Abstract
YBa 2 Cu 3 O 7 step-edge junctions are fabricated on SrTiO 3 -substrates. The steps of 300nm height are milled by argon-ion-beam-etching (IBE). The films are deposited by high-pressure on-axis magnetron sputter technique patterned to microbridges with widths down to 0.5 μm by electron beam lithography and argon ion etching. For ratios of film thickness to step height of t/h 1/2 the current-voltage characteristics show Shapiro steps under microwave irradiation and RSJ-(resistively shunted junction)-like behavior. The periodic dependence of the critical current upon the magnetic field resembles a Fraunhofer-pattem. The period of the variation ΔB 0 follows a l/w/ 2 -dependence in agreement with the theoretical prediction for planar thin Josephson junctions: ΔB 0 = 1.84Φ 0 /w 2 . Junctions with widths of 0.7μm possess a large magnetic field stability with ΔB 0 100G. Small junctions (w<1 μm) exhibit voltage jumps in the Fraunhofer pattern, Which are explained by flux penetration of single vortices into the superconducting electrodes. The developed preparation technique for 'field-stable' Josephson junctions will be used for wafer scaling on 2-inch substrates and for the production of magnetically stable rf-SQUIDS.
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