Excess low-frequency flux noise in dc SQUIDs

Author

Huber, M.E. ; Cromar, M.W. ; Ono, R.H.

Author_Institution

Colorado Univ., Denver, CO, USA

Volume

7

Issue

2

fYear

1997

fDate

6/1/1997 12:00:00 AM

Firstpage

2882

Lastpage

2885

Abstract

We have fabricated dc superconducting quantum interference devices (SQUIDs) incorporating Nb/Al-oxide/Nb Josephson junctions in both stripline and washer geometries. Low-frequency noise in excess of that predicted by the resistively-shunted junction model is present in both geometries and is demonstrated to be flux noise. This flux noise is not environmental. Improvements in fabrication processing over the past four years have reduced the level of this flux noise. SQUIDs are now fabricated with PdAu resistors, Nb wiring layers, and SiO/sub 2/ interlayer dielectric. In our best well-coupled SQUIDs, the white-noise energy sensitivity is 5/spl times/10/sup -31/ J/spl middot/s, with a 1/f knee below 0.1 Hz. We believe further reduction in the flux noise might be obtained with the use of on-chip flux shielding and/or trapping structures.

Keywords

1/f noise; Josephson effect; SQUIDs; aluminium compounds; magnetic shielding; niobium; superconducting device noise; superconducting device testing; white noise; 0.1 to 100 Hz; 1/f knee; Nb wiring layers; Nb-AlO-Nb; Nb/Al-oxide/Nb Josephson junctions; PdAu; PdAu resistors; SiO/sub 2/; SiO/sub 2/ interlayer dielectric; dc SQUIDs; excess low-frequency flux noise; fabrication processing; on-chip flux shielding; resistively-shunted junction model; stripline geometry; trapping structures; washer geometry; white-noise energy sensitivity; Geometry; Interference; Josephson junctions; Low-frequency noise; Niobium; Noise reduction; SQUIDs; Superconducting device noise; Superconducting devices; Working environment noise;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.621893

Filename

621893