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Fatermans J (2019) Quantitative atom detection from atomic-resolution transmission electron microscopy images. 155 p
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Atom column detection”. Fatermans J, de Backer A, den Dekker AJ, Van Aert S Advances in imaging and electron physics
T2 – Advances in imaging and electron physics. page 177 (2021).
Abstract: By combining statistical parameter estimation and model-order selection using a Bayesian framework, the maximum a posteriori (MAP) probability rule is proposed in this chapter as an objective and quantitative method to detect atom columns from high-resolution scanning transmission electron microscopy (HRSTEM) images. The validity and usefulness of this approach is demonstrated to both simulated and experimental annular dark-field (ADF) STEM images, but also to simultaneously acquired annular bright-field (ABF) and ADF STEM image data.
Keywords: H2 Book chapter; Electron microscopy for materials research (EMAT); Vision lab
DOI: 10.1016/BS.AIEP.2021.01.006
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“Image-quality evaluation and model selection with maximum a posteriori probability”. Fatermans J, de Backer A, den Dekker AJ, Van Aert S Advances in imaging and electron physics
T2 – Advances in imaging and electron physics. page 215 (2021).
Abstract: The maximum a posteriori (MAP) probability rule for atom column detection can also be used as a tool to evaluate the relation between scanning transmission electron microscopy (STEM) image quality and atom detectability. In this chapter, a new image-quality measure is proposed that correlates well with atom detectability, namely the integrated contrast-to-noise ratio (ICNR). Furthermore, the working principle of the MAP probability rule is described in detail showing a close relation to the principles of model-selection methods.
Keywords: H2 Book chapter; Electron microscopy for materials research (EMAT); Vision lab
DOI: 10.1016/BS.AIEP.2021.01.007
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“Single Atom Detection from Low Contrast-to-Noise Ratio Electron Microscopy Images”. Fatermans J, den Dekker A J, Müller-Caspary K, Lobato I, O’Leary C M, Nellist P D, Van Aert S, Physical review letters 121, 056101 (2018). http://doi.org/10.1103/PhysRevLett.121.056101
Abstract: Single atom detection is of key importance to solving a wide range of scientific and technological problems. The strong interaction of electrons with matter makes transmission electron microscopy one of the most promising techniques. In particular, aberration correction using scanning transmission electron microscopy has made a significant step forward toward detecting single atoms. However, to overcome radiation damage, related to the use of high-energy electrons, the incoming electron dose should be kept low enough. This results in images exhibiting a low signal-to-noise ratio and extremely weak contrast, especially for light-element nanomaterials. To overcome this problem, a combination of physics-based model fitting and the use of a model-order selection method is proposed, enabling one to detect single atoms with high reliability.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 8.462
Times cited: 6
DOI: 10.1103/PhysRevLett.121.056101
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“Atom column detection from simultaneously acquired ABF and ADF STEM images”. Fatermans J, den Dekker Aj, Müller-Caspary K, Gauquelin N, Verbeeck J, Van Aert S, Ultramicroscopy 219, 113046 (2020). http://doi.org/10.1016/j.ultramic.2020.113046
Abstract: In electron microscopy, the maximum a posteriori (MAP) probability rule has been introduced as a tool to determine the most probable atomic structure from high-resolution annular dark-field (ADF) scanning transmission electron microscopy (STEM) images exhibiting low contrast-to-noise ratio (CNR). Besides ADF imaging, STEM can also be applied in the annular bright-field (ABF) regime. The ABF STEM mode allows to directly visualize light-element atomic columns in the presence of heavy columns. Typically, light-element nanomaterials are sensitive to the electron beam, limiting the incoming electron dose in order to avoid beam damage and leading to images exhibiting low CNR. Therefore, it is of interest to apply the MAP probability rule not only to ADF STEM images, but to ABF STEM images as well. In this work, the methodology of the MAP rule, which combines statistical parameter estimation theory and model-order selection, is extended to be applied to simultaneously acquired ABF and ADF STEM images. For this, an extension of the commonly used parametric models in STEM is proposed. Hereby, the effect of specimen tilt has been taken into account, since small tilts from the crystal zone axis affect, especially, ABF STEM intensities. Using simulations as well as experimental data, it is shown that the proposed methodology can be successfully used to detect light elements in the presence of heavy elements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.2
