bluuebunny/crossref_metadata_2025 huggingface dataset:
Bismuth Ferrite Harmonic Nanoparticles and Biphotonic Microscopy: Innovative Approach to Track In Vivo Muscle Stem Cells, a Promising Candidate for Cell Therapy of Muscular Dystrophy
Authors: Dubreil Laurence , leroux Isabelle , Ledevin Mireille , Lovo Claire , Schleder Cindy , Lagalice Lydie , Gerber Sandrine , Bonacina Luigi , Rouger Karl
Published: December 2016

Bismuth Ferrite Harmonic Nanoparticles and Biphotonic Microscopy: Innovative Approach to Track
In Vivo
Muscle Stem Cells, a Promising Candidate for Cell Therapy of Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal X‐linked recessive muscle disease that represents the most common form of muscular dystrophy, affecting one in 5,000 male births. It is caused by mutations or deletions in the gene encoding dystrophin leading to the lack of dystrophin protein. This results in muscle fiber degeneration followed by severe endomysial sclerosis, leading to progressive muscle weakness and premature death at the age of 20‐30 years. Currently, there is no effective treatment for DMD. In 2011, we showed that a stem cell population (named MuStem cells) isolated from healthy dog skeletal muscle induces long‐term muscle repair and striking clinical efficacy after its systemic delivery in the dystrophic dog representing the clinically relevant DMD animal model. During last years, our group isolated the human counterparts (hMuStem) and demonstrated that they share the same phenotypic and
in vitro
behavioral features of canine cells. Currently, little is known about the homing in the muscle tissue and the whole body distribution of the MuStem cells following a systemic delivery which are nevertheless essential to determine the safety and efficacy aspect of the therapeutic strategy. To address this need, we use bismuth ferrite harmonic nanoparticles (BFO‐NP, 100‐120 nm range) as probes for the tracking of MuStem cells to study
in vivo
the hMuStem cell engraftment.

The nanoparticles are very interesting tools because capable to generate both Second Harmonic Generation (SHG) and Third Harmonic Generation (THG) signals. The origin of the signals is related to the crystalline properties of the nanoparticles, in particular its peculiar non‐centrosymmetric structure. Cell tracking is therefore possible from the NPs SHG and THG signals detected with a two‐photon confocal microscope A1RMP Nikon and this work provides the opportunity for long‐term, three‐dimensional cell tracking.

Uncoated and poly‐ethylene glycol(PEG)‐coated BFO‐NP were investigated to label hMuStem cells
in vitro
. The cells were exposed to BFO‐NP and BFO‐PEG‐NP. Localisation and cytotoxicity of the NPs were investigated
in vitro
during two weeks.BFO‐labeled cells were tracked in the mouse
Tibialis anterior
muscle after their intramuscular injection by using biphotonic microscopy.
Time resolvedHREMofAl crystal surface
Authors: Lereah Yossi , Biskupek Johannes , Kaiser Ute
Published: December 2016

The crystallization of Ge:Al amorphous films was studied by time resolve TEM intensively in previous years and reported[1]. These studies included the geometry and the dynamics of Al‐amorphous interface with time resolution of 40 milliseconds by conventional bright‐field (BF) and dark‐field (DF) TEM imaging of films of 50 nm thickness and by conventional high resolution (HR) TEM of films of 25nm thickness. The propagation of the Al interface is diffusion controlled, i.e. the velocity is temperature dependent [1]. The Al‐amorphous interface was found to be rough with a fractal dimension of 1.2 for the projected image [2]. However, the quantitative analysis of the interface propagation indicates a long range interaction in the Al‐amorphous phase interface [3]. These interactions were attributed to existence of ramified clusters of Al in the Ge:Al amorphous phase [4].

Here we will report on quantitative measurements that were obtained with 5 nm thick films heated locally by the electron beam resulting in the modification of the surface. The quantitative measurements will be based on observations that include aberration corrected HRTEM with low time resolution (1 sec) and by conventional HRTEM with high time resolution (few milliseconds). The later will be used also for evaluating the stability of the interface toward its 3D construction.
Spatial organization of microtubules within the ring canals in the male germ‐line clusters of Dendrobaena veneta
Authors: Małota Karol , Świątek Piotr
Published: December 2016

The formation of syncytial groups of germ‐line cells (cysts, clusters) is a widespread phenomenon in animal gametogenesis. There are three major types of the spatial organization of germ‐line cysts – linear, branched and cysts that have a central cytoplasmic mass (cytoplasmic core). In our studies, we focused on cysts with a central cytoplasm mass because this type of cyst is still poorly understood. We chose the earthworm
Dendrobaena veneta
as the model organism because it is easy to cultivate and a large number of germ cells clusters can be obtained from a single specimen.

Generally, clustered germ cells are interconnected via broad cell junctions called intercellular bridges or ring canals (Fig. 1, 2 and 3). Ring canals allow the cytoplasm to flow freely from one cell to another in the entire cluster. Ring canals are nothing more than modified contractile rings that do not close during late cytokinesis. The role of ring canals in the proper functioning of germ‐cell clusters is best known in such model species as
Caenorhabditis elegans
,
Drosophila melanogaster
and
Mus musculus
, in which any disorders in the construction and functioning of ring canals result in infertility. Not only is the functioning of ring canals well known in the model species but also their structure and molecular composition. Numerous studies have shown that a rich F‐actin cytoskeleton is present in the cortical layer of ring canals (Fig. 3) and that it is required to stabilize the bridges in order to keep them unobstructed, which is necessary for correct exchange of the cytoplasm. On the other hand, it is also known that microtubules play an active role in the development and functioning of germ‐cell cysts(Fig. 2). Ring canals are places in which F‐actin and microtubules cooperate together with other proteins (e.g. anilin) in order to stabilize the cytoplasmic channel and to optimize its functioning.

