Imaging of spatial structures in superconducting tunnel junctions by electron-beam scanning

The voltage change caused in a current-biased superconducting tunnel junction by scanning the junction surface with an electron beam can serve to generate a two-dimensional image of spatial structures within the specimen. Depending upon the bias point during the scanning process, an image of local variations in the tunneling current density due to variations of the tunnel barrier resistance or in the energy gaps of the electrodes is obtained. PbAuIn/PbBi cross-line and SiO-window junctions have been used to demonstrate this imaging technique.