Magnetic field modulation of critical currents in YBaCuO co-planar Josephson junctions using focused ion beam

Abstract

The YBa2Cu3O7-delta co-planer Josephson junctions by Focused Ion Beam were fabricated by changing the width and the thickness of a YBa2Cu3O7-delta thin film The magnetic properties of the junctions were measured at different temperatures. In the junction with 300 nm thickness, the magnetic field modulation of the critical current at 4.2K was not observed. Near the critical temperature of the junction, the magnetic modulation curve was similar to that of a dc-SQUID. From the SEM observation, some microshorts were observed on the junction. In the junction with 200 nm thickness, the I-V curve was changed for flux-flow junction type to RSJ type. The magnetic modulation curve of the 7 mu m wide junction at 4.2 K was similar to a Fraunhofer pattern. Thus it is considered that the coupling region was changed from a microshort to weak coupling region, when the thickness of the YBaCuO film was decreased from 300 nm to 200 nm.