In clusters with a central cytoplasmic mass (called a cytophore in annelids), each germ cell has only one intercellular bridge that connects it to the cytophore (Fig. 1, 2 and 3). Therefore, the cytophore is an intermediate structure that mediates cytoplasm sharing between clustering cells.

Our previous studies showed that both F‐actin (Fig. 3) and microtubules (Fig. 2) are present in
D. veneta
germ‐line clusters. The aim of the presented studies was to investigate the spatial organization of the microtubules within the ring canals of the male germ‐cell clusters in
D. veneta
. To achieve this goal, we used immunofluorescent methods to visualize the F‐actin and microtubules and confocal microscopy to collect high‐resolution images. Based on the collected images, we reconstructed the cytoskeletal network within the ring canals.
Understanding Single‐Crystal Paleomagnetism: A Multiscale Approach
Authors: Einsle Joshua Franz , Fu Roger R. , Gelb Jeff , Weiss Benjamin P. , Harrison Richard J. , Midgley Paul A.
Published: December 2016

The development of the single‐crystal paleomagnetic approach has resulted in a new paradigm for paleomagnetism, enabling some of the most challenging paleomagnetic problems to be tackled for the first time: from measurements of the magnetic fields in the early solar system
1
to the search for evidence of Earth's oldest magnetic field
2
. Until now, characterization of the magnetic signal carriers in such unique samples has relied solely on two‐dimensional cross sections of crystals measured using either TEM or SEM. This leaves many unanswered questions about the three‐dimensional properties of the magnetic ensemble, without which single‐crystal paleomagnetic measurements can be subject to uncertainties and errors caused by magnetic anisotropy or the presence of secondary magnetic minerals
3,4
. We present a multi‐scale paleomagnetic approach, which employs both nondestructive and destructive tomographic techniques combined with correlative magnetic measurements and micromagnetic modeling. This multi‐scale approach addresses many of the shortcomings inherent in current single‐crystal paleomagnetic studies by providing a sound physical framework for interpreting the magnetic behavior. We demonstrate this concept using results from focused ion beam nanotomography (FIB‐nT) combined with finite element micromagnetic modeling to reconstruct the magnetic architecture of a single crystal from a chondritic meteorite
5
(Fig. 1A and B). Magnetic anisotropy in the grain arises from the sheet‐like arrangement of Fe nanoparticles forming along sub grain boundaries (Fig. 1B). Using individual particle geometries from the FIB nT volume micromagnetic modeling reveals new insights into the fundamental rock magnetic behaviour of particles with realistic shapes (Fig. 1C). We extend this methodology further by performing a correlative study of a zircon grain from the Bishop Tuff formation. The quantum diamond magnetometer (QDM) allows us to measure and map out localized magnetic sources in the zircon grain (Fig. 2A). Correlative measurements of the sample using the SEM and EDS do not identify all the magnetic sources originating on the sample surface. Using high‐resolution x‐ray microscope (XRM) tomography we observe the presence of buried magnetic signal carriers in inclusions below the polished surface of the zircon grain (Fig 2B). Using our correlative workflow we can determine the relationship between magnetic signal carriers and the host zircon grain as well as other mineral inclusions. We demonstrate that understanding single‐crystal paleomagnetism requires quantitative multiscale tomographic characterization in order to have confidence in the magnetic measurements reported.
Principle component analysis applied to high resolution cross sectional
STEM
imaging: Quantitative analysis of
2D
heterostructures
Authors: Rooney Aidan , Kozikov Aleksey , Prestat Eric , Withers Freddie , Geim Andre , Novoselov Konstantin , Haigh Sarah
Published: December 2016

Monolayers of 2D transition metal dichalcogenides (TMDCs) provide excellent semiconducting counterparts to insulating hexagonal boron nitride (hBN) and conductive graphene.[1] Combining all three materials in a Van der Waals vertical heterostructure allows the electronic, photovoltaic and electroluminescent properties of the TMDCs to be studied.[2] Whilst transport and optoelectronic measurements can probe the properties of exotic charge carriers, and ARPES can map the bandstructure such systems, direct high resolution imaging of the buried interfaces is only possible via high resolution cross sectional (S)TEM imaging.[3] The nature of these van der Waals interfaces not only determines the carrier injection between components[4], but also affects the bandstructure of the device and its ultimate functionality[5].