Times cited: 9
DOI: 10.1016/j.ultramic.2020.113046
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“Atomic-scale detection of individual lead clusters confined in Linde Type A zeolites”. Fatermans J, Romolini G, Altantzis T, Hofkens J, Roeffaers MBJ, Bals S, Van Aert S, Nanoscale (2022). http://doi.org/10.1039/D2NR01819E
Abstract: Structural analysis of metal clusters confined in nanoporous materials is typically performed by X-ray-driven techniques. Although X-ray analysis has proved its strength in the characterization of metal clusters, it provides averaged structural information. Therefore, we here present an alternative workflow for bringing the characterization of confined metal clusters towards the local scale. This workflow is based on the combination of aberration-corrected transmission electron microscopy (TEM), TEM image simulations, and powder X-ray diffraction (XRD) with advanced statistical techniques. In this manner, we were able to characterize the clustering of Pb atoms in Linde Type A (LTA) zeolites with Pb loadings as low as 5 wt%. Moreover, individual Pb clusters could be directly detected. The proposed methodology thus enables a local-scale characterization of confined metal clusters in zeolites. This is important for further elucidation of the connection between the structure and the physicochemical properties of such systems.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.7
Times cited: 2
DOI: 10.1039/D2NR01819E
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“The maximum a posteriori probability rule for atom column detection from HAADF STEM images”. Fatermans J, Van Aert S, den Dekker AJ, Ultramicroscopy 201, 81 (2019). http://doi.org/10.1016/j.ultramic.2019.02.003
Abstract: Recently, the maximum a posteriori (MAP) probability rule has been proposed as an objective and quantitative method to detect atom columns and even single atoms from high-resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) images. The method combines statistical parameter estimation and model-order selection using a Bayesian framework and has been shown to be especially useful for the analysis of the structure of beam-sensitive nanomaterials. In order to avoid beam damage, images of such materials are usually acquired using a limited incoming electron dose resulting in a low contrast-to-noise ratio (CNR) which makes visual inspection unreliable. This creates a need for an objective and quantitative approach. The present paper describes the methodology of the MAP probability rule, gives its step-by-step derivation and discusses its algorithmic implementation for atom column detection. In addition, simulation results are presented showing that the performance of the MAP probability rule to detect the correct number of atomic columns from HAADF STEM images is superior to that of other model-order selection criteria, including the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). Moreover, the MAP probability rule is used as a tool to evaluate the relation between STEM image quality measures and atom detectability resulting in the introduction of the so-called integrated CNR (ICNR) as a new image quality measure that better correlates with atom detectability than conventional measures such as signal-to-noise ratio (SNR) and CNR.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 1
DOI: 10.1016/j.ultramic.2019.02.003
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“Clustering of vacancies on {113} planes in Si layers close to Si-Si3N4 interfaces and further aggregation of self-interstitials inside vacancy clusters during electron irradiation”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J, Institute of physics conference series
T2 –, Conference on Microscopy of Semiconducting Materials, MAR 22-25, 1999, UNIV OXFORD, OXFORD, ENGLAND , 495 (1999)
