Planar YBa2Cu3O7-δ ion damage Josephson junctions and arrays

Reproducible low resistance lumped element Josephson junction arrays are desired for many microwave applications. Using our established process of electron beam lithography and ion damage, we have fabricated and demonstrated high quality YBa₂Cu₃O_7-δ superconductor-normal superconductor-superconductor (SS´S) in-plane Josephson junctions. Single junctions and multiple junction arrays with as many as 50 junctions in series have been investigated. These junctions are in close proximity and offer several possible applications. Current-voltage characteristics for single junctions are consistent with the resistively shunted junction model. Junction in pairs have been fabricated which show nearly identical characteristics. Rounding near the critical current occurs for larger number arrays which we attribute to junction nonuniformity. Microwave measurements reveal sharp giant Shapiro steps for junction pairs and 10 junction arrays, rounded steps appear for larger arrays.