Here we present a novel strategy to denoise high resolution HAADF STEM images of cross sections using principal component analysis (PCA).[6] Cross sections are fabricated in a dual‐beam FIB‐SEM instrument using the in situ lift‐out method and polished with low energy ions to achieve electron transparency.[7] Cross sections were imaged in high resolution HAADF STEM using a probe‐side aberration corrected FEI Titan G2 80–200 kV with an X‐FEG electron source. By treating each line profile perpendicular to the fringes as a signal, components associated with noise and scattering can be separated by their variance. Removing the noise components allows us to accurately determine the separation between dissimilar crystals at these unique interfaces. More widely, the approach developed here also has application in a variety of layered material systems.
Atomic‐level elastic strain measurement of amorphous materials by quantification of local selected area electron diffraction patterns
Authors: Ebner Christian , Sarkar Rohit , Rajagopalan Jagannathan , Rentenberger Christian
Published: December 2016

Metallic glasses have been promising materials for application as structural materials. Therefore, intense research has been carried out to understand their mechanical properties and the underlying physical phenomena [1]. An important aspect of this research is measuring the response of metallic glasses to external and/or internal stresses and the resulting atomic displacements. These atomic level strains can be measured by quantification of the peak shifts in synchrotron diffraction experiments as demonstrated by Poulsen et. al. [2].

Here, we present a novel TEM method for measuring the atomic level strains on a local scale by means of electron diffraction. A series of selected area electron diffraction (SAD) patterns of amorphous TiAl tensile test samples are recorded in a CM200 electron microscope equipped with a Gatan Orion CCD camera. External stress is applied in‐situ and the evolution of the 2D strain tensor is calculated from the distortion of the characteristic amorphous diffraction halo. The full evaluation is carried out automatically by a plugin written for the Digital Micrograph
TM
platform: The peak maxima positions are extracted with sub‐pixel accuracy from azimuthal integrated sectors of 1° (cf. Fig.1(a)). This is achieved by a non‐linear least squares fit using a pseudo‐Voigt model function (cf. Fig.1(b)). By fitting an ellipse to the maxima positions also the center is determined with sub‐pixel accuracy. By iteration the data is refined and the polar form of the maxima positions is obtained. Using an unstrained SAD pattern as reference, the 2D strain tensor can be calculated from the difference of the peak maxima positions. By fitting the polar form of the strain tensor finally the principal strain magnitude and direction can be obtained relative to the SAD patterns coordinate system (cf. Fig. 2).

Simulated diffraction patterns with known parameters and different levels of noise are used to check the strain accuracy of the method. The relative error is calculated with respect to the known input parameters. The method has an accuracy of about 1x10
‐4
in determination of the parameters, the relative error in principal stress is below 3% even at principal strain below 0.5% (cf. Fig. 3).

In addition to measure the atomic‐level strain response to an applied external stress the method allows also to map the strains on a local scale, limited in principle only by selected aperture size and intensity fluctuations of the diffraction data for small sampling volumes. An example for such mapping capabilities is given in Fig. 4, where the strain distribution over the width of a strained specimen is given. In this case the strain distribution is non‐uniform and varies between 1.3% at center and 1.35% at edge regions.
In‐situ
E
(
S
)
TEM
Observations of Single Atom Dynamics in Catalytic Reactions
Authors: Gai Pratibha , Yoshida Kenta , Ward Michael , Boyes Edward
Published: December 2016

In heterogeneous catalysis gas (or liquid)‐solid catalyst reactions take place at the atomic level at elevated temperatures. Understanding and control of complex catalytic reactions on the atomic scale are crucial for the rational development of improved catalysts and processes. The development of the first atomic resolution environmental (scanning) transmission electron microscope (E(S)TEM) is described (1–6) including for the direct visualisation of reacting individual atoms in gas‐solid reactions in the working state in real time (3–6), opening up striking new opportunities for studies of catalysis at the atomic level. Our development of the atomic resolution ETEM (2) is now used globally. Benefits of the in‐situ studies include new knowledge, improved and more environmentally beneficial technological processes for healthcare and renewable energy as well as better or replacement mainstream technologies in the chemical and energy industries.

Examples include heterogeneous catalysis of biomass conversion into bioenergy and water gas shift (WGS) reaction (employing carbon monoxide and water) which is the basis of heterogeneous catalysis important in the generation of clean hydrogen energy for fuel cells, transportation fuels and in ammonia manufacture (7). Potential supported noble metal catalysts are examined for low temperature WGS catalysis (Fig.1) and compared with reaction data and modelling. The in‐situ observations in WGS have revealed the formation of clusters of only a few noble metal atoms resulting from single atom dynamics and the catalytic effect of low coordination surface sites. The new insights have important implications for applications of nanoparticles in chemical process technologies including for transportation fuels and emission control.
Combining Current Imaging and Electrical Probing for fast and reliable in situ Electrical Fault Isolation
Authors: Kleindiek Stephan , Rummel Andreas , Schock Klaus , Kemmler Matthias
Published: December 2016

Within the last decades, the feature widths of semiconductor devices have become too small to be resolved by state‐of the art optical microscopes, and other imaging techniques like Scanning Electron Microscopes (SEM) or Scanning Probe Microscopes (SPM) have become indispensable. For some analyses of device failures a combination of imaging and electrical measurements is required. Nowadays, one can find nanoprobers that are either based on SPM or SEM imaging techniques. For the SPM based nanoprobers, each probe consists of an Atomic Force Microscope (AFM) equipped with a conductive tip. For the SEM based systems, nanopositioners without force feedback are placed within a SEM.

