The Laplace Project: An integrated suite for preparing and transferring atom probe samples under cryogenic and UHV conditions
The Laplace Project: An integrated suite for preparing and transferring atom probe samples under cryogenic and UHV conditions
Leigh T. StephensonID 1 2
Agnieszka Szczepaniak 0 1 2
Isabelle Mouton 1 2
Kristiane A. K. Rusitzka 1 2
Andrew J. Breen 1 2
Uwe Tezins 1 2
Andreas Sturm 1 2
Dirk Vogel 1 2
Yanhong Chang 1 2
Paraskevas Kontis 1 2
Alexander Rosenthal 2
Jeffrey D. Shepard 0 2
Urs Maier 2
Thomas F. Kelly 0 2
Dierk Raabe 1 2
Baptiste GaultID 1 2
0 Cameca Instruments Inc. , 5470 Nobel Dr, Fitchburg, WI 53711 , United States of America, 3 Microscopy Improvements e.U. , Rudolf von Eichthal str. 66/6, 7000 Eisenstadt, Austria, 4 Ferrovac GmbH, Thurgauerstrasse 72, 8050 Z u ̈rich , Switzerland
1 Max-Planck-Institut f u ̈r Eisenforschung GmbH , Max-Planck-Straße 1, 40237 D u ̈sseldorf , Germany
2 Editor: Arun Devaraj, Pacific Northwest National Laboratory , UNITED STATES
We present sample transfer instrumentation and integrated protocols for the preparation and atom probe characterization of environmentally-sensitive materials. Ultra-high vacuum cryogenic suitcases allow specimen transfer between preparation, processing and several imaging platforms without exposure to atmospheric contamination. For expedient transfers, we installed a fast-docking station equipped with a cryogenic pump upon three systems; two atom probes, a scanning electron microscope / Xe-plasma focused ion beam and a N2atmosphere glovebox. We also installed a plasma FIB with a solid-state cooling stage to reduce beam damage and contamination, through reducing chemical activity and with the cryogenic components as passive cryogenic traps. We demonstrate the efficacy of the new laboratory protocols by the successful preparation and transfer of two highly contaminationand temperature-sensitive samples-water and ice. Analysing pure magnesium atom probe data, we show that surface oxidation can be effectively suppressed using an entirely cryogenic protocol (during specimen preparation and during transfer). Starting with the cryogenically-cooled plasma FIB, we also prepared and transferred frozen ice samples while avoiding significant melting or sublimation, suggesting that we may be able to measure the nanostructure of other normally-liquid or soft materials. Isolated cryogenic protocols within the N2 glove box demonstrate the absence of ice condensation suggesting that environmental control can commence from fabrication until atom probe analysis.
Data Availability Statement: All relevant data are
within the manuscript.
Funding: The acquisition, development and
maintenance for the various machines were
supported in part by Germany’s
Bundesministerium fu¨r Bildung und Forschung
funding the UGSLIT and Laplace projects. KAKR is
funded by Volkswagen Stifftung through the
Experiment! program. YC is funded by a Chinese
Scholarship Council scholarship. The funders had
Atom probe tomography (APT) is now an essential analytical tool for advancing modern
material science applied to engineering materials [
], the life sciences [
] and geology [
Experimentation remains challenging, chiefly in fabricating undamaged APT samples and,
no role in study design, data collection and
analysis, decision to publish, or preparation of the
once made, transferring those samples between microscopes without environmental
contamination or modification. Addressing these difficulties could facilitate many unique studies in
materials, surface sciences and, possibly, the life sciences.
