DC Superconducting Quantum Interference Device of YBa2Cu3O7-x Step-Edge Junctions

Abstract
DC superconducting quantum interference devices (DC-SQUIDs) are made of YBa2Cu3O7-x (YBCO) thin films by conventional photolithography and argon ion milling. The YBCO thin films are prepared on magnesia substrates with step edges by the rf magnetron sputtering method. The step-edge junctions for the SQUIDs exhibit clear DC and AC Josephson effects. The SQUIDs respond well to change of magnetic flux and have a white flux noise at 51.4 K of 8.1×10-5 Φ0/Hz1/2 at 1 Hz, 5.8×10-5 Φ0/Hz1/2 at 10 Hz and a noise increase at a low-frequency range of less than 10 Hz.