“Direct evidence for the existence of multi-walled carbon nanotubes with hexagonal cross-sections”. He Z, Ke X, Bals S, Van Tendeloo G, Carbon 50, 2524 (2012). http://doi.org/10.1016/j.carbon.2012.01.075
Abstract: Carbon nanotubes (CNTs) with a polygonal cross-section have been paid increasing attention since their three-dimensional structure is related to specific physical properties, which are found to be different in comparison to CNTs with a circular cross-section. Here, we report the existence of novel multi-walled CNTs yielding walls with a rounded-hexagonal configuration. This structure was directly confirmed for the first time by both cross-sectional transmission electron microscopy and electron tomography. The morphology of the Fe catalytic particle also exhibits hexagonal characteristics, and is proposed as the origin of the formation of the rounded-hexagonal walls of the CNT. This observation is of great importance with respect to the design of polygonal (such as pentagonal or hexagonal) cross-sectional CNTs. By controlling the morphology of the catalytic nanoparticles it will be possible to grow CNTs with desired electronic and mechanical properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.337
Times cited: 8
DOI: 10.1016/j.carbon.2012.01.075
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“Direct observation of ferrielectricity at ferroelastic domain boundaries in CaTiO3 by electron microscopy”. Van Aert S, Turner S, Delville R, Schryvers D, Van Tendeloo G, Salje EKH, Advanced materials 24, 523 (2012). http://doi.org/10.1002/adma.201103717
Abstract: High-resolution aberration-corrected transmission electron microscopy aided by statistical parameter estimation theory is used to quantify localized displacements at a (110) twin boundary in orthorhombic CaTiO3. The displacements are 36 pm for the Ti atoms and confined to a thin layer. This is the first direct observation of the generation of ferroelectricity by interfaces inside this material which opens the door for domain boundary engineering.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 19.791
Times cited: 150
DOI: 10.1002/adma.201103717
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“Direct structure inversion from exit waves: part 1: theory and simulations”. Wang A, Chen FR, Van Aert S, van Dyck D, Ultramicroscopy 110, 527 (2010). http://doi.org/10.1016/j.ultramic.2009.11.024
Abstract: In order to interpret the amplitude and phase of the exit wave in terms of mass and position of the atoms, one has to invert the dynamic scattering of the electrons in the object so as to obtain a starting structure which can then be used as a seed for further quantitative structure refinement. This is especially challenging in case of a zone axis condition when the interaction of the electrons with the atom column is very strong. Based on the channelling theory we will show that the channelling map not only yields a circle on the Argand plot but also a circular defocus curve for every column. The former gives the number of atoms in each column, while the latter provides the defocus value for each column, which reveals the surface roughness at the exit plane with single atom sensitivity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 25
DOI: 10.1016/j.ultramic.2009.11.024
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“Direct structure inversion from exit waves : part 2 : a practical example”. Wang A, Chen FR, Van Aert S, van Dyck D, Ultramicroscopy 116, 77 (2012). http://doi.org/10.1016/j.ultramic.2012.03.011
Abstract: This paper is the second part of a two-part paper on direct structure inversion from exit waves. In the first part, a method has been proposed to quantitatively determine structure parameters with atomic resolution such as atom column positions, surface profile and the number of atoms in the atom columns. In this part, the theory will be demonstrated by means of a Au[110] exit wave reconstructed from a set of focal-series images. The procedures to analyze the experimentally reconstructed exit wave in terms of quantitative structure information are described in detail.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 8
DOI: 10.1016/j.ultramic.2012.03.011
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“Effect of deposition rate on the microstructure of electron beam evaporated nanocrystalline palladium thin films”. Amin-Ahmadi B, Idrissi H, Galceran M, Colla MS, Raskin JP, Pardoen T, Godet S, Schryvers D, Thin solid films : an international journal on the science and technology of thin and thick films 539, 145 (2013). http://doi.org/10.1016/j.tsf.2013.05.083
