Vendredi 09 juillet
09:40

Vendredi 09 juillet

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SC4
09:40 - 12:15

Symposium Commun 4
Assistance machine pour acquisition, analyse, interprétation/modélisation de données de microscopies

Modérateurs : Arnaud DEMORTIÈRE (chargé de recherche CNRS - CR1) (UPJV, Amiens), Perrine PAUL-GILLOTEAUX (IRS, Nantes)
Le numérique a pris aujourd’hui une place prépondérante en microscopie, que ce soit dans le domaine des sciences des matériaux, de la médecine ou de la biologie. L’utilisation d’approches en apprentissage profond (“deep learning”) est devenue une solution incontournable dans le traitement et l’analyse des données massives acquises en microscopie. Elles permettent leur classification ou leur modélisation sur la base de lois statistiques, et peuvent également nous assister dans la prise de décision et la visualisation de ces données. Les algorithmes “ad hoc” et les approches de “deep learning” démontrent depuis quelques années leur capacité à pouvoir aider à la prise de décision sur les paramètres d’acquisition à choisir et viennent même dans certain cas remplacer l'opérateur. Par exemple, l’analyse des images au cours de l’acquisition peut aider à décider de la suite et guider le microscope, ou permettre de rechercher les événements rares de manière automatique. Ils permettent également d’extraire de l’image des informations qui n’y semblaient pas présentes, en utilisant une connaissance a priori, formalisée ou non, comme dans le cas du débruitage, de correction d’artefact ou d’amélioration de la résolution de l’image. Ils sont aussi capables d’extraire des données de phénotypages ou caractérisation de manière automatique et sans comparaison de vitesse avec un opérateur humain, avec un biais de quantification reproductible, par la segmentation, le tracking, ou l’analyse des signaux et les mesures dérivées. La mise au point de ces algorithmes et en particulier des modèles de machine learning pour toutes ces applications requièrent le partage de données annotées afin de les mettre au point, ce qui appelle également à de nouvelles solutions de partage et d’annotation.
09:40 - 10:10 Microscopy Image Analysis: The Shift to Deep Learning. Daniel SAGE (EPFL, Lausanne, Suisse)
The quantification of microscopy images require automatic tools to extract relevant information from complex data. To tackled this task, numerous image analysis algorithms have been designed, commonly based on prior knowledge and on physical modeling. However, the recent success of the deep learning (DL) in computer science have drastically changed the bioimage analysis workflows to a data-centric paradigm. While this DL technology remains relatively inaccessible to end-users, recent efforts has been proposed to facilitate the deployment of DL for some bioimage applications through new open-source software packages.
Here, we present a set of user-friendly tools that allows to test DL models and to gain proficiency in DL technology: the centralized repository of bioimage model (Bioimage Model Zoo), the readytouse notebooks for the training, and the plugin deepImageJ that can run a DL model in ImageJ.
We provide also good practice tips to avoid the risk of misuses. We address some practical issues such as the availability of massive amount of images, the understanding of generalizability concept, or the selection of the pre-trained models. The shift to deep learning also questions the community about the trust, the reliability and the validity of such trained deep learning models.
10:10 - 10:20 Discussion.
10:20 - 10:50 From regularized methods to deep learning in imaging sciences. Nelly PUSTELNIK (Chargée de recherche CNRS CRCN) (ENS, Lyon)
During the last 20 years, imaging sciences, including inverse problems or segmentation, have known two major revolutions: (i) sparsity and proximal algorithms and (ii) deep learning. Non-smooth convex optimization became the main thrust behind significant advances in signal processing, image processing, and machine learning. Behind non-smooth functions, there is the concept of sparsity which is central in the contributions in inverse problems and compressed sensing but also proximal algorithms allowing to handle with large scale data. These concepts will be described as well as the objective functions relying on it, going from Mumford-Shah model to the most advanced restoration and segmentation methods. Ten years after the start of proximal revolution, deep learning has started to provide a new framework for solving imaging problems going from agnostic techniques to models combining deep learning with standard regularized formulations. The second part of the talk will be dedicated to these recent advances in the specific context of image restoration.
10:50 - 11:00 Discussion.
11:00 - 11:15 #26238 - Utilisation d’outils d’intelligence artificielle pour la segmentation d’images 3D d’ovaire de poisson.
Utilisation d’outils d’intelligence artificielle pour la segmentation d’images 3D d’ovaire de poisson.

L’analyse quantitative du contenu cellulaire d’organes entiers par microscopie permet de comprendre leur organisation en conditions physiologiques ou pathologiques. Dans certains cas, l’analyse exhaustive est essentielle pour évaluer par exemple l’impact d’une mutation sur la mise en place d’une fonction biologique clé. 

Chez le médaka (Oryzias latipes), un poisson modèle classiquement utilisé pour l’étude de la reproduction, la fertilité des femelles est directement dépendante de la croissance asynchrone des follicules ovariens. Recrutés à partir de pools de cellules germinales, les ovocytes évoluent, en fonction de leur stade de développement, au sein de follicules de différentes classes de tailles (de 20um à plus de 1000um). Chaque jour, une vingtaine d’œufs sont ainsi pondus dans des conditions de photopériode contrôlée. Pour étudier cette dynamique de croissance, notamment dans le cas d’une lignée mutante présentant une fertilité réduite (miR-202-5p Knock-out), nous cherchons à dénombrer et mesurer l’ensemble des follicules contenus dans les ovaires des femelles juvéniles et adultes.

A partir d’images d’ovaires en 3D de médaka obtenus en microscopie confocale à fluorescence, nous avons mis en place une séquence d’analyse qui s’appuie sur des réseaux de neurones pré-entraînés accessibles en opensource. La segmentation 3D des follicules a été réalisée avec l’algorithme Cellpose, récemment développé par Stringer.C et al [1], et ce sans nécessiter une étape d’apprentissage sur nos images. Une étape de débruitage appliquée en amont via l’outil Noise2void [2] a également permis d’augmenter la qualité de la segmentation. Grâce aux récents développements des approches de « deep-learning » appliqués aux données de microscopie, nous avons ainsi obtenu des données quantitatives tridimensionnelles jusqu’alors inaccessibles avec des méthodes classiques (Figure 1).

Ces nouveaux outils, rendus de plus en plus disponibles aux non-spécialistes du domaine, ont ainsi ouvert la voie à un phénotypage cellulaire profond, dès les stades larvaires précoces chez les femelles invalidées pour le miR-202.

Références:
[1] Stringer, C., Wang, T., Michaelos, M. et al. Cellpose : a generalist algorithm for cellular segmentation. Nat Methods 18 (2021), p.100–106. https://doi.org/10.1038/s41592-020-01018-x
[2] Krull, A., Buchholz, T. O., & Jug, F. Noise2void-learning denoising from single noisy images (2019). arXiv:1811.10980v2.


Manon LESAGE (Rennes)
11:15 - 11:25 Discussion.
11:25 - 11:40 #26239 - Méthodes d’imagerie computationnelle par ptychographie 3D et hyperspectrale par contraste de phase : algorithmes et applications.
Méthodes d’imagerie computationnelle par ptychographie 3D et hyperspectrale par contraste de phase : algorithmes et applications.

Les valeurs de résolution spatiale les plus élevées dans les microscopies aux rayons-X et électronique d'aujourd'hui sont obtenues par ptychographie[1]. Cette nouvelle méthode de nanoimagerie computationnelle ne repose pas sur l'utilisation de lentilles, qui sont remplacées par l’ordinateur et des algorithmes avancés de récupération de phase. Différemment d’autres méthodes, la résolution spatiale dans la ptychographie ne dépend pas de la taille de sonde et le faisceau incident n’a pas besoin d’être une onde plane sans aberrations, ce qui allège les contraintes sur l'optique du microscope.

Nous présentons ici cette méthode innovante ainsi que ses algorithmes de reconstruction. Elle peut être réalisée soit dans le régime holographique[2] soit dans le régime de champ lointain[3,4]. Quatre informations quantitatives sont obtenues à partir d’une seule expérience : les images d’absorption et de contraste de phase de l’échantillon, ainsi que l’amplitude et phase du faisceau incident (sonde)[5]. En combinaison avec la tomographie, nous présentons comment la tomographie ptychographique aux rayons X (PXCT) a révolutionné la caractérisation des matériaux hétérogènes (Fig.1). En fournissant une carte 3D quantitative de l'indice de réfraction du matériau, des informations chimiques locales sur l’échantillon peuvent être obtenues[3]. Pour compléter, nos derniers développements méthodologiques combinent la ptychographie avec des méthodes spectroscopique dans une méthode la nanoimagerie hyper spectrale pour extraire la localisation et état chimique des éléments chimique d’intérêt dans l’échantillon.

Pour finir, nous discuterons nos outils open-source d’analyses de données en Python sur lesquelles nous travaillons : (i) Ptypy : un framework computationnel pour la reconstruction ptychographique optimisé pour les calculs en parallèle ou sur GPUs (Fig.2a) ; (ii) Toupy : une librairie d’outils pour de reconstruction tomographique qui comprend des algorithmes de déroulage de phase, correction de la rampe de phase, alignement de projections basée sur la consistance tomographique, et la reconstruction tomographique (Fig.2b).

Références :
[1] da Silva & Menzel, Optics Express 23 (2015), p. 33812-33821.
[2] Gussone, et al., Applied Materails Today 20 (2020), p. 100767.
[3] da Silva, et al., Langmuir 31 (2015), p. 3779-3783.
[4] da Silva, et al., ChemCatChem 7 (2015), p. 413-416.
[5] da Silva, et al., Optica 4 (2017), p. 492-495.


Julio DA SILVA (Grenoble)
11:40 - 11:50 Discussion.
11:50 - 12:05 #26240 - Développement de simulation de microscope électronique en transmission pour l’optimisation des expérimentations.
Développement de simulation de microscope électronique en transmission pour l’optimisation des expérimentations.

Le microscope électronique en transmission est un instrument extrêmement puissant et flexible, capable d’explorer la matière à des échelles inférieures au nanomètre, mais aussi de sonder des propriétés spécifiques, comme les états magnétiques ou les détails de la microstructure. Sa complexité d’utilisation le rend cependant difficile à maîtriser, pour le débutant comme l’expert. Cela signifie un coût financier et de temps de formation, mais aussi une perte d’efficacité pour l’expérimentateur, qui ne peut pas utiliser le microscope comme il le souhaite, ni au maximum de ses capacités.

Ce problème est une conséquence du manque d'information accessible sur la configuration optique du microscope. N'ayant accès simplement qu’à l'image produite en sortie, le microscopiste doit faire appel à des stratégies, ou méthodes d'alignements, pour manipuler l'état optique de l'instrument.

Nous proposons ici d’introduire un paradigme différent, basé sur  représentation fidèle de l’état optique interne. Nous avons ainsi développé deux simulations complémentaires du microscope I2TEM [1, 2] du CEMES :  une pour des trajectoires électroniques exactes à l'aide du logiciel SIMION [3] et une autre basée sur l’approximation paraxiale à l’aide d’une bibliothèque python.Les champs électriques et magnétiques du microscope sont préalablement simulés à partir de la forme exacte des pièces par SIMION. Les simulations se synchronisent en temps réel avec le microscope. La mise en place de ces simulations pour d’autres microscopes est également facilitée grâce à un logiciel d'automatisation réalisé aussi en interne.

Cependant les résultats de telles simulations optiques sont complexe à visualiser. Nous  avons ainsi développé une interface dédiée en collaboration avec des étudiants et chercheurs en Interaction Homme-Machine, de l'équipe SINA de l'ENAC.

Ce système, qui s'adresse tant au novice qu'à l'expert, offre la possibilité de rendre plus accessible la réalisation d'expériences complexes, de les  préparer en amont, et fournit un outil pédagogique innovant pour la formation et la vulgarisation.

Références
[1] Y. Kubo, C. Gatel, E. Snoeck, et F. Houdellier, Ultramicroscopy, 175 (2017).
[2] J. Dupuy, Contrôle dynamique et optimisation des observations en microscopie électronique en transmission, Thèse de doctorat, Université de Toulouse (2021).
[3] David A. Dahl, International Journal of Mass Spectrometry, 200 (2000).


Julien DUPUY (Toulouse)
12:05 - 12:15 Discussion.
Room 1
12:15 Pause
13:00

Vendredi 09 juillet

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POS2
13:00 - 15:00

Session Posters 2

13:00 - 15:00 #26242 - IN SITU GROWTH AND SHAPE TRANSFORMATION OF Co NANOPARTICLES AND Co-Ni NANOALLOYS.
IN SITU GROWTH AND SHAPE TRANSFORMATION OF Co NANOPARTICLES AND Co-Ni NANOALLOYS.

Arthur MOISSETChristophe PETITPascal ANDREAZZADamien CHAUDANSONOlivier MARGEATSuzanne GIORGIO *,

  • Sorbonne Université,CNRS, MONARIS, UMR 8233, 4 place Jussieu, 75005 Paris
  • Université d’Orléans, CNRS, ICMN, UMR 7374, 1 rue de la Ferollerie, 45100 Orléans
  • Aix-Marseille Université, CNRS, CINaM, UMR 7325, Campus de Luminy, 13288 Marseille


The control of the shape and structure of metal nanoparticles or nanoalloys is important for applications. It mainly depends on the crystal growth mechanism. Co nanoparticles (NPs) and Co-Ni nanoalloys, grown from solution, exhibited a shape transformation from nanospheres to nanorods [1]. The growth mechanism from nanospheres to nanowires as in figure 1, was studied by the association of two in situ techniques, liquid microscopy and SAXS. In situ SAXS measurements have shown a textured media between the oleylamine (OAm) and the cobalt precursor. The shape transformation of pure Co NPs and Co-Ni nanoalloys was observed by TEM in a drop of OAm solution diluted in toluene or heptane, encapsulated between graphene layers, as described in previous works [2]. The growth of the NPs and alloys in an OAm visquous solution allows a growth mechanism by direct adsorption of the monomers and an homogeneous size and shape distribution, as seen in figures 2 a-c (a), after 5mn (b), 15 mn(c) . At RT, after the growth of NPs in the encapsulated solution, the OAM has a tendency to texture while the metal NPs are dissolved (figure 2d-e, 17 mn (d) and 18 mn (e)). Then, Co re-crystallizes as nanorods as in figures 2 f-g-h (19 mn (f), 23 mn (g), 27 mn (h)). The same mechanism was observed with Co-Ni nanoalloys. Careful observation of NPs in diluted OAm during the NPs dissolution in the electron beam, shows residual metal clusters with sizes below 1 nm, as in figure.2i (scale bar 50 nm). By the following, these remaining small clusters are the results of the beginning of the Co NRs’ formation and tend to align along the OAm texture then, they grow as nanorods. Références: [1] L.Meziane, C.Salzemann, C.Aubert, H.Gérard, C.Petit , M.Petit, Nanoscale, 8 (2016), p.18640 [2] De Clercq, W. Dachraoui, O. Margeat; C.R.Henry, S.Giorgio; J. Phys. Chem. Letters, 5 (2014) p.2126 [3] A. Vivien, M. Guillaumont, L. Meziane, C. Salzemann, C. Aubert, S. Halbert, H. Gérard, M. Petit and C. Petit, Chem.Mater., 31, 3, (2019), p. 96
Suzanne GIORGIO (Marseille)
13:00 - 15:00 #26243 - Phase evolution in Si-graphite electrodes mapped by VEELS in the transmission electron microscope.
Phase evolution in Si-graphite electrodes mapped by VEELS in the transmission electron microscope.