Abstract: In situ HREM irradiation of (110) FZ-Si crystals covered with thin Si3N4 films was carried out in a JEOL-4000EX microscope, operated at 400 keV at room temperature. It is found that clustering of vacancies on (113) planes is realised in a Si layer close to the Si-Si3N4 interface at the initial stage of irradiation. Further aggregation of self-interstitials inside vacancy clusters is considered as an alternative way of point defect recombination in extended shape, to be accomplished with the formation of the extended defects of interstitial type upon interstitial supersaturation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“Extended defects formation in Si crystals by clustering of intrinsic point defects studied by in-situ electron irradiation in an HREM”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J, Physica status solidi: A: applied research
T2 –, International Conference on Extended Defects in Semiconductors (EDS 98), Sept. 06-11, 1998, Jaszowiec, Poland 171, 147 (1999). http://doi.org/10.1002/(SICI)1521-396X(199901)171:1<147::AID-PSSA147>3.0.CO;2-U
Abstract: In situ irradiation experiments in a high resolution electron microscope JEOL-4000EX at room temperature resulted in discovery of the isolated and combined clustering of vacancies and self-interstitial atoms on {111}- and {113}-habit planes both leading to an extended defect formation in Si crystals. The type of the defect is strongly affected by the type of supersaturation of point defects depending on the crystal thickness during electron irradiation. Because of the existence of energy barriers against recombination of interstitials with the extended aggregates of vacancies, a large family of intermediate defect configurations (IDCs) is formed on {113}- and {111}-habit planes at a low temperature under interstitial supersaturation in addition to the well-known {133}-defects of interstitial type. The formation of metastable IDCs inside vacancy aggregates prevents a way of recombination of defects in extended shape.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 40
DOI: 10.1002/(SICI)1521-396X(199901)171:1<147::AID-PSSA147>3.0.CO;2-U
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“Extended defects formation in Si crystals by clustering of intrinsic point defects studied by in-situ irradiation in an HREM”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J, Physica status solidi: A: applied research 171, 147 (1999)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 40
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“Intrinsic point defect clustering in Si: a study by HVEM and HREM in situ electron irradiation”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J Kluwer Academic, s.l., page 63 (1997).
Keywords: H3 Book chapter; Electron microscopy for materials research (EMAT)
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“New intermediate defect configuration in Si studied by in situ HREM irradiation”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J, Conference series of the Institute of Physics 157, 43 (1997)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“On the mechanism of {111}-defect formation in silicon studies by in situ electrin irradiation in a high resolution electron microscope”. Fedina L, Gutakovskii A, Aseev A, van Landuyt J, Vanhellemont J, Philosophical magazine: A: physics of condensed matter: defects and mechanical properties 77, 423 (1998)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 23
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“In-situ HREM irradiation study of point defect clustering in strained GexSi1-x/(001)Si heterostructure”. Fedina L, Lebedev OI, Van Tendeloo G, van Landuyt J, Conference series of the Institute of Physics 157, 55 (1997)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 1
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“In situ HREM irradiation study of point-defect clustering in MBE-grown strained Si1-xGex/(001)Si structures”. Fedina L, Lebedev OI, Van Tendeloo G, van Landuyt J, Mironov OA, Parker EHC, Physical review : B : condensed matter and materials physics 61, 10336 (2000). http://doi.org/10.1103/PhysRevB.61.10336