Amongst the issues regularly faced is the analysis of highly reactive metals: the bare surface
of a fresh specimen tends to rapidly react with the gaseous environment and hence what gets
analysed is not the actual material of interest any longer. Beyond difficulties inherent to
preparing specimens for surface analyses, environmental degradation of a specimen’s surface and
sub-surface region has hindered exploiting of the full promise of APT for the analysis of
catalysts despite some valiant efforts in this space [4, 5] using in-situ techniques [
innovations for sample transfer methods permit the characterization of environmentally sensitive
materials , recently used to provide a unique analysis of the liquid-solid interfaces in glass
. This work has provided perspective upon some possible modifications that could assist in
cryo-FIB preparation. Deuterium distribution in a ferritic steel [
] and a palladium alloy
 were isolated with the development of cryogenic transfer protocols. A novel experiment
preparing liquid has been assisted by the use of a modified Leica cryogenic suitcase at ETH,
Zurich [12, 13]. Although in development for several years, these approaches are far from
routine and existing instrumentation usually maintains the specimens under high-vacuum
conditions (approx. 10−6 mbar), which may be above the partial pressure necessary to activate
surface reactions (e.g. oxidation).
The comprehensive modular protocol developed at the Max-Planck-Institut fu¨r
Eisenforschung (MPIE) and presented here caters to multiple research streams requiring these
capabilities to be carried out simultaneously. A modular approach is employed where samples are
kept isolated from the environment during transport through the use of a cryogenic ultrahigh
vacuum (UHV) carry transfer suitcase (CTS), matching the ultrahigh vacuum (below 10−9
mbar) and the low-temperature capabilities of experimental platforms. This UHVCTS enables
the movement of specimens under ultrahigh vacuum conditions and with cryogenic
temperatures, transferring between the various preparation and analytical platforms that are equipped
with cryogenically-cooled stages.
In the cryo-UHVCTS, the low temperature is maintained through liquid nitrogen (LN2). It
was recently shown that maintaining a specimen “cold chain” transfer at LN2 temperature is
sufficient to immobilise a detectable amount of deuterium within the structure of a steel
specimen upon electrochemical charging . This aspect is critical to enable hydrogen mapping,
which is one of the major opportunities for APT [
]. Hydrogen is the smallest of all
atoms, is very mobile, and at room temperature the desorption rate from steels can be
significant. For the sample preparation and nanocharacterisation of hydrogen-charged alloys, two
UV laser-assisted atom probes, including one with a reflectron, and a xenon-plasma
focusedion beam (PFIB) microscope were equipped to dock with the UHV suitcase. Cryogenic cooling
on the PFIB stage additionally allows for sample preparation with less defect agglomeration
introduced by ion knock-on damage, radiolysis and heating  all of which can be
suppressed by the use of lower beam energies, lower currents and sample cooling [16–18]. We
hypothesize that sample cooling can also reduce the contamination of the surface and
sub-surface volumes, whether by chemisorbed gases (typically H2 and H2O) diffusing into the bulk or
via oxidation (absorbed O2). Sample cooling also prevents the sublimation of some materials
which on the nanoscale can completely destroy the targeted structure. For controlled
processing and electrolytic hydrogen/deuterium-charging, as well as other experiments sensitive to
the exposure to atmospheric moisture or oxygen, a dedicated N2 glovebox was also interfaced.
We present here the first results obtained with this setup.