Jianhan XIONGNicolas DUPREPhilippe MOREAU *, Bernard LESTRIEZ

  • Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France


Negative electrodes based on silicon have been considered for some time (due to their theoretical high capacity) [1], but present long term performance not meeting the current requirements. This is due to the large change of volume of the material with its reaction with lithium ions and its unstable passivation against the electrolyte. In order to mitigate this downfall evolution, mixtures of silicon with graphite (a long used and efficient material) are now being developed and studied [2]. This is the objective of the ANR project SILMARILION concerning the negative electrode of the complete lithium-ion battery to be produced. Since interactions between the different constituents of the composite electrode (Si, graphite, binder) are essential to the behaviour during cycling and occurs at very small scale, (S)TEM experiments are quite useful. In this study, we have used valence electron energy-loss spectroscopy to map the different constituents of the pristine electrodes as well as the reaction products along cycling. The use of this method was shown [3] to be very effective even on highly beam sensitive materials such as lithium fluoride or polymeric entities. Thanks to a method developed by M. Boniface in his PhD thesis [4], it was even possible to grasp the evolution of these constituents along cycling in a quantitative way. To that end, the Gatan 969 spectrometer (equipped with a K2) of the Nant’Themis, some PCA post-processing and MLLS fitting routines were used. They allow identifying and, visualising the role of the PAA polymer binder (Figure 1) and the presence of a hairy silicon (Figure 2) as soon as 30 cycles, despite the presence of graphite [5].
Philippe MOREAU (IMN, Nantes)
13:00 - 15:00 #26246 - Defect creation in Transition Metal Dichalcogenides by Ion Bombardment and further characterization by Scanning Tunneling Microscopy.
Defect creation in Transition Metal Dichalcogenides by Ion Bombardment and further characterization by Scanning Tunneling Microscopy.

Pedro Lourenco *, Nadine WITKOWSKIGeoffroy PRÉVOTHervé CRUGUELRomain BERNARD

  • Institut de Nanosciences de Paris, Sorbonne Université, Paris, France


Transition-metal dichalcogenides (TMDC), such as WS2 and WSe2, are layered two dimensional materials, having a wide number of applications in optoelectronics, energy storage or catalysis. Epitaxial films are usually synthesized by chemical vapor deposition (CVD), leading to high-quality stoichiometric crystals with large domain sizes. Recently, there have been efforts to synthesize high-quality WS2 and WSe2 films through the use of reactive magnetron sputtering,[1] a versatile physical vapor deposition (PVD) process already implemented in the semi-conductor industry. As compared to CVD, more structural defects and smaller domain sizes are however observed. This could be explained by the impact of energetic species at the surface of the film during the growth. These structural defects play an important role in the characteristics of the TMDC. For example, chalcogenide vacancies are known to decrease the carrier mobility and thus to deteriorate the device performance. [2] To better understand the impact of energetic particles on the TMDC surface, we have generated single defects on the surface of WS2 and WSe2 crystals using low energy (50 eV to 500 eV) Ar+ ions with a controlled fluence. The irradiated samples were then analyzed by Scanning Tunneling Microscopy (STM). When imaged at negative sample bias, the defects appear as a bright protrusion due to the presence of a localized electronic state, associated with chalcogenide vacancies (see Fig. 1). Whereas a strong dependance with Ar+ energy of the probability of defect creation is observed, the shape and size of each defect, when imaged by STM, appears to be independent of the energy (see Fig. 1). In order to have an atomistic view of the collision phenomena, we have performed Molecular Dynamics (MD) simulations. These simulations show that there is a higher probability of creating defects at higher Ar energies, agreeing with the experimental results. They also show that there are more defects created which are located into the layers underneath the surface due to the collision cascade. This might explain why there is no clear difference in defect morphology with varying Ar+ energy, as the effect of the generated structures in the layers underneath cannot be fully probed by STM. Références/References : [1] Villamayor, M. et al, Vacuum, 188 (2021). [2] Yu, Z. et al. , Nat Commun 5, 5290 (2014)
Pedro LOURENCO (Paris)
13:00 - 15:00 #26349 - In-situ TEM techniques of magnetic nanotubes for 3D spintronics.
In-situ TEM techniques of magnetic nanotubes for 3D spintronics.

Mahdi Jaber *

  • Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France.
  • CEA, IRIG/MEM, France.


A major driving force in applied spintronics is magnetic memories. While existing products rely on uniformly-magnetized elements, data storage using the motion of magnetic domain walls in two-dimensional strips using spin-polarized current is also investigated [1]. The three-dimensional geometry like in cylindrical nanowires and nanotubes is researched [2]. Magnetic domain walls in the latter are distinct from those in flat films and strips, opening perspectives for new physics. In comparison to cylindrical nanowires, isolated ferromagnetic nanotubes have given rise to relatively few experimental reports. Here, we describe the characterization of high-aspect ratio CoNiB nanotubes, grown chemically by electroless plating, using various TEM techniques such as Energy-dispersive X-ray spectroscopy EDX, Electron energy-loss spectroscopy EELS, and in-situ Electron Holography. Previous experimental studies revealed the possibility for orthoradial magnetization (i.e. azimuthal domains), a phenomenon not expected by theory, but interesting for the application side [3] (Figure 1.a,b). Based on that, we performed TEM electron holography to explore the magnetic configuration in nanotubes, as well as their magnetic history under applied fields (Figure 1.c,d). We also evidence that Nickel tends to segregate on both side of the CoNi layer, which is supposed to affect the system magnetic behavior (Figure 2). To help the physical and the theoretical interpretation of the measurements, reasonable efforts on data analysis and micromagnetism simulations will be made. As a result, a deeper understanding of the spin textures in nanotubes will contribute to enhance the productivity in spintronics. References: [1] J. Hurst et al. Theoretical study of current-induced domain wall motion in magnetic nanotubes with azimuthal domains. Phys. Rev. B 103, 024434 (2021). [2] Magnetic nanowires and nanotubes, M. Staňo, O. Fruchart, Handbook of Magnetic Materials. Ed. Ekkes Brück vol. 27, 2018, Pages 155-267 [3] Staňo, M. et al. Imaging magnetic flux-closure domains and domain walls in electroless-deposited CoNiB nanotubes. SciPost Phys. 5 (2018) p 038.
Jaber MAHDI (CEA, Grenoble)
13:00 - 15:00 #26247 - CONTROLLING POROSITY IN CONDUCTING POLYMER CRYOGEL VIA THE ICE-TEMPLATING METHOD.
CONTROLLING POROSITY IN CONDUCTING POLYMER CRYOGEL VIA THE ICE-TEMPLATING METHOD.

Naoures HMILI *, Swapneel THAKKARQuentin WEINBACHPatrick allgayerMarc SCHMUTZLaure BINIEKAlain CARVALHO

  • CNRS – Institut Charles Sadron – 23 Rue du Lœss 67034 Strasbourg, France.


Porous bulk polymers are of great interest for their advantageous properties like low bulk density, flexibility and high surface area. These properties among many others, open new doors for diverse applications such as the hot topic of thermoelectricity. In that field, the porous polymer should be electrically conductive and thermally isolating. Ideally, an anisotropic structure with well oriented pores is crucial to reach high thermoelectric efficiency. Porous conducting polymers can be prepared by freeze-drying a hydrogel (PEDOT:PSS) leading to a porous cryogel. But, with a classic flash freeze-drying a non-controlled porous structure is obtained as shown in the SEM image (fig.1) (taken by Hitachi SU 8010 Ultra High Resolution Field Emission Scanning Electron Microscope). In this project, our team applies the ice templating technique [1] on PEDOT:PSS gels to control the porous structure. This involves the unidirectional growth of ice crystals in the gel as a texturing agent for the porosity. We demonstrate by cryoSEM that while freezing, the ice crystals grow and push apart the polymer fibers to create the walls of the pores. Once freezing is complete, the sample is dried by sublimation. A porous cryogel is then obtained in which the pores are the replica of the ice crystals. Via this method, and by controlling the cooling rate and temperature [2], we have succeeded to channel the pores and obtain a well aligned honeycomb structure as seen in fig.2 (a) and (b). Finally, the pore size as well as the directionality of the channelled pores were analysed by ImageJ (using respectively “analyse particles” and the plug-in “orientation J”). References: [1] Deville, S. (2013). Ice-templating, freeze casting: Beyond materials processing. Journal of Materials Research, 28(17), 2202–2219. doi:10.1557/jmr.2013.105 [2] S. Deville, Ice-Templating: Processing Routes, Architectures, and Microstructures. 2017. This Master internship work has been supported by a Sfμ grant.
Naoures HMILI (Strasbourg)
13:00 - 15:00 #26350 - Highlights of 15R crystal phase in Au-catalyzed ZnS nanowires.
Highlights of 15R crystal phase in Au-catalyzed ZnS nanowires.

Sumit Kumar *, Frédéric FossardGaëlle AmiriJean-Michel ChauveauVincent Sallet

  • GEMaC, CNRS - UVSQ, Université Paris-Saclay
  • LEM, ONERA-CNRS, Université Paris-Saclay


Unique growth mechanisms involved in semiconductor nanowires (NWs) pave the way to the achievement of new crystallographic phases and remarkable material properties. Interestingly, in the case of 1D nanostructures, polytypism can arise due to the particular growth mode below a catalyst droplet, which may induce stacking faults along the length of the nanowire. Moreover, these stacking faults can be correlated and form ordered arrays, until giving rise to new phases (polytypes) with distinct properties[1]. Hence, 4H, 6H, 8H, and 10H (so-called high order polytypes) can be observed in nanowires[2]. Hence, studying polytypism in semiconductor NWs arouses a strong interest for the next generation of electronic and photonic applications. In this framework, ZnS is an important II-VI semiconductor that has a wide range of optoelectronic applications including luminescent devices, infrared windows, and UV-photodetectors[3]. In this work, Au-assisted ZnS nanowires were grown by MOCVD on GaAs (111B) substrate (VLS mode or VSS mode). The idea is to provide a change in the growth mechanism via the physical state of catalyst droplets (liquid or solid) and hence, study the induced polytypism in ZnS nanowires. ZnS nanowires with length up to 1.4 µm and diameter in the range 10–34 nm was successfully achieved. The obtained morphologies and densities of the NWs have been systematically inspected by scanning electron microscopy (SEM) directly on the substrate (illustrated in Fig 1). Transmission Electron Microscopy has been also used to investigate the crystallographic structures and compositions of both catalysts and nanowires. HRTEM observations revealed that the NWs exhibits periodic stacking faults, and the resulting structure was accurately identified as 3 sequences of 5 planes ABCBA-BCACB-CABAC (i.e. 5th order superstructure), giving rise to an astonishing 15R crystal structure (Fig 2)[4]. This structure is highlighted for the first time in ZnS nanowires. We modeled this 15R structure in the framework of the classical nucleation theory and axial-next-nearest-neighbour-Ising model (ANNNI). References [1] G. Priante et al. Phys Rev B. 89 (2014) 241301 [2] Y. Jiang et al. Adv. Mater. 15 (2003) 1195 [3] S. Premkumar et al. Sci. Rep. 9 (2019) 18704 [4] S. Kumar et al. Nano Res. (2021) https://doi.org/10.1007/s12274-021-3487-8
Sumit KUMAR (Paris-Saclay)
13:00 - 15:00 #26347 - Impact of irradiation and nano-oxides dispersion on alpha prime phase formation in Oxide Dispersion Strengthened steels: a combined TEM and APT study.
Impact of irradiation and nano-oxides dispersion on alpha prime phase formation in Oxide Dispersion Strengthened steels: a combined TEM and APT study.

Marie-Jose SALEH AFIF *, Stephanie JUBLOT-LECLERCJoel RIBISAurelie GENTILSMarie LOYER-PROST

  • Université Paris-Saclay, CEA, Service de Recherches de Métallurgie Physique, 91191 Gif-sur-Yvette, France
  • Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France


Because of industrial development and the growth of the world population, nuclear reactors are developed to cover the increase in energy consumption. The nuclear energy produced through fission and fusion reactions is indeed capable of producing a very large amount of electrical power. One of the problems encountered during these nuclear reactions is the irradiation swelling of fuel cladding materials. Hence nanostructured materials such as Oxide Dispersion Strengthened (ODS) steels were especially developed to resist to irradiation [1] and high temperature [2]. These steels are composed of a metallic body-centered cubic matrix (FeCrW or FeCrMo) reinforced with nano-oxides of titanium and yttrium. As the ODS steel matrix is mainly a Fe-Cr system, a Cr-rich phase, alpha’, can precipitate under irradiation [3] and brittle the system. This study focuses on the impact of the nano-oxides dispersion and the irradiation conditions on the formation of the alpha’ phase in an ODS steel: MA957 [4]. A MA957 steel and a corresponding steel without nano-oxides are irradiated on the JANNuS platform [5] at 400°C with Fe ions at different damage doses (from 0,5 to 9 dpa). Samples are characterized at the nanometric scale using Transmission Electron Microscopy (TEM), Energy Filtered TEM (EFTEM) and Atomic Probe Tomography (APT). The drastic impact of the nano-oxide distribution and the influence of injected ions on the alpha’ distribution are revealed and discussed. References: [1] R.L. Klueh et al., Journal of Nuclear Materials 341 (2005), p.103 [2] T.R. Allen et al., Journal of Nuclear Materials 375 (2008), p. 26 [3] N.A. Bailey, Journal of Nuclear Materials 459 (2015), p. 225 [4] J. Ribis et al., J. Mater. Res. 30 (2015), p.2210 [5] A. Gentils, C. Cabet, Nucl. Instrum. Methods B 447 (2019), p.107
Marie-Jose SALEH AFIF (Orsay)
13:00 - 15:00 #26248 - Quantitative STEM imaging: from the SiGe model toward application to interfacial phase-change memories (iPCMs).
Quantitative STEM imaging: from the SiGe model toward application to interfacial phase-change memories (iPCMs).

