Challenges of scanning hall microscopy using batch fabricated probes

Kodai Hatakeyama

    Research output: ThesisPhD Thesis - Research UT, graduation UT

    100 Downloads (Pure)

    Abstract

    Scanning Hall probe microscopy is a widely used technique for quantitative high resolution imaging of magnetic stray fields. Up to now probes with nanometer spatial resolution have only been realized by electron beam lithography, which is a slow and expensive fabrication technique. In this thesis, we employ corner lithography to enable batch fabrication of high resolution scanning Hall probes. The initial design consisted of a sub-&m Hall cross supported by four free standing wires in a pyramidal configuration, located at the end of an AFMtype cantilever. This implementation was mechanically and electrically too fragile to operate. Therefore the design was improved by supporting the wires with a robust silicon-nitride membrane. These robust probes allowed for scanning operation, but we discovered that the output signals suffered from large topographic crosstalk. We determined that this crosstalk was caused by the combination of cross asymmetry, resulting from fabrication imperfections, and topography induced probe-sample distance modulation, leading to temperature variation. To circumvent the crosstalk, we introduced an electronic compensation method to suppress the effect of temperature variation on the detected Hall signal. The method suppresses the temperature effect by at least a factor of ten, provided that the probe temperature varies uniformly over the entire structure. However, the method is not capable of compensating temperature changes within the probe structure itself, for instance caused by asymmetric probe cooling at step edges on the sample, or cantilever torsion. To increase the signal-to-noise ratio and improve the electrical robustness of the probes even more, we improved the probe design further by widening the leads to the Hall cross and increasing its dimensions. Using this final design, we successfully demonstrated imaging on a thermo-magnetically patterned magnetic sample with domains of 10 &m£10 &m, at a sensitivity of 4.12 V/T.
    Original languageEnglish
    Awarding Institution
    • University of Twente
    Supervisors/Advisors
    • Abelmann, Leon , Supervisor
    • Krijnen, G. , Supervisor
    Award date2 Sep 2016
    Place of PublicationEnschede
    Publisher
    Print ISBNs978-90-365-4163-3
    DOIs
    Publication statusPublished - 2 Sep 2016

    Fingerprint

    microscopy
    scanning
    probes
    crosstalk
    fabrication
    lithography
    wire
    temperature probes
    theses
    torsion
    nitrides
    temperature
    temperature effects
    topography
    signal to noise ratios
    spatial resolution
    asymmetry
    electron beams
    membranes
    modulation

    Keywords

    • IR-101056
    • METIS-317603

    Cite this

    Hatakeyama, Kodai. / Challenges of scanning hall microscopy using batch fabricated probes. Enschede : University of Twente, 2016. 78 p.
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    abstract = "Scanning Hall probe microscopy is a widely used technique for quantitative high resolution imaging of magnetic stray fields. Up to now probes with nanometer spatial resolution have only been realized by electron beam lithography, which is a slow and expensive fabrication technique. In this thesis, we employ corner lithography to enable batch fabrication of high resolution scanning Hall probes. The initial design consisted of a sub-&m Hall cross supported by four free standing wires in a pyramidal configuration, located at the end of an AFMtype cantilever. This implementation was mechanically and electrically too fragile to operate. Therefore the design was improved by supporting the wires with a robust silicon-nitride membrane. These robust probes allowed for scanning operation, but we discovered that the output signals suffered from large topographic crosstalk. We determined that this crosstalk was caused by the combination of cross asymmetry, resulting from fabrication imperfections, and topography induced probe-sample distance modulation, leading to temperature variation. To circumvent the crosstalk, we introduced an electronic compensation method to suppress the effect of temperature variation on the detected Hall signal. The method suppresses the temperature effect by at least a factor of ten, provided that the probe temperature varies uniformly over the entire structure. However, the method is not capable of compensating temperature changes within the probe structure itself, for instance caused by asymmetric probe cooling at step edges on the sample, or cantilever torsion. To increase the signal-to-noise ratio and improve the electrical robustness of the probes even more, we improved the probe design further by widening the leads to the Hall cross and increasing its dimensions. Using this final design, we successfully demonstrated imaging on a thermo-magnetically patterned magnetic sample with domains of 10 &m£10 &m, at a sensitivity of 4.12 V/T.",
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    Challenges of scanning hall microscopy using batch fabricated probes. / Hatakeyama, Kodai.

    Enschede : University of Twente, 2016. 78 p.

    Research output: ThesisPhD Thesis - Research UT, graduation UT

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    AB - Scanning Hall probe microscopy is a widely used technique for quantitative high resolution imaging of magnetic stray fields. Up to now probes with nanometer spatial resolution have only been realized by electron beam lithography, which is a slow and expensive fabrication technique. In this thesis, we employ corner lithography to enable batch fabrication of high resolution scanning Hall probes. The initial design consisted of a sub-&m Hall cross supported by four free standing wires in a pyramidal configuration, located at the end of an AFMtype cantilever. This implementation was mechanically and electrically too fragile to operate. Therefore the design was improved by supporting the wires with a robust silicon-nitride membrane. These robust probes allowed for scanning operation, but we discovered that the output signals suffered from large topographic crosstalk. We determined that this crosstalk was caused by the combination of cross asymmetry, resulting from fabrication imperfections, and topography induced probe-sample distance modulation, leading to temperature variation. To circumvent the crosstalk, we introduced an electronic compensation method to suppress the effect of temperature variation on the detected Hall signal. The method suppresses the temperature effect by at least a factor of ten, provided that the probe temperature varies uniformly over the entire structure. However, the method is not capable of compensating temperature changes within the probe structure itself, for instance caused by asymmetric probe cooling at step edges on the sample, or cantilever torsion. To increase the signal-to-noise ratio and improve the electrical robustness of the probes even more, we improved the probe design further by widening the leads to the Hall cross and increasing its dimensions. Using this final design, we successfully demonstrated imaging on a thermo-magnetically patterned magnetic sample with domains of 10 &m£10 &m, at a sensitivity of 4.12 V/T.

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