Solving the materials design problems presented by metallic materials in hydrogenating
environments hinge upon understanding hydrogen’s role in the various phenomena which
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may exacerbate or even directly cause catastrophic failure. Characterisation of nanostructural
features, like grain boundaries, stacking faults, dislocations, vacancies, voids, small precipitates
and hydrides, is necessary to obtain insight into how hydrogen diffuses through and can be
sequestered by these features. Atom probe microscopy can serve as a high-throughput
technique for this purpose, as it gives both three-dimensional structural and chemical information
with near-atomic resolution. Unfortunately, experiments concerning hydrogen in these
materials face challenges that other common approaches employing atom probe do not face
Over the past few decades, atom probe tomography has evolved to provide
compositionally-resolved three-dimensional structure on sub-nanometre scales within comparatively
large volumes (typically 100 x 100 x 750 nm3). Practical atom probe requires the refinement
of many steps and proponents of atom probe still grapple with basic concerns regarding
data validity and interpretation. The question “to what extent does an atom probe
measurement reflect reality and how can this be improved?” often requires input from additional
microscopy techniques. In answer to this, electron microscopy techniques cannot be used by
themselves to retrieve all desired information, as their associated compositional analysis is
limited and often confined to two dimensional images. Significant efforts have been devoted
to establishing correlative microscopy protocols that lead to a more complete understanding
of the microstructure of an atom probe specimen . Transmission electron microscopy
has been used to image atom probe specimens before  or after acquisition [22, 23],
and some efforts characterising both before and after [24, 25]. Electron microscopy in
conjunction with atom probe tomography has, in several cases [26–33], even been applied to
atomic-scale resolution TEM imaging of complex microstructures with full chemical
These solutions are potentially better than palliative strategies that correct for obvious
reconstruction flaws. The apparatus described herein demonstrates that UHV transport of
specimens (with or without cryogenic preservation), can be an effective component of
correlative studies by preventing environmental alteration of the atom probe specimen. The
possibility to perform back-and-forth transfers though the cryo-UHVCTS enables imaging
of the specimen at various stages of the analysis, which enables recording of the emitter
Another expected outcome of the project, and a future direction of this research, is the
exploitation of this information to inform improved data reconstruction protocols and enable
mapping of the very positions of atoms and the chemical compositions at the atomic level in
three-dimensions , hence the allusion to the ‘Laplace demon’. Simon Pierre Laplace indeed
postulated that knowing the position and nature of all particles in the universe at a given point
in time, one could predict the future and know all of the past. Modern quantum mechanics
has supplanted such perspectives, but ambitions of understanding material evolution still
require accurate measurements. Here, we describe the necessary instrumentation to further
these ambitions and showcase some of the preliminary results obtained that exploit these
We describe in detail our new suite of instruments and the modifications necessary to
enable cryogenic UHV sample transfers. We itemize each individual component and its utility,
acknowledging that different designs and alternate off-the-shelf components may provide
similar capabilities. Fig 1 depicts the interconnectivity between our experimental platforms that
the new UHV sample transfer protocols provide. Multiple exchanges can be performed upon
the same specimen for investigations requiring additional fabrication, chemical treatment or
correlative electron microscopy.
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Fig 1. Experimental overview of the Laplace Project. The ultrahigh vacuum carry transfer suitcase (UHVCTS—top left) can be securely fastened to
every experimental platform via an ultrahigh vacuum loadlock (top right) which is pumped as necessary to maintain conditions in either microscope or
glovebox. It is planned to mount the suitcase upon future instruments. Schematics detailing the basic configuration of the transfer are detailed for each
Ultra-high vacuum carry transfer suitcase (UHVCTS)
The key enabling technology is the two UHVCTS units (Ferrovac VSN40S). Their internal
assembly is cooled by liquid N2 (LN2), and each is modified to accept a modified CAMECA
atom probe puck (detailed below). Each UHVCTS has a 500-mm wobblestick that ends with a
PEEK-insulated puck manipulator. The two cryo-UHVCTS only differ in their small ion
pumps with non-evaporable getter (NEG) cartridges, rated to pump 100 L/s and 200 L/s
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respectively (NexTorr D-100-5 vs D-200-5). With proper use, each can easily attain 10−10
mbar. The UHVCTS are mounted on the experimental platforms via specially designed
loadlocks (Ferrovac VSCT40 fast pump-down docks), pumped by a 80 L/s turbopump (Pfeiffer
HiPace 80). The contained cryogenic pump is used either when minimizing loading time is
essential or for improving the vacuum quality via cold trap action. Fig 1 depicts both the
UHVCTS and the UHV booster loadlock.
Atom probe and loadlock
Two state-of-the-art commercial APT microscopes are available; namely a straight-flight-path
instrument, the Cameca LEAP 5000XS, and a reflectron-fitted instrument, the LEAP 5000XR.
A docking station was added to both LEAPs.
APT specimens are mounted upon easily manipulated specimen pucks. For the Laplace
Project, we used specially designed pucks that are thermally insulated from any direct contact
with vacuum transfer rods or wobble-sticks through a 2mm-thick layer of polyether ether
ketone (PEEK) that replaces a part usually made of metal. PEEK is a UHV-compatible polymer
that has good strength, low thermal diffusivity, and can be baked. Coupon clip-holders are
screwed into the puck from the front of the puck, thereby allowing a slim profile which is
advantageous for multiple transfers through a maze of vacuum chambers.
