attoAFM/CFM

combined atomic force and confocal microscope

unique combination of AFM and CFM

platform for NV based nanomagnetometry (ODMR)

independent xyz-positioning of AFM tip and sample

precisely position NV centers in focus & scan sample

closed loop scanning (optional)

easy retrieval of regions-of-interest

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The attoAFM/CFM is a combined atomic force and confocal microscope designed for use at variable temperature down to mK, and in high magnetic fields. Featuring an apochromatic, cryogenic objective with high numerical aperture and low working distance for high collection efficiency over a wide wavelength range, the challenge to integrate an AFM tip in between the extremely tight space between objective and sample was solved by using a socalled inverted Akiyama probe AFM tip. This special self-sensing and self-actuating AFM sensor is based on a microcantilever attached to a tuning fork, which turns the horizontal oscillation of its prongs into a vertical oscillation of the cantilever.

The most typical application of this microscopy platform is its use for optically detected magnetic resonance (ODMR) using nitrogenvacancy color centers (NV centers) as highly sensitive and ultrasmall sensors. This atomic-sized spin system which shows spin dependent photoluminescence, and can be used as a well-controlled single photon source. Its exceptionally long spin coherence times translate into extremely high magnetic sensitivities beyond the nT range. In order to employ the outstanding properties of NV centers for magnetic imaging, the combination of an AFM (which controls the position of the sensor with respect to the sample surface), and a confocal microscope (which provides the optical spin state preparation and readout in reflection mode) is used. Local magnetic fields can subsequently be measured via the Zeeman shifts of the NV defect spin sublevels which are directly proportional to the local magnetic fields encountered by the tip.

This condition can be detected by a decrease in photoluminescence intensity of the NV center under resonant microwave excitation, referred to as ODMR.

The attoAFM/CFM is available with an optional interferometric encoder for closed loop scanning. The microscope uses two sets of xyz-positioners for coarse positioning, and hence allows for independent positioning of the sample and AFM tip over a range of several mm. Typically, the AFM sensor hosting the NV center as sensor is positioned exactly into the focal spot of the high NA objective, and then the sample is scanned underneath both sensors. The additional piezo-based xyz scanner for both tip and sample each provide a large scan range even at cryogenic temperatures; usually however, only one set of xyz scanners is used during most experiments.

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

Detection
detection modee.g. optically detected magnetic resonance (ODMR), luminescence, fluorescence
detection wavelength rangedetector upon user`s choice, typically Si detector (coupling of the light to other detectors)
detection port specificationFC/ APC-connector for single mode fibers or free-beam configuration
Sample Positioning
total travel rangeindependent degrees of freedom for tip and sample of 2 mm x 3 mm x 2.5 mm (closed loop)
step size0.05..3 µm @ 300 K, 10..500 nm @ 4 K
fine scan range30 x 30 x 4.3 µm³ @ 300 K, 12 x 12 x 2 µm³ @ 4 K (open loop)
closed loop scanningoptional
sample holderTi plate with integrated heater and calibrated temperature sensor
General Specifications
type of instrumentcombined confocal (CFM) and atomic force microscope (AFM)
sensor head specificsAFM: Akiyama probe (quartz tuning fork combined with a mircomachined cantilever); CFM: attoCFM I external optics head and low temperature apochromatic
Modes of Operation
imaging modesoptically detected magnetic resonance (ODMR), AFM, CFM
slope compensation2 axis scan plane correction
z feedbackAFM: PI feedback loop for amplitude modulation (AM), phase modulation (PM) or frequency modulation (FM) using included PLL
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)
Resolution
measured RMS z-noise (constant force @ 4 K, 5 ms pixel time)< 0.2 nm (expected for attoLIQUID1000), < 0.5 nm (guaranteed for attoLIQUID1000)
z bit resolution @ 4 K7.6 pm at 2 µm scan range
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
Confocal Unit
configurationcompact and modular design, two or more optical channels; standard configuration: one excitation and one detection channel
key benefitsquick and reliable alignment of each channel, steering mirror for combined beams long-term stability
quick-exchange of optical componentsbeamsplitters, filter mounts for up to 4 filters/polarizers, (1" diameter); optional piezoelectric rotator with filter mount
pinhole configurationtwo pinholes (fiber apertures), different illumination and collection wavelength possible
pinhole sizedependent on fibers, typically 3 .. 9 µm mode field diameter
compatible LT-objectiveLT-APO/VIS, LT-APO/VISIR, LT-APO/NIR (see accessory section for more information)
inspection unitsample imaging with large field of view: ~54 µm (attoDRY), ~40 µm (attoLIQUID)
Compatibility with Electronics
scan controller and softwareASC500 (for detailed specifications please see attoCONTROL section)
Options and Upgrades
closed loop scanning & global sample coordinatesinterferometric encoders for scan linearization and closed loop sample navigation
in-situ inspection opticsresolution approx. 20 µm (depending on cryostat, distance top-flange to field center)
closed loop upgrade for coarse positionersresistive encoder, range 3 mm, sensor resolution approx. 200 nm, repeatability 1-2 µm
Illumination
excitation wavelength range400 .. 1000 nm, default 650 nm (others on request)
illumination port specificationFC/ APC-connector for single mode fibers or free-beam configuration
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Customer Feedback

Dr. Vincent Jacques

LPQM, ENS-Cachan, France

Owing to the high stability and easy operation of the attoAFM/CFM, we were able to perform first magnetometry experiments within only a few months. Support from attocube engineers was always very prompt and efficient. The system is now operated since two years and I must say that it has been the cornerstone of the rapid development of scanning probe magnetometry in our group.

Prof. Dr. Patrick Maletinsky

Department of Physics, University of Basel, Switzerland

Our attoLIQUID1000-based attoAFM/CFM system was a complete game-changer for starting up my research group. Instead of spending years developing a highly complex technical system on our own, we had a fully operational, high-performance cryogenic AFM/CFM system at hand within a relatively short timespan. This allowed us to plunge into our scientific endeavours with highest efficiency. As always, this attocube product stands out due to it’s reliability, ease of use and excellent performance. A particular further asset is the systems versatility - interfacing it with our existing experiments was straight-forward due to the clever system design and excellent support from attocube’s application engineers.