Abstract: We present a detailed analysis of the point-defect clustering in strained Si/Si(1-x)Ge(x)/(001)Si structures, including the interaction of the point defects with the strained interfaces and the sample surface during 400 kV electron irradiation at room temperature. Point-defect cluster formation is very sensitive to the type and magnitude of the strain in the Si and Si(1-x)Ge(x) layers. A small compressive strain (-0.3%) in the SiGe alloy causes an aggregation of vacancies in the form of metastable [110]-oriented chains. They are located on {113} planes and further recombine with interstitials. Tensile strain in the Si layer causes an aggregation of interstitial atoms in the forms of additional [110] rows which are inserted on {113} planes with [001]-split configurations. The chainlike configurations are characterized by a large outward lattice relaxation for interstitial rows (0.13 +/-0.01 nm) and a very small inward relaxation for vacancy chains (0.02+/-0.01 nm). A compressive strain higher than -0.5% strongly decreases point-defect generation inside the strained SiGe alloy due to the large positive value of the formation volume of a Frenkel pair. This leads to the suppression of point-defect clustering in a strained SiGe alloy so that SiGe relaxes via a diffusion of vacancies from the Si layer, giving rise to an intermixing at the Si/SiGe interface. In material with a 0.9% misfit a strongly increased flow of vacancies from the Si layer to the SiGe layer and an increased biaxial strain in SiGe bath promote the preferential aggregation of vacancies in the (001) plane, which relaxes to form intrinsic 60 degrees dislocation loops.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 27
DOI: 10.1103/PhysRevB.61.10336
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“Observation of vacancy clustering in Si crystals during in situ electron irradiation in a high voltage electron microscope”. Fedina L, van Landuyt J, Vanhellemont J, Aseev A, Materials Research Society symposium proceedings 404, 189 (1996)
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 1
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“Observation of vacancy clustering in FZ-Si crystals during in situ electron irradiation in a high voltage electron microscope”. Fedina L, van Landuyt J, Vanhellemont J, Aseev AL, Nuclear instruments and methods in physics research B112, 133 (1996). http://doi.org/10.1016/0168-583X(95)01277-X
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.124
Times cited: 4
DOI: 10.1016/0168-583X(95)01277-X
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“Single-walled carbon nanotube reactor for redox transformation of mercury dichloride”. Fedoseeva YV, Orekhov AS, Chekhova GN, Koroteev VO, Kanygin MA, Seovskiy BV, Chuvilin A, Pontiroli D, Ricco M, Bulusheva LG, Okotrub AV, ACS nano 11, 8643 (2017). http://doi.org/10.1021/ACSNANO.7B04361
Abstract: <script type='text/javascript'>document.write(unpmarked('Single-walled carbon nanotubes (SWCNTs) possessing a confined inner space protected by chemically resistant shells are promising for delivery, storage, and desorption of various compounds, as well as carrying out specific reactions. Here, we show that SWCNTs interact with molten mercury dichloride (HgCl2) and guide its transformation into dimercury dichloride (Hg2Cl2) in the cavity. The chemical state of host SWCNTs remains almost unchanged except for a small p-doping from the guest Hg2Cl2 nanocrystals. The density functional theory calculations reveal that the encapsulated HgCl2 molecules become negatively charged and start interacting via chlorine bridges when local concentration increases. This reduces the bonding strength in HgCl2, which facilitates removal of chlorine, finally leading to formation of Hg2Cl2 species. The present work demonstrates that SWCNTs not only serve as a template for growing nanocrystals but also behave as an electron-transfer catalyst in the spatially confined redox reaction by donation of electron density for temporary use by the guests.'));
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 11
DOI: 10.1021/ACSNANO.7B04361
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“Tuning the crystal structure of A2CoPO4F(A=Li,Na) fluoride-phosphates : a new layered polymorph of LiNaCoPO4F”. Fedotov SS, Aksyonov DA, Samarin AS, Karakulina OM, Hadermann J, Stevenson KJ, Khasanova NR, Abakumov AM, Antipov E V, European journal of inorganic chemistry 2019, 4365 (2019). http://doi.org/10.1002/EJIC.201900660
