The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Baptiste Gault - One of the best experts on this subject based on the ideXlab platform.

  • calibration of Atom Probe Tomography reconstructions through correlation with electron micrographs
    Microscopy and Microanalysis, 2019
    Co-Authors: Isabelle Mouton, Leigh T Stephenson, Oana Cojocarumiredin, Dierk Raabe, Shyam Katnagallu, Surendra Kumar Makineni, Torsten Schwarz, Baptiste Gault
    Abstract:

    Although Atom Probe Tomography (APT) reconstructions do not directly influence the local elemental analysis, any structural inferences from APT volumes demand a reliable reconstruction of the point cloud. Accurate estimation of the reconstruction parameters is crucial to obtain reliable spatial scaling. In the current work, a new automated approach of calibrating Atom Probe reconstructions is developed using only one correlative projection electron microscopy (EM) image. We employed an algorithm that implements a 2D cross-correlation of microstructural features observed in both the APT reconstructions and the corresponding EM image. We apply this protocol to calibrate reconstructions in a Cu(In,Ga)Se2-based semiconductor and in a Co-based superalloy. This work enables us to couple chemical precision to structural information with relative ease.

  • Interfaces and defect composition at the near-Atomic scale through Atom Probe Tomography investigations
    Journal of Materials Research, 2018
    Co-Authors: Baptiste Gault, Andrew J Breen, Isabelle Mouton, Surendra Kumar Makineni, Yanhong Chang, Eric A. Jägle, Paraskevas Kontis, Philipp Kürnsteiner, Alisson Kwiatkowski Da Silva, Zirong Peng
    Abstract:

    Atom Probe Tomography (APT) is rising in influence across many parts of materials science and engineering thanks to its unique combination of highly sensitive composition measurement and three-dimensional microstructural characterization. In this invited article, we have selected a few recent applications that showcase the unique capacity of APT to measure the local composition at structural defects. Whether we consider dislocations, stacking faults, or grain boundary, the detailed compositional measurements tend to indicate specific partitioning behaviors for the different solutes in both complex engineering and model alloys we investigated.

  • On the detection of multiple events in Atom Probe Tomography
    Ultramicroscopy, 2018
    Co-Authors: Zirong Peng, Dierk Raabe, François Vurpillot, Pyuckpa Choi, Baptiste Gault
    Abstract:

    In Atom Probe Tomography (APT), multiple events can arise as a consequence of e.g. correlated field evaporation and molecular ion dissociation. They represent challenging cases for single-particle detectors and can cause compositional as well as spatial inaccuracies. Here, two state-of-the-art Atom Probe microscopes (Cameca LEAP 5000 XS and 5000 XR) were used to investigate cemented tungsten carbide, which exhibits high amounts of multiple events. By advanced data analysis methods, the natural character of the multiple events, as well as the performance of the APT detectors, are assessed. Accordingly, possible signal loss mechanisms are discussed.

  • reflections on the projection of ions in Atom Probe Tomography
    Microscopy and Microanalysis, 2017
    Co-Authors: F. De Geuser, Baptiste Gault
    Abstract:

    There are two main projections used to transform, and reconstruct, field ion micrographs or Atom Probe Tomography data into Atomic coordinates at the specimen surface and, subsequently, in three dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison with the more widely used and well-established point projection (or pseudo-stereographic projection), which underpins data reconstruction in most software packages currently in use across the community. After an overview of the reconstruction methodology, we demonstrate that the azimuthal equidistant is more robust with regards to errors on the parameters used to perform the reconstruction and is therefore more likely to yield more accurate tomographic reconstructions.

  • spatial resolution in Atom Probe Tomography
    arXiv: Instrumentation and Detectors, 2015
    Co-Authors: Baptiste Gault, Michael P Moody, F. De Geuser, Leigh T Stephenson, Alex La Fontaine, Daniel Haley, Simon P Ringer
    Abstract:

    This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in Atom Probe Tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of Atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the Atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific.

M K Miller - One of the best experts on this subject based on the ideXlab platform.