Both approaches described above have advantages and disadvantages. Landing probes on a desired device is much easier for the SEM prober, as the SEM image gives immediate visual feedback. In contrast, the AFM prober requires many subsequent AFM images by each probe in order to align the probes with respect to each other and with respect to the device, which can be very time consuming. One advantage of the conductive AFM probing is the combination of topography images with electrical transport properties, i.e. images of local resistance (analogue to Scanning Tunneling Microscope (STM)). This allows easy identification of leakages or shorts on the chip.

In this work we present a very compact nanoprober that combines the advantages of SEM and SPM nanoprobers in one system.

The setup consists of a nanoprober with eight probes and an xyz substage mounted on the stage of an SEM (Zeiss Supra 40). Positioning the probes and the sample with nanometer precision as well as the controls for all electrical measurements are provided by a unified software interface. These can be used to quickly and easily probe contacts on technologies with line widths down to 10 nm and less. The probing experiments can include transistor characterization, electron beam induced current (EBIC) imaging, among others.

In order to locate leakages or shorts as described above, a voltage biased probe is scanned at constant height over the sample surface. The resulting current flow to a second probe or to the bulk contact can be simultaneously monitored with sub‐pA resolution. A typical current image can be acquired in a few seconds in a scan range of up to 1.5 µm × 1.5 um.

Each probe (or the substage) can be selected as the “scanning” voltage source or the “stationary” current sink, which allows for a very flexible definition of the expected current path enabling a powerful method for the visualization of faults in the integrated circuits.

The combination of the SEM image (the probes can be observed while the scan takes place) and the resulting current images enables correlative microscopy. Figure 2 shows an overlay image of the SEM image with current images on a 22 nm chip. Depending on the polarity (+/‐ 1V) of the voltage biased tip, n‐MOS or p‐MOS contacts become visible in the current image.
In situ and cryo
(S)TEM
imaging of internal microgel architectures
Authors: Caumanns Tobias , Gelissen Arjan , Oppermann Alexander , Hebbeker Pascal , Tiwari Rahul , Turnhoff Sarah , Wöll Dominik , Walther Andreas , Mayer Joachim , Richtering Walter
Published: December 2016

More than ever polymer science focuses on complex molecular structures and supramolecular assemblies. Microgels are responsive polymer materials and structures, which can be manipulated in e.g. charge or size by external parameters like pH or temperature variation. The investigated microgels are soft particulate polymer networks that can be dispersed in an aqueos medium. They reveal unique features providing new opportunities to develop smart bio‐inspired materials. In contrast to rigid colloidal particles, which lack the possibility to adapt their size and shape to enviromental requirements, microgels have switchable properties of form and function that make them very useful in a wide range of e.g. biological sciences and medical applications. They combine properties of dissolved macromolecules with those of colloidal particles.

The direct visualization of the internal structure of materials is very important to analyse the spatial distribution of different compartments and, thus, to design novel materials with tailored properties. Microgels can be prepared with various morphologies and functions in different compartments. Careful analysis of the correlation between architecture and function requires powerful methods to visualize inner structure and compartmentalization in the nanometer range.

Here, the direct visualization of different compartments within microgels using a combination of in situ and cryo transmission electron microscopy methods is shown. In particular, the challenge of determing the radial distribution of appropriately labeled compartments within single microgels and particles from 2D projections is adressed.

Microgels with core‐shell architecture were obtained by precipitation polymerization. First a particle was synthesized and purified before a shell was synthesized on top by the seed and feed method. Core and shell have oppositely charged copolymers to create a two compartment amphoteric microgel system, that is alternately stained with gold and magnetite nanoparticles. [1], [2]

For
in situ
liquid cell experiments, a thin layer of liquid was embedded between two hermetically sealed, electron transparent Si
3
N
4
‐windows. The used holder is an
in situ
‐liquid cell holder manufactured by Hummingbird Company and the microscope is a Zeiss Libra 200FE with an acceleration voltage of 200 kV. The resolution is mainly limited by the thickness of the liquid.

Figure 1 shows a comparison between
cryo
TEM and
in situ
STEM. Due to the liquid layer thickness the resolution is limited in (b). Also the Brown emotion leads to a defocused and smudged image.

Figure 2 shows the comparison of the radial distribution of nanoparticles according to the two images above calculated by a MATLAB routine. For the
cryo
TEM image in (b) the relative particle density as a function of the relative particle radius is plotted. (c) shows a 3D reconstruction of the model.
Kinetics of precipitation in new generation of cobalt‐based superalloys
Authors: Azzam Ahmad , Blavette Didier , Hauet Annie , Philippe Thomas , Danoix Frederic
Published: December 2016

Superalloys are key materials in aircraft engines and power generation systems. They are subjected to very high stress under temperatures in the range of 700‐1000°C. Currently Ni‐based superalloys are the most widely used materials for high temperature applications. These alloys owe their excellent mechanical proprieties to their microstructure characterized by the presence of a high volume fraction (up to 70%) of thermodynamically stable, coherent L1
2
ordered γ' precipitates (Ni
3
Al or Ni
3
Nb type) embedded in a disordered fcc γ matrix. Compared to Ni based superalloys, conventional Co based alloys exhibit hot corrosion, oxidation and wear resistance but their applications are restricted to temperatures below 750°C due to their instability at high temperatures. In 2006 J. Sato et al. [1] discovered a new stable L1
2
ordered, Co
3
(Al,W) phase embedded in the disordered γ‐Co solid‐solution matrix. Mechanical properties (creep and plastic deformation, elastic property, structural stability) of Co‐based alloy have been widely investigated but the precipitation process have been the subject of very few studies [2,3].