Abstract: Co-containing fluoride-phosphates are of interest in sense of delivering high electrode potentials and attractive specific energy values as positive electrode materials for rechargeable batteries. In this paper we report on a new Co-based fluoride-phosphate, LiNaCoPO4F, with a layered structure (2D), which was Rietveld-refined based on X-ray powder diffraction data [P2(1)/c, a = 6.83881(4) angstrom, b = 11.23323(5) angstrom, c = 5.07654(2) angstrom, beta = 90.3517(5) degrees, V = 389.982(3) angstrom(3)] and validated by electron diffraction and high-resolution scanning transmission electron microscopy. The differential scanning calorimetry measurements revealed that 2D-LiNaCoPO4F forms in a narrow temperature range of 520-530 degrees C and irreversibly converts to the known 3D-LiNaCoPO4F modification (Pnma) above 530 degrees C. The non-carbon-coated 2D-LiNaCoPO4F shows reversible electrochemical activity in Li-ion cell in the potential range of 3.0-4.9 V vs. Li/Li+ with an average potential of approximate to 4.5 V and in Na-ion cell in the range of 3.0-4.5 V vs. Na/Na+ exhibiting a plateau profile centered around 4.2 V, in agreement with the calculated potentials by density functional theory. The energy barriers for both Li+ and Na+ migration in 2D-LiNaCoPO4F amount to 0.15 eV along the [001] direction rendering 2D-LiNaCoPO4F as a viable electrode material for high-power Li- and Na-ion rechargeable batteries. The discovery and stabilization of the 2D-LiNaCoPO4F polymorph indicates that temperature influence on the synthesis of A(2)MPO(4)F fluoride-phosphates needs more careful examination with perspective to unveil new structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.444
DOI: 10.1002/EJIC.201900660
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“AVPO4F (A = Li, K): A 4 V Cathode Material for High-Power Rechargeable Batteries”. Fedotov SS, Khasanova NR, Samarin AS, Drozhzhin OA, Batuk D, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Chemistry of materials 28, 411 (2016). http://doi.org/10.1021/acs.chemmater.5b04065
Abstract: A novel potassium-based fluoride-phosphate, KVPO4F, with a KTiOPO4 (KTP) type structure is synthesized and characterized. About 85% of potassium has been electrochemically extracted on oxidation producing a cathode material with attractive performance for Li-ion batteries. The material operates at the electrode potential near 4V vs Li/Li+ exhibiting a sloping voltage profile, extremely low polarization, small volume change of about 2% and excellent rate capability, maintaining more than 75% of the initial capacity at 40C discharge rate without significant fading.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/acs.chemmater.5b04065
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“Synthesis, structure and electrochemical properties of LiNaCo0.5Fe0.5PO4F fluoride-phosphate”. Fedotov SS, Kuzovchikov SM, Khasanova NR, Drozhzhin OA, Filimonov DS, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Journal of solid state chemistry 242, 70 (2016). http://doi.org/10.1016/j.jssc.2016.02.042
Abstract: LiNaCo 0.5 Fe 0.5 PO 4 F fluoride-phosphate was synthesized via conventional solid-state and novel freeze-drying routes. The crystal structure was refined based on neutron powder diffraction (NPD) data and validated by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The alkali ions are ordered in LiNaCo 0.5 Fe 0.5 PO 4 F and the transition metals jointly occupy the same crystallographic sites. The oxidation state and oxygen coordination environment of the Fe atoms were verified by 57 Fe Mössbauer spectroscopy. Electrochemical tests of the LiNaCo 0.5 Fe 0.5 PO 4 F cathode material demonstrated a reversible activity of the Fe 3+ /Fe 2+ redox couple at the electrode potential near 3.4 V and minor activity of the Co 3+ /Co 2+ redox couple over 5 V vs Li/Li + . The material exhibits a good capacity retention in the 2.4÷4.6 V vs Li/Li + potential range with the delivered discharge capacity of more than 82% (theo.) regarding Fe 3+ /Fe 2+ .
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 1
DOI: 10.1016/j.jssc.2016.02.042
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“Chemistry of Shape-Controlled Iron Oxide Nanocrystal Formation”. Feld A, Weimer A, Kornowski A, Winckelmans N, Merkl J-P, Kloust H, Zierold R, Schmidtke C, Schotten T, Riedner M, Bals S, Weller PD Horst, ACS nano 13, 152 (2018). http://doi.org/10.1021/acsnano.8b05032
Abstract: Herein we demonstrate that meticulous and in-depth analysis of the reaction mechanisms of nanoparticle formation is rewarded by full control of size, shape and crystal structure of superparamagnetic iron oxide nanocrystals during synthesis. Starting from two iron sources – iron(II)- and iron(III) carbonate -a strict separation of oleate formation from the generation of reactive pyrolysis products and concomitant nucleation of iron oxide nanoparticles was achieved. This protocol enabled us to analyze each step of nanoparticle formation independently in depth. Progress of the entire reaction was monitored via matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and gas chromatography (GC) gaining insight into the formation of various iron oleate species prior to nucleation. Interestingly, due