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
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.
|Modes of Operation|
|slope compensation||2 axis scan plane correction|
|z feedback||STM distance tracking (usually only for autoapproach)|
|imaging modes||constant height|
|Options and Upgrades|
|closed loop upgrade for coarse positioners||resistive encoder, range 5 mm, sensor resolution approx. 200 nm, repeatability 1-2 µm|
|closed loop scanning & global sample coordinates||interferometric encoders for scan linearization and closed loop sample navigation|
|ultra-large scan range upgrade||80 x 80 µm² @ 300 K, 125 x 125 µm² @ 4 K|
|in-situ inspection optics||tip/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)|
|size of Hall cross on sensor||400 nm (high resolution), 250 mm (ultra high resolution)|
|field sensitivity @ 4 K||1500 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 K||57 pm at 15 µm scan range|
|total travel range||5 x 5 x 5 mm³ (open loop)|
|step size||0.05..3 µm @ 300 K, 10..500 nm @ 4 K|
|fine scan range||50 x 50 x 24 µm³ @ 300 K, 30 x 30 x 15 µm³ @ 4 K (open loop)|
|closed loop scanning||optional|
|sample holder||ASH/QE/4CX quick-exchange sample holder with 8 electrical contacts, integrated heater with calibrated temperature sensor|
|Suitable Operating Conditions|
|temperature range||1.5 K..300 K (dependent on cryostat); mK compatible setup available on request|
|magnetic field range||0..15 T+ (dependent on magnet)|
|operating pressure||designed for He exchange gas (vacuum compatible version down to 1E-6 mbar on request)|
|Suitable Cooling Systems|
|titanium housing diameter||48 mm|
|bore size requirement||designed for a 2" (50.8 mm) cryostat/magnet bore|
|compatible cryostats||attoDRY1000/1100/2100, attoLIQUID1000/2000/3000/5000|
|Compatibility with Electronics|
|scan controller and software||ASC500 (for detailed specifications please see attoCONTROL section)|
|type of instrument||Scanning Hall Probe Microscope with STM tip for tip-sample distance control|
|sensor head specifics||MBE grown hall cross sensor (GaAs/AlGaAs heterostructure) on a 2-axis tiltable sensor mount|
Fields of Applications
Imaging and scanning probe microscopy of surface properties on the nanoscale at variable temperatures down to milli Kelvin and combination with high magnetic fields.
Systems for microscopy and nanoscale analysis of material properties at ambient and low temperature and in high magnetic fields.