  • Atom Probe Tomography analysis of precipitation during tempering of a nanostructured bainitic steel
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2011
    Co-Authors: F G Caballero, M K Miller, C Garciamateo
    Abstract:

    Carbon distribution during tempering of a nanostructured bainitic steel was analyzed by Atom Probe Tomography (APT). Three different types of particles are detected on samples tempered at 673 K (400 °C) for 30 minutes: lower bainite cementite with a carbon content of ~25 at. pct, e-carbides with a carbon content close to 30 at. pct, and carbon clusters, small features with a carbon content of ~14 at. pct indicative of a stage of tempering prior to precipitation of e-carbide. After tempering at 773 K (500 °C) for 30 minutes, the e-carbide-to-cementite transition was observed. Solute concentration profiles across carbide/ferrite interfaces showed the distribution of substitutional elements in e-carbide and cementite for all the tempering conditions.

  • characterization of nanoscale nial type precipitates in a ferritic steel by electron microscopy and Atom Probe Tomography
    Scripta Materialia, 2010
    Co-Authors: Zhenke Teng, M K Miller, K F Russell, Gautam Ghosh, Shenyan Huang, M E Fine, P K Liaw
    Abstract:

    The microstructure of NiAl-type (β′) precipitates in an aged ferritic steel (Fe–12.7Al–9Ni–10.2Cr–1.9Mo, at.%) is characterized by transmission and analytical electron microscopy (AEM) and Atom Probe Tomography (APT). The alloy shows a duplex precipitation of β′ particles: primary with an average diameter of 130 nm and secondary with an average diameter of 3 nm. Based on APT, the primary and secondary β′ have compositions of Ni41.2Al43.6Fe12.7Cr0.8Mo1.4 and Ni26.3Al41.6Fe26.9Cr3.3Mo1.7, respectively.

  • invited review article Atom Probe Tomography
    Review of Scientific Instruments, 2007
    Co-Authors: Thomas F. Kelly, M K Miller
    Abstract:

    The technique of Atom Probe Tomography (APT) is reviewed with an emphasis on illustrating what is possible with the technique both now and in the future. APT delivers the highest spatial resolution (sub-0.3-nm) three-dimensional compositional information of any microscopy technique. Recently, APT has changed dramatically with new hardware configurations that greatly simplify the technique and improve the rate of data acquisition. In addition, new methods have been developed to fabricate suitable specimens from new classes of materials. Applications of APT have expanded from structural metals and alloys to thin multilayer films on planar substrates, dielectric films, semiconducting structures and devices, and ceramic materials. This trend toward a broader range of materials and applications is likely to continue.

  • Atom Probe Tomography characterization of solute segregation to dislocations and interfaces
    Journal of Materials Science, 2006
    Co-Authors: M K Miller
    Abstract:

    The level and extent of solute segregation to individual dislocations and interfaces may be visualized and quantified by Atom Probe Tomography. The large volume of analysis and high data acquisition rate of the local electrode Atom Probe (LEAP®) enables the solute distribution in the region of and along the core of dislocations to be estimated. Solute segregation at precipitate-matrix interfaces of precipitates as small as 2-nm diameter may be quantified. Examples are presented of solute segregation to dislocations and clustering/precipitation in a neutron irradiated Fe–Ni–P model alloy and the neutron irradiated beltline weld from the Midland reactor.

  • Atom Probe Tomography characterization of solute segregation to dislocations
    Microscopy Research and Technique, 2006
    Co-Authors: M K Miller
    Abstract:

    The extent and level of solute segregation to individual dislocations may be quantified by Atom Probe Tomography. The technique is best applied to materials with high dislocation densities, such as cold worked, mechanically alloyed, or neutron-irradiated materials. Dislocations may be observed in field ion images by a change of the normal concentric Atom terraces at crystallographic poles to spirals. Solute segregation is evident in field ion images by brightly imaging Atoms near the core of the dislocation. Dislocations are evident in Atom maps in the three-dimensional Atom Probe by linear regions of enhanced solute concentration. The maximum separation envelope and tracer methods may be used to quantify the levels of solute at the dislocation at the subnanometer scale. Examples of interstitial and substitutional element segregation in a mechanically alloyed, oxide dispersion strengthened ferrite steel and phosphorus segregation to dislocations in neutron-irradiated pressure vessel steels are presented. Microsc. Res. Tech. 69:359–365, 2006. Published 2006 Wiley-Liss, Inc.

Simon P Ringer - One of the best experts on this subject based on the ideXlab platform.

