title: Scanning SQUID susceptometers with sub-micron spatial resolution.
abstract: 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/Hz1/2. 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.
authors: Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: John R
authors: JR
authors: Kirtley
authors: Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008-5252, USA.
authors: Lisa
authors: L
authors: Paulius
authors: Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: Aaron J
authors: AJ
authors: Rosenberg
authors: Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: Johanna C
authors: JC
authors: Palmstrom
authors: Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: Connor M
authors: CM
authors: Holland
authors: Department of Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: Eric M
authors: EM
authors: Spanton
authors: Attocube Systems AG, Königinstraße 11A, 80539 Munich, Germany.
authors: Daniel
authors: D
authors: Schiessl
authors: Department of Physics, Cornell University, Cornell, Ithaca, New York 14853, USA.
authors: Colin L
authors: CL
authors: Jermain
authors: Department of Physics, Cornell University, Cornell, Ithaca, New York 14853, USA.
authors: Jonathan
authors: J
authors: Gibbons
authors: IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Y-K-K
authors: YK
authors: Fung
authors: Department of Physics, University of Colorado Denver, Denver, Colorado 80217-3364, USA.
authors: Martin E
authors: ME
authors: Huber
authors: Department of Physics, Cornell University, Cornell, Ithaca, New York 14853, USA.
authors: Daniel C
authors: DC
authors: Ralph
authors: OcteVue, Hadley, Massachusetts 01035, USA.
authors: Mark B
authors: MB
authors: Ketchen
authors: IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors: Gerald W
authors: GW
authors: Gibson
authors: Department of Applied Physics, Stanford University, Stanford, California 94305-4045, USA.
authors: Kathryn A
authors: KA
authors: Moler