Scanning electron microscope identification of weak links in superconducting thin films

We have used a pulsed electron beam in a scanning electron microscope to produce highly localized (∼1 μm) changes in the electrical properties of a heterogeneous thin film of YBa₂Cu₃O_7-δ. The predominant effect of the beam is to locally heat the film, producing a measurable shift in the current-voltage characteristic. In particular, we have precisely located the part of the film responsible for a sharp feature in the current-voltage characteristic corresponding to a single Josephson junction. The technique should also be useful more generally in identifying specific weak links in superconducting thin films.