The aim of this work is to study precipitation kinetics in model CoAlW superalloys at the atomic scale. This work is focused on the kinetics transformation paths during precipitation. The temporal evolution of average size, volume fraction and number density of γ' precipitates as well as that of phase composition has been studied as a function of aging time at 900°C employing three dimensional Atom Probe Tomography (APT). In addition Transmission and Scanning Electron Microscopy (TEM, SEM) have been used to complement APT studies. Different alloy compositions will be studied in this work, figures 1 and 2 show respectively bright field transmission electron micrographs of Co‐9.7Al‐10.8W (atomic %) alloy and dark field image of Co‐9.1Al‐7W alloy after annealing at 900°C for 10h. The microstructures reveal precipitates of cuboidal shape, respectively 100 nm (Fig 1) and 50 nm (Fig 2) in size, homogeneously distributed in the parent γ phase. The γ and γ' phase compositions are major parameters controlling the properties of superalloys, that have been measured by APT. Figure 2 shows 3D reconstruction in the Co‐7Al‐9W aged at 900°C for 10h, showing γ' precipitates delineated by a 12 at.% W isoconcentration surface. Composition profile across γ/γ' interface reveals that W shows a very strong tendency to partition to the γ' phase unlike Al that exhibit a very weak tendency to partition between γ and γ' phases. The summation of Al content and W content in the γ' phase is close to 25 atomic % that is to the expected stoichiometry of the γ' Co
3
(Al,W) ordered phase. It can this suggests that Al and W occupy preferentially the corner sites of the same sub‐lattice in the ordered L1
2
structure. This presentation will come in more details on the temporal evolution of both the microstructure and phase composition.
Quantitative electron diffraction tomography for the structure solution of cathode materials for
L
i‐ion batteries
Authors: Karakulina Olesia , Fedotov Stanislav , Sumanov Vasiliy , Drozhzhin Oleg , Khasanova Nellie , Antipov Evgeny , Abakumov Artem , Hadermann Joke
Published: December 2016

Quantitative electron diffraction tomography (EDT) is a perfect tool for studying electrode materials for Li‐ion batteries due to its ability to obtain diffraction data from submicron crystals (typically 100‐200 nm), sensitivity to “light” atoms as Li and reduced dynamical effects (enhanced by the intrinsic property of the electrode materials to comprise only lightest possible elements to maximize the capacity). Here we demonstrate applications of EDT to the crystal structure analysis of polyanion cathodes, including location and occupancy refinement of the Li positions.

We applied EDT for monitoring the deintercalation process in LiMn
0.5
Fe
0.5
PO
4
(LMFP) olivine [1]. We investigated a pristine and two delithiated phases (mid (3.7 V vs. Li/Li
+
) and fully‐charged (4.2 V), since upon charge two first‐order phase transformations take place). All structures keep the
Pnma
space group and unit cell metrics and no sign of local ordering was found. The difference Fourier maps of the electrostatic potential calculated from EDT data, allow to localize the Li atoms (Fig 1). The refined occupancies of the Li positions for all samples are in excellent agreement with the Li contents measured from the E‐x dependence obtained with galvanostatic cycling. Regarding the role of Jahn‐Teller distortion due to Mn
3+
in the delithiation mechanism, this effect is not of cooperative nature, since the octahedral distortions in pristine and fully‐charged samples vary insignificantly (5%).

EDT sheds light on the family of (Li,A)‐ion cathode materials that are obtained by subsequent chemical or electrochemical exchange of Na/K by Li. This allows obtaining new polymorphs that are not attainable by direct synthesis due to thermodynamic reasons. We synthesize new KVPO
4
F fluorophosphates with KTiOPO
4
(KTP) structure, having a 3D system of continuous spatial cavities and two potassium positions [2]. Upon charge up to 5.0 V vs Li/Li
+
the K1 site becomes empty whereas residual potassium (17%) resides in the K2 site (Fig. 2). At the same time, the structure changes from noncentrosymmetric (Pna2
1
) to centrosymmetric (Pnan). After lithiation, the K2 sites are shared by K and Li but K1 still remains empty. Li occupies a new Li3 position having [4 + 2] coordination with four short 1.99−2.14 Å Li3−O bonds. Both Li sites reside in the channels along the
b
axis and form a row of Li atoms.

The discussed exapmles show that EDT is a relible technique for the crystal structure solution and refinement. It can be used as a routine method for the study of cathode materials, since no special sample preparation is required. Furthermore, EDT provides valuable information of the lithium atom positions and occupancies.
Determining the structure/property relation at oxide interfaces by means of advanced
TEM
spectroscopy and imaging
Authors: Gauquelin Nicolas , van Aert Sandra , Verbeeck Johann , Tendeloo Gustaff Van
Published: December 2016

The study of novel physical properties appearing when two materials are interfaced has become one of the major fields of research in solid state physics over the last decade. For example, in the strive for novel non‐silicon based electronics, the discovery of the formation of a conductive layer right at the interface region between 2 insulators (for example LaAlO
3
and SrTiO
3
); a so‐called two‐dimensional electron gas (2DEG) or two dimensional electron liquid appears. Another important example of such emergent phenomena is the appearance of interface magnetism or superconductivity. As the materials involved in those new physical phenomena are often complex oxides, many factors such as strain, oxygen stoichiometry, cation intermixing, oxygen octahedral coupling.…[1,2] have to be considered when discussing their origin. The exact understanding of those phenomena is a key factor in order to turn these research ideas into working devices and in order to search for the most optimal materials.

