Superconducting properties of YBa₂Cu₃O₇step-edge Josephson junctions prepared on CeO₂-buffered sapphire substrates

Abstract

Step-edge Josephson junctions in the c-axis oriented YBa 2 Cu 3 O 7 films were fabricated on the CeO 2 -buffered sapphire substrates. The step angles were controlled in the wide range of 20-75 • by an Ar ion milling technique. The I -V curves of junctions fabricated on the 35 • step with the film thickness to the step height ratio of about 0.8 exhibited a resistively shunted junction-like behaviour with an I C R N product of about 250 µV and a critical current density of about 2 × 10 4 A cm −2 at 77 K. The critical currents of the step-edge junctions increased approximately linearly with decreasing temperature but the normal resistance remained almost constant. All the samples of the step-edge Josephson junctions satisfied a scaling behaviour of I C R N ∝ (J C ) 0.5 , and a dc SQUID made out of those junctions exhibited a typical voltage modulation in an applied magnetic field.

Developing a trilayer processing technique for superconducting Y Ba2Cu3O7−δthin films by using Ge ion implantation

“…The processing of YBCO thin films as Josephson junctions and SQUIDs, constructed vertically on a substrate, has been reserving an important place in the multilayer fabrication [1][2][3][4][5][6]. There is a demand for multilayer fabrication for the purpose of reducing the noise problems and improving the sensitivity of these devices [7][8][9].…”