to the intrinsic strongly reductive pyrolysis conditions of the oleate intermediates and redox process in early stages of the synthesis, pristine iron oxide nuclei were composed exclusively from wustite, irrespective of the oxidation state of the iron source. Controlling the reaction conditions provided a very broad range of size- and shape defined monodisperse iron oxide nanoparticles. Curiously, after nucleation star shaped nanocrystals were obtained, which underwent metamorphism towards cubic shaped particles. EELS tomography revealed ex post oxidation of the primary wustite nanocrystal providing a full 3D image of Fe2+ and Fe3+ distribution within. Overall, we developed a highly flexible synthesis, yielding multigram amounts of well-defined iron oxide nanocrystals of different sizes and morphologies.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 54
DOI: 10.1021/acsnano.8b05032
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“Incorporation and study of SiV centers in diamond nanopillars”. Felgen N, Naydenov B, Turner S, Jelezko F, Reithmaier JP, Popov C, Diamond and related materials 64, 64 (2016). http://doi.org/10.1016/j.diamond.2016.01.011
Abstract: We report on the incorporation of SiV centers during hot filament chemical vapor deposition of diamond on top of diamond nanopillars with diameters down to 100 nm. The nanopillars themselves were prepared from nano crystalline diamond films by applying electron beam lithography and inductively coupled plasma reactive ion etching. The optical investigations revealed the presence of ensembles of SiV color centers incorporated during the overgrowth step. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 14
DOI: 10.1016/j.diamond.2016.01.011
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“Nucleation of metal clusters on plasma treated multi wall carbon nanotubes”. Felten A, Bittencourt C, Colomer J-F, Van Tendeloo G, Pireaux J-J, Carbon 45, 110 (2007). http://doi.org/10.1016/j.carbon.2006.07.023
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.337
Times cited: 40
DOI: 10.1016/j.carbon.2006.07.023
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“Electronic structure of Pd nanoparticles on carbon nanotubes”. Felten A, Ghijsen J, Pireaux J-J, Drube W, Johnson RL, Liang D, Hecq M, Van Tendeloo G, Bittencourt C, Micron 40, 74 (2009). http://doi.org/10.1016/j.micron.2008.01.013
Abstract: The effect of the oxygen plasma treatment on the electronic states of multi-wall carbon nanotubes (MWCNTs) is analyzed by X-ray photoemission measurements (XPS) and UPS, both using synchrotron radiation. It is found that the plasma treatment effectively grafts oxygen at the CNT-surface. Thereafter, the interaction between evaporated Pd and pristine or oxygen plasma-treated MWCNTs is investigated. Pd is found to nucleate at defective sites, whether initially present or introduced by oxygen plasma treatment. The plasma treatment induced a uniform dispersion of Pd clusters at the CNT-surface. The absence of additional features in the Pd 3d and C I s core levels spectra testifies that no Pd-C bond is formed. The shift of the Pd 3d core level towards high-binding energy for the smallest clusters is attributed to the Coulomb energy of the charged final state. (C) 2008 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
Times cited: 44
DOI: 10.1016/j.micron.2008.01.013
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“Effect of oxygen rf-plasma on electronic properties of CNTs”. Felten A, Ghijsen J, Pireaux J-J, Johnson RL, Whelan CM, Liang D, Van Tendeloo G, Journal of physics: D: applied physics 40, 7379 (2007). http://doi.org/10.1088/0022-3727/40/23/019
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.588
Times cited: 25
DOI: 10.1088/0022-3727/40/23/019
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“Photoemission study of CF4 rf-plasma treated multi-wall carbon nanotubes”. Felten A, Ghijsen J, Pireaux J-J, Whelan CM, Liang D, Van Tendeloo G, Bittencourt C, Carbon 46, 1271 (2008). http://doi.org/10.1016/j.carbon.2008.04.027
Abstract: Multi-wall carbon nanotubes (MWCNTs) were exposed to a CF4 rf-plasma. X-ray photoelectron spectroscopy analysis shows that the treatment effectively grafts fluorine atoms onto the MWCNTs. The fluorine atomic concentration and the nature of the CF bond (semi-ionic or covalent) can be tuned by varying the exposure time. Ultraviolet photoelectron spectroscopy analysis confirms that the valence electronic states are altered by the grafting of fluorine atoms. Characterization with high-resolution transmission electron microscopy reveals that while the plasma treatment does not induce significant etching impact on the CNT-surface, it does increase the number of active sites for gold cluster formation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.337