One of the positions in the carousel used to store specimen pucks in the airlock and
intermediate buffer chamber of the LEAPs was also modified and is thermally insulated through
the use of PEEK. An additional component for rapidly loading a sample puck onto the
cryogenic analysis stage was developed. A piggyback puck with a large thermal mass is pre-cooled,
typically to a temperature below 50K, by placing it on the cryo-stage of the analysis chamber.
The sample puck is passively cooled by this piggyback puck placed into this insulated position
on the carousel. This makes it possible to maintain the transferred specimen puck at low
temperature between the transfer from the cooled-down suitcase to the analysis position in the
microscope. This is important for temperature-sensitive samples or samples that could be
chemically-unstable even at liquid N2 temperatures. Their assembly are shown in Fig 2(a).
Fig 2. Atom probe modifications. (a) A side-view of the cryogenic ultrahigh vacuum transfer into the buffer chamber of the local electrode atom probe
(LEAP 5000XR). The connection is made at the labelled CF40 flange. (b) An expanded view of the interlocking pieces used to transfer
cryogenicallycooled samples from the suitcase to the atom probe’s analysis stage with no increase in temperature. (CF40: ConFlat 40 mm flange; UHV: ultrahigh
vacuum; CTS: carry transfer suitcase; PEEK: polyether ether ketone).
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Fig 3. Xenon plasma focussed ion beam microscope modifications. (a) The configuration of the solid-state cooling bands in the scanning electron
microscope (SEM) chamber with PT100 resistance thermometers. (b) An aerial view of the SEM side-chamber allowing for the cryogenic sample
transfer between the two different vacuum regimes of the suitcase and the SEM chamber. The connection is made at the labelled CF40 flange (ConFlat
40 mm). UHV: ultrahigh vacuum; CTS: carry transfer suitcase.
Dual-beam focussed ion beam modifications
Fig 3 depicts a schematic for the specimen exchange on the xenon-plasma focussed ion beam
(PFIB) microscope. The suitcase is attached via a VSCT40 fast pump-down loadlock to an
intermediate buffer chamber with optional cryogenic cooling (via LN2 dewar) on the puck
transfer shuttle (-130 ˚C) and a surrounding cryo-shield. The shuttle is used to transport up to
two sample pucks between suitcase and SEM chamber insertion positions. The microscope
chamber only achieves a high vacuum (5 × 10−7 mbar) and this intermediate transfer protocol
serves to maintain the suitcase’s ultra-high vacuum (typically 5 × 10−10 mbar). The buffer
has a quick loadlock gate for the insertion of pucks upon the shuttle if required.
The plasma FIB has a bespoke SEM stage which accepts atom probe pucks and is thermally
isolated from the stage mount by polyether ether ketone (PEEK) plastic. The dual beams’
eucentric points is at 4-mm working distance. We can cool the stage with flexible copper
bands attached to a nickel/gold-coated copper cold-finger cooled to -184 ˚C degrees by an
external LN2 dewar. With the copper bands attached, a full range of tilt (-10 ˚ to 54 ˚) is
available. We measured temperature on the stage and at two points on the cold finger with standard
PT100 resistive temperature sensors with the minimum stage temperature being
approximately -140 ˚C after three hours (the addition of a second set of bands improved this
performance to ¡ -150 ˚C after two hours). Next to each sensor, a MOSFET chip can be used to
provide rapid heating of the cold finger. Controlled heating can be implemented for
sublimation or recrystallization studies.
