Planar MgB_2 superconductor-normal metal-superconductor Josephson junctions fabricated using epitaxial MgB_2/TiB_2 bilayers

摘要

We have fabricated planar superconductor-normal metal-superconductor MgB_2 Josephson junctions using TiB_2 as the barrier material. On a bilayer film of MgB_2/TiB_2 on SiC substrate, MgB_2 was locally removed to create a gap of ≤ 50 nm, separating the MgB_2 film into two electrodes. A Josephson coupling is established through the TiB_2 film across the gap by proximity effect. The junctions exhibit resistively shunted junction like current-voltage characteristics up to 31 K. An ac Josephson effect was observed and the behavior of the Shapiro steps are in good agreement with theoretical predictions. The magnetic field modulation of the critical current also agrees with the thin film planar junction behavior.