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Publication
IEEE Transactions on Magnetics
Paper
Specific capacitance of josephson tunnel junctions
Abstract
The specific capacitance of several types of Josephson tunnel junctions has been measured by observing resonances in lightly-damped 2-junction interferometers. The capacitance was calculated using the resonance voltage, obtained by analyzing steps in the I-V characteristics, and the interferometer inductance, which was measured directly by the injection of a control current. Using this technique, the specific capacitance Cs was determined for tunnel junctions with Pb-In-Au alloy base electrodes and Pb-Bi counterelectrodes, as well as for junctions made on Nb films with Pb-In-Au counterelectrodes. In both cases, barriers were produced by rf plasma oxidation. Junctions with Josephson current densities jy between 200 and 5000 A/cm2 were investigated. It was found that 1/C, decreased with log j1, and that at jl = 1000 A/cm2, C, was 4.2±0.3 μF/cm2 for the Pb-alloy junctions and 13.4+1 μF/cm2 for the Nb junctions. These results are discussed in relation to available data on oxide thickness and dielectric constant. © 1981 IEEE