The two UHVCTS are mountable on a modified Syletec glovebox. For this instrument, the
UHV loadlock has been augmented with a Agilent Starlab ion pump (isolated from high
pressures by a UHV valve) and the venting performed with ultra-clean N2. For specimen transfer,
the UHVCTS is opened directly to a clean N2 glovebox atmosphere with 0.5 ppm O2 and a
dew-point < −105 ˚C (below the measurement limit). The UHVCTS vacuum adequately
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recovers with the support of the pumping system on the fast-docking station as well as the
additional ion pump. The UHVCTS ion pump can then maintain 10−8 mbar but the ion
pump’s non-evaporable getter must be reactivated to restore optimal performance.
Pure magnesium samples were prepared in the Helios PFIB using an in-built
micromanipulator and Pt-precursor gas injection system (GIS) to provide standard liftout techniques to then
mount samples upon a silicon microtip array. We then used a 30kV Xe-ion accelerating
voltage for rough milling and an 8kV accelerating voltage for fine milling. Each sample was
transferred via the UHVCTS to the LEAP 5000XR using with slightly different protocols. Fig 4
shows four reconstructions from atom probe measurements with corresponding
compositional profiles running through the specimen. Up to 4 at. % oxygen was detected in the surface
layers when cryogenic protocols was not obeyed at all, i.e. room temperature milling, exposure
to atmosphere and prolonged storage in the LEAP5000XR buffer. The mass-to-charge spectra
of Fig 4(e) demonstrates that negligible hydrogen was detected. In the case where the cold
stage was used, a cryogenic UHV transfer was made. The sample was run immediately and
negligible levels of surface oxygen were detected.
Processing or preparing specimens within the controlled environment inside the
glovebox is also expected to allow for an additional level of control over the formation of
spurious surface species. This is particularly true for the development of frost or ice that develops
on the surface of specimens after electrochemical charging with e.g. deuterium used as a proxy
for hydrogen in some recently reported studies [9, 11]. Upon charging, specimens are
quenched and kept in LN2 to prevent further migration of the deuterium, and when this is
done in air, the moisture condenses onto the specimen’s surface and prevents its direct
analysis. Performing these tasks in the glovebox is expected to alleviate or limit the influence of such
Glovebox isolation and aqueous solutions
A good “cold-chain” protocol as presented in  is necessary, not only in introducing a
specimen to an atom probe chamber without changing the specimen, but also to minimise
contamination of condensed atmospheric gases. Fig 5(a) shows the accumulation of moisture
condensation at approximately 90 seconds after removal from an LN2 bath upon silicon
microtip coupon specimens. Using the N2 atmosphere glovebox, we eliminated the formation
of ice over the same time period after removal from an LN2 bath (Fig 5(b)).
Microcopic analyses of soft materials often implies cooling them to cryogenic temperatures,
and often vitrifying them as required, so as to minimise modification of the structure during
the preparation of the specimens. Techniques related to atom probe have been used to
investigate thin layers of vitreous specimens as reported by [35, 36]. However, their use has been
rather limited. A protocol to prepare specimens with dimensions suitable for atom probe was
tried. First, a drop of water (boiled to remove dissolved gases and doped with 55 p.p.m. NaCl
to increase conductivity) was micro-pipetted upon the flat-top of a 0.3-mm stainless steel wire
mounted into a typical puck, pre-cooled with liquid nitrogen and loaded through the quick
load-lock chamber attached to the PFIB. The puck was then transferred onto the dedicated
pre-cooled stage inside the main chamber of the PFIB. The frozen drop was first cut into a
cuboidal shape using the Xe-plasma beam (1.6 nA @ 30kV), and subsequently sharpened into
a needle by using a two stage annular milling at 30kV, with no low kV clean up milling
performed. These successive steps resulted in producing an APT needle as displayed in Fig 5(d).