Vitomir Sever *, Nicolas BernierPierre NoéJean-Luc Rouvière

  • Université Grenoble Alpes, CEA, LETI, F-38000 Grenoble


GeTe-Sb2Te3 superlattices (SL’s) are the most promising materials for iPCMs, but the physical switching mechanism is still under debate. To improve this emerging technology, it becomes mandatory to describe the iPCMs structures at an atomic scale since the involved mechanism upon switching is expected to rely on local atomic motion. Using atomic resolution HAADF STEM images, acquired on a FEI Titan Themis microscope, two analyses were performed. However, before studying the more complex case of iPCM SL’s, we explored the experimental approaches on a reference Si-SiGe multilayer sample calibrated by XRD. Various sets of data were acquired and analyzed using Python programming. First, images recorded with an HAADF detector were interpreted quantitatively by means of comparison between experimental and simulated intensities. We used the STEMsim software from the Rosenauer’s group [1] for HAADF image simulations. From this comparison, the local thickness can be obtained. If the thickness is known, the unknown chemical concentration of a single element can be measured. Here, PACBED measurements give the thickness and Ge concentration in SiGe layers was extracted [1]. Additionally, the position of atomic columns can be precisely determined utilizing a template-matching approach [2]. After acquiring a stack of low-dose images, rigid and non-rigid alignments were performed using the SmartAlign software. Then the center of gravity method is used to find the precise position of the correlation peaks between a template and an experimental image. Hence, a reference lattice can be calculated. Therefore, atomic displacements and strain maps were obtained on the same reference sample. For robust and fast analysis, two Python libraries have been developed and corresponding notebooks were deployed at the CEA Grenoble. After validating these methods on the reference sample, these analyses were applied to numerous HAADF images of iPCM SL’s and the first results on Sb2Te3 blocks will be presented. References: [1] Rosenauer et al., Ultramicroscopy 111 (2011), p.1316-27. [2] Zuo et al., Ultramicroscopy 136 (2014), p. 50-60
Vitomir SEVER (Grenoble)
13:00 - 15:00 #26244 - Segregation in Au-Cu nanoparticles: a theoretical and experimental approach.
Segregation in Au-Cu nanoparticles: a theoretical and experimental approach.

Grégoire Breyton *, Hakim AmaraJaysen NelayahDamien AlloyeauGuillaume WangJérôme CreuzeChristian Ricolleau

  • MPQ, Univ. de Paris
  • LEM, CNRS / ONERA
  • ICCMO, Univ. Paris Saclay


Nanoparticles (NPs) are primarily known for their high surface to volume ratio making them perfect candidate as catalyst for reactivity process. Another attractive aspect of these nano-objects lies in the unexpected reactivity of some materials. For example, gold is known to be inert at bulk scale but very reactive in small sized nanoparticles (< 5 nm) for the CO to CO2 transformation [1]. Interestingly, this phenomenon is enhanced by alloying gold with copper [2]. However, little is known on the surface structure of the Au-Cu alloy and more precisely of their surface composition which plays a crucial role during reactivity process. In this context, our work aims at characterizing the AuxCu1-x nanoparticles structure in order to highlight surface segregations or not by using both a theoretical and experimental approaches. Atomic scale Monte Carlo simulations based on semi-empirical potential [3] have been performed (Fig 1 Left). A strong segregation of gold over the entire surface is observed whatever the size of octahedron NPs (Fig 1 Middle). Simulations of nanocubes seem to strengthen these results where only (100) facets are present. Experimentally, octahedron NPs and nano-cubes have been synthesized by Pulsed Laser Deposition (PLD) on a substrate of NaCl. This substrate has a cubic structure which favors cubo-octaedron morphologies. Their chemical analysis and structural characterization on an aberration corrected JEOL ARM 200F in TEM and STEM modes are still ongoing (Fig 1 Right). References: 1. Lopez Nuria et al. Journal of Catalysis223.1 (2004): 232-235. 2. Liu Xiaoyan et al. Catalysis today 160.1 (2011): 103-108. 3. Rosato Vittorio et al. Philosophical Magazine A59.2 (1989): 321-336.
Grégoire BREYTON (Paris)
13:00 - 15:00 #26355 - Wave contrast analysis in High Resolution TEM : Rhombohedral Pr5Co19 structure and polytypes.
Wave contrast analysis in High Resolution TEM : Rhombohedral Pr5Co19 structure and polytypes.

Farah Chafaï *, Loïc PatoutKhalid HoummadaLotfi BessaisNajeh MlikiAhmed Charaï,

  • Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire Matériaux Organisation et Propriétés, 2092, Tunis, Tunisie
  • Aix-Marseille Université, CNRS, Université de Toulon, IM2NP - Campus de St Jérôme, 13397 Marseille cedex 20, France
  • ICMPE UMR CNRS 7182 – Université Paris Est Créteil, 94320, Thiais, France


Les intermétalliques à base de terre-rares (RE) et d’éléments de transition sont parmi les meilleurs candidats pour une utilisation comme aimants permanents. Les composés nanocristallins ont été très étudiés notamment par rapport aux techniques de préparation et l’état approprié du matériau pour obtenir le champ coercitif optimisé [1]. En particulier, le composé Pr5Co19 constitue un alliage attractif dû à ses propriétés significatives donnant lieu à une grande variété d’applications technologiques telles que la réfrigération magnétique à haute température [2]. Quelques travaux montrent l’importance de réduire les défauts microstructuraux qui peuvent influencer localement les forces de pinning [3]. Une poudre nanocristalline Pr5Co19 de structure rhomboédrique a été préparée par fusion à arc et broyage à haute énergie. Les analyses MET montrent une structure en forme de plaquettes avec des alternances de contraste séparées par des distances non périodiques le long de l’axe c (c = 48,75 Å). Une projection HREM [100] tiltée le long de c* met en évidence des décalages d’empilement de part et d’autre des plaquettes sombres qui sont en partie intrinsèques à la structure (Fig. 1). En effet, l’analyse des empilements dans une image en axe de zone [210] et des réflexions FOLZ dans la FFT correspondante montrent que des fautes apparaissent dans la séquence des blocs A-B-C (ou 3R) (Fig. 2). La présence de polytypes, notamment les structures hexagonales Pr5Co19 et Pr2Co7, forment des structures d’inter-croissance où un bloc est retiré pour former localement des séquences bicouches de blocs A-B (ou 2H). Ces défauts semblent difficiles à éviter dû à la gamme de solubilité solide très limitée de la phase Pr5Co19 dans le système binaire et aux très faibles différences d’énergie entre les différentes stœchiométries et entre les structures stables 3R et métastables 2H. References [1] R. Fersi, et al.. J. Alloys Compd. 522 (2012) 14-18 [2] V. K. Pecharsky, et al. Phys. Rev. B, 64 ; 144406, 2001 [3] M. Duerrschnabel, et al. Nat. Commun. 8 (2017) 54
Farah CHAFAÏ ()
13:00 - 15:00 #26416 - Quantitative study of temperature effects on the nucleation and growth of gold nanocrystals in water.
Quantitative study of temperature effects on the nucleation and growth of gold nanocrystals in water.

Temperature is a crucial parameter in the liquid-phase synthesis of metal nanoparticles (NPs) that directly impacts all the atomic-scale processes that drive the size dispersion of colloidal assemblies and the shape of nanostructures1-2. As the temperature concomitantly affects the kinetics of chemical reactions and the thermodynamic equilibrium of nanomaterials in solution, the full understanding of thermal effects on the nucleation and growth processes requires direct in situ observations at the nanoscale.   

Here, we exploit for the first time temperature controled liquid-cell TEM to study thermal effects on the radiolysis-driven formation of gold nanocrystals in water between 25 °C and 85 °C (Figure 1)3. The huge impacts of temperature on the nucleation and growth rates of nanostructures measured using automated video processing are quantitatively explained in the framework of the classical theories. Thus, we show that the increase of molecular diffusion and nanoparticle solubility governs the drastic changes in the formation dynamics of nanostructures in solution with temperature. In contradiction with the common view of coarsening processes in solution, we also demonstrate that the dissolution of nanoparticles and thus the Ostwald ripening are not only driven by size effects (Figure 2). Furthermore, visualizing thermal effects on faceting processes at the single nanoparticle level reveals how the competition between the growth speed and the surface diffusion dictates the final shape of nanocrystals. Our method and data-analysis workflow can be applied to other dynamical processes in nanochemistry where temperature plays an important role.

Acknowledgments:

We gratefully acknowledge the help of Maxime Moreaud in the processing of our videos using the PlugIM plateform developed at IFPEN. 

References:

[1] N. T. Thanh, N. Maclean and S. Mahiddine, Chemical reviews, 2014, 114, 7610-7630.

[2] X. Xia, S. Xie, M. Liu, H.-C. Peng, N. Lu, J. Wang, M. J. Kim and Y. Xia, Proceedings of the National Academy of Sciences, 2013, 110, 6669-6673.

[3] A. Khelfa, J. Nelayah, G. Wang, C. Ricolleau, D. Alloyeau, JOVE Vis. Exp. (168), e62225, doi:10.3791/62225 (2021).


Abdelali KHELFA (Paris)
13:00 - 15:00 #26418 - Morphological and structural thermal stability of Pt-based hollow nanoparticles under different environments.
Morphological and structural thermal stability of Pt-based hollow nanoparticles under different environments.

Josephine REZKALLAH *, Simona MOLDOVANBernhard WITULSKIXavier SAUVAGE

  • GPM Laboratory, CNRS UMR 6634, Rouen University, Normandy
  • LCMT Laboratory, CNRS UMR 6507, ENSICAEN & Caen University, Normandy.


Owing to their high reactivity, Pt nanoparticles (NPs) are commonly used in catalysis.[1,2] Shape, size, morphology and catalytic performance of NPs can be engineered by different synthetic methodologies;[3] and one of the strategies aiming at the active surface maximization is the use of hollow nanospheres.[4] Since catalytic reactions often occur under a well-controlled environment including conditions of high temperature and high pressure, a deeper knowledge on the catalytic materials behavior is necessary to understand, control and improve materials properties under reaction conditions. In this context, the approach proposed herein concern the use of Environmental TEM to probe microstructural changes in real time and under real-life conditions with notably atomic resolution. Two syntheses that differ each other in the well-defined ratio of Pt salts (H2PtCl6) and Co nanoparticles as precursors have been carried out for the elaboration of discrete Pt hollow nanospheres. [4] From a morphological point of view, the Pt-based NPs are spherical with a diameter of 15-20nm. They exhibit a core-shell structure with a polycrystalline shell (Fig. 1a and 2a). The chemical composition of these NPs was measured by EDX (Fig. 1(d-g) and 2(d-g)). It is strongly influenced by the Pt/Co ratio during the synthesis. The cobalt content of these hollow-sphere NPs produced from a Pt/2Co = 1.5 and a Pt/2Co = 0.75 ratio is 10% and 20%, respectively. Here we report on the influence of temperature, pressure and exposed gas (H2, Ar) on the morphological (coarsening, agglomeration and/or collapsing) and structural stability (phase transformation) of those hollow-sphered Pt nanoparticles. A windowed gas cell in-situ TEM holder (atmosphere-Protochips) was used in the 20-300°C temperature range and up to 1 atm pressure for this study. Acknowledgment The authors acknowledge the financial support of the French Agence Nationale de la Recherche and LabEx EMC3 through the Project ZeoMah (Grant No. ANR-10-LABX-09-01) References: [1] T.S. Ahmadi et M.A. El-Sayed, Science, 272 (1996), 1924. [2] Z. Zhou et Q. Xin, Chem.Commun., (2003). [3] T. Altantzis and S. Bals, Nano Letters, 19 (2019), 477. [4] H.‐P. Liang and C.‐L. Bai, Angew. Chem. Int. Ed., 43 (2004),1540.
Josephine REZKALLAH (Rouen)
13:00 - 15:00 #26419 - Investigation of the elastic properties of Au nanoparticles by in-situ TEM nanocompression experiments and Brillouin spectroscopy.
Investigation of the elastic properties of Au nanoparticles by in-situ TEM nanocompression experiments and Brillouin spectroscopy.

Mariana Timm *, Rongrong ZhangKarine Masenelli-VarlotJérémie MargueritatLucile Joly-Pottuz

  • Univ-Lyon, INSA, UCBL, CNRS, MATEIS UMR 5510, 69621 Villeurbanne, France
  • Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5306, 69622 Villeurbanne, France


The mechanical behavior of materials at the nanometer scale is strongly different from the one observed in bulk materials [1]. However, the measurements at the nanoscale remain extremely challenging, and the same is true concerning their interpretation. Thus, we combine two different techniques, nanocompression and Brilloun spectroscopy, on the same system to reach a high characterization level. Initially, the elastic properties of monocrystalline Au nanoparticles with sizes around 100 nm was assessed with low-frequency Raman/Brillouin spectroscopy using the dependency of the acoustic vibrational modes. The measurement of acoustic vibrational modes is fundamental to the full comprehension of the mechanical properties of nano-objects, since they are connected to the intrinsic characteristics of the material, such as crystallinity, size, shape and elasticity [2]. We show that changes in the environment around the particles modify the distribution of the electrical field inside the NPs, therefore affecting their acoustic response. The same particles were submitted to nanocompression in the TEM to characterize their deformation behavior and to obtain the stress-strain curve. The in-situ nanocompression experiments were performed with a Cs-corrected FEI-Titan microscope using a Hysitron pico-indenter. Finally, using the pico-indenter sample-holder adapted to the Brillouin experimental set-up, the measurement of the acoustic vibrational modes of single Au NPs was performed during compression tests. References : [1] O. Kraft et al., Annu. Rev. Mater. Res 40 (2010) 293-317 [2] Hodak, J. H.; Martini, I.; Hartland, G. V. J. Phys. Chem. B 102 (1998), 6958−6967
Mariana TIMM (Lyon)
13:00 - 15:00 #26420 - In situ nanocompression tests in an environmental TEM to study plasticity of cerium oxides.
In situ nanocompression tests in an environmental TEM to study plasticity of cerium oxides.