In parallel, advances in electron microscopy instrumentation and techniques such as the introduction of aberration‐correctors of the probe‐forming lens have made it possible to achieve sub‐angstrom spatial resolution allowing the study of materials on an atom column by atom column basis. High Angle Annular Dark Field (HAADF) combined with Annular Bright Field (ABF) imaging have made it possible to study and understand respectively the cationic and the oxygen sub‐lattices in these materials.

As a first example, in the case of a (La,Sr)MnO
3
(LSMO) film grown on a NdGaO
3
(NGO) substrate, the magnetic easy axis of the LSMO film can be reversed by adding a SrTiO
3
(STO) buffer layer between the substrate and the film. Using the statistical analysis of STEM ABF images, we could reveal that even one single STO layer is enough to remove the transferred octahedral tilt of NGO into the LSMO film reversing its magnetic easy axis from the a to the b axis(see ref 1 and figure 1).

In a second part, The appearance of superconductivity in a superlattice of (Sr,Ca)CuO
2
(SCCO) and BaCuO
2
(BCO) will be investigated. Comparing two different heterostructures where 8 layers of SCCO are sandwiched with STO (no superconductivity) and BCO (superconductivity) the effect of the structure of the different layers (orientation of the CuO
2
in the form of planes or chains) on the appearance of superconductivity will be presented.
HRTEMstudy of structural defects and related deformation mechanisms induced by nanocompression of silicon
Authors: Merabet Amina , Texier Michaël , Tromas Christophe , Verdier Marc , Talneau Anne , Thomas Olivier , Godet Julien
Published: December 2016

Over the last years, progress in nanomaterials design and manufacturing has revolutionized technology and opened up prospects for many scientific researches. The investigations of material properties (optical, electronic, mechanical…) at small scales have revealed amazing behaviors, different from those currently observed in bulk samples. For instance, silicon, which is known to behave at room temperature as a brittle material, shows an unexpected ductile behavior when the sample size decreases below a few hundreds of nanometers [1]. The mechanisms leading to this phenomenon remain, however, poorly understood. In this context, this research project aims at investigating in more details the deformation behavior of silicon nanopillars by combining experimental techniques (SEM, FIB, HRTEM) and molecular dynamics simulations. In this work, various nanopillars with different orientations and diameters (from 100 nm to 1 µm), were patterned by Reactive‐Ion Etching and FIB micromachining. These pillars were then compressed with a slow‐strain‐rate (10‐4s‐1) at room temperature using a nanoindenter equipped with a flat punch and operated in displacement‐control mode.Post mortemobservations of deformed nanopillars performed by SEM and TEM reveal the activation of different slip systems. The comparison between experimental and simulated HRTEM images notably evidences the simultaneous propagation of partial and perfect dislocations in {111} planes. In addition, unexpected plastic events have also been observed in {113} planes. On the basis of the microscopic observations, various possible deformation mechanisms involved during the nano‐compression of the pillars are proposed.
A Compressive Sensing based acquisition design for quantitative ultra‐low dose high‐resolution imaging and spectroscopy in the
STEM
Authors: Muecke‐Herzberg Dorothea , Abellan Patricia , Sarahan Michael , Godfrey Iain , Saghi Zineb , Leary Rowan , Stevens Andrew , Ma Jackie , Kutyniok Gitta , Azough Feridoon , Freer Robert , Midgley Paul , Browning Nigel , Ramasse Quentin
Published: December 2016

Typically, the Nyquist frequency determines the sampling rate required to resolve a specific feature in a dataset. In practice this requires oversampling by twice the maximum relevant frequency. As such this provides a lower limit for the electron dose necessary to acquire the data experimentally. However, by applying the compressive sensing (CS) principles of sparsity and incoherence, this limit can be overcome and therefore a substantial reduction of the total electron dose can be achieved. CS theory then allows a recovery of the essential image information from randomly undersampled images. The theory of CS has been successfully applied in a number of areas, e.g. astronomy, MRI scanning, electron tomography [1], and most recently first experimental designs for STEM have been reported [2,3]. Despite these developments, CS acquisition schemes able to recover quantifiable information from atomically resolved images of beam‐sensitive materials, time‐changing processes and spectroscopic datasets have so far not been established for STEM.

