attoSHPM

scanning hall probe microscope

ultra-high field sensitivity & sub-micron resolution

quantitative & non-invasive magnetic information

closed loop scanning (optional)

easy retrieval of regions-of-interest

sensor incorporates simple STM tip

enables auto-approach on conducting samples

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The attoSHPM is a compact scanning Hall probe microscope, designed particularly for operation at low temperature and high magnetic fields. At the heart of the attoSHPM, a molecular beam epitaxy (MBE) grown GaAs/AlGaAs Hall sensor measures magnetic fields with unrivalled sensitivity and high spatial resolution down to 250 nm. Local measurements of the magnetization of a sample are obtained by scanning the sample underneath the Hall sensor and simultaneously recording the Hall voltage, directly yielding the local magnetic stray field. While other local probes such as MFM may outperform the Hall sensor with respect to its lateral resolution, its ability to non-invasively obtain quantitative values for the local magnetic field makes the Hall sensor a unique tool for the study of superconductors and magnetic materials.

The microscope uses a set of xyz-positioners for coarse positioning of the sample over a range of several mm, and dedicated mechanically amplified piezo based xyz scanners with a very large scan range even at cryogenic temperatures.

The attoSHPM can be equipped with an interferometric encoder for closed loop scanning with down to 1 nm lateral resolution, and an ultra large range scanner with 125 μm scan range at 4 K.

Last but not least, due to the open signal architecture of our powerful and flexible ASC500 SPM controller, the needs of experts are addressed to have control over all signals, while maintaining a very user-friendly software interface that also supports measurement routines based on LabVIEW scripts. All in- and output signals are accessible via front panel BNCs, and can hence easily be monitored, stored and used for additional control loops or spectroscopies. Finally, our unique closed loop scan option allows for global sample navigation over the complete range of the microscope at cryogenic temperatures, and hence enables the retrieval of regions of interest very precisely. For more info please refer to the fundamentals section.

Cryogenic Tablet

Specifications

Modes of Operation
slope compensation2 axis scan plane correction
z feedbackSTM distance tracking (usually only for autoapproach)
imaging modesconstant height
Options and Upgrades
closed loop upgrade for coarse positionersresistive encoder, range 5 mm, sensor resolution approx. 200 nm, repeatability 1-2 µm
closed loop scanning & global sample coordinatesinterferometric encoders for scan linearization and closed loop sample navigation
ultra-large scan range upgrade80 x 80 µm² @ 300 K, 125 x 125 µm² @ 4 K
in-situ inspection opticstip/sample monitoring via in-situ LT-LED for illumination, mirrors, lenses and CCD camera (outside), field of view approx. 3 x 2 mm, resolution approx. 20 µm (depending on cryostat)
Resolution
size of Hall cross on sensor400 nm (high resolution), 250 mm (ultra high resolution)
field sensitivity @ 4 K1500 V/AT
noise-equivalent magnetic field (theoretical)15 nT/vHz @ 4 K and 40 µA Hall current, 80 nT/vHz @ 77 K and 40 µA Hall current
typical attainable field detection limit (measured)15 µT typ. (bandwith 10 Hz @ frequency 277 Hz)
z bit resolution @ 4 K57 pm at 15 µm scan range
Sample Positioning
total travel range5 x 5 x 5 mm³ (open loop)
step size0.05..3 µm @ 300 K, 10..500 nm @ 4 K
fine scan range50 x 50 x 24 µm³ @ 300 K, 30 x 30 x 15 µm³ @ 4 K (open loop)
closed loop scanningoptional
sample holderASH/QE/4CX quick-exchange sample holder with 8 electrical contacts, integrated heater with calibrated temperature sensor
Suitable Operating Conditions
temperature range1.5 K..300 K (dependent on cryostat); mK compatible setup available on request
magnetic field range0..15 T+ (dependent on magnet)
operating pressuredesigned for He exchange gas (vacuum compatible version down to 1E-6 mbar on request)
Suitable Cooling Systems
titanium housing diameter48 mm
bore size requirementdesigned for a 2" (50.8 mm) cryostat/magnet bore
compatible cryostatsattoDRY1000/1100/2100, attoLIQUID1000/2000/3000/5000
Compatibility with Electronics
scan controller and softwareASC500 (for detailed specifications please see attoCONTROL section)
General Specifications
type of instrumentScanning Hall Probe Microscope with STM tip for tip-sample distance control
sensor head specificsMBE grown hall cross sensor (GaAs/AlGaAs heterostructure) on a 2-axis tiltable sensor mount
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