Properties of new types of niobium weak links

Measurements have been made of the characteristics of weak links fabricated in several different ways from thin films of niobium. Weak links have been made in films of uniform thickness by implanting ions into a narrow line across a long thin Nb strip and in variable thickness (thick-thin-thick) form by depositing thick films of Nb, Sn, In or Pb on top of a thin Nb strip, leaving a short thin bridge joining two large thick pads. Bridges about 1 μm long and 1-30 μm wide have been studied by measuring the I-V curves as a function of temperature, applied microwave power and magnetic field. These weak links exhibit Josephson effects, have characteristics that can be interpreted as multiple flux flow, and have other features that can be explained phenomenologically in terms of a relaxation time of the order parameter.