Magnetic field behavior of small sputtered step-edge junctions

• Published in: Applied physics letters Vol. 68; no. 25; pp. 3623 - 3625
• Main Authors: Vaupel, M., Ockenfuss, G., Wördenweber, R.
• Format: Journal Article
• Language: English
• Published: 17-06-1996
• DOI: 10.1063/1.115750
• EISSN: 1077-3118
• ISSN: 0003-6951

YBa2Cu3O7 step-edge junctions with widths down to 0.5 μm are fabricated on SrTiO3 substrates by Ar ion-beam milling of the steps, high-pressure on-axis magnetron sputtering, electron beam patterning and ion-beam etching of the microbridge. For ratios of film thickness to step height of ∼1/2 the current-voltage characteristics show Shapiro steps under microwave irradiation and resistively shunted junction like behavior. The periodic dependence of the critical current upon the magnetic field resembles a Fraunhofer pattern. The period of the current variation ΔB0 depends upon the width w of the junction according to the theoretical prediction for planar thin Josephson junctions: ΔB0=1.84φ0/w2. Junctions with widths of 0.7 μm possess a large magnetic field stability with ΔB0≊100 G. Small junctions (w<1 μm) exhibit voltage jumps in the Fraunhofer pattern, which are explained by flux penetration of single vortices into the electrodes.