Rongrong ZHANG *, Lucile Joly-PottuzGaëtan LaurensTristan AlbaretEpicier ThierryKarine Masenelli-Varlot

  • Univ Lyon, INSA-Lyon, MATEIS
  • Univ Lyon, UCB Lyon 1, ILM


As one of the most important ceramic materials, cerium oxide is widely used in many applications, such as in solid oxide fuel cell electrodes, catalysis, and is also used as superior abrasive particles in chemical mechanical planarization [1]. Ceria is sensitive to electron beam irradiation leading to a reduction [2]. Nevertheless, the use of the environment allows to control or avoid this reduction [publi Matthieu]. It is, thus, possible to test a CeO2 structure or a structure CeOx (1.5
Rongrong ZHANG (Lyon)
13:00 - 15:00 #26421 - Multimodal study of dis-sodiation mechanism within individual Na3V2(PO4)2F3 cathode crystals using 4D-STEM-ASTAR & STXM-XANES.
Multimodal study of dis-sodiation mechanism within individual Na3V2(PO4)2F3 cathode crystals using 4D-STEM-ASTAR & STXM-XANES.

Nicolas Folastre *, Kirill CHEREDNOCHENKO François CADIOU Matthieu BUGNET Edgar RAUCH Jacob OLCHOWKAStefan STANESCUSufal SWARAJ Rachid BELKHOU Antonella IadecolaChristian MASQUELIER Laurence CROGUENNEC Arnaud DEMORTIERE

  • Laboratoire de Réactivité et de Chimie des Solides (LRCS), CNRS UMR 7314, Amiens, France
  • MATEIS Laboratory – CNRS UMR 5510/University of Lyon, Lyon, France
  • Laboratoire Science et Ingénierie des Matériaux et Procédés (SIMaP) – Grenoble INP/CNRS/UJF, Saint Martin D’Hères, France
  • Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS/Université de Bordeaux, Pessac, France
  • SOLEIL Synchrotron - Science Division - Gif-sur-Yvette, Ile-de-France, France
  • Laboratoire de Réactivité et de Chimie des Solides (LRCS), CNRS UMR 7314, Amiens, France
  • Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS/Université de Bordeaux, Pessac, France


In situ liquid electrochemical TEM [1] is one of the most powerful analytical tools allowing to follow structural and chemical transformations in Li-ion battery active materials at nanoscale with high spatial resolution and in conventional liquid electrolytes. For instance, very recently, the changes in the unit cell structure of cathode materials (LFP) during electrochemical cycling in liquid electrolyte were determined using in situ electron diffraction tomography [2]. The same compound was earlier comprehensively studied by 4D-STEM ASTAR (parallel beam) [3] and other techniques as electron ptychography [4]. Sodium vanadium (III) fluorophosphate, Na3V2(PO4)2F3 (NVPF) is attracting great interest as a potential positive electrode for Na-ion batteries due to its exceptional rate and electrochemical cycling capabilities. During the charging process, the disinsertion of two Na+ ions leads to the change of vanadium oxidation state and corresponds to structural transformations which can be registered with 4D-STEM ASTAR system. In our work we employed Poseidon in situ electrochemical liquid cell TEM holder (Protochips) and TEM equipped with Oneview camera (GATAN) and 4D STEM ASTAR system. Thanks to 4D-STEM system we succeeded to follow the structural and, thus, phase transformations of NVPF grains during the charge/discharge process in coin-cell battery. The results of obtained phase mapping are in good agreement with corresponding galvanostatic curves and available X-ray diffraction synchrotron data. More recently, we mapped by STXM-XANES (SOLEIL, beamline HERMES) (energies of V and O) then by STEM-EELS (energies of Na) the same individual grains of NVPF de-sodiated ex-situ at different charge states[5] (Fig. 1). These results Added to 4D-STEM mappings will provide some answers concerning the (dis)-sodiation mechanisms in the NVPF material. Based on this multimodal study, we correlated structural and chemical behaviors in high resolution maps to improve reliability and draw evidence of Na diffusion pathway inside single grains. References: [1] Protochips, Micros. Today. 25 (2017) 13–13. [2] O.M. Karakulina, et al. , Nano Lett. 18 (2018) 6286–6291. [3] E.F. Rauch et al. Zeitschrift Für Kristallographie. 225 (2010). [4] Y. Jiang et al. Nature. 559 (2018) 343–349 [5] S. Adams, et a. Springer Berlin Heidelberg, Berlin, Heidelberg, 2014: pp. 129–159.
Nicolas FOLASTRE (Amiens)
13:00 - 15:00 #26429 - In situ liquid TEM experiments for material dissolution kinetics investigation: application to Li-ion battery materials.
In situ liquid TEM experiments for material dissolution kinetics investigation: application to Li-ion battery materials.

Julie Poulizac *, Adrien BoulineauEmmanuel BillyKarine Masenelli-Varlot

  • CEA Grenoble
  • MATEIS Lyon


Liquid in situ TEM is a powerful technique to observe various phenomena in their native environment such as nanoparticles nucleation and growth, alive biological samples or battery cycling, with high spatial and temporal resolution [1]. In this study, we applied this technique to investigate the dissolution kinetics of LiFePO4 cathode material for Li-ion battery recycling by hydrometallurgy. As the specimen studied here is a highly agglomerated powder, we applied the ultramicrotomy technique to prepare samples for the in situ experiment in order to control the sample size and avoid breaking the Si/SiN liquid cell. Thanks to this sample preparation method, we were able to observe in situ a complete dissolution of LiFePO4 by sulfuric acid, as shown in figure 1. We used BF-STEM technique to image the dissolution and the resulting images were post-processed with ImageJ software [2] to extract the reaction kinetics (figure 2). In parallel, ex situ dissolution experiments were done on LiFePO4 in order to obtain the ex situ reaction kinetics. Both ex situ and in situ kinetics were compared. Even though the in situ kinetics appears to be much slower than the ex situ one, by taking into account the samples geometry (spheres vs. disks) and the reacting surfaces, we show that the reaction kinetics are equivalent and could be overlaid. We demonstrate here that we are able to investigate in situ dissolution kinetics by the combination of the sample preparation method and image-processing routine. References : [1] S. Pu, C. Gong, and A. W. Robertson, “Liquid cell transmission electron microscopy and its applications,” R. Soc. open sci., vol. 7, Jan. 2020. [2] M. D. Abràmoff, P. J. Magalhães, and S. J. Ram, “Image Processing with ImageJ,” Biophotonics international, vol. 11, 2004.
Julie POULIZAC (Grenoble)
13:00 - 15:00 #26431 - Unveiling MoS2 behavior in biomimetic and biological media: In situ and ex vivo complementary study.
Unveiling MoS2 behavior in biomimetic and biological media: In situ and ex vivo complementary study.

Nathaly ORTIZ PEÑA *, Kondareddy CHERUKULAAlberto BIANCOCecilia MENARD-MOYONFlorence GAZEAUDamien ALLOYEAU

  • Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS/Université Paris Diderot, 75013 Paris, France
  • Laboratoire Matière et systèmes complexes, CNRS UMR 7057, Université de Paris, Paris Cedex 13, 75205, France
  • CNRS, Institut de Biologie Moléculaire et Cellulaire, Laboratoire d'Immunopathologie et Chimie Thérapeutique, 67084 Strasbourg, France


In the booming of 2D materials for a variety of applications, transition metal dichalcogenides, in particular molybdenum disulfide, have raised as an attractive subject thanks to their exceptional electronic, optical, mechanical and chemical properties.1 Notably, the large surface area with tunable electronic properties, the intercalable layers and the readiness for functionalization makes them good candidates for biomedical proposes such as biosensing, bioimaging, and drug delivery, among others. Furthermore, MoS2 have shown to have a better biocompatibility and stability in comparison with their carbon-based analogues. Prior publications assessing the degradation products from the biotransformation of MoS2 point to the oxidation of the sheets leading to the formation of free Mo+4 ions and molybdenum oxides.2 Such degradation process appears to be innocuous for the cell life. Nonetheless, additional insight in the biotransformation mechanism of exfoliated MoS2 nanosheets is key in the assessment of its viability for biomedical applications. Herein, we have implemented a complementary approach by using in situ liquid phase transmission electron microscopy and ex-vivo studies to unveil a new aspect of the behavior of MoS2 patches in conditions mimicking those within cells, in particular those with high concentrations of ROS and H2O2. We have observed in direct the scrolling of MoS2 sheets in situ and verified the presence of the same structures ex vivo (Figure 1-2). Additionally, we determined that freestanding unrolled sheets can undergo oxidation and etching. The oxidized fragments were found in post-in situ samples and extra-cellular vesicles recovered from ex vivo experiments. Further studies enquiring on the effect of the scrolling in the stability of the nanoscrolls should be conducted in order to prove that this can constitute a protective mechanism of the structure. We would like to acknowledge the financial support of the French national research agency for the CYCLYS project. References: (1) Bazaka, K.; Levchenko, I.; Lim, J. W. M.; Baranov, O.; Corbella, C.; Xu, S.; Keidar, M. J. Phys. D. Appl. Phys. 2019, 51, 1–39. (2) Kurapati, R.; Muzi, L.; de Garibay, A. P. R.; Russier, J.; Voiry, D.; Vacchi, I. A.; Chhowalla, M.; Bianco, A. Adv. Funct. Mater. 2017, 27.
Nathaly ORTIZ PEÑA (Paris)
13:00 - 15:00 #26433 - The role of functionalized organic surfaces in metal biomineralization: insights from liquid-cell STEM experiments.
The role of functionalized organic surfaces in metal biomineralization: insights from liquid-cell STEM experiments.

Nathaly ORTIZ PEÑA *, Charlotte DEJEANBenedicte MENEZCyril GADALDamien ALLOYEAUAlexandre GELABERT

  • Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162 CNRS/Université Paris Diderot, 75013 PARIS, France
  • Université de Paris, Institut de physique du globe de Paris, CNRS UMR 7154, Paris, France


Recent direct observations in liquid phase of mineral nucleation and growth on bacterial cells highlighted, at the nanoscale, the critical role of chemical functions in cell surfaces and exopolymers in metal biomineralization [1]. Harnessing the possibilities of liquid-cell scanning transmission electron microscopy (LC-STEM), and using the incident electron beam to trigger and observe the precipitation of Mn-bearing minerals, differences in the morphology and distribution of Mn precipitates were observed. Differences in nucleation site density and accessibility on bacterial cell surfaces and exopolymers were correlated to the in situ observations. Herein, we use functionalized polystyrene beads of 1 µm diameter as simple analogues of bacteria cells, in order to better understand and characterize independently the role of the various chemical functions encountered on biological surfaces on Mn precipitation. Ten representative types of functionalization were selected for LC-STEM experiments, ranging from basic ones, like carboxylic groups (–COOH) or amine functions (–NH ), to chelating agents like nitrilotriacetic acid (NTA) or to protein compounds like streptavidin. This allows to characterize the specific impact of individual chemical function taken independently. Manganese mineralization was tracked for each type of functionalized beads, displaying significant difference in growth rates and mineralization patterns. As illustrated in figure 1, at the same electron dose rate, Mn precipitation for COOH-bearing beads is much faster (Figure 1b), compared to non-functionalized beads (Figure 1a) and, exhibit massive dendritic precipitates at the bead surface. Bulk measurements of electrophoretic mobility for each type of bead will be use to correlate surface charge to mineral growth rate on beads. The bulk surface charge explains only partially Mn mineralization properties at the beads surface but other parameters like steric effect need to be explored. We would like to acknowledge the financial support of the French national research agency for the MAMBA project. References [1] Couasnon, T., Alloyeau, D., Ménez, B., Guyot, F., Ghigo, J. M., & Gélabert, A. (2020). In situ monitoring of exopolymer-dependent Mn mineralization on bacterial surfaces. Science advances, 6(27), eaaz3125
Nathaly ORTIZ PEÑA (Paris)
13:00 - 15:00 #26435 - Growth of MgO Nanocrystals by self-assembly in Molten Salts.
Growth of MgO Nanocrystals by self-assembly in Molten Salts.

Isabel Gómez-Recio *, Ram KumarDris IhiawakrimAlmudena Torres-PardoJose M. González-CalbetOvidiu ErsenDavid Portehault

  • Sorbonne Université, CNRS, Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, 75005 Paris, France
  • Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504 CNRS-Université de Strasbourg, BP 43 Strasbourg Cedex 2, France
  • Dpt. of Inorganic Chemistry, Faculty of Chemistry, Universidad Complutense de Madrid, Madrid (28040) Spain


Metal oxides exhibit a wide range of properties combined to stability under ambient conditions that have given rise to an extensive range of applications. The decrease of oxides particle size at the nanoscale is well known to modify or enhance their properties. Developing synthesis methods is then important to widen the compositional range of oxides accessible at the nanoscale. Among several strategies, synthesis in molten salts is particularly appealing as a liquid-mediated pathway that allows extensive nucleation with limited grain growth to enable particle size control.[1] Nonetheless, the reaction mechanisms underlying molten salts syntheses are currently unknown. Real time observations of nucleation and growth steps can unveil the key mechanisms of nanocrystals formation, as well as provide guidelines towards selected morphologies. [2] Of particular interest is the search of self-assembly processes driving the crystallization and that could play an essential part of the toolkit for designing inorganic nanocrystals. In situ techniques, as in situ transmission electron microscopy, strongly contribute to the advancement of such knowledge, but have never been applied to the specific conditions of molten salts syntheses that encompass high temperatures and liquid phase. In this work the self-assembly is suggested to be one of the MgO crisytallization mechanisms in molten salts. Oriented attachment is a characteristic feature of colloidal syntheses, never observed before in molten salts medium. This growth mechanism gives rise to enthalpy drops in a thermodynamic spontaneous process due to crystal surface energy reduction. [3] TEM low magnification images evidence that the number of primary nanoparticles belonging to a cluster increase over the reaction time (Fig. 1), and that particle attachment occurs preferentially face-to-face. TEM images (Fig. 2) show the same crystallographic orientation at both sides of primary nanoparticles boundary. This information is complemented by in situ TEM studies which allow direct monitoring of MgO crystallization. For the in situ TEM study an environmental gas holder (Atmosphere from Protochips) was used.
Isabel GÓMEZ-RECIO (Paris)
13:00 - 15:00 #26436 - The influence of organic molecules on the mineralization of calcium carbonate by Liquid Phase Transmission Electron Microscopy (LPTEM).
The influence of organic molecules on the mineralization of calcium carbonate by Liquid Phase Transmission Electron Microscopy (LPTEM).