  • Atom Probe Tomography of size controlled phosphorus doped silicon nanocrystals
    Physica Status Solidi-rapid Research Letters, 2017
    Co-Authors: Keita Nomoto, Margit Zacharias, Gavin Conibeer, Daniel Hiller, S Gutsch, Anna V Ceguerra, Andrew J Breen, Ivan Perezwurfl, Simon P Ringer
    Abstract:

    Doping of silicon nanocrystals is essential to control their electronic and optical properties. The incorporation of an impurity into a silicon nanovolume is a nontrivial task due to the self-purification effect. Here, a systematic Atom Probe Tomography study of the phosphorus distribution and incorporation in size-controlled silicon nanocrystals embedded in silicon dioxide is presented. Qualitatively, it turns out that the phosphorus distribution in the system follows a universal, nanocrystal-size independent trend: phosphorus-enrichment at the interface with a substantial phosphorus-incorporation in the silicon nanocrystal as small as 2 nm in diameter. This clearly contradicts strict self-purification. These observations are explained by the bulk-solubility and -segregation behaviour, kinetic effects related to the diffusion lengths, and nanoscale interface strain. The quantitative determination of the amount of phosphorus Atoms per quantum dot enables a systematic understanding of phosphorus-induced effects on optical and electronic properties of silicon nanovolumes.

  • new approaches to nanoparticle sample fabrication for Atom Probe Tomography
    Ultramicroscopy, 2015
    Co-Authors: Peter Felfer, Simon P Ringer, G.d.w. Smith, David C Bell, Katja Eder, Henning Galinski, Andrew P Magyar, Norbert Kruse, Julie M. Cairney
    Abstract:

    Abstract Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the Atomic scale, especially in three dimensions (3D). Atom Probe Tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for Atom Probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate Atom Probe samples from this composite. Using these approaches, data has been achieved from 10–20 nm core–shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ±1 nm.

  • spatial resolution in Atom Probe Tomography
    arXiv: Instrumentation and Detectors, 2015
    Co-Authors: Baptiste Gault, Michael P Moody, F. De Geuser, Leigh T Stephenson, Alex La Fontaine, Daniel Haley, Simon P Ringer
    Abstract:

    This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in Atom Probe Tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of Atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the Atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific.

  • a new approach to the determination of concentration profiles in Atom Probe Tomography
    Microscopy and Microanalysis, 2012
    Co-Authors: Peter Felfer, Simon P Ringer, Baptiste Gault, Gang Sha, Leigh T Stephenson, Julie M. Cairney
    Abstract:

    Atom Probe Tomography ~APT! provides three-dimensional analytical imaging of materials with near-Atomic resolution using pulsed field evaporation. The processes of field evaporation can cause Atoms to be placed at positions in the APT reconstruction that can deviate slightly from their original site in the material. Here, we describe and model one such process—that of preferential retention of solute Atoms in multicompo- nent systems. Based on relative field evaporation probabilities, we calculate the point spread function for the solute Atom distribution in the "z," or in-depth direction, and use this to extract more accurate solute concentration profiles.

  • The future of Atom Probe Tomography
    Materials Today, 2012
    Co-Authors: Thomas F. Kelly, Krishna Rajan, Simon P Ringer
    Abstract:

    The dream of the microscopy and materials science communities is to see, identify, accurately locate, and determine the fundamental physical properties of every Atom in a specimen. With this knowledge together with modern computer models and simulations, a full understanding of the properties of a material can be determined. This fundamental knowledge leads to the design and development of more advanced materials for solving the needs of society. The technique of Atom Probe Tomography is the closest to fulfilling this dream but is still significantly short of the goal. The future of Atom Probe Tomography, and the prospects for achieving this ultimate goal are outlined.

Michael P Moody - One of the best experts on this subject based on the ideXlab platform.

  • Atom Probe Tomography study of gettering in high performance multicrystalline silicon
    IEEE Journal of Photovoltaics, 2020
    Co-Authors: David Tweddle, Phillip Hamer, Zhao Shen, Friedemann D Heinz, Patricia Krenckel, Stephen Riepe, Florian Schindler, P R Wilshaw, Michael P Moody
    Abstract:

    During the production of high-performance multicrystalline silicon (HPMC-Si) solar cells, gettering occurs inherently during the formation of an emitter. The material benefits with an increase in minority carrier lifetime from the external gettering of impurities into the diffused layer. However, depending on the thermal budget and parameters of the emitter diffusion, as well as the specific material properties, the process can also be detrimental in terms of increased recombination activity of specific crystallographic defects. Thus, it is important to understand the root causes behind the change in recombination activity of defects following gettering. Here, we present a correlative Atom Probe Tomography study of grain boundaries in both p- and n-type HPMC-Si before and after gettering. The presence of nitrogen was found to directly correlate with the increase in recombination activity at grain boundaries. Additionally, an estimation of the Atom Probe Tomography detection limit for transition metals in silicon is made and found to be greater than known impurity levels in commercial HPMC-Si.