Abstract: The influence of the deposition rate on the formation of growth twins in nanocrystalline Pd films deposited by electron beam evaporation is investigated using transmission electron microscopy. Statistical measurements prove that twin boundary (TB) density and volume fraction of grains containing twins increase with increasing deposition rate. A clear increase of the dislocation density was observed for the highest deposition rate of 5 Å/s, caused by the increase of the internal stress building up during deposition. Based on crystallographic orientation indexation using transmission electron microscopy, it can be concluded that a {111} crystallographic texture increases with increasing deposition rate even though the {101} crystallographic texture remains dominant. Most of the TBs are fully coherent without any residual dislocations. However, for the highest deposition rate (5 Å/s), the coherency of the TBs decreases significantly as a result of the interaction of lattice dislocations emitted during deposition with the growth TBs. The analysis of the grain boundary character of different Pd films shows that an increasing fraction of high angle grain boundaries with misorientation angles around 5565° leads to a higher potential for twin formation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 13
DOI: 10.1016/j.tsf.2013.05.083
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“Effect of lone-electron-pair cations on the orientation of crystallographic shear planes in anion-deficient perovskites”. Batuk D, Batuk M, Abakumov AM, Tsirlin AA, McCammon CM, Dubrovinsky L, Hadermann J, Inorganic chemistry 52, 10009 (2013). http://doi.org/10.1021/ic4012845
Abstract: Factors affecting the structure and orientation of the crystallographic shear (CS) planes in anion-deficient perovskites are investigated using the (Pb1−zSrz)1−xFe1+xO3−y perovskites as a model system. The orientation of the CS planes in the system varies unevenly with z. A comparison of the structures with different CS planes revels that the orientation of the CS planes is governed mainly by the stereochemical activity of the lone-electron-pair cations inside the perovskite blocks.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 11
DOI: 10.1021/ic4012845
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“Effect of nanoprecipitates on the transformation behavior and functional properties of a Ti50.8 at.% Ni alloy with micron-sized grains”. Wang X, Kustov S, Li K, Schryvers D, Verlinden B, Van Humbeeck J, Acta materialia 82, 224 (2015). http://doi.org/10.1016/j.actamat.2014.09.018
Abstract: In order to take advantage of both grain refinement and precipitation hardening effects, nanoscaled Ni4Ti3 precipitates are introduced in a Ti50.8 at.% Ni alloy with micron-sized grains (average grain size of 1.7 μm). Calorimetry, electrical resistance studies and thermomechanical tests were employed to study the transformation behavior and functional properties in relation to the obtained microstructure. A significant suppression of martensite transformation by the obtained microstructure is observed. The thermomechanical tests show that the advantageous properties of both grain refinement and precipitation hardening are combined in the developed materials, resulting in superior shape memory characteristics and stability of pseudoelasticity. It is concluded that introducing nanoscaled Ni4Ti3 precipitates into small grains is a new approach to improve the functional properties of NiTi shape memory alloys.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 51
DOI: 10.1016/j.actamat.2014.09.018
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“Electrodeposition of Ag nanoparticles onto carbon coated TEM grids : a direct approach to study early stages of nucleation”. Ustarroz J, Gupta U, Hubin A, Bals S, Terryn H, Electrochemistry communications 12, 1706 (2010). http://doi.org/10.1016/j.elecom.2010.10.002
Abstract: An innovative experimental approach to study the electrodeposition of small nanoparticles and the early stages of electrochemical nucleation and growth is presented. Carbon coated gold TEM grids are used as substrates for the electrodeposition of silver nanoparticles so that electrochemical data, FESEM, HAADFSTEM and HRTEM data can be acquired from the same sample without the need to remove the particles from the substrate. It is shown that the real distribution of nanoparticles cannot be resolved by FESEM whereas HAADFSTEM analysis confirms that a distribution of small nanoparticles (d ≈ 12 nm) coexist with large nanoparticles corresponding to a bimodal size distribution. Besides, particles grown under the same conditions have been found to present different structures such as monocrystals, polycrystals or aggregates of smaller particles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.396
Times cited: 52
DOI: 10.1016/j.elecom.2010.10.002
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“Electron-diffraction structure refinement of Ni4Ti3 precipitates in Ni52Ti48”. Tirry W, Schryvers D, Jorissen K, Lamoen D, Acta crystallographica: section B: structural science 62, 966 (2006). http://doi.org/10.1107/S0108768106036457
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 30
DOI: 10.1107/S0108768106036457
