Step Edge YBa sub 2 Cu sub 3 O sub 7-- delta DC SQUIDS on Sapphire Substrates

• Published in: Applied physics letters Vol. 60; no. 20; pp. 2552 - 2554
• Main Authors: Yuan, C W, Berezin, A B, de Lozanne, A L
• Format: Journal Article
• Language: English
• Published: 18-05-1992
• ISSN: 0003-6951

YBa sub 2 Cu sub 3 O sub 7-- delta (YBCO) thin film dc superconducting interference devices (SQUIDs) on sapphire substrates that operate > 77K were constructed. The YBCO thin films are free of weak links and have critical current densities (J sub c ) of 10 exp 6 A/cm exp 2 at 77K. Across the step edge, typical J sub c ranges from 10 exp 5 -10 exp 3 A/cm exp 2 at 77K and increases linearly with decreasing temperature. Typically, I sub c R sub n products near 30 mu V were obtained, at 77K. The dc SQUIDs were operated between 4.2 and 77K and voltage modulation in rough agreement with the expected values was observed. The flux noise is typically 1 x 10 exp --10 Phi exp 2 sub 0 /Hz, with a corresponding noise energy, S sub E , of 1.3 x 10 exp --29 J/Hz at 77K and 1/kHz.