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Fig 4. Preparation and ultrahigh vacuum transfer of magnesium. Atom probe reconstructions of pure magnesium samples prepared and transferred
in the following protocols. In each of the shown reconstructions, MgO, Mg2O and O species are shown by green, red and blue dots respectively. (a)
Room temperature fabrication, stored for 1 week in buffer, removed to atmosphere for 3 minutes before the atom probe. (b) Room temperature
fabrication, stored for 2 weeks in buffer before atom probe. (c) Milled using the cryogenically-cooled stage, stored for 1 week in buffer before atom
probe. (d) Milled using the cryogenically-cooled stage, transferred with the cryogenic ultrahigh vacuum carry transfer suitcase, and then atom probe
immediately). (e) The mass-to-charge spectra of experiments (a) & (b) demonstrating that, while oxygen was definitely present, little hydrogen is
PLOS ONE | https://doi.org/10.1371/journal.pone.0209211
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Fig 5. Condensation and ice samples. (a) A 36-microtip array photographed approximately 90 seconds after removal from a liquid nitrogen bath
( −196 ˚C) and evidencing significant ice condensation in a laboratory atmosphere. (b) The same 36-microtip array, 90 seconds after removal from
the liquid nitrogen bath, this time showing no ice condensation while standing in the glovebox’s dry N2 atmosphere. (c) A 1-mm sphere of pure water
ice upon a 0.3-mm stainless steel wire. (d) From the sphere, a 50-nm atom probe needle was fashioned in the plasma focussed ion beam microscope
with the cold-stage and transferred to the local electrode atom probe (LEAP 5000XS) with the cryogenic ultrahigh vacuum carry transfer suitcase.
Laser-pulsed APT analysis of such a thick layer of ice could not be conducted, likely due to
ice’s extremely low electrical conductivity. A 60K specimen temperature was used, and a
standing voltage up to 10kV with a laser pulse energy up to 1 nJ was spanned, but no ions were
detected in the manner of a specimen “turning on”. Voltage pulsing was subsequently
performed also with a pulse fraction 20% of the standing voltage with similar negative result.
Specimen preparation has often been regarded as the most challenging aspect of performing
meaningful APT experiments. An extension of this is to consider transfer and even the atom
probe as being part of this preparation process. Exercising higher levels of control over the
specimen fabrication and transport will affect both experimental yield and data quality.
Moreover, field evaporation is a gradually eroding process which makes atom probe experiments
destructive; acquiring microscopic snapshots of APT specimens during this process is crucial
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to better understand field evaporation and to formulate more accurate three dimensional
Such observations can only be performed when specimens are held in and transferred
through controlled environments, preventing any surface transformation that, at the
approximately < 100-nm scale of an atom probe specimen, can be a substantial part of the
analysed specimen volume. The intricacies of specimen preparation, the protocol of specimen
transfer and even the routine of specimen storage must be examined. For example, preparation
of samples susceptible to O2, moisture, or residual chamber gases (even down to 10−10 mbar) is
problematic, so it can be imagined that a new generation of atom probe experiments will focus
on such materials sensitive to parameters like temperature and atmospheric exposure. Our
results demonstrated that not only should the atmosphere around the specimen be controlled
during the transfer of the specimens, but also during the preparation itself.
By use of a cryogenic cold stage in our plasma FIB, and by maintaining cryogenic
temperatures under UHV transfer, we demonstrated in the analysis of a magnesium alloy (Fig 4) that
we can successfully suppress surface oxidation and thus sub-surface modification. Comparing
two Mg samples fabricated at room temperature (Fig 4a and 4b)), where both samples were
transferred by UHVCTS and one was briefly removed into atmosphere, we demonstrated that
storing the sample in the vacuum chamber was no guarantee that oxidation would not occur
(for this particular material at least). Even considering the results for the
cryogenically-prepared samples (Fig 4c and 4d), we could suppose that longer storage times can still influence
surface oxidation. This is not surprising but we suggest that best practice is immediate
experimentation of cryo-UHVCTS samples. The complete chain of specimen preparation and
handling must thus be controlled.
How does using the cryogenically-cooled stage in the plasma FIB result in less oxygen being
detected? As the literature suggests, cooling the specimen can reduce beam-induced damage
[15–18]. Sample cooling may also prevent the radiolysis of adsorbed chamber gases, the
radicals of which can then react and transform the specimen’s surface. A solution could also be
offered through unintentional cryo-pumping. In the setup in Fig 3, the cold finger and the
copper bands present a large surface area and so could provide a large cold surface for H2O, CO2
and other oxygen-containing hydrocarbons to condense upon. The cold finger reaches -184
˚C, and though molecular oxygen condenses at -183 ˚C at standard pressure and temperature,
it would not condensed at the vapour pressures present in the plasma FIB. This could suggest
that better vacuum management could improve specimen preparation.
