All YBa2Cu3O7−δ trilayer junctions with YBa2Cu3O7−δ wiring layers

Abstract

We have fabricated all YBa2Cu3O7−δ (YBaCuO) trilayer junctions with YBaCuO wiring layers using CeO2 insulating layers. The trilayer junctions consist of YBaCuO/PrBa2Cu3O7−δ (PrBaCuO)/YBaCuO structures on (100) MgO substrate. Both YBaCuO wiring layer and base-YBaCuO electrode have the critical temperature Tc of ⩾87 K. A 5×5-μm2 junction with a PrBaCuO barrier thickness of 25 nm shows a resistively-shunted-junction (RSJ)-like current–voltage (I–V) characteristic with a critical current density Jc of 1.7×102 A/cm2 and a critical current×normal resistance (IcRn) product of 0.40 mV, and no contact resistance at 4.2 K. The magnetic field dependence of Ic for the junction shows a Fraunhofer interference pattern with a modulation period of 3.5 mT, which is in good agreement with the value estimated from the junction size of 5 μm. In addition, the YBaCuO wiring layers have no structures in the I–V characteristics due to grain–boundary junctions. These facts confirm that the observed Josephson properties come from the YBaCuO/PrBaCuO/YBaCuO trilayer structure.