Graphoepitaxial Josephson junctions and DC SQUIDs

We have prepared high-T_c superconducting heterostructures for DC SQUIDs with graphoepitaxial step edge Josephson junctions on single crystal MgO substrates and investigated them using complementary characterization techniques, including atomic force microscopy, scanning electron microscopy and high-resolution transmission electron microscopy. Combined epitaxial (out-of-plane) and graphoepitaxial (in-plane) growth of YBa₂Cu₃O_7-x (YBCO) films on the tilted surfaces of step edges on MgO substrates was observed. The high-T_c step-edge Josephson junctions demonstrated a good reproducibility and an I_cR_n product of about 600 μV at 77 K. The DC SQUIDs with step edge junctions showed voltage swings δVpp of up to about 60 μV at 77 K. High values of R_n of the graphoepitaxial step edge Josephson junctions can be advantageous for their applications as qubits.