Vinavadini Ramnarain *, Nathaly ORTIZ PEÑADris IHIAWAWKRIMMariana LONGUINHOTristan GEORGESThierry AZAISClément SANCHEZOvidiu ERSEN

  • Institut de Physique et Chimie des Matériaux Strasbourg (IPCMS)
  • CBPF, Rio de Janeiro, Brasil
  • Laboratoire de Chimie de Matière Condensé de Paris, Sorbonne Université, Paris, France
  • USIAS, Université de Strasbourg, France


Biominerals have complex hierarchical structures, often combined with exceptional properties, such as high mechanical, electrical or magnetic properties, which are achieved under the direct control of biomolecules. This level of control originates from an intimate association of an organic matrix comprised of macromolecules and inorganic components in a localized environment of the organisms1. Thus, scientists seek inspiration from the properties of biominerals to produce advanced materials by means of biomimetic material design. The key factors which influence the final properties of the crystal are predominantly proteins of the organic matrix which may consist of various amino acids2. Whilst several studies have been carried out on the growth of biominerals controlled by macromolecules, the early steps before growth are not fully understood. Therefore, it is of great interest to study the impact of these amino acids on the early nucleation stages of biomineralization and to provide a direct mechanistic insight into these phenomena. Herein, we present the study of the mineralization processes of calcium carbonate. This system is chosen because of its abundance in nature and it is a relatively simple model. Furthermore, we have investigated the role of L-Aspartic acid on biomineralization. We have used the Liquid Phase Transmission Electron Microscopy to assess the incipient steps of mineralization within a liquid environment confined between two silicon nitride windows. In this study, we have been able to unravel, in real time, novel visual insights on the incipient steps, that is pre-nucleation and nucleation of CaCO3. In particular, we could experimentally determine the presence of pre-nucleation clusters and their dynamic behavior (Fig 1), Moreover we could observe a real time nucleation taking place where the pre-nucleation species are transformed to liquid nanodroplets upon crossing a binodal limit (Fig 2). The liquid nanodroplets further aggregated to form hydrated amorphous calcium carbonate by an annealing process. These results allowed us to understand the influence of organic matter during biomineral formation and hence establish a mechanistic picture. References: [1] Weiner, S.; Addadi, L. Annu. Rev. Mater. Res. 2011, 41 (1), 21–40. [2] Tavafoghi, M.; Cerruti, M. J. R. Soc. Interface 2016, 13 (123), 20160462
Vinavadini RAMNARAIN (Strasbourg)
13:00 - 15:00 #26437 - Probing and mapping the structural and electronic evolution of metal/insulating V2O3 nanodomains by electron spectromicroscopy under variable temperatures.
Probing and mapping the structural and electronic evolution of metal/insulating V2O3 nanodomains by electron spectromicroscopy under variable temperatures.

Ibrahim Koita *, Xiaoyan LiLuiz H. G. TizeiJean-Denis BlazitNathalie BrunEtienne JanodJulien TranchantBenoît CorrazeLaurent CarioMarcel TencéOdile StéphanLaura Bocher

  • Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405, Orsay, France
  • Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 Rue de la Houssinière, 44322 Nantes, France


V2O3 présente différentes transitions métal-isolant (TMIs) induites en température, sous pression ou par dopage chimique[1]. Ces TMIs présentent des scenarii complexes du point de vue de leurs évolutions électronique et structurale qui rendent encore leurs compréhensions incomplètes[2]. Lorsqu’il est refroidi en dessous de 160 K, V2O3 subit une transition structurale (rhomboédrique vers monoclinique) et une TMI avec une hausse de résistivité de 7 ordres de grandeur. Cette TMI activée en température a été largement étudiée à l’échelle macroscopique (Fig.1a)[1], récemment la coexistence de domaines isolant/métallique (I/M) a été cartographiée in situ par photoémission[3] et nano-IR[4] avec une résolution respective de 1 µm et de 25 nm au mieux. Or cette séparation de phases électroniques peut être due localement à des mécanismes structuraux d’où la nécessité de coupler cartographies structurale et électronique à l’échelle locale et sous températures variables. Ici nous avons réalisé des expériences STEM/EELS monochromatées de ultra-haute résolution spectrale sur le NION CHROMATEM 200 MC associé au porte-objet cryo double-tilt Henny Z refroidi à l’azote et utilisant des MEMS (Fig.1b) pour accéder à des conditions de températures variables à partir de 120 K. Lors des cycles thermiques à travers la TMI, les spectres EELS acquis dans le domaine des pertes proches présentent une signature plasmonique caractéristique à 1.1eV uniquement pour la phase métallique (Fig.2a)[5]. A température intermédiaire, la coexistence de nanodomaines I/M est cartographiée à l’échelle nanométrique (Fig.2b et 2c). Des analyses par K-means clustering confirment l’homogénéité électronique de chaque domaine (Fig.2d). En parallèle, des expériences 4DSTEM de nanodiffraction permettent de révéler l’évolution structurale des domaines I/M en température. Ces expériences visent à sonder localement les mécanismes physiques mis en jeu lors de la transition et en particulier la relation entre les degrés de libertés structuraux et électroniques. Les auteurs remercient l’EDPIF, l’ANR IMPULSE No. ANR-19-CE42-0001 et le programme de futur investissement TEMPOS No. ANR-10-EQPX-50. References: [1] McWhan, et al., PRB,2 (1970), 3734 [2] Kalcheim, et al., PRL.,122 (2019), 057601. [3] Lupi,et al., Nat. Commun.,1(2010),105. [4] McLeod, et al., Nat. Phys.,13 (2017),80. [5] Abe, et al., Jpn. JAP., 37 (1998), 584
Ibrahim KOITA (Paris-Saclay)
13:00 - 15:00 #26438 - Modeling electric fields in nanocapacitors observed by operando electron holography.
Modeling electric fields in nanocapacitors observed by operando electron holography.

Kilian Gruel *, Raphaël SerraAurélien MasseboeufChristophe Gatel *, Martin Hÿtch *

  • CEMES-CNRS, Toulouse, France
  • Université de Toulouse, Toulouse, France


Electron holography has the potential to become a powerful technique to measure electric fields in microelectronics devices such as capacitors during their operation. However, we first need to show that measurements can be performed quantitatively, and in operando conditions, for model systems [1]. The experimental results need to be compared with modeling that takes into account factors such as specimen geometry, FIB damage, stray fields and charging [2]. The model dielectric capacitor that has been studied experimentally is composed of an insulating layer of silicon nitride (Si3N4) between a bottom electrode (substrate) of highly P-doped silicon (Si) and a top electrode of deposited titanium (Ti). Electron holography experiment has been performed on this sample using the I2TEM microscope (Hitachi HF3300-C) operating at 300 kV whilst applying different voltages from – 10V to 10V. Finite element method (FEM) was used to model the electrostatic potential (COMSOL Multiphysics). Parameters were adjusted to produce an excellent fit with the experimentally measured phase shift (Figure 2). The curvature of the phase in the electrodes is well reproduced and is caused by the stray field around the sample. In the silicon nitride, there is a slight disagreement with the experimental curvature and can be modelled by introducing charges in the insulating layer. This work was supported by the French national project IODA (ANR-17-CE24-0047). The research leading to these results has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No. 823717 – ESTEEM3. Références/References : [1] AC Twitchett et al., Phys. Rev. Lett. 88 (2002), p. 238302 [2] S Yazdi et al., Ultramicroscopy 152 (2015), p. 10
Kilian GRUEL (Toulouse)
13:00 - 15:00 #26440 - New insights into the growth mechanism of WO3 gels by in-situ liquid-phase TEM and time-resolved DLS.
New insights into the growth mechanism of WO3 gels by in-situ liquid-phase TEM and time-resolved DLS.

Charles Sidhoum *, Mateusz OdziomekDris IhiawakrimDoru ConstantinFrançois SchosselerClément SanchezOvidiu Ersen

  • Institut de Physique et Chimie des Matériaux de Strasbourg, 23 rue du Lœss, BP 43, Strasbourg Cedex 2, France
  • Laboratoire de Chimie de Matière Condensé de Paris, Sorbonne Université, Paris, France
  • Institut Charles Sadron, UPR22, 6 rue Boussingault, 67083 Strasbourg cedex, France


The electrochromic and photocatalytic properties of tungsten oxide (WO3) find broad applications in display devices, smart windows or degradation of pollutants. The synthesis of WO3 does not require high temperatures, and soft methods fitting into “chimie douce” concept are well-established. Following the sol-gel routes, it is possible to obtain WO3 gels by acidification of tungsten salt solutions. The acidification leads to hydrolysis and consecutive condensation first to polyoxotungstate species and further to gel-like structure. Although the process has been studied by various techniques1, we still lack the understanding on how the charged polyoxometallate species react with each other and form a gel. Several models have been proposed, based on the condensation of a hypothetical “zero-charge complex” by hydroxylation and oxolation2. The recent developments in TEM, in particular the emergence of the in-situ Liquid Phase TEM (LP-TEM), may provide new insight into the nucleation and growth processes of WO3-based nanostructures, with a particular focus on the early steps of gel formation. Herein, using the ability of LP-TEM to monitor nanometric processes in real space, we report a first picture of the growth of WO3 gels. This in situ analysis highlights several possible pathways for the growth mechanism, including the diffusion-limited cluster aggregation process. Indeed, a closer look into the reaction environment (Figure 1) reveals the presence of well-defined clusters, with a nanometric size, which apparently plays the role of elemental bricks for gel formation3. To further improve the comprehension of the first growth events, we have also carried out time-resolved DLS measurements for different tungsten salt concentration. As expected, a decrease in concentration (Figure 2b) leads to a decrease in intensity but, at the same time, we find similar sizes (Figure 2a), indicating the presence of precursors of few nm. In complement to DLS data obtained during the first 30 minutes, cryo-TEM studies are ongoing in order to complete the mechanistic picture and to provide a complete description of the growth process. References: [1] Pope, M. T.Heteropoly and Isopoly Oxometalates;Springer:Berlin, 1983. [2] J-P. Jolivet. (2015). De la solution à l’oxyde. EDP Sciences [3] Chemseddine, A. J. Solid State Chem. 2008, 2731–2736.
Charles SIDHOUM (Strasbourg)
13:00 - 15:00 #26402 - Kinetics of the parent grain growth in a 20MND5-type bainitic steel with micro-segregations.
Kinetics of the parent grain growth in a 20MND5-type bainitic steel with micro-segregations.

Suzanne Vernier *, Pierre JolyLydia LaffontEric Andrieu

  • CIRIMAT - INPT
  • FRAMATOME
  • CIRIMAT - INPT/ENSIACET


L’acier 20MND5 (0,2%C-1,4%Mn-0,7%Ni-0,5%Mo) est un acier faiblement allié utilisé dans l’industrie nucléaire pour fabriquer des générateurs de vapeur. Ces pièces en 20MND5 sont obtenues par forgeage de lingots de très grandes dimensions qu’il est difficile d’homogénéiser chimiquement. Ainsi, des micro-ségrégations, héritage des ségrégations entre bras de dendrite secondaires, sont classiquement observées dans ces pièces. Les micro-ségrégations sont responsables de la microstructure en « bandes » obtenue après un refroidissement de l’acier à vitesse modérée [1] : des bandes de bainite supérieure (matrice non ségrégée) alternent avec des bandes de bainite inférieure (micro-ségrégation) (Figure 1). La structure en bandes de l’acier 20MND5 est suspectée d’être à l’origine d’une dispersion des valeurs de résilience à basse température, en particulier dans la zone de transition ductile-fragile. Or, l’étude de la microstructure a montré que les grains parents, c’est-à-dire les anciens grains austénitiques, sont plus gros dans les micro-ségrégations que dans la matrice non ségrégée. Cette plus grande taille de grains austénitiques combinée à la ségrégation des éléments d’alliage et des impuretés pourrait expliquer une plus grande fragilité des micro-ségrégations à basse température. Afin de comprendre les raisons d’une telle croissance des grains austénitiques dans les micro-ségrégations, l’évolution de la taille des grains parents a été suivie dans chaque type de zone au cours d’un traitement d’austénitisation (montée lente puis maintien en température – Figure 2.a). Des images en microscopie optique et électronique, des essais de micro-dureté et des analyses EBSD ont été réalisés à différentes étapes du traitement (Figure 2). En particulier, les analyses EBSD ont permis de reconstruire les cartographies des grains parents en se basant sur la relation d’orientation entre grains enfants et grains parents [2]. Ainsi, il est apparu que l’écart de taille de grains entre les deux types de zone se creuse une fois la transformation austénitique terminée, lors du maintien en température. Des nitrures d’aluminium de taille nanométrique pourraient être à l’origine du ralentissement de la croissance des grains dans la matrice non ségrégée. Références : [1] R.A. Grange, Metall. Trans., vol. 2 (1971), p. 417 [2] T. Nyyssönen, Metall. Mater. Trans. A, vol. 49 (2018), p. 6426
Suzanne VERNIER (CIRIMAT INPT)
13:00 - 15:00 #26404 - Low Dose Electron Diffraction Tomography (LD-EDT) in TEM: Application on a hydrated Al arsenate mineral.
Low Dose Electron Diffraction Tomography (LD-EDT) in TEM: Application on a hydrated Al arsenate mineral.

Emre Yörük *, Holger KleinStéphanie Kodjikian

  • CNRS Néel Institute, University of Grenoble Alpes


3D electron diffraction (3D ED) has recently emerged as an alternative to x-ray diffraction to elucidate atomic structures of nano-sized crystals [1]. High scattering cross-sections of electrons allows for a diffraction data quality on par with synchrotron x-rays, albeit at a reduced cost. However, electron beam damage is still a major issue in the 3D ED field [2], and exposure conditions need to be optimized for beam sensitive compounds. LD-EDT [3] is a low dose 3D ED technique for ab initio structure determination of beam sensitive crystals such as hydrated minerals or MOFs. High quality diffraction data can be obtained from individual single crystalline particles in a powder without damaging the structure, and a precise sampling of the reciprocal space is assured by beam precession. We recently applied LD-EDT on Bulachite [4], a hydrated Al arsenate mineral, and solved its atomic structure. Difficulties related to the small size of crystals as well as beam sensitivity due to the presence of H2O molecules inside the lattice were overcome by LD-EDT, where synchrotron x-ray powder diffraction previously failed. The resulting structure [5] is comprised of layers containing edge-sharing Al-O octahedra, inter-connected with As-O tetrahedra by corner sharing. The localization of light atoms in the lattice showcases the potential of electron crystallography for yielding high quality diffraction data even under low dose conditions. References : [1] M. Gemmi et al., ACS Cent. Sci., 5 (2019), p. 1315−1329. [2] J. Hattne et al., Structure, 26 (2018), p. 759-766. [3] S. Kodjikian, H. Klein, Ultramicroscopy, 200 (2019), p. 12-19. [4] K. Walenta, Aufschluss., 34 (1983), p. 445-451. [5] I.E. Grey., E. Yoruk et al., Mineralogical Magazine, 84 (2020), p. 608-615.
Emre YÖRÜK (Grenoble)
13:00 - 15:00 #26411 - NANOSTRUCTURED LaFeO3 THIN FILMS GROWN ON SILICON.
NANOSTRUCTURED LaFeO3 THIN FILMS GROWN ON SILICON.