We shall soon make minor modifications to the plasma FIB stage, addressing the efficiency
of the stage cooling but also the frequent failure of the MOSFET heater chips, likely replacing
these in the future with small resistive heaters. This will increase the speed of specimen
preparation but also allow for specific temperatures to be reached upon the stage. One useful
application would be to allow the platinum precursor, introduced by the plasma FIB’s gas injection
system, to be used at non-cryogenic temperatures < 0 ˚C. A low cryogenic temperatures, this
precursor condenses upon the cooled specimen without site specificity. This issue has already
begun to be addressed elsewhere in the literature  with suggestions for gas injection
replacements (e.g. water/propane). Another use for variable temperature will be for sublimation
control of an aqueous substrate.
We have proven that the N2 glovebox provides a workspace for experiments requiring
isolation from the atmosphere. Such experiments may include electrolytic hydrogen charging of
materials where the sample can then be subsequently plunged to liquid nitrogen temperatures.
Fig 5(b) demonstrates that water vapour is scrubbed from the glovebox to negligible levels.
With the glovebox, we will be able to safely handle oxygen-sensitive materials like hydrides for
energy applications or reactive alkali metals. Thereafter, introducing such samples to the
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closed UHVCT protocols (with possible cryogenic capabilities) will allow for atom probe
investigations which have previously not been considered realistic.
We have demonstrated the basic functionality and effectiveness of our ultrahigh vacuum carry
transfer suitcases and associated protocols. The level of control of the environment of the
specimen pre- and post-preparation, up until the actual atom probe analysis, is unprecedented. We
demonstrate that application of our protocols can alleviate the formation of an oxide layer
formed on the surface of a reactive metal such as Mg, and also that we can reduce the depth of
penetration of spurious O that can extend over tens of nanometers below the surface. This
should greatly improve O-impurity measurements in such systems. We expect that the use of
such cryo-protocols will become more widely spread in the coming years.
Sigrun Ko¨ster from Ferrovac is acknowledged for her support to the project and fruitful
discussions. We are also grateful to Dr. Abhishek Tripathi for providing the magnesium samples
and Laila Moreno Ostertag for concocting a dilute saline solution that we used for the
preparation of our ice atom probe specimen.
Conceptualization: Kristiane A. K. Rusitzka, Thomas F. Kelly, Dierk Raabe, Baptiste Gault.
Funding acquisition: Dierk Raabe.
Investigation: Leigh T. Stephenson, Agnieszka Szczepaniak, Isabelle Mouton, Kristiane A. K.
Rusitzka, Yanhong Chang.
Methodology: Leigh T. Stephenson, Agnieszka Szczepaniak, Andrew J. Breen, Uwe Tezins,
Dirk Vogel, Paraskevas Kontis, Alexander Rosenthal, Jeffrey D. Shepard, Baptiste Gault.
Resources: Uwe Tezins, Andreas Sturm, Dirk Vogel, Alexander Rosenthal, Jeffrey D. Shepard,
Urs Maier, Thomas F. Kelly, Baptiste Gault.
Supervision: Leigh T. Stephenson, Baptiste Gault.
Visualization: Leigh T. Stephenson, Agnieszka Szczepaniak.
Writing – original draft: Leigh T. Stephenson, Baptiste Gault.
Writing – review & editing: Leigh T. Stephenson, Agnieszka Szczepaniak, Isabelle Mouton,
Kristiane A. K. Rusitzka, Andrew J. Breen, Uwe Tezins, Andreas Sturm, Dirk Vogel,
Yanhong Chang, Paraskevas Kontis, Alexander Rosenthal, Jeffrey D. Shepard, Urs Maier,
Thomas F. Kelly, Dierk Raabe, Baptiste Gault.
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