Here we demonstrate such a CS‐based STEM acquisition implementation and benchmark its performance at atomic resolution using a variety of materials, including complex oxide ceramics with an inhomogeneous distribution of point defects as illustrated in fig. 1, but also highly beam‐sensitive catalysts with atomic resolution [4]. The implementation relies on custom‐built hardware and software which controls an electrostatic beam shutter to blank the electron beam during all but a few randomly chosen pixels through a regular image (or indeed spectrum image) acquisition. The total electron dose used to form a whole dataset can thus be tailored according to the electron damage threshold of the sample under investigation whilst maintaining all other acquisition parameters identical to regular data acquisition, allowing a seamless transition from ‘fully sampled’ to ultra‐low‐dose conditions. It will be shown that datasets acquired in this fashion down to a few % of the total incoming dose (see fig. 2) can be reconstructed to yield a truthful atomic resolution representation of the sample, using a variety of reconstruction algorithms [5,6]. We show that this implementation of CS can also be extended to 2D spectroscopy mapping and simultaneous HAADF image acquisition.. These results open the door to practical ultra‐low dose high‐resolution imaging and spectroscopy in the STEM for very beam sensitive samples, where the level of sampling can simply be chosen depending on the damage threshold of the material being investigated [7].
Nanoscale quantitative characterization of
22nm CMOS
transistor using Scanning Transmission Electron Microscopy (
STEM
)
Authors: Weng Weihao , Ortolland Claude
Published: December 2016

22nm Silicon‐On‐Insulator (SOI) complementary metal‐oxide semiconductor (CMOS) technology has a number of performance boosters, such as third generation embedded DRAM, embedded stressor technology and 15 levels of copper interconnect.
[1]
In addition to geometric scaling, strain engineering in CMOS transistors has provided another enabler for device performance improvement. A compressive strain in PMOS channel can increase the hole mobility, and a tensile strain in NMOS channel can increase the electron mobility. In PMOS of 22nm SOI technology, epitaxial SiGe source/drain (S/D) is used to introduce compressive strain in the channel, and SiGe layer in the channel is used to control threshold voltage of device. Hence obtaining the nanoscale chemical composition and strain information of them is vital during the semiconductor development.

In this work, energy‐dispersive X‐ray spectroscopy (EDX) in STEM is used to determine the Ge atomic concentration (%Ge) based on the Cliff‐Lorimer ratio method.
[2]
The Cliff‐Lorimer factor is calibrated by measuring a standard Si
0
.664
Ge
0.336
blanket sample with a relative error smaller than 1%. An improved high angle annular dark field (HAADF) STEM image is obtained by STEM with Drift Corrected Frame Integration (DCFI). DCFI technique integrates successive STEM images via calculating and correcting the drift from cross correlation. The produced STEM image has minimal drift and a high signal‐to‐noise ratio. It is analyzed by Geometrical Phase Analysis (GPA) to extract strain information.
[3]

Figure 1(a) shows a typical PMOS transistor with <110> in‐plane direction and <001> out‐of‐plane direction. SiGe channel and dual‐layer embedded SiGe source/drain (S/D) can be clearly observed in HAADF‐STEM mode. Since HAADF image intensity is proportional to atomic number Z
1.7
,
[4]
SiGe layers with different %Ge are clearly seen, and can be further related to %Ge measured from EDX. In Figure 1(b), EDX map shows that channel SiGe has around 22% Ge. In S/D the buffer layer has 20‐21% Ge, and the main layer has 25 ‐ 30% Ge. HAADF micrograph and the corresponding deformation maps are shown in Figure 2. A compressive strain of 0.3% in the <110> direction is observed in the channel Si. There is no deformation between channel SiGe and channel Si in the <110> direction, suggesting that channel SiGe is compressed in this direction to match underneath Si lattice. This agrees with the finding that a deformation as high as 1.9% in channel SiGe is observed in the <001> direction. In addition the channel Si shows a tensile strain of 0.3% in the <001> direction. Results show that a combination of STEM‐based techniques, including HAADF‐STEM, STEM‐GPA and STEM‐EDX, can reveal the nanoscale chemical composition and strain distribution of a transistor. These information are used to monitor and control the process.
Visualization of 2‐dimensional potential map in multilayer organic electroluminescence materials by phase‐shifting electron holography
Authors: Sato Takeshi , Yamamoto Kazuo , Tsuchiya Miki , Ito Katsuji , Yoshimoto Noriyuki , Taniguchi Yoshifumi
Published: December 2016

Electron holography (EH) is a TEM method which can quantitatively measure electromagnetic fields of various samples [1‐3]. In this study, we tried observing a local two‐dimensional electric distribution, formed in multilayer organic electroluminescence (OEL) quantitatively with phase‐shifting EH [4‐5] by HF‐3300EH Cold‐FE TEM operated at 300 kV equipped with multiple biprism system.

An OEL multilayer sample (CuPc/α‐NPD/Rubrene/Alq3/LiF/Ag) was fabricated on a Si substrate using a vacuum evaporation method. Each layer's thickness and the surface morphology of the OEL multilayer sample were evaluated by X‐Ray Reflectometry (XRR) and Atomic Force Microscopy (AFM), respectively.

The sample for phase‐shifting EH observation was fabricated by focused ion beam (FIB) technique. A part of the multilayer sample, which formed a multilayer structure on a Si substrate, was picked up by the microsampling technique and was fixed onto a W deposition on the mesh for TEM observation. Then, a thin film sample of thickness 450 nm was fabricated by FIB processing. Generally, the OEL sample is vulnerable to water, and the structure may change in quality in reaction to atmospheric water vapor, depending on the formed materials. Therefore, in this study, after thin film processing, contact with the atmosphere was prevented by using an air protection mesh holder.

Figure 1 shows a TEM image, and a hologram by double‐biprism EH technique [6]. The model structure of an OEL multilayer is inserted in the TEM image. Sample thickness was about 450 nm. From the TEM image, some contrast is observed in the position of the CuPc layer, but we cannot confirm the image contrast corresponding to the other layers.