Christian Turquat *, Mateusz JĘDRUSIKŁukasz CIENIEKAgnieszka KOPIAChristine LEROUX

  • Université de Toulon, AMU, CNRS, IM2NP (UMR 7334), CS 60584, Toulon, F- 83041, France
  • Wydział Inżynierii Metali i Informatyki Przemysłowej, Akademia Górniczo – Hutnicza, al. Mickiewicza 30, 30-059 Kraków, Polska


In this paper, our attention has been focused on lanthanum iron oxide (LaFeO3) as thin films because of its potential in silicon microelectronics-based gas sensing technologies [1]. More precisely, the purpose of this research is to investigate the influence of process temperature on the morphology and crystallographic structure of LaFeO3 (LFO) thin films obtained by a Pulsed Laser Deposition (PLD) method on silicon (Si) substrates, in particular the nature of the exposed crystallographic facets. Three deposition temperatures, 750°C, 850°C, and 1000°C were investigated. Morphologic information was secured via Scanning Electron Microscopy and Atomic Force Microscopy while crystallographic information was gained via grazing incidence X-ray Diffraction and Transmission Electron Microscopy. At all temperatures, the films are crystallized in the Pnma orthorhombic structure. Thin films with a temperature deposition of 750°C and 850°C exhibit a microstructure of columnar grains with different LFO thicknesses, respectively 80 and 150 nm, and a similar intriguing surface structuration (see Figure 1). However, films grown at 750 °C show cracks, which disqualify them for applications. Two types of columnar grains are observed, with a tip termination and a columnar width from 15 to 20 nm, and broader flat terminated grains (see Figure 2). They correspond to two different growth direction [101] (flat) and [200] (tip), but in both cases {101} facets are exposed. The microstructure of the sample with a temperature deposition of 1000°C contrasts with the lower temperature samples and shows an active layer thickness of around 130 nm with a random arrangement of grains. HREM evidenced a reaction between the silicon substrate and the LaFeO3 layer, with the formation of La2Si2O7, indicating diffusion of Si through the native SiO2 barrier. This phenomenon was also observed in LaCoO3/Si [2]. These disparities will be discussed in terms of the structure and composition variation with the LFO layer. Références/References: [1] H. Zhu, P. Zhang, S. Dai, ACS Catalysis, 5 (2015) 6370-6385. [2] M. Jedrusik, Ł. Cieniek, A. Kopia, Ch. Turquat, Ch. Leroux, Arch. Metall. Mater. 65 (2020), 793-797
Christian TURQUAT (Toulon)
13:00 - 15:00 #26414 - eCHORD as a tool to characterize internal misorientation of strained samples.
eCHORD as a tool to characterize internal misorientation of strained samples.

Romain Facchinetti *, Cyril LangloisSophie CazottesThierry DouillardClaire MauriceJuliette ChevyChristine Nardin

  • MATEIS – Institut National des Sciences Appliquées (INSA Lyon) - Lyon – France
  • Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, Centre SMS, F-42023 Saint-Etienne France
  • Constellium – Voreppe - France


Understanding the relationship between microstructure and properties is a necessary step for the improvement of existing materials or the development of new materials. The microstructure can be characterised using orientations maps, from which information like grain size distribution and deformation state can be extracted. Apart from EBSD (Electron Backscattered Diffraction), a promising approach to obtain orientation maps with the SEM (Scanning Electron Microscope) is the eCHORD method [1], which is based on electron channelling contrast. This method has the advantage that the sample tilt is only about 10°, and that the accelerating voltage can be lowered to a few kV, resulting in an improved spatial resolution. A series of BSE images is recorded during the rotation of the sample around its tilted normal direction, from which the intensity profiles of each pixel can be extracted as a function of the rotation angle. By comparing the obtained intensity profiles with the one calculated from ECP (Electron Channelling Patterns) simulations [2], the orientation of each pixel can be determined. The angular resolution achieved on Aluminium alloys is about 0.1°. In addition to orientation maps, we present here an original method to characterize the local misorientation using eCHORD. One objective is to determine the fraction of recrystallized grains in a partially recrystallized Aluminium. In fact eCHORD identify the internal misorientation by comparing the distances between profiles of adjacent pixels, without the need to compute pixels orientation. The results are compared with EBSD Kernel maps obtained on Aluminium with different levels of strain and different fractions of recrystallized grains. Références/References : [1] C.Lafond, T.Douillard, S.Cazottes, P.Steyer, and C.Langlois. Electron CHanneling Orientation Determination (eCHORD): An original approach to crystalline orientation mapping. Ultramicroscopy, 186 :146–149, (March 2018). [2] Singh, S., Ram, F., & De Graef, M. EMsoft: Open source software for electron diffraction/image simulations, Microscopy and Microanalysis, 23(S1), 212-213. (July 2017)
Romain FACCHINETTI (Lyon)
13:00 - 15:00 #26415 - FAST AND AUTOMATED ACQUISITION OF THE RECIPROCAL SPACE FOR MONOCRISTAL STRUCTURE DETERMINATION.
FAST AND AUTOMATED ACQUISITION OF THE RECIPROCAL SPACE FOR MONOCRISTAL STRUCTURE DETERMINATION.

Nicolas Gautier *, Anne-Claire Gaillot

  • Institut des Matériaux Jean Rouxel (IMN), UMR6502 CNRS, 2 rue de la Houssinière BP32229, 44322 Nantes cedex3, France


Depuis une dizaine d’années, la résolution de la structure d’un monocristal par diffraction électronique s’est fortement développée [1]. Différentes techniques ont été mises au point, basées sur la diffraction électronique en mode tomographie (EDT), associée ou non à la précession électronique, permettant un meilleur échantillonnage du réseau réciproque en ne se limitant plus aux principaux axes de zones [2]. Des programmes tels que PETS2, implémenté dans Jana2006, permettent de résoudre et d’affiner les structures cristallines à partir des données de diffraction électronique en mode tomographie avec précession (PEDT) en prenant en compte également les effets dynamiques [3]. Mais les techniques classiques d’EDT sont difficilement applicables aux cristaux très sensibles au faisceau d’électrons. Des conditions d’acquisition spécifiques doivent être mises en œuvre pour limiter le courant du faisceau d’électrons (« low dose ») ou augmenter la vitesse d’acquisition pour limiter le temps d’exposition. C’est ce que permet le script “Continuous Rotation movie acquisition” (CRmov) intégré au programme libre SerialEM [4]. CRmov permet de contrôler la platine goniométrique pour tourner le porte-objet à l’angle de départ, collecter une série de clichés de diffraction en continu jusqu’à l’angle final et sauvegarder les données automatiquement en quelques minutes. Les données acquises sur un monocristal peuvent ensuite être traitées à l’aide de logiciels tels que PETS2 et JANA, afin de déterminer les paramètres de maille du composé, jusqu’à la résolution structurale. Installé sur Nant’Themis (S/TEM ThermoScientific Themis Z), ce dispositif nous a permis grâce à cette rapidité d’acquisition, de collecter des données de diffraction électronique en mode tomographie avec précession (PEDT) sur des échantillons organiques. Il a également été mis à profit sur des échantillons moins sensibles sous le faisceau, pour enregistrer dans un temps limité plusieurs jeux de données dans des conditions expérimentales différentes. Références : [1] Gemmi et al. ACS Central Science 2019, 5 (8), p.1315– 1329, [2] Kolb et al., Ultramicroscopy 107 (2007) 507–513 [3] Palatinus, L., Petricek, V. & Correa, C. A. (2015). Acta Cryst. A71, 235-244 [4] De la Cruz et al., Ultramicroscopy, 201 (2019), 77-80
Nicolas GAUTIER (Nantes)
13:00 - 15:00 #26382 - Analytical TEM Radiation-Induced Segregation (RIS) study at grain boundaries of a baffle-former bolt irradiated up to 45dpa coming from a French Pressurized Water (nuclear) Reactor (PWR).
Analytical TEM Radiation-Induced Segregation (RIS) study at grain boundaries of a baffle-former bolt irradiated up to 45dpa coming from a French Pressurized Water (nuclear) Reactor (PWR).

Priscille Cuvillier *, Eric DerniauxRémi MercierYannick ThébaultMarylou BoissonRoch MenandVirginie Boulay

  • EDF – DI, CNPE de Chinon - BP23 - 37420 Avoine, France
  • EDF – DI, 2 rue Ampère – 93206 Saint-Denis, France
  • EDF UNIE, 1 place Pleyel 93200 Saint-Denis, France
  • EDF – DT, 19 rue Pierre Bourdeix – 69007 Lyon, France


Radiation-Induced Segregation (RIS), causing in particular Cr depletion at grain boundaries (GB), is a phenomena suspected in the embrittlement of nuclear component during service [1]. RIS in a bolt stayed 26 years under neutron irradiation in a civil nuclear reactor (PWR) has been studied by TEM using a FEI TECNAI Osiris equipped with a energy dispersion X-ray spectrometers (four SDD detectors). This is the first time EDF investigates a deposited baffle-former bolt from PWR at such levels of irradiation (≈ 45dpa) [2] thanks to new sampling preparation [3] using a FIB-SEM Lyra3 TESCAN in a high-activity cell [4] making it possible to prepare remotely lamellae from an initially highly radioactive sample. The bolt, with no indication of cracking, and its anti-rotation lock-bar (Figure 1) are respectively in a 316L and 304L austenitic stainless steel. As RIS is subjected to be affected by several parameters such as dose, temperature, material composition or crystallographic orientation of the GB, three samples at different pairs of dose/temperature, in different material and for different disorientation of GB have been studied: 45dpa/295°C (304L anti-rotation strip), 40dpa/305°C (316L bolt head) and 24dpa/340°C (316L bolt shank). Depletions of Cr, Fe, Mn and Mo and enrichment of Ni and Si have been observed at GB and maximum Cr depletion reaches ΔCr≈6 wt% (Figure 2). Some GB decorated with precipitates (probably γ’ (Ni3Si) or G (M6Ni16Si7) phases) are also observed. RIS is larger for the pair “higher” dose / “lower” temperature and seems to be more pronounced for highly disoriented GB and more disadvantageous for 316L than 304L (initially richer in Cr). Further work on higher dose and cracked bolts is planned to better understand the evolution of RIS and its influence on GB embrittlement. References: [1] A. J. Ardell and P. Bellon, Solid State and Materials Science 20 (2016), p. 115-139 [2] É. Fargeas et al, Fontevraud 9, (2018) [3] L. Legras et al., European Microscopy Congress (2016) p. 443-444 [4] S. Miloudi et al., European Microscopy Congress (2016) p. 368 The authors would like to thank all the persons of EDF hot laboratory that contributed to the examinations.
Priscille CUVILLIER (Avoine)
13:00 - 15:00 #26383 - STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications.
STEM-EELS investigation of c-Si/a-AlOx interface for solar cell applications.

Guillaume Noircler *, Fabien LebretonEtienne DrahiPatricia De CouxBénédicte Warot-Fonrose

  • CEMES-CNRS
  • Total SA
  • Institut Photovoltaïque d’Ile-de-France (IPVF)
  • LPICM


Amorphous aluminum oxide (a-AlOx) capped with amorphous silicon nitride (a-SiNx:H) is nowadays a common passivation stack for p-type silicon surfaces and is a good candidate to passivate the rear side of two-terminal perovskite/silicon tandem cells. The combination of atomic layer deposition (ALD) for a-AlOx with plasma-enhanced chemical vapor deposition (PECVD) for the capping made its success. Chemical passivation is insured by hydrogen from a-SiNx:H that can easily diffuse to the c-Si/AlOx interface. The field effect passivation is provided by a-AlOx which contains a high negative fixed charge density. The origin of the latter one is still a matter of debate and therefore requires additional research to be more controlled. 3 different samples have been studied with different process for the annealing step and a-SiNx:H composition (figure 1). In an attempt to better understand these negative fixed charges, local scale investigation by STEM-EELS has been performed at the c-Si/a-AlOx interface on 3 different samples. However, the extreme sensitivity of a-AlOx and a-SiNx:H to the electrons beam has led us to carry out a detailed study of the electron irradiation process. The c-Si/a-AlOx interface can undergo several electron-beam irradiation damage like sputtering, knock-on or radiolysis which have a direct impact on the structure and the chemical composition if precautions are not taken. We have shown that the radiolysis process was the dominant radiation damage and that it could drastically be limited by reducing the acceleration voltage and by modifying the scan orientation. Once the radiation damage has been understood and brought under control, STEM-EELS analysis has been done using Si and Al L2,3 and O K edges to determine the composition of the c-Si/a-AlOx interface (figure 2). Just above the c-Si, an ultrathin a-SiOx layer was found. Between the latter and the a-AlOx, a non-stoichiometric aluminum silicate has been characterized containing tetrahedrally coordinated Al in its first layers. The tetrahedral coordination of Al is known to have a net negative charge and high catalytic activity. Thus, this coordination could strongly participate in the production of negative fixed charge which improves the field effect passivation of this amorphous stack.
Bénédicte WAROT-FONROSE (CEMES, Toulouse)
13:00 - 15:00 #26387 - Spectral unmixing of EELS spectrum-images.
Spectral unmixing of EELS spectrum-images.