Times cited: 21
DOI: 10.1016/j.carbon.2008.04.027
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“Measuring point defect density in individual carbon nanotubes using polarization-dependent X-ray microscopy”. Felten A, Gillon X, Gulas M, Pireaux J-J, Ke X, Van Tendeloo G, Bittencourt C, Najafi E, Hitchcock AP, ACS nano 4, 4431 (2010). http://doi.org/10.1021/nn1002248
Abstract: The presence of defects in carbon nanotubes strongly modifies their electrical, mechanical, and chemical properties. It was long thought undesirable, but recent experiments have shown that introduction of structural defects using ion or electron irradiation can lead to novel nanodevices. We demonstrate a method for detecting and quantifying point defect density in individual carbon nanotubes (CNTs) based on measuring the polarization dependence (linear dichroism) of the C 1s → π* transition at specific locations along individual CNTs with a scanning transmission X-ray microscope (STXM). We show that STXM can be used to probe defect density in individual CNTs with high spatial resolution. The quantitative relationship between ion dose, nanotube diameter, and defect density was explored by purposely irradiating selected sections of nanotubes with kiloelectronvolt (keV) Ga+ ions. Our results establish polarization-dependent X-ray microscopy as a new and very powerful characterization technique for carbon nanotubes and other anisotropic nanostructures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 26
DOI: 10.1021/nn1002248
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“The role of oxygen at the interface between titanium and carbon nanotubes”. Felten A, Suarez-Martinez I, Ke X, Van Tendeloo G, Ghijsen J, Pireaux J-J, Drube W, Bittencourt C, Ewels CP, ChemPhysChem : a European journal of chemical physics and physical chemistry 10, 1799 (2009). http://doi.org/10.1002/cphc.200900193
Abstract: We study the interface between carbon nanotubes (CNTs) and surface-deposited titanium using electron microscopy and photoemission spectroscopy, supported by density functional calculations. Charge transfer from the Ti atoms to the nanotube and carbide formation is observed at the interface which indicates strong interaction. Nevertheless, the presence of oxygen between the Ti and the CNTs significantly weakens the Ti-CNT interaction. Ti atoms at the surface will preferentially bond to oxygenated sites. Potential sources of oxygen impurities are examined, namely oxygen from any residual atmosphere and pre-existing oxygen impurities on the nanotube surface, which we enhance through oxygen plasma surface pre-treatment. Variation in literature data concerning Ohmic contacts between Ti and carbon nanotubes is explained via sample pre-treatment and differing vacuum levels, and we suggest improved treatment routes for reliable Schottky barrier-free Ti-nanotube contact formation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.075
Times cited: 38
DOI: 10.1002/cphc.200900193
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“Antiferromagnetic order breaks inversion symmetry in a metallic double perovskite, Pb₂NiOsO₆”. Feng HL, Kang C-J, Manuel P, Orlandi F, Su Y, Chen J, Tsujimoto Y, Hadermann J, Kotliar G, Yamaura K, McCabe EE, Greenblatt M, Chemistry Of Materials 33, 4188 (2021). http://doi.org/10.1021/ACS.CHEMMATER.1C01032
Abstract: A polycrystalline sample of Pb2NiOsO6 was synthesized under high-pressure (6 GPa) and high-temperature (1575 K) conditions. Pb2NiOsO6 crystallizes in a monoclinic double perovskite structure with a centrosymmetric space group P2(1)/n at room temperature. Pb2NiOsO6 is metallic down to 2 K and shows a single antiferromagnetic (AFM) transition at T-N = 58 K. Pb2NiOsO6 is a new example of a metallic and AFM oxide with three-dimensional connectivity. Neutron powder diffraction and first-principles calculation studies indicate that both Ni and Os moments are ordered below T-N and the AFM magnetic order breaks inversion symmetry. This loss of inversion symmetry driven by AFM order is unusual in metallic systems, and the 3d-Sd double-perovskite oxides represent a new class of noncentrosymmetric AFM metallic oxides.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
DOI: 10.1021/ACS.CHEMMATER.1C01032
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