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“Electron microscopy study of Nb-rich nanoprecipitates in NiTiNb and their influence on the martensitic transformation”. Shi H, Pourbabak S, Van Humbeeck J, Schryvers D, Scripta materialia 67, 939 (2012). http://doi.org/10.1016/j.scriptamat.2012.08.020
Abstract: Nb-rich nanoprecipitates in the matrix of an annealed commercial NiTiNb alloy are investigated by scanning and transmission electron microscopy, including slice-and-view and chemical analysis. The precipitates have a diameter of around 100 nm, are faceted and have a cube-on-cube relation with the B2 matrix. In situ TEM cooling shows that the martensitic transformation is hampered by the presence of these precipitates. The latter could explain the increase in hysteresis when compared with the binary system.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.747
Times cited: 29
DOI: 10.1016/j.scriptamat.2012.08.020
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“Electron tomography based on a total variation minimization reconstruction technique”. Goris B, van den Broek W, Batenburg KJ, Heidari Mezerji H, Bals S, Ultramicroscopy 113, 120 (2012). http://doi.org/10.1016/j.ultramic.2011.11.004
Abstract: The 3D reconstruction of a tilt series for electron tomography is mostly carried out using the weighted backprojection (WBP) algorithm or using one of the iterative algorithms such as the simultaneous iterative reconstruction technique (SIRT). However, it is known that these reconstruction algorithms cannot compensate for the missing wedge. Here, we apply a new reconstruction algorithm for electron tomography, which is based on compressive sensing. This is a field in image processing specialized in finding a sparse solution or a solution with a sparse gradient to a set of ill-posed linear equations. Therefore, it can be applied to electron tomography where the reconstructed objects often have a sparse gradient at the nanoscale. Using a combination of different simulated and experimental datasets, it is shown that missing wedge artefacts are reduced in the final reconstruction. Moreover, it seems that the reconstructed datasets have a higher fidelity and are easier to segment in comparison to reconstructions obtained by more conventional iterative algorithms.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 171
DOI: 10.1016/j.ultramic.2011.11.004
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“Electronically coupled complementary interfaces between perovskite band insulators”. Huijben M, Rijnders G, Blank DHA, Bals S, Van Aert S, Verbeeck J, Van Tendeloo G, Brinkman A, Hilgenkamp H, Nature materials 5, 556 (2006). http://doi.org/10.1038/nmat1675
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 39.737
Times cited: 315
DOI: 10.1038/nmat1675
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“Evolution of the phase stability of NiAl under low energy ball milling”. Zelaya E, Esquivel MR, Schryvers D, Advanced powder technology 24, 1063 (2013). http://doi.org/10.1016/j.apt.2013.03.008
Abstract: Low energy mechanical alloying of Ni35 at.%Al and Ni40 at.%Al material was performed and the resulting structures were investigated by XRD and TEM. The final intermetallics observed consist of two phases, NiAl(B2) and Ni3Al while 7R and 3R martensite was observed in post-annealed samples. Different integrated milling times were associated to the intermetallic consolidation and initial blend dissociation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.659
Times cited: 10
DOI: 10.1016/j.apt.2013.03.008
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“Fabrication and characterization of functionally graded Ni-Ti multilayer thin films”. Tian H, Schryvers D, Mohanchandra KP, Carman GP, van Humbeeck J, Functional materials letters 2, 61 (2009). http://doi.org/10.1142/S1793604709000570
Abstract: A functionally graded multilayer NiTi thin film was deposited on a SiO2/Si substrate by d.c. sputtering using a ramped heated NiTi alloy target. The stand-alone films were crystallized at 500°C in vacuum better than 10-7 Torr. Transmission electron microscopy micrographs taken along the film cross section show two distinct regions, thin and thick, with weak R and B2 phases, respectively. The film compositions along the thickness were measured and quantified using the standard-less EELSMODEL method. The film deposited during the initial thermal ramp (thin regions) displays an average of 54 at.% Ni while the film deposited at a more elevated target temperature (thick regions) shows about 51 at.% Ni.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.234
Times cited: 9
DOI: 10.1142/S1793604709000570
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“First-principles calculation of the electronic structure and energy loss near edge spectra of chiral carbon nanotubes”. Bertoni G, Calmels L, Micron 37, 486 (2006). http://doi.org/10.1016/j.micron.2005.10.011
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
Times cited: 12
DOI: 10.1016/j.micron.2005.10.011