Nathalie Brun *, Guillaume LambertLaura Bocher

  • CNRS Université Paris Saclay Laoratoire de Physique des Solides
  • Université Paris Saclay M1 Mathématiques Appliquées


Le développement de la microscopie électronique analytique en mode STEM banalise l'acquisition de spectres-images représentant un grand volume de données, de l'ordre de 10k pixels x 1000 canaux en énergie. Il est possible d'appliquer les techniques classiques de traitement des données EELS à chaque spectre. Toutefois il est préférable de considérer le spectre-image comme un tout et d'exploiter le caractère redondant de l'information. Les techniques d'analyse statistiques commencent ainsi à être couramment utilisées, notamment l'analyse par composantes principales (ACP) mise en œuvre par l'intermédiaire de la Toolbox Hyperspy [1]. Néanmoins l'ACP est en général utilisée pour débruiter le spectre-image, auquel on applique ensuite le processus classique (soustraction du fond continu/somme des canaux correspondants au seuil caractéristique). En effet le but du traitement est de passer d'un cube de données difficilement visualisable à des données 2D exploitables sous forme de cartes. Le moyen d'obtenir directement ces cartes en exploitant pleinement l'information contenue dans le spectre-image est d'utiliser des techniques de démélange spectral [2]. Le démélange spectral repose sur l'hypothèse que chaque spectre individuel d'un spectre-image peut être décrit comme une combinaison linéaire d'un petit nombre de n spectres représentatifs des composants présents dans l'échantillon. Le spectre-image peut être alors complètement décrit par ces n composantes et les n cartes correspondantes. Outre d'être souvent beaucoup plus rapides, ces méthodes ont l'avantage de s'affranchir de problèmes tels que la superposition de seuils ou la difficulté de soustraire le fond continu, voire de cartographier indirectement certains éléments dont le seuil n'est pas détecté avec la dispersion utilisée. Je montrerai des exemples obtenus avec différentes techniques de démélange; on s'intéressera en particulier à l'intérêt de l'utilisation du Deep Learning pour ce type de problème. Références: [1] https://hyperspy.org/index.html [2] Dobigeon, N., & Brun, N. Spectral mixture analysis of EELS spectrum-images. Ultramicroscopy, 120 (2012) p.25-34. Remerciements : nous remercions André Thiaville (LPS, Orsay), William Legrand, Nicolas Reyren et Vincent Cros (UMP CNRS/Thales, Palaiseau) pour l’échantillon Pt/Co/Ru.
Nathalie BRUN (Paris-Saclay)
13:00 - 15:00 #26388 - Probing Whispering Gallery Mode Resonators With Electron Beams.
Probing Whispering Gallery Mode Resonators With Electron Beams.

Yves Auad *, Cyrille HamonMarcel TencéVahagn MkhitaryanOdile StephanJavier Garcia de AbajoLuiz Galvão TizeiMathieu Kociak

  • Laboratoire de Physique des Solides, Orsay
  • ICFO, Barcelona


Whispering gallery mode resonators confine light using total internal reflection and take advantage of its several and narrowband circulating resonances for applications in optomechanics [1], quantum electrodynamics [2] and sensing [3]. The spherical symmetry and the low radiation loss make them difficult to study under free-space light. The ability of fast electrons to excite confined light modes in the near-field of photonic objects paves the way to probe these circulating modes with high spatial resolution. Electron Energy Loss Spectroscopy (EELS) has already been performed in small ( 1 μm) silica spheres with high quality factors. References: [1] Tobias Kippenberg et al. Analysis of radiation-pressure induced mechanical oscillation of an optical microcavity. Physical Review Letters, 95, 2005. [2] D. Vernooy et al. Cavity qed with high-q whispering gallery modes. Physical Review A, 57, 1998. [3] Yu Zheng et al. Sensing and lasing applications of whispering gallery mode microresonators. Opto-Electronic advances, 1, 2018. [4] Jerome Hyun et al., Measuring far-ultraviolet whispering gallery modes with high energy electrons. Applied Physics Letters, 12 2008. [5] Ofer Kfier et al. Controlling free electrons with optical whispering-gallery modes. Nature, 2020.
Yves AUAD (Orsay)
13:00 - 15:00 #26389 - Multi-phase nucleus inside a spheroidal graphite nodule analyzed by STEM-EDS.
Multi-phase nucleus inside a spheroidal graphite nodule analyzed by STEM-EDS.

Alessandro PUGLIARA *, Lydia LAFFONTTeresa HUNGRIAClaudie JOSSEJacques LACAZE

  • CIRIMAT-ENSIACET, Université de Toulouse, Toulouse, France
  • Centre de Microcaractérisation Raimond Castaing, Université de Toulouse, UPS – CNRS – Toulouse INP – INSA, Toulouse, France


Spheroidal graphite cast irons are alloys with excellent ductility (mechanical characteristics close to those of mild steels). In these alloys, spheroidizing and inoculation treatments, using Fe-Si-Mg and Fe-Si alloys respectively, interact to give the final particles acting as nuclei for generating the spheroidal graphite nodule [1]. Many observations of these nuclei reported the presence of multi-phase nanometric structure containing oxides, sulfides, oxysulfides [1], and sometimes nitrides [2, 3]. Accordingly, the chemical characterization of nuclei is of prime importance to establish the sequence of phase transformations leading to the formation of spheroidal graphite nodules. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS) is carried out on a thin diametric section of a graphite nodule. Bright field (BF) STEM image shows the presence of a nucleus in the middle of the graphite nodule (Fig. 1a). This nucleus appears composed of two parts: a round head loosely connected to an elongated tail (Fig. 1b). High-angle annular dark-field (HAADF) STEM images evidence the presence of at least one element much heavier than carbon in both parts (Fig. 1c). Moreover, the presence of different contrasts in the head indicates a multi-phase nature with a fan-like faceted precipitate (Fig. 1d). STEM-EDS cartography shows that the tail is composed of Al, Mg, Si and N, with however a few isolated small iron rich precipitates. In contrast, the head exhibits at least four different phases: 1) an inner facetted center rich in Fe; 2) a shell rich in S and Mg surrounding the center; 3) the fan-like precipitate mainly composed of Ti and developing outwards from this shell; and 4) a structure having the same composition as the elongated tail (Fig. 2). In this study, transmission and analytical electron microscopy allowed determining an organized multi-phase graphite nucleus at nanometric scale in a spheroidal graphite cast irons and a formation sequence could be proposed [4]. References: [1] T Skaland, Metall Trans A, 24A (1993), p. 2321 [2] H Nakae, Mater Trans, 43 (2002), p.2826 [3] JK Solberg, Mater. Sci. Tech., 17 (2001) p.1238 [4] L Laffont, J Mater. Res. Technol., 9 (2020) p.4665
Alessandro PUGLIARA (Toulouse)
13:00 - 15:00 #26391 - Dynamic effect of field evaporation on the distribution of the light emitted by a quantum well analyzed witin a photonic atom probe.
Dynamic effect of field evaporation on the distribution of the light emitted by a quantum well analyzed witin a photonic atom probe.

Eric Maximilian Weikum *, Georges BeainyJonathan HouardIvan BlumSimona MoldovanJean-Michel ChauveauMaxime HuguesDenis LefebvreNolwenn le BiavanAngela Vella Lorenzo Rigutti

  • UNIROUEN, CNRS, Groupe de Physique des Matériaux, Normandie Université, 76000 Rouen, France.
  • Centre de Recherche sur l’Hétéro-Epitaxie et ses Applications, UPR10 CNRS, 06560 Valbonne, France.


The Photonic Atom Probe (PAP) [1] uses the pulsed laser of a Laser-assisted Atom Probe Tomograph (La-APT) to excite electronic states in semiconductor materials. The radiation caused from the relaxation of these excited electronic states is analyzed by a Photoluminescence (PL) set-up. Simultaneously the sample can be field-evaporated by the La-APT set-up. This destructive analysis method offers compositional information on the atomic scale. The combination of both analysis methods allows to correlate the PL spectra with the evaporation state of the sample. This instrument allows performing super-resolution PL analysis correlated with 3D chemical mapping [2] and stress measurements on tip specimens [3]. In this contribution we report about the effect of the dynamical development of the tip specimen morphology during evaporation on intensity of the collected PL. The experiment shows indeed that the collected PL intensity from a single MgZnO/ZnO-QW (quantum well) shows a dependence on the amount of field-evaporated atoms. Using the FTDT method of the LUMERICAL software (Fig. 1), the emission of PL was simulated for different evaporation states of the tip and compared to the experiment. The calculation was performed taking into account the microscopic APT-reconstruction of the tip, which allows determining the location, the composition and the geometry of the light-emitting quantum well (Fig. 2). The numerical results show that the change in the tip’s geometry, due to the removal of atoms by field evaporation, leads to a change in the spatial distribution of the emitted light, resulting in a change in the measured PL intensity. A good agreement between experimental and numerical results is observed. In addition to the analysis of the intensity as a function of the evaporation state, the Polarization dependence of the measured data was compared to the simulated results. It was found experimentally that the emission from the ZnO-QW shows a different favored Polarization direction (σ) than the MgZnO-barrier (π), which is not to be expected, since the ZnO-QW shares its Wurzite crystal structure with the MgZnO-barrier. References [1] Review of Scientific Instruments 91.8 (2020): 083704. [2] Nano Letters 20.12 (2020): 8733-8738. [3] Physical Review Applied 15.2 (2021): 024014.
Eric Maximilian WEIKUM (Rouen)
13:00 - 15:00 #26390 - Characterization STEM/XPS of a passive film formed on additive manufactured 17-4PH stainless steel.
Characterization STEM/XPS of a passive film formed on additive manufactured 17-4PH stainless steel.

Lydia Laffont *, Adrien BarrouxThomas DuguetNadège DucommunEric NivetJulien DelgadoChristine Blanc

  • CIRIMAT/Toulouse INP-Ensiacet
  • CIRIMAT/CETIM Nantes
  • CETIM Nantes


L’acier inoxydable martensitique 17-4PH (17%Cr, 5%Ni, 5%Cr) est utilisé dans l’industrie nucléaire, aéronautique et biomédicales en raison d’une bonne résistance à la corrosion intergranulaire et de très bonnes propriétés mécaniques (précipités nanométriques riches en Cu). Ces pièces sont obtenues par forgeage (REF) mais depuis quelques années par fusion laser sur lit de poudre (procédé de fabrication additive métallique -FA) [1]. La microstructure de ces pièces obtenues après le traitement thermique de référence H900 est équivalente mais présente néanmoins des différences en ce qui concerne la quantité d’austénite, la taille des lattes de martensite et celle des précipités de NbC (Figure 1) [2]. Dans cette étude, la spectroscopie de photoélectrons (XPS) et la microscopie électronique en transmission (MET/STEM) associée à la spectroscopie de dispersion en énergie des rayons X (EDS) ont été utilisés afin de caractériser le film passif nanométrique formé après immersion en milieu NaCl sur l’acier obtenu par FA en comparaison à l’acier de référence. Ce film présente une structure duplex constituée d’hydroxydes/oxydes de Fe et de Cr suivie d’une couche intermédiaire enrichie en Cr, Cu et Ni. La couche d’oxyde externe est composée principalement d’oxy/hydroxydes de fer alors que la couche interne est enrichie en chrome au niveau de l’oxyde de fer (Figure 2). Des différences significatives au niveau de l’épaisseur et de la distribution en chrome dans le film passif ont été observées pour les deux aciers. De plus, un film d’oxyde particulier est formé sur les précipités de NbC présents à la surface. Ces différences de composition chimique et de structure au niveau du film passif pour ces deux aciers permettent d’expliciter les différences de comportement en corrosion obtenues en ce qui concerne la résistance à la corrosion par piqûres [3]. Références : [1] X. Lou J. Nucl. Mater. vol. 499 (2018) p.182 [2] A. Barroux, Corr.Sci., vol. 169 (2020), p. 108594 [2] A. Barroux, Surf Int., vol. 22 (2021), p. 100874
Lydia LAFFONT (Toulouse)
Room 1
15:00 Pause
15:15

Vendredi 09 juillet

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SDV4
15:15 - 17:05

Symposium Sciences de la Vie 4
Imageries, spectroscopies en applications environnementales (Ecotoxicologie, Sols, Végétaux, milieux aquatiques)

Modérateurs : Arash JAMALI (UPJV, Amiens), Corentin SPRIET (TISBIO, Lille)
Le thème de ce symposium est large et couvre les développements récents et l'application des techniques de microscopie et de spectroscopie en sciences de l'environnement, leurs défis actuels et les solutions possibles.
La science de l'environnement est l'étude multidisciplinaire des environnements physiques, chimiques et biologiques de la terre. Les sujets englobent donc de nombreux domaines, notamment les sciences du sol, de l'eau et de l'atmosphère, l'écologie, l'écotoxicologie, les sciences végétales et animales, leurs sous-domaines, leurs processus et leurs interactions. La diversité et la complexité de ce domaine nécessitent souvent une approche et une expertise multidisciplinaire. L'utilisation de diverses techniques de microscopie et de spectroscopie contribue à la recherche environnementale en fournissant à la fois des informations qualitatives (identification) et quantitatives.Ce symposium est l'occasion de présenter des résultats de recherche originaux et exploratoires, ainsi que le développement, la validation et l'évaluation d'outils ou de méthodes innovants en recherche environnementale. Les modalités comprennent, mais sans s'y limiter, la microscopie photonique, électronique, et les méthodes d’analyses spectroscopiques associées.
15:15 - 15:45 La paroi secondaire décryptée par la microscopie optique multimodale. Guy COSTA (LCSN, Limoges)
Le bois est un matériau composite constitué principalement de cellules mortes. Le bois, ou xylème pourrait se réduire à l’étude de paroi secondaire des plantes. Paroi secondaire qui est constituée de lignines (polymère de phénol), de cellulose (polymère de ß-glucose) et dans une moindre mesure d’hémicelluloses (polymère de ß-galactose, ß-mannose, etc…). Usuellement, l’analyse de la composition pariétale nécessite l’utilisation de techniques de biochimie souvent complexe, consommatrice de temps et destructrices d’informations inhérentes aux méthodes biochimiques utilisées. La microscopie optique multimodale (immunomarquage, microscopie infrarouge, microscopie RAMAN, microscopie CARS, microscopie multiphotonique) offre alors des alternatives permettant une analyse fine de la paroi sans provoquer aucune modification des polymères pariétaux.
Les travaux présentés ici, visent à montrer en quoi l’imagerie optique multimodale permet d’analyser la distribution des polymères pariétaux. Pour ce faire, nous comparerons les résultats d’immunomarquage de la paroi avec des études d’imageries sans marquage, comme la microscopie vibrationelle CARS (Coherent Anto-Stokes Raman Scattering microscopy). Cette technique ne pouvant certainement pas à elle seule expliquer l’organisation et la distribution des biomolécules dans la paroi, elle sera complétée par de nouvelles approches comme la microscopie biphotonique, et la SHG.
15:45 - 15:55 Discussion.
15:55 - 16:25 Explore the functional organization of the vacuolar system by multiscale 3D reconstruction. Romain LE BARS (I2BC, Paris-Saclay)
The secretory glands of carnivorous plants undergo major remodeling when they enter a digestive process, making them an ideal model to study the morphodynamics of the endomembrane system (reticulum, Golgi apparatus, vacuoles). Understanding the functional mechanics of these changes requires the use of high-resolution techniques and 3D visualization of the entire secretory apparatus. To study how the vacuolar system adapts to this situation, electron microscopy studies allowed us to characterize morphologically these modifications. Nevertheless, the quantification of this process was not achievable as the vacuolar system is a very complex tridimensional network of interconnected compartments. To overcome this challenge we decided to combine electron microscopy sample preparation, light microscopy imaging and machine learning based image segmentation to generate 3D models of the vacuolar system. This complete workflow allowed us to quantify the vacuolar system evolution and is also a great alternative for any laboratory to reach high resolution at the sub-cellular scale on complex and challenging tissues.
16:25 - 16:35 Discussion.
16:35 - 16:55 #26366 - Investigation of the methylmecury detoxification into nano-HgSe in subantartic seabirds tissues.
Investigation of the methylmecury detoxification into nano-HgSe in subantartic seabirds tissues.

