YBa2Cu3O7 step-edge Josephson junction dc SQUID magnetometers prepared on sapphire substrates

摘要

YBa2Cu3O7 direct coupled de SQUID magnetometers based on the step-edge junctions on sapphire substrates have been fabricated. 15-nm-thick CeO2 buffer layer and 120-nm-thick YBa2Cu3O7 film were in situ deposited on the 35 degrees steps formed on the sapphire substrates by Ar ion milling. Large ICRN product of 250 muV with junction resistance R-N similar to 5 Omega and critical current I-c similar to 50 muA at 77 K could be obtained reproducibly with 5 CM microbridges. The SQUID magnetometers fabricated on the 1x1 cm(2) sapphire substrates based on the step-edge junctions exhibit a voltage modulation depth of 16 muV and magnetic field noise of 170 fT/root Hz at 100 Hz for the 70 pH-SQUID. [References: 4]