Figure 2 shows the result of the visualization of the 2‐dimensional potential map of an OEL multilayer. We can clearly observe the contrast of the OEL multilayer, as shown in the reconstruction image (Figure 2b). Because the inner potential of the materials in each layer is constant, we can consider phase shifts to be an electric potential change in the sample. In the future, we will investigate the accuracy of this experimental data by comparing our data with a simulation.
Apical chitinous matrix and basal lamina ‐ the ultrastructure and formation of two distinct extracellular matrices of crustacean hindgut cells
Authors: Bogataj Urban , Mrak Polona , Štrus Jasna , Žnidaršič Nada
Published: December 2016

Ectodermally derived gut and epidermal cells in crustaceans are covered by cuticle, a chitinous apical extracellular matrix, and at the opposite side they are underlined by a basal lamina. Thus, the same cell performs synthesis and spatiotemporal control of elaboration of two extracellular matrices that differ in ultrastructure, composition and functions. Differentiation of the extracellular matrix in epithelial tissues is an integrative part of the establishment and maintenance of the characteristic apicobasal polarized cell architecture. We present here the ultrastructural description of the hindgut cells' apical matrix differentiation during embryonic and larval development of crustacean
Porcellio scaber
. In addition, in the same developmental stages the ultrastructure of basal lamina was described.

The ultrastructural hallmarks of the hindgut cells and their extracellular matrices (ECM) in adults are: (i) apical ECM is a chitinous cuticle, consisting of distinct horizontal layers ‐ electron dense epicuticle and electron lucent procuticle (Fig. 1), (ii) extensive apical and basal plasma membrane infoldings, forming prominent membrane labyrinths, (iii) basal lamina that is forming an extensive interface surface to hemolymph space (Fig. 2). The ultrastructure of cuticle differs in the two anatomic regions of the hindgut, namely the anterior chamber and the papillate region. In the anterior chamber the epicuticle is much thinner than procuticle and lamellae are discernible in the procuticle due to helicoidally arranged chitin protein fibers (Fig. 1). In papillate region epicuticle and procuticle are of approximately equal thicknesses and no lamellae could be discerned in the procuticle.

Differentiation of the hindgut cuticular matrix during embryonic and larval development involves a sequential formation and shedding of several apical matrices, which gradually display ultrastructural features characteristic for adults. The outline of the pre‐cuticluar apical matrix in embryos is ruffled and consists of homogenous lucent material and a distal electron dense lamina. In late embryos of stage 18 the first deposition of the apical cuticle was evidenced. In marsupial larvae the cuticle follows the outline of apical hindgut surface and is already differentiated into thin electron dense epicuticle and thicker electron lucent procuticle. In the epicuticle a trilayered surface lamina and electron dense material beneath are discernible (Fig. 3). The procuticle is homogenous along the whole length of the hindgut and non‐lamellate as is characteristic in anterior chamber of adults. The basal side of the hindgut epithelium of marsupial larvae is in contact with basal lamina (Fig. 4) exhibiting fibrillary structure in certain section profiles.
Novel
MAX
resembling Phase
Mo2Ga2C
Authors: Lu Jun , Hu Chunfeng , Lai Chung‐Chuan , Tao Quanzheng , Halim Joseph , Hultman Lars , Eklund Per , Rosen Johanna , Barsoum Michel
Published: December 2016

MAX phases are layered transition metal carbides/nitrides with specific properties e.g. electrical/heat conductivity and machinability as metals. The MAX phases have hexagonal structure with a general M
n+1
AX
n
formula, where M is an early transition metal, A is an A‐group element (mostly IIIA and IVA) and X is either C and/or N
1,2
. Their unit cells consist of M
6
X octahedral, interleaved by layers of A elements. The difference between them is in the number of M layers separated by the A element layers: 2 layers for 211 structure, 3 layers for 312 and 4 layers for 413. All MAX phases reported to date have only one A layer. So far more than 70 ternary M
n+1
AX
n
phases were found
2
. The MAX family, however, is still being extended as new phases are discovered and/or by creating quaternary and higher, solid solutions. While challenges with their crystal structural determination are addressed,
3,4
also exploration is made for phases that do not follow the traditional M
n+1
AX
n
chemistry. In this work, we present a novel crystal structure: Mo
2
Ga
2
C.
5

EDX measurement revealed that the Mo/Ga ratio of the material is approximately 1, which implies a new phase. The detailed atomic structure of the new phase was characterized with analytical high resolution scanning electron microscopy. Both Z‐contrast images and EDX mappings along [11‐20] and [10‐10] demonstrate that this phase is layered with two Ga layers separating each 2 Mo layers. Thus, a new structure is found, which has hexagonal structure with lattice parameters of a=3.034Å, c=18.081Å and space group of P6
3
/mmc (194). The structure does not follow the MAX formula M
n+1
AX
n
, but is related to Mo
2
GaC. It can be described as a Ga pair replacing Ga in Mo
2
GaC structure, shifted in opposite directions along the c axis, positioned exactly on top of each other and at 4f positions instead of 2c positions. The final detailed atomic coordinates are obtained by using XRD Rietveld refinement and are listed in Table 1. The highlight of the work is not only finding a new phase, but also giving directions for a potential new family of related structures, on par with the MAX phases.