High-performance DC SQUIDs with submicrometer niobium Josephson junctions

Journal Article · Tue Nov 01 00:00:00 EST 1983 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00682481· OSTI ID:5151702

de Waal, V J; Klapwijk, T M; van den Hamer, P

We report on the fabrication and performance of low-noise, all-niobium, thin-film planar dc SQUIDs with submicrometer Josephson junctions. The junctions are evaporated obliquely through a metal shadow evaporation mask, which is made using optical lithography with 0.5 ..mu..m tolerance. The Josephson junction barrier is formed by evaporating a thin silicon film and with a subsequent oxidation in a glow discharge. The junction parameters can be reproduced within a factor of two. Typical critical currents of the SQUIDs are about 3 ..mu..A and the resistances are about 100 ..cap omega... With SQUIDs having an inductance of 1 nH the voltage modulation is a least 60 ..mu..V. An intrinsic energy resolution of 4 x 10/sup -32/ J/Hz has been reached. The SQUIDs are coupled to wire-wound input coils or with thin-film input coils. The thin-film input coil consists of a niobium spiral of 20 turns on a separate substrate. In both cases the coil is glued onto a 2-nH SQUID with a coupling efficiency of at least 0.5. Referred to the thin-film input coil, the best coupled energy resolution achieved is 1.2 x 10/sup -30/ J/Hz measured in a flux-locked loop at frequencies above 10 Hz. As far as we know, this is the best figure achieved with an all-refractory-metal thin-film SQUID. The fabrication technique used is suited for making circuits with SQUID and pickup coil on the same substrate. We describe a compact, planar, first-order gradiometer integrated with a SQUID on a single substrate. The gradient noise of this device is 3 x 10/sup -12/ Tm/sup -1/. The gradiometer has a size of 12 mm x 17 mm, is simple to fabricate, an is suitable for biomedical applications.

• Research Organization: Department of Applied Physics, Delft University of Technology, Delft, Netherlands
• OSTI ID: 5151702
• Journal Information: J. Low Temp. Phys.; (United States), Vol. 53:3
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
JOSEPHSON JUNCTIONS
FABRICATION
SQUID DEVICES
NOISE
PERFORMANCE
NIOBIUM
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
FLUXMETERS
JUNCTIONS
MEASURING INSTRUMENTS
METALS
MICROWAVE EQUIPMENT
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TRANSITION ELEMENTS
420201* - Engineering- Cryogenic Equipment & Devices