YBa2Cu3O7/noble metal composite thin films for applications in fluxonic and flux-flow devices

This research involves the study of thin films for use in three-terminal, non-linear two-terminal, and photodetector superconducting devices. The morphological and electrical properties of composite films fabricated from YBCO and noble metals have been investigated for use in these devices. Films of Ag and Au, when heated to YBCO deposition temperatures, coalesce into small, approximately micron-sized islands. We take advantage of this property to form a composite film with distinct YBCO and noble metal regions by depositing a layer of YBCO on the array of noble metal islands. With certain compositions the films exhibit reduction of critical current density by a factor of 65 over YBCO and show no significant degradation of critical temperature. Also, the current-voltage characteristics of the composites are sensitive to small, applied magnetic fields. These properties make the YBCO/noble metal composites potentially well suited for the fabrication of devices whose transport is dependent upon vortex motion. Photoresponse measurements taken on a 1 mm x 1 mm YBCO/Au bridge irradiated by red laser light showed a possible non-bolometric response below the composite superconducting transition temperature.