFFECT OF ELECTRODE MATERIALS ON PB ALLOY SUPERCONDUCTING TUNNEL-JUNCTIONS FOR SUBMILLIMETER-WAVE HETERODYNE RECEIVER APPLICATION

Submicron superconducting tunnel junctions were fabricated for submill imetre wavelength heterodyne detection. To this end three types of Pb alloy electrodes were investigated. All have shown good I-V do charact eristics but only the Pb-In-Au alloy produced stable and reliable junc tions in vacuum and thermal cycling. Au-free junctions were found to b e unreliable and would fail, i.e would form a short circuit, when plac ed in vacuum by desorption of water from the oxide barrier. This effec t was subsequently stopped by alloying the electrode with 1% wt of Au leading to cathodic corrosion which in turn protects the junction from failing in vacuum.