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“Fluorine doped Fe2O3 nanostructures by a one-pot plasma-assisted strategy”. Carraro G, Gasparotto A, Maccato C, Bontempi E, Lebedev OI, Turner S, Sada C, Depero LE, Van Tendeloo G, Barreca D, RSC advances 3, 23762 (2013). http://doi.org/10.1039/c3ra43775b
Abstract: The present work reports on the synthesis of fluorine doped Fe2O3 nanomaterials by a single-step plasma enhanced-chemical vapor deposition (PE-CVD) strategy. In particular, Fe(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) was used as molecular source for both Fe and F in Ar/O2 plasmas. The structure, morphology and chemical composition of the synthesized nanosystems were thoroughly analyzed by two-dimensional X-ray diffraction (XRD2), field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). A suitable choice of processing parameters enabled the selective formation of α-Fe2O3 nanomaterials, characterized by an homogeneous F doping, even at 100 °C. Interestingly, a simultaneous control of the system nanoscale organization and fluorine content could be achieved by varying the sole growth temperature. The tailored properties of the resulting materials can be favourably exploited for several technological applications, ranging from photocatalysis, to photoelectrochemical cells and gas sensing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.108
Times cited: 23
DOI: 10.1039/c3ra43775b
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“Focused ion beam/scanning electron microscopy tomography and conventional transmission electron microscopy assessment of Ni4Ti3 morphology in compression-aged Ni-rich Ni-Ti single crystals”. Cao S, Somsen C, Croitoru M, Schryvers D, Eggeler G, Scripta materialia 62, 399 (2010). http://doi.org/10.1016/j.scriptamat.2009.11.040
Abstract: The size, morphology and configuration of Ni4Ti3 precipitates in a single-crystal NiTi alloy have been investigated by two-dimensional transmission electron microscopy-based image analysis and three-dimensional reconstruction from slice-and-view images obtained in a focused ion beam/scanning electron microscopy (FIB/SEM) dual-beam system. Average distances between the precipitates measured along the compression direction correlate well between both techniques, while particle shape and configuration data is best obtained from FIB/SEM. Precipitates form pockets of B2 of 0.54 ìm in the compression direction and 1 ìm perpendicular to the compression direction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.747
Times cited: 16
DOI: 10.1016/j.scriptamat.2009.11.040
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“From spin induced ferroelectricity to dipolar glasses : spinel chromites and mixed delafossites”. Maignan A, Martin C, Singh K, Simon C, Lebedev OI, Turner S, Journal of solid state chemistry 195, 41 (2012). http://doi.org/10.1016/j.jssc.2012.01.063
Abstract: Magnetoelectric multiferroics showing coupling between polarization and magnetic order are attracting much attention. For instance, they could be used in memory devices. Metal-transition oxides are provided several examples of inorganic magnetoelectric multiferroics. In the present short review, spinel and delafossite chromites are described. For the former, an electric polarization is evidenced in the ferrimagnetic state for ACr2O4 polycrystalline samples (A=Ni, Fe, Co). The presence of a JahnTeller cation such as Ni2+ at the A site is shown to yield larger polarization values. In the delafossites, substitution by V3+ at the Cr or Fe site in CuCrO2 (CuFeO2) suppresses the complex antiferromagnetic structure at the benefit of a spin glass state. The presence of cation disorder, probed by transmission electron microscopy, favors relaxor-like ferroelectricity. The results on the ferroelectricity of ferrimagnets and insulating spin glasses demonstrate that, in this research field, transition-metal oxides are worth to be studied.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 27
DOI: 10.1016/j.jssc.2012.01.063
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“Fully automated measurement of the modulation transfer function of charge-coupled devices above the Nyquist frequency”. van den Broek W, Van Aert S, van Dyck D, Microscopy and microanalysis 18, 336 (2012). http://doi.org/10.1017/S1431927611012633
Abstract: The charge-coupled devices used in electron microscopy are coated with a scintillating crystal that gives rise to a severe modulation transfer function (MTF). Exact knowledge of the MTF is imperative for a good correspondence between image simulation and experiment. We present a practical method to measure the MTF above the Nyquist frequency from the beam blocker's shadow image. The image processing has been fully automated and the program is made public. The method is successfully tested on three cameras with various beam blocker shapes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 1.891
Times cited: 15
DOI: 10.1017/S1431927611012633
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“High precision measurements of atom column positions using model-based exit wave reconstruction”. de Backer A, Van Aert S, van Dyck D, Ultramicroscopy 111, 1475 (2011). http://doi.org/10.1016/j.ultramic.2011.07.002