  • Atom Probe Tomography investigations of microstructural evolution in an aged nickel superalloy for exhaust applications
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2019
    Co-Authors: H M Gardner, Michael P Moody, S Pedrazzini, James O Douglas, Didier De Lille, Paul A J Bagot
    Abstract:

    The formation and evolution of nanoscale γ″ (Ni3(Nb, Ti, Al)) precipitates formed during thermal aging in the nickel superalloy Inconel 625 has been characterized using Atom Probe Tomography. The onset of γ″ precipitation has been found to occur after only one hour, markedly shorter than the aging time reported in the current literature. Evolution of precipitate composition and morphology during aging has been analyzed, and the potential onset of the γ″ → δ (Ni3(Nb, Mo, Cr, Fe, Ti)) transformation after long aging times is discussed.

  • advances in Atom Probe Tomography instrumentation implications for materials research
    Mrs Bulletin, 2016
    Co-Authors: Michael P Moody, Stephan S.a. Gerstl, A Vella, Paul A J Bagot
    Abstract:

    A series of recent instrumental advances have facilitated the application of Atom Probe Tomography (APT) to the characterization of an increasingly wide range of materials and devices. Whereas APT was previously mostly limited to the analysis of alloys, advances in areas such as laser pulsing and detectors have enabled characterization of semiconductors and brittle materials. Most recently, ultraviolet laser pulsing has facilitated the analysis of materials previously considered not viable for the Atom Probe, such as minerals and large bandgap insulator materials. The development of in situ gas reaction cells fully integrated in Atom Probe instruments has enabled the characterization of surface reactions of materials exposed to highly controlled environments. Finally, current work toward an integrated cryo-transfer system is anticipated to create new directions for APT research.

  • spatial resolution in Atom Probe Tomography
    arXiv: Instrumentation and Detectors, 2015
    Co-Authors: Baptiste Gault, Michael P Moody, F. De Geuser, Leigh T Stephenson, Alex La Fontaine, Daniel Haley, Simon P Ringer
    Abstract:

    This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in Atom Probe Tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of Atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the Atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific.

  • Atom Probe Tomography of stress corrosion crack tips in sus316 stainless steels
    Corrosion Science, 2015
    Co-Authors: Martina Meisnar, Michael P Moody, S Lozanoperez
    Abstract:

    Abstract Novel Atom Probe Tomography (APT) data of an intergranular stress corrosion crack tip has been acquired. Using APT for stress corrosion cracking research, very small, localized features and their distribution around the crack tip can be studied in 3D. This work details the development of a technique for the preparation of Atom Probe needles. Initial characterization via analytical transmission electron microscopy provides with a complementary analysis and accurately locates features that can be correlated with the reconstructed APT data. Ni enrichment and intergranular oxidation ahead of the crack tip have been studied with APT in 3D and with near-Atomic resolution.

Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.

  • calibration of Atom Probe Tomography reconstructions through correlation with electron micrographs
    Microscopy and Microanalysis, 2019
    Co-Authors: Isabelle Mouton, Leigh T Stephenson, Oana Cojocarumiredin, Dierk Raabe, Shyam Katnagallu, Surendra Kumar Makineni, Torsten Schwarz, Baptiste Gault
    Abstract:

    Although Atom Probe Tomography (APT) reconstructions do not directly influence the local elemental analysis, any structural inferences from APT volumes demand a reliable reconstruction of the point cloud. Accurate estimation of the reconstruction parameters is crucial to obtain reliable spatial scaling. In the current work, a new automated approach of calibrating Atom Probe reconstructions is developed using only one correlative projection electron microscopy (EM) image. We employed an algorithm that implements a 2D cross-correlation of microstructural features observed in both the APT reconstructions and the corresponding EM image. We apply this protocol to calibrate reconstructions in a Cu(In,Ga)Se2-based semiconductor and in a Co-based superalloy. This work enables us to couple chemical precision to structural information with relative ease.

