Properties of high-resistance superconducting microbridges based on lead alloy films

We have fabricated high-resistance, type-II microbridges with submicron dimensions and well-characterized lead alloy films, and studied their Josephson-effect properties. Bridge resistances of 2-18 Ω have been achieved in uniform-thickness structures which are 2000-20,000 Å wide. Critical currents of narrow bridges near Tcare found to agree with theory for uniform depairing. The microwave response of the bridges agrees with theory at low power levels, but self-heating limits microwave steps to voltages < 375 μV. Specific predictions for heating limits of alloy microbridges in the variable thickness geometry are presented.