Abstract: In this paper, it has been investigated how to measure atom column positions as accurately and precisely as possible using a focal series of images. In theory, it is expected that the precision would considerably improve using a maximum likelihood estimator based on the full series of focal images. As such, the theoretical lower bound on the variances of the unknown atom column positions can be attained. However, this approach is numerically demanding. Therefore, maximum likelihood estimation has been compared with the results obtained by fitting a model to a reconstructed exit wave rather than to the full series of focal images. Hence, a real space model-based exit wave reconstruction technique based on the channelling theory is introduced. Simulations show that the reconstructed complex exit wave contains the same amount of information concerning the atom column positions as the full series of focal images. Only for thin samples, which act as weak phase objects, this information can be retrieved from the phase of the reconstructed complex exit wave.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 8
DOI: 10.1016/j.ultramic.2011.07.002
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“High resolution mapping of surface reduction in ceria nanoparticles”. Turner S, Lazar S, Freitag B, Egoavil R, Verbeeck J, Put S, Strauven Y, Van Tendeloo G, Nanoscale 3, 3385 (2011). http://doi.org/10.1039/c1nr10510h
Abstract: Surface reduction of ceria nano octahedra with predominant {111} and {100} type surfaces is studied using a combination of aberration-corrected Transmission Electron Microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (EELS) at high energy resolution and atomic spatial resolution. The valency of cerium ions at the surface of the nanoparticles is mapped using the fine structure of the Ce M4,5 edge as a fingerprint. The valency of the surface cerium ions is found to change from 4+ to 3+ owing to oxygen deficiency (vacancies) close to the surface. The thickness of this Ce3+ shell is measured using atomic-resolution Scanning Transmission Electron Microscopy (STEM)-EELS mapping over a {111} surface (the predominant facet for this ceria morphology), {111} type surface island steps and {100} terminating planes. For the {111} facets and for {111} surface islands, the reduction shell is found to extend over a single fully reduced surface plane and 12 underlying mixed valency planes. For the {100} facets the reduction shell extends over a larger area of 56 oxygen vacancy-rich planes. This finding provides a plausible explanation for the higher catalytic activity of the {100} surface facets in ceria.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 127
DOI: 10.1039/c1nr10510h
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“Highly disordered crystal structure and thermoelectric properties of Sn3P4”. Zaikina JV, Kovnir KA, Sobolev AN, Presniakov IA, Kytin VG, Kulbachinskii VA, Olenev AV, Lebedev OI, Van Tendeloo G, Dikarev EV, Shevelkov AV, Chemistry of materials 20, 2476 (2008). http://doi.org/10.1021/cm702655g
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 33
DOI: 10.1021/cm702655g
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“Imaging from atomic structure to electronic structure”. Xu Q, Zandbergen HW, van Dyck D, Micron 43, 524 (2012). http://doi.org/10.1016/j.micron.2011.10.024
Abstract: This paper discusses the possibility of retrieving the electron distribution (with highlighted valence electron distribution information) of materials from recorded HREM images. This process can be achieved by solving two inverse problems: reconstruction of the exit wave and reconstruction of the electron distribution from exit waves. The first inverse problem can be solved using a focal series reconstruction method. We show that the second inverse problem can be solved by combining a series of exit waves recorded at different thickness conditions. This process is designed based on an improved understanding of the dynamical scattering process. It also explains the fundamental difficulty of obtaining the valence electron distribution information and the basis of our solution.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 1.98
DOI: 10.1016/j.micron.2011.10.024
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“Imaging of intact MOF-5 nanocrystals by advanced TEM at liquid”. Wiktor C, Turner S, Zacher D, Fischer RA, Van Tendeloo G, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 162, 131 (2012). http://doi.org/10.1016/j.micromeso.2012.06.014
Abstract: First results on the imaging of intact metalorganic framework (MOF) pores in MOF-5 nanocrystals by aberration corrected transmission electron microscopy (TEM) under liquid nitrogen conditions are presented. The applied technique is certainly transferable to other MOF systems, permitting detailed studies of MOF interfaces, MOFnanoparticle interaction and MOF thin films.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.615