Mercury is a global contaminant which readily bioaccumulates in aquatic organisms and biomagnifies in marine food webs mainly as neurotoxic methylmercury (MeHg). Being high in the food webs, large seabirds are particularly exposed to MeHg. Because mercury has huge affinity for selenium, resistance to high amounts up to 1500 ppm of toxic mercury is thought to be achieved by detoxification in association with Se through biomineralization as HgSe, similarly to marine mammals, though no direct proof of such precipitates in birds was brought. To assess the Hg exposure risk, the Hg:Se ratio in cells is widely used as it is related to the capacity to detoxify MeHg which becomes more hazardous when Hg:Se≥1. But this approach relies on the hypothesis that the cells contain no other selenious form of Hg than HgSe.

This hypothesis was tested on the southern giant petrel Macronectes giganteus. The Hg speciation in dead-birds tissues was determined by coupling Hg L3-edge X-ray absorption spectroscopy with scanning transmission electron microscopy (STEM) using a Cs-probe-corrected and monochromated Themis-Z-G3.

STEM imaging at 80 kV using a High-Angle-Annular-Dark-Field detector (HAADF) allowed imaging for the first time large aggregates (up to 1 µm) of HgSe nanoprecipitates  with a grain size between 5 nm in kidneys and pectoral muscles, up to 40 nm in the liver (Figure 1). A 80 kV voltage with a curent of ~100 A was chosen to maximize the X-rays emission for EDS elemental mapping while preserving at most the beam-sensitive organic tissues. It confirmed the precipitates composition with a Hg:Se~1. No selenium was found in the HgSe pecipitates vicinity. High-resolution (HR) TEM images of individuel gains in liver and kidneys were aquired to explore the crystal structure at the atomic scale, using a 300 kV to maximize the phase contrast. Fast-Fourier transform (FFT) images and electron diffraction of large HgSe aggregates demontrate their cubic F43m structure (a = 6.08 Å). HR images of the more challenging muscle sample were obtained in STEM-HAADF at 300 kV, 60 pA current and -170°C. A collection of 80 images (0.1 sec/frame) were drift-corrected and summed, confirming a similar cubic structure.


Anne-Claire GAILLOT (NANTES Cedex 3)
16:55 - 17:05 Discussion.
Room 1

Vendredi 09 juillet

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SDM4
15:15 - 18:10

Symposium Sciences de la Matière 4
Spectroscopies, analyses et imageries chimique multi-échelles

Modérateurs : Philippe MOREAU (IMN, Nantes), Michaël WALLS (LPS, Orsay)
La puissance de la microscopie dans sa capacité d’interprétation des phénomènes à différentes échelles réside souvent de son association possible à une spectroscopie. Des analyses et/ou cartographies chimiques peuvent alors être produites, sur des dimensions micrométriques comme sub-nanométriques. La diversité des spectroscopies permet d’obtenir différentes informations qu’elles soient vibrationnelles, élémentaires ou donnant accès au type de liaison chimique, par exemple. La même diversité existe sur les types de microscopie (électronique, photonique, à sonde locale…) ce qui donne un caractère très ouvert et général à ce symposium. Les contributions présentant un caractère multi-échelle fort seront donc privilégiées, notamment en montrant l’intérêt de la complémentarité des techniques et les différences/similarités constatées aux différentes échelles. Les apports respectifs des analyses quantitatives précises et des cartographies de phases pourront être mises en avant. Les réflexions sur les résolutions spatiales adaptées en fonction de la technique, de l’information recherchée et de l’échantillon considéré sont aussi les bienvenues.
15:15 - 15:45 Modeling vibrational EELS of a single point defect. Guillaume RADTKE (CNRS Senior Researcher) (IMPMC, Paris Sorbonne)
Vibrational excitations are now accessible to high-energy-resolution electron- energy-loss spectroscopy (EELS) in a growing number of materials [1]. Combined with the very high spatial resolution of transmission electron microscopy, this technique therefore opens exciting perspectives for investigating the vibrational properties of condensed matter systems down to the atomic scale. In this context, EELS brings a direct insight into localized modes associated with structural defects, which strongly influence the macroscopic properties of materials and in particular, heat transport.
Most of these systems however, display complex atomic structures whose dynamics can seldom be understood using empirical models or through simple comparisons with known references. A proper assessment of the origin of the different structures observed experimentally therefore relies both on first-principles calculations and on an accurate description of the scattering process [2,3].
The major part of this talk will be devoted to the modeling of atomic-resolution vibrational EELS acquired on point defects in graphene [4]. After discussing the general features of impurity-induced vibrational modes in solids and the insights EELS could provide in this field, we will present state-of-the art DFT calculations carried out on the particular case of a trivalent substitutional impurity of silicon. Results obtained from first- principles on supercells as large as 96 x 96 (18432 atoms) graphene unit cells, required to isolate the substitutional silicon atom, show how resonant modes result from the hybridization of local impurity modes with the continuum of “bulk” graphene. We will show how the projected phonon density of states (PPDOS) mimics the dominant features of atomically-resolved “dark EELS” spectra and appears in this context as a simple and useful quantity to interpret qualitatively experimental spectral features. Finally, these results will be compared to those obtained theoretically on other point defects and their impact on the lifetime of “bulk” phonons in graphene, and thus on the thermal pransport properties of this material, will be discussed.

[1] O.L. Krivanek, T. C. Lovejoy, N. Dellby, T. Aoki, R.W. Carpenter, P. Rez, E. Soignard, J. Zhu, P. E. Batson, M.J. Lagos, R.F. Egerton and P.A. Crozier, Nature 514 (2014) 209.
[2] G. Radtke, D. Taverna, M. Lazzeri and E. Balan, Phys. Rev. Lett. 119 (2017) 027402.
[3] G. Radtke, D. Taverna, N. Menguy, S. Pandolfi, A. Courac, Y. Le Godec, O. L. Krivanek, and T. C. Lovejoy, Phys. Rev. Lett. 123 (2019) 256001.
[4] F. S. Hage, G. Radtke, D. M. Kepaptsoglou, M. Lazzeri and Q. M. Ramasse, Science 367 (2020) 1124.
15:45 - 15:55 Discussion.
15:55 - 16:25 Séparation de phases dans des minéraux complexes grâce à des techniques de "machine learning". Cécile HÉBERT (Prof.) (EPFL, Lausanne, Suisse)
16:25 - 16:35 Discussion.
16:35 - 16:50 #26385 - A Photonic Atom Probe allowing for super-resolution photoluminescence spectroscopy and 3D microscopy of nanoscale light emitters.
A Photonic Atom Probe allowing for super-resolution photoluminescence spectroscopy and 3D microscopy of nanoscale light emitters.

The laser pulses controlling the ion evaporation in Laser-assisted Atom Probe Tomography (La-APT) can simultaneously excite photoluminescence in semiconductor or insulating specimens [1]. An atom probe equipped with approriate focalization and collection optics can thus be coupled with an in-situ micro-photoluminescence (µPL) bench [2] that can be operated even during APT analysis. Our team has recently developed a coupled µPL-APT instrument operating at 400 kHz, controlled by 150 fs laser pulses tunable in energy in a large spectral range (spanning from deep UV to near IR). Micro-PL spectroscopy is performed using a 320 mm focal length spectrometer equipped with a CCD camera for time-integrated and with a streak camera for time-resolved acquisitions. Such a Photonic Atom Probe (PAP) has been applied to the study of the optical properties of nanoscale emitters in an in-situ correlative microscopy approach. The evolution of the PL signal during the APT analysis is an original source of information. In this work we analyzed specimens containing ZnO/(Mg,Zn)O quantum wells (QWs) of different thicknesses, and we show that it is possible to distinguish the optical signatures of separate QWs distant as few as 20 nm – well below the diffraction limit of the laser [3]. This information is then correlated with the chemical 3D distribution obtained by APT. The analysis of the PL spectral shifts during the APT analysis also allows determining the stress state induced by the electrostatic field [4].

[1] Mancini, Lorenzo, et al. ""Carrier localization in GaN/AlN quantum dots as revealed by three-dimensional multimicroscopy."" Nano letters 17.7 (2017): 4261-4269.

[2] Houard, Jonathan, et al. ""A photonic atom probe coupling 3D atomic scale analysis with in situ photoluminescence spectroscopy."" Review of Scientific Instruments 91.8 (2020): 083704.

[3] Di Russo, Enrico, et al. ""Super-resolution Optical Spectroscopy of Nanoscale Emitters within a Photonic Atom Probe."" Nano Letters 20.12 (2020): 8733-8738.

[4] Dalapati, P., et al. ""In Situ Spectroscopic Study of the Optomechanical Properties of Evaporating Field Ion Emitters."" Physical Review Applied 15.2 (2021): 024014.


Lorenzo RIGUTTI (Rouen)
16:50 - 17:00 Discussion.
17:00 - 17:15 #26392 - Quantification of hydrogen in nanoscale structures using correlative TEM, SIMS and APT analysis.
Quantification of hydrogen in nanoscale structures using correlative TEM, SIMS and APT analysis.

Transmission Electron Microscopy (TEM) is a widely used technique for atomic scale imaging and chemical analysis of materials [1]. However, the analysis of elements in trace concentrations, low-Z elements and isotopic selectivity are very difficult or impossible using the typical chemical analysis techniques available in a TEM such as Energy Dispersive X-ray Spectroscopy (EDS) or Electron Energy-Loss Spectroscopy (EELS). Atom Probe Tomography (APT) allows 3D nanoscale chemical imaging and it is capable of distinguishing isotopes. However, the analysed volume is small (~ 10^6 nm^3) and the data is prone to artefacts. Specifically, a precise 3D APT reconstruction requires the local morphology of the sample tip at each instance in time which is often lacking. Furthermore, limited mass resolution and differences in the field evaporation of different elements can also introduce artefacts in the APT data. Secondary Ion Mass Spectrometry (SIMS) is a high-sensitivity technique to detect concentrations down to the ppm range. Moreover, all elements and isotopes in the periodic table can be analysed. However, the main limitation of SIMS is that the quantification is difficult because of matrix effects (i.e. strong variations in ionization yields depending on matrix elements). Relatively large volumes (~ 10^3 um^3) are typically analysed in SIMS and the lateral resolution in SIMS imaging is fundamentally limited to ~ 10 nm by the ion-solid interaction volume. To overcome the limitations of the individual techniques, we present a correlative TEM-APT-SIMS method [2] for the quantification of hydrogen, deuterium and other trace elements (dopants) in passivating contact layers used in silicon photovoltaics. The analysis and data treatment methodologies will be discussed in detail and other new methods to quantify SIMS images will also be briefly introduced [3, 4]. 

This work was partially funded by the Luxembourg National Research Fund (FNR) by the grants C18/MS/12661114 (MEMPHIS) and INTER/SNF/16/11536628 (NACHOS).

References:

[1] D. B. Williams & C. B. Carter, Transmission Electron Microscopy, Springer, US 2009

[2] S. Pal et al, Appl. Surf. Sci, 555, 149650, 2021

[3] S. Eswara et al, MRS Comm., 9, 916–923, 2019

[4] L. Yedra et al, J. Anal. Atom. Spectrom., 36, 56-63, 2021


Santhana ESWARA (Esch-sur-Alzette, Luxembourg)
17:15 - 17:25 Discussion.
17:25 - 17:40 #26394 - Low-Energy Excitations in Transition-Metal Oxides by STEM-EELS Spectromicroscopy.
Low-Energy Excitations in Transition-Metal Oxides by STEM-EELS Spectromicroscopy.

The transition metal oxides exhibit a variety of interesting properties, such as ferroelectricity, superconductivity, etc. The atomic structural degrees of freedom and the electron’s degrees of freedom (charge and spin) lead to various phenomena through phase transitions. All these orders can be studied through collective excitations. By scanning transmission electron microscopy (STEM) with monochromator, the energy resolution can go as low as 5meV [1], and such low-energy excitations can thus be investigated by electron energy-loss spectroscopy (EELS) [2, 3]. 

In this work, we focus on the low-energy electronic excitations, id est, the plasmon and the d-d excitations on the SrVO3 oxides. The SrVO3 is an attractive earth‐abundant transparent conducting oxide. It is also described as a typical correlated metal where low-energy plasmon fluctuation can also leads to an appreciable renormalization of the low-energy band. Nevertheless, the experimental occurrence of plasmons is poorly reported. The observations of plasmonic type d-d excitations (dipolar contribution, strong surface delocalization in aloof beam) on SrVO3 by EELS are shown in Figure 1. Furthermore, the dispersion curve of the bulk plasmon, as measured for different slabs thicknesses, will be presented and discussed with respect to ab-initio calculation. The Figure 2 shows that the nanostructures based on SrVO3 exhibit the Fabry-Perot type surface plasmon modes. Several surface plasmons modes are visible on “rod-type” geometries, such as half-rod or slit and have been compared to the finite-difference time-domain (FDTD) simulation. We will report energy widths of surface plasmon as low as 50 meV in the sub 0.5eV loss range..It suggests that SrVO3 could be one alternative plasmonic materials due to the high quality factor in the near-infrared range, and thereby providing a reference for searching for better plasmonic materials.

References :

[1] O.L. Krivanek et al., Nature 514 (2014), 209.

[2] A. Gloter et al., Ultramicroscopy 109 (2009), 1333.

[3] V. Mkhitaryan et al., Nano letters 21 (2021), 2444.

Figure 1: (a) Disperson curve and (b) bulk/aloof measurements on SrVO3. (c) Dispersion curve of the plasmon peaks.

Figure 2: The Fabry-Perot type d-d based surface plasmon modes in SrVO3 of (a) half-rod and (c) slit nanostructures. (b) FDTD simulation of (a).


Chia-Ping SU (Orsay)
17:40 - 17:50 Discussion.
17:50 - 18:00 Electron detectors for counted EELS acquisition - Gatan. Ray TWESTEN (Product Manager – Analytical Instruments) (GATAN, Etats-Unis)
18:00 - 18:10 Discussion.
Room 2