tuning-fork based atomic force microscope
tuning fork based AFM sensor with wire-type tip
high Q-factor for high sensitivity
closed loop scanning (optional)
easy retrieval of regions-of-interest
non-optical deflection detection
scanning gate microscopy on 2DEGs down to mK
The attoAFM III is an atomic force microscope designed particularly for applications at low and ultra low temperature. Due to the non-optical shear force detection based on a tuning fork, this system is ideally suited for applications where input of light is problematic, either because of light-sensitive samples, or due to the additonal heat load and power dissipation generated by a laser based deflection detection system. A typical application of the attoAFM III microscope is scanning gate microscopy (SGM) on semiconductor structures. This microscope is compatible with wire-type tips glued onto one prong of a small quartz tuning fork as well as with commercially available tuning forks with integrated tips. The decrease in the horizontal oscillation amplitude due to tip-sample interaction when approaching the sample is monitored and/or used as a feedback signal. The force resolution of this technique is typically 0.1 pN.
The attoAFM III is available with an optional interferometric encoder for closed loop scanning. 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.
For scanning gate microscopy experiments, the attoAFM III can be equipped with a 20 pin chip carrier sample holder, which allows for simultaneous transport measurements while imaging to explore the effect of a movable local gate onto the current flow in the mesoscopic device under investigation.
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.
|type of instrument||tuning-fork based AFM with shear-force or standard detection|
|sensor head specifics||etched metal wires, etched or pulled optical fiber probes, STM tips, Akiyama probes (also compatible with NaugaNeedles commercial tips)|
|Modes of Operation|
|imaging modes||non-contact mode AFM, EFM, SGM|
|slope compensation||2 axis scan plane correction|
|z feedback||PI feedback loop for amplitude modulation (AM), phase modulation (PM) or frequency modulation (FM) using included PLL, constant force|
|optional upgrades||AFM/STM mode|
|measured z-noise density||< 16 pm/√Hz|
|z bit resolution @ 4 K||7.6 pm at 2 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 4.2 µm³ @ 300 K, 30 x 30 x 2 µm³ @ 4 K (open loop)|
|sample holder||ASH/QE/0 quick exchange sample holder and 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|
|Compatibility with Electronics|
|scan controller and software||ASC500 (for detailed specifications please see attoCONTROL section)|
|Options and Upgrades|
|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)|
|closed loop upgrade for coarse positioners||resistive encoder, range 5 mm, sensor resolution approx. 200 nm, repeatability 1-2 µm|
|sample holder upgrade||ASH/QE/4CX quick-exchange sample holder (8 electrical contacts, integrated heater & T-sensor)|
Fields of Applications
Systems for microscopy and nanoscale analysis of material properties at ambient and low temperature and in high magnetic fields.
Imaging and scanning probe microscopy of surface properties on the nanoscale at variable temperatures down to milli Kelvin and combination with high magnetic fields.
Dr. Stefan Heun NEST
Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa, Italy
Directly after the set up in our labs, the attoAFM III in a 3He cryostat - used for scanning gate microscopy experiments - has started to produce great data for us. It runs more than 5 years now, and we have published several papers since then. The instrument worked within specifications from the first day and we really appreciate the excellent attocube support throughout the years!