Times cited: 30
DOI: 10.1016/j.micromeso.2012.06.014
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“Incorporation and localization of substitutional Mn2+ ions in cubic ZnS quantum dots”. Nistor SV, Stefan M, Nistor LC, Goovaerts E, Van Tendeloo G, Physical review : B : condensed matter and materials physics 81, 035336 (2010). http://doi.org/10.1103/PhysRevB.81.035336
Abstract: Multifrequency electron paramagnetic resonance (EPR) and high resolution transmission electron microscopy (HRTEM) investigations were performed on small (2 nm) cubic ZnS nanocrystals (quantum dotsQDs) doped with 0.2% mol Mn2+, self-assembled into a mesoporous structure. The EPR data analysis shows that the substitutional Mn2+ ions are localized at Zn2+ sites subjected to a local axial lattice distortion, resulting in the observed zero-field-splitting parameter |D|=41×10−4 cm−1. The local distortion is attributed to the presence in the second shell of ligands of a stacking fault or twin, which alters the normal stacking sequence of the cubic structure. The HRTEM results confirm the presence of such extended planar defects in a large percentage of the investigated QDs, which makes possible the proposed substitutional Mn2+ impurity ions localization model. Based on these results it is suggested that the high doping levels of Mn2+ ions observed in cubic ZnS and possible in other II-VI semiconductor QDs prepared at low temperatures can be explained by the assistance of the extended lattice defects in the impurities incorporation.
Keywords: A1 Journal article; Nanostructured and organic optical and electronic materials (NANOrOPT); Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 55
DOI: 10.1103/PhysRevB.81.035336
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“Interpretation of “Energy-filtered electron-diffracted beam holography&rdquo, by R.A. Herring”. Verbeeck J, Ultramicroscopy 106, 461 (2006). http://doi.org/10.1016/j.ultramic.2005.12.004
Abstract: A straightforward application of the theoretical framework presented by Verbeeck et al. [Ultramicroscopy 102 (2005) 239] is presented to explain the energy-filtered electron-diffracted beam holography experiments published by Herring [Ultramicroscopy 104 (2005) 261]. It is shown that the theory is in agreement with all experimental findings, which leads to the interpretation that the experiments are mainly measuring the angular coherence of the source image rather than exposing details on the coherence properties of inelastic scattering. A change in experimental parameters is proposed, which could result in interesting information about the coherence in all inelastic scattering process. (c) 2006 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 8
DOI: 10.1016/j.ultramic.2005.12.004
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“Lattice deformations in quasi-dynamic strain glass visualised and quantified by aberration corrected electron microscopy”. Lu J, Martinez GT, Van Aert S, Schryvers D, Physica status solidi: B: basic research 251, 2034 (2014). http://doi.org/10.1002/pssb.201350351
Abstract: Advanced transmission electron microscopy and statistical parameter estimated quantification procedures were applied to study the room temperature quasi-dynamical strain glass state in NiTi alloys. Nanosized strain pockets are visualised and the displacements of the atom columns are quantified. A comparison is made with conventional high-resolution transmission electron microscopy images of point defect induced strains in NiAl alloys.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.674
Times cited: 2
DOI: 10.1002/pssb.201350351
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“Linear versus non-linear structural information limit in high-resolution transmission electron microscopy”. Van Aert S, Chen JH, van Dyck D, Ultramicroscopy 110, 1404 (2010). http://doi.org/10.1016/j.ultramic.2010.07.001
Abstract: A widely used performance criterion in high-resolution transmission electron microscopy (HRTEM) is the information limit. It corresponds to the inverse of the maximum spatial object frequency that is linearly transmitted with sufficient intensity from the exit plane of the object to the image plane and is limited due to partial temporal coherence. In practice, the information limit is often measured from a diffractogram or from Young's fringes assuming a weak phase object scattering beyond the inverse of the information limit. However, for an aberration corrected electron microscope, with an information limit in the sub-angstrom range, weak phase objects are no longer applicable since they do not scatter sufficiently in this range. Therefore, one relies on more strongly scattering objects such as crystals of heavy atoms observed along a low index zone axis. In that case, dynamical scattering becomes important such that the non-linear and linear interaction may be equally important. The non-linear interaction may then set the experimental