Selected Applications
optically detected magnetic resonance at mK
Our integrated dry mK-SPM solutions are based on state-of-the-art
dry dilution refrigerators with a cooling power of up to 1500 µW, fully
automated gas handling systems and wiring that is perfectly matched
to both the operation of the microscope as well as to the additional
requirements of the customer. We are working very closely with the
leading suppliers of dry dilution refrigerators, and have achieved
outstanding results both in terms of base temperature and noise
specifications. The biggest advantage of a one-supplier-solution for
the end customer is that there is a clear responsibility for the overall
performance of the mK-SPM. Over the last few years, we have put all of
our experience into optimizing the critical parameters to achieving the
one thing that counts the most: a reliably working mK-SPM for the user
right after installation.
The combined AFM/CFM features a free-beam confocal microscope, with
the attoCFM I external optics head sitting on top of the toploading
insert. Despite the long distance to the magnetic field center where
the sample is mounted, this allows for the full range of confocal
applications with all the flexibility of having several optical channels
with easy alignment and very high long-term stability.
The microscope module itself has been completely redesigned for
the mK environment, and is carefully thermalized and wired. In this
configuration, a base temperature of 38 mK at the sample location was
reached.
In close collaboration with Leiden Cryogenics and the Quantum Sensing
group of Prof. Patrick Maletinsky (Basel, CH), we have developed a
complete mK AFM/CFM for based on a closed-cycle toploading dilution
refrigerator. The system will be used for quantum sensing and imaging
at mK temperatures in Basel. A toploading probe is a crucial feature
for SPM, in order to minimize the turnaround time upon tip or sample
exchange. Thanks to the sophisticated design of the cryostat with
a toploading probe, this takes only about 8 hours instead of 24-48
hours for bottom-loading systems, especially with heavy magnets.
This can quickly become a prohibitive shortcoming for efficient SPM
measurements.
PRODUCT KEY FEATURES
• dry dilution refrigerator with toploading insert
• base temperature (DR): 8 mK
• cooling power (DR): 1 mW@100 mK
• cooling power (toploading probe): 100 μW @120 mK
• cooldown time (toploading probe): ~8 hours
• 5-1-1 vector magnet
• mK-compatible attoAFM/CFM combined atomic force and confocal
microscope with free-beam optical access and external optics head
• independent tip and sample positioning
• 38 mK base temperature at sample in microscope
attoAFM III Mounted on Mixing Chamber
1 µm
This AFM-topography test-measurement of an 20 nm high calibration grating was performed in a pulse-tube based
dilution fridge from Leiden Cryogenics. Even though the sample was scanned with 3 μm/s, the temperature did not
rise above 80 mK, while the base temperature of the (not yet optimized) braid cooled sample was at around 62 mK.
Geophone measurements verified the low vibrations of the platform and showed that it is a suitable approach for high
resolution, ultra-low temperature AFM-type experiments.
(attocube applications in collaboration with Leiden Cryogenics, 2011)
attoAFM/CFM in Toploading Insert
This data was taken with a mk-compatible version of the attoAFM/CFM mounted on a toploading insert of a Leiden
Cryogenics closed-cycle dilution refrigerator (see images and project description on the left page). The sample tem-
perature was 60 mK during an AFM scan with a speed of 400nm/s. The images nicely demonstrates that the delicate
microscope works very well even under these extreme conditions.
attoMICROSCOPY
Sophisticated Tools for Science
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