Planar MgB2 superconductor-normal metal-superconductor Josephson junctions fabricated using epitaxial MgB2∕TiB2 bilayers

Abstract

We have fabricated planar superconductor-normal metal-superconductor MgB2 Josephson junctions using TiB2 as the barrier material. On a bilayer film of MgB2∕TiB2 on SiC substrate, MgB2 was locally removed to create a gap of ⩽50nm, separating the MgB2 film into two electrodes. A Josephson coupling is established through the TiB2 film across the gap by proximity effect. The junctions exhibit resistively shunted junction like current-voltage characteristics up to 31K. 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.