cut-off frequency observed in a diffractogram. The goal of this paper is to quantify both the linear and the non-linear information transfer in terms of closed form analytical expressions. Whereas the cut-off frequency set by the linear transfer can be directly related with the attainable resolution, information from the non-linear transfer can only be extracted using quantitative, model-based methods. In contrast to the historic definition of the information limit depending on microscope parameters only, the expressions derived in this paper explicitly incorporate their dependence on the structure parameters as well. In order to emphasize this dependence and to distinguish from the usual information limit, the expressions derived for the inverse cut-off frequencies will be referred to as the linear and non-linear structural information limit. The present findings confirm the well-known result that partial temporal coherence has different effects on the transfer of the linear and non-linear terms, such that the non-linear imaging contributions are damped less than the linear imaging contributions at high spatial frequencies. This will be important when coherent aberrations such as spherical aberration and defocus are reduced.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 6
DOI: 10.1016/j.ultramic.2010.07.001
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“Metal@COFs : covalent organic frameworks as templates for Pd nanoparticles and hydrogen storage properties of Pd@COF-102 hybrid material”. Kalidindi SB, Hyunchul O, Hirscher M, Esken D, Wiktor C, Turner S, Van Tendeloo G, Fischer RA, Chemistry: a European journal 18, 10848 (2012). http://doi.org/10.1002/chem.201201340
Abstract: Three-dimensional covalent organic frameworks (COFs) have been demonstrated as a new class of templates for nanoparticles. Photodecomposition of the [Pd(eta 3-C3H5)(eta 5-C5H5)]@COF-102 inclusion compound (synthesized by a gas-phase infiltration method) led to the formation of the Pd@COF-102 hybrid material. Advanced electron microscopy techniques (including high-angle annular dark-field scanning transmission electron microscopy and electron tomography) along with other conventional characterization techniques unambiguously showed that highly monodisperse Pd nanoparticles ((2.4 +/- 0.5) nm) were evenly distributed inside the COF-102 framework. The Pd@COF-102 hybrid material is a rare example of a metal-nanoparticle-loaded porous crystalline material with a very narrow size distribution without any larger agglomerates even at high loadings (30 wt %). Two samples with moderate Pd content (3.5 and 9.5 wt %) were used to study the hydrogen storage properties of the metal-decorated COF surface. The uptakes at room temperature from these samples were higher than those of similar systems such as Pd@metalorganic frameworks (MOFs). The studies show that the H2 capacities were enhanced by a factor of 2-3 through Pd impregnation on COF-102 at room temperature and 20 bar. This remarkable enhancement is not just due to Pd hydride formation and can be mainly ascribed to hydrogenation of residual organic compounds, such as bicyclopentadiene. The significantly higher reversible hydrogen storage capacity that comes from decomposed products of the employed organometallic Pd precursor suggests that this discovery may be relevant to the discussion of the spillover phenomenon in metal/MOFs and related systems.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 88
DOI: 10.1002/chem.201201340
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“A method to determine the local surface profile from reconstructed exit waves”. Wang A, Chen FR, Van Aert S, van Dyck D, Ultramicroscopy 111, 1352 (2011). http://doi.org/10.1016/j.ultramic.2011.04.005
Abstract: Reconstructed exit waves are useful to quantify unknown structure parameters such as the position and composition of the atom columns at atomic scale. Existing techniques provide a complex wave in a flat plane which is close to the plane where the electrons leave the atom columns. However, due to local deviation in the flatness of the exit surface, there will be an offset between the plane of reconstruction and the actual exit of a specific atom column. Using the channelling theory, it has been shown that this defocus offset can in principle be determined atom column-by-atom column. As such, the surface roughness could be quantified at atomic scale. However, the outcome strongly depends on the initial plane of reconstruction especially in a crystalline structure. If this plane is further away from the true exit, the waves of the atom columns become delocalized and interfere mutually which strongly complicates the interpretation of the exit wave in terms of the local structure. In this paper, we will study the delocalization with defocus using the channelling theory in a more systematic way.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 3
DOI: 10.1016/j.ultramic.2011.04.005
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