  • On the detection of multiple events in Atom Probe Tomography
    Ultramicroscopy, 2018
    Co-Authors: Zirong Peng, Dierk Raabe, François Vurpillot, Pyuckpa Choi, Baptiste Gault
    Abstract:

    In Atom Probe Tomography (APT), multiple events can arise as a consequence of e.g. correlated field evaporation and molecular ion dissociation. They represent challenging cases for single-particle detectors and can cause compositional as well as spatial inaccuracies. Here, two state-of-the-art Atom Probe microscopes (Cameca LEAP 5000 XS and 5000 XR) were used to investigate cemented tungsten carbide, which exhibits high amounts of multiple events. By advanced data analysis methods, the natural character of the multiple events, as well as the performance of the APT detectors, are assessed. Accordingly, possible signal loss mechanisms are discussed.

  • grain boundary segregation in multicrystalline silicon correlative characterization by ebsd ebic and Atom Probe Tomography
    Progress in Photovoltaics, 2015
    Co-Authors: Andreas Stoffers, Stephan Riepe, Oana Cojocarumiredin, W Seifert, Stefan Zaefferer, Dierk Raabe
    Abstract:

    This study aims to better understand the influence of crystallographic structure and impurity decoration on the recombination activity at grain boundaries in multicrystalline silicon. A sample of the upper part of a multicrystalline silicon ingot with intentional addition of iron and copper has been investigated. Correlative electron-beam-induced current, electron backscatter diffraction, and Atom Probe Tomography data for different types of grain boundaries are presented. For a symmetric coherent Σ3 twin boundary, with very low recombination activity, no impurities are detected. In case of a non-coherent (random) high-angle grain boundary and higher order twins with pronounced recombination activity, carbon and oxygen impurities are observed to decorate the interface. Copper contamination is detected for the boundary with the highest recombination activity in this study, a random high-angle grain boundary located in the vicinity of a triple junction. The 3D Atom Probe Tomography study presented here is the first direct Atomic scale identification and quantification of impurities decorating grain boundaries in multicrystalline silicon. The observed deviations in chemical decoration and induced current could be directly linked with different crystallographic structures of silicon grain boundaries. Hence, the current work establishes a direct correlation between grain boundary structure, Atomic scale segregation information, and electrical activity. It can help to identify interface–property relationships for silicon interfaces that enable grain boundary engineering in multicrystalline silicon. Copyright © 2015 John Wiley & Sons, Ltd.

  • microstructural evolution of a ni based superalloy 617b at 700 c studied by electron microscopy and Atom Probe Tomography
    Acta Materialia, 2012
    Co-Authors: Darius Tytko, Pyuckpa Choi, Jutta Klower, Gerhard Inden, Dierk Raabe
    Abstract:

    Abstract We report on the microstructural evolution of a polycrystalline Ni-based superalloy (Alloy 617B) for power plant applications at a service temperature of 700 °C. The formation of secondary M23C6-carbides close to grain boundaries (GBs) and around primary Ti(C,N) particles is observed upon annealing at 700 °C, where γ′ is found to nucleate heterogeneously at M23C6 carbides. Using Atom Probe Tomography, elemental partitioning to the phases and composition profiles across phase and grain boundaries are determined. Enrichments of B at γ/M23C6 and γ′/M23C6 interfaces as well as at grain boundaries are detected, while no B enrichment is found at γ/γ′ interfaces. It is suggested that segregation of B in conjunction with γ′ formation stabilizes a network of secondary M23C6 precipitates near GBs and thus increases the creep rupture life of Alloy 617B. Calculations of the equilibrium phase compositions by Thermo-Calc confirm the chemical compositions measured by Atom Probe Tomography.

  • Atom Probe Tomography characterization of heavily cold drawn pearlitic steel wire
    Ultramicroscopy, 2011
    Co-Authors: Pyuckpa Choi, Dierk Raabe, C Borchers, Y Z Chen, Shoji Goto, R Kirchheim
    Abstract:

    Atom Probe Tomography (APT) was used to analyze the carbon distribution in a heavily cold drawn pearlitic steel wire with a true strain of 6.02. The carbon concentrations in cementite and ferrite were separately measured by a sub-volume method and compared with the literature data. It is found that the carbon concentration in ferrite saturates with strain. The carbon concentration in cementite decreases with the lamellar thickness, while the carbon Atoms segregate at dislocations or cell/grain boundaries in ferrite. The mechanism of cementite decomposition is discussed in terms of the evolution of dislocation structure during severe plastic deformation.