Scanning SQUID susceptometers with sub-micron spatial resolution

Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between thi...

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Bibliographic Details
Published in:Review of scientific instruments 2016-09, Vol.87 (9), p.093702-093702
Main Authors: Kirtley, John R., Paulius, Lisa, Rosenberg, Aaron J., Palmstrom, Johanna C., Holland, Connor M., Spanton, Eric M., Schiessl, Daniel, Jermain, Colin L., Gibbons, Jonathan, Fung, Y.-K.-K., Huber, Martin E., Ralph, Daniel C., Ketchen, Mark B., Gibson, Gerald W., Moler, Kathryn A.
Format: Article
Language:English
Subjects:
Batch processing
Coils
COMPARATIVE EVALUATIONS
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
DESIGN
FABRICATION
FEEDBACK
Field coils
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
INTERFERENCE
MAGNETIC FIELDS
Magnetic permeability
MAGNETIZATION
Microscopes
MICROSCOPY
Noise sensitivity
Scanning
Scientific apparatus & instruments
SENSITIVITY
SENSORS
SIMULATION
SPATIAL RESOLUTION
SQUID DEVICES
Superconducting quantum interference devices
SURFACES
White noise
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Summary:Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz 1/2. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4961982