High Tc SNS Edge Junctions and SQUIDs With YBCO Groundplanes

This work examines the properties of epitaxial edge-geometry SNS weak links integrated with YBa_2Cu_3O_7-δ (YBCO) groundplanes and SrTiO₃ insulator layers. The multilayer structures are produced using off-axis-sputtering and an omnidirectional device edge formation process. Junctions over YBCO groundplanes with Co-doped-YBCO normal metal layers show excellent performance, comparable to devices produced without groundplanes. At 65 K, these devices have I_cR_n products of 500-700 μV for 100-150 Åthick normal metal layers with 1-σ J_c spreads down to 20%. I_c(B) modulation studies at 77 K of junctions over a groundplane show 80-100% modulation with a period four times longer than the case of no groundplane. Test structures on the chips demonstrate groundplane-to-junction isolation >10^6 Ω-cm at room temperature and base-electrode-to-groundplane via contacts superconducting above 80 K. Measurements on SQUIDs with groundplanes show voltage modulation up to 95 μV and microstrip inductance values down to 1 pH/square at 65 K. version of Brian's abstract