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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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“An emission-potential multislice approximation to simulate thermal diffuse scattering in high-resolution transmission electron microscopy”. Rosenauer A, Schowalter M, Titantah JT, Lamoen D, Ultramicroscopy 108, 1504 (2008). http://doi.org/10.1016/j.ultramic.2008.04.002
Abstract: Thermal diffuse scattered electrons significantly contribute to high-resolution transmission electron microscopy images. Their intensity adds to the background and is peaked at positions of atomic columns. In this paper we suggest an approximation to simulate intensity of thermal diffuse scattered electrons in plane-wave illumination transmission electron microscopy using an emission-potential multislice algorithm which is computationally less intensive than the frozen lattice approximation or the mutual intensity approach. Intensity patterns are computed for Au and InSb for different crystal orientations. These results are compared with intensities from the frozen lattice approximation based on uncorrelated vibration of atoms as well as with the frozen phonon approximation for Au. The frozen phonon method uses a detailed phonon model based on force constants we computed by a density functional theory approach. The comparison shows that our suggested emission-potential method is in close agreement with both the frozen lattice and the frozen phonon approximations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 25
DOI: 10.1016/j.ultramic.2008.04.002
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“Experiments on inelastic electron holography”. Potapov P, Lichte H, Verbeeck J, van Dyck D, Ultramicroscopy 106, 1012 (2006). http://doi.org/10.1016/j.ultramic.2006.05.012
Abstract: Using the combination of an electron biprism and an energy filter, the coherence distribution in an inelastically scattered wave-field is measured. It is found that the degree of coherence decreases rapidly with increasing distance between two superimposed points in the object, and with increasing energy-loss. In a Si sample, coherence of plasmon scattering increases in vacuum with the distance from the edge of the sample. (c) 2006 Published by Elsevier B.V.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 28
DOI: 10.1016/j.ultramic.2006.05.012
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“Exploring different inelastic projection mechanisms for electron tomography”. Goris B, Bals S, van den Broek W, Verbeeck J, Van Tendeloo G, Ultramicroscopy 111, 1262 (2011). http://doi.org/10.1016/j.ultramic.2011.02.007
Abstract: Several different projection mechanisms that all make use of inelastically scattered electrons are used for electron tomography. The advantages and the disadvantages of these methods are compared to HAADFSTEM tomography, which is considered as the standard electron tomography technique in materials science. The different inelastic setups used are energy filtered transmission electron microscopy (EFTEM), thickness mapping based on the log-ratio method and bulk plasmon mapping. We present a comparison that can be used to select the best inelastic signal for tomography, depending on different parameters such as the beam stability and nature of the sample. The appropriate signal will obviously also depend on the exact information which is requested.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 21
DOI: 10.1016/j.ultramic.2011.02.007
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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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“A holographic biprism as a perfect energy filter?”.Verbeeck J, Bertoni G, Lichte H, Ultramicroscopy 111, 887 (2011). http://doi.org/10.1016/j.ultramic.2011.01.042
Abstract: It has often been stated that a holographic biprism represents a near perfect energy filter and only elastically scattered electrons can participate in the interference fringes. This is based on the assumption that the reference wave does not contain inelastically scattered electrons. In this letter we show that this is not exactly true because of the delocalised inelastic interaction of the reference wave with the sample. We experimentally and theoretically show that inelastic scattering plays a role in the fringe formation, but it is shown that this contribution is small and can usually be neglected in practice. (C) 2011 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 13
DOI: 10.1016/j.ultramic.2011.01.042
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“Image simulation of high resolution energy filtered TEM images”. Verbeeck J, Sc hattschneider P, Rosenauer A, Ultramicroscopy 109, 350 (2009). http://doi.org/10.1016/j.ultramic.2009.01.003
Abstract: Inelastic image simulation software is presented, implementing the double channeling approximation which takes into account the combination of multiple elastic and single inelastic scattering in a crystal. The approach is described with a density matrix formalism. Two applications in high resolution energy filtered (EFTEM) transmission electron microscopy (TEM) images are presented: thickness-defocus maps for SrTiO3 and exit plane intensities for an (LaAlO3)3(SrTiO3)3 multilayer system. Both systems show a severe breakdown in direct interpretability which becomes worse for higher acceleration voltages, thicker samples and lower excitation edge energies. Since this effect already occurs in the exit plane intensity, it is a fundamental limit and image simulations in EFTEM are indispensable just as they are indispensable for elastic high resolution TEM images.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 36
DOI: 10.1016/j.ultramic.2009.01.003
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“Improved multislice calculations for including higher-order Laue zones effects”. Lobato I, van Dyck D, Ultramicroscopy 119, 63 (2012). http://doi.org/10.1016/j.ultramic.2012.01.003
Abstract: A new method for including higher-order Laue zones (HOLZs) effects in an efficient way in electron scattering simulations has been developed and tested by detail calculations. The calculated results by the conventional multislice (CMS) method and the improved conventional multislice (ICMS) method using a large dynamical aperture to avoid numerical errors are compared with accurate results. We have found that the zero-order Laue zones (ZOLZs) reflection cannot be properly described only using the projected potential in the whole unit cell; in general, we need to subslice the electrostatic potential inside the unit cell. It is shown that the ICMS method has higher accuracy than the CMS method for the calculation of the ZOLZ, HOLZ and Pseudo-HOLZ reflections. Hence, ICMS method allows to use a larger slice thickness than the CMS method and reduces the calculation time. (C) 2012 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 6
DOI: 10.1016/j.ultramic.2012.01.003
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“In situ HREM study of electron irradiation effects in AgCl microcrystals”. Goessens C, Schryvers D, van Landuyt J, de Keyzer R, Ultramicroscopy 40, 151 (1992). http://doi.org/10.1016/0304-3991(92)90056-P
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.436
Times cited: 10
DOI: 10.1016/0304-3991(92)90056-P
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“Inelastic electron holography as a variant of the Feynman thought experiment”. Potapov PL, Verbeeck J, Schattschneider P, Lichte H, van Dyck D, Ultramicroscopy 107, 559 (2007). http://doi.org/10.1016/j.ultramic.2006.11.003
Abstract: Using a combination of electron holography and energy filtering, interference fringes produced after inelastic interaction of electrons with hydrogen molecules are examined. Surprisingly, the coherence of inelastic scattering increases when moving from the surface of a hydrogen-containing bubble to the vacuum. This phenomenon can be understood in terms of the Feynman two-slit thought experiment with a variable ambiguity of the which-way registration. (C) 2006 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 13
DOI: 10.1016/j.ultramic.2006.11.003
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“Inelastic scattering of high-energy electrons in a crystal in thermal equilibrium with the environment: 1: theoretical framework”. Fanidis C, van Dyck D, van Landuyt J, Ultramicroscopy 41, 55 (1992). http://doi.org/10.1016/0304-3991(92)90094-Z
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.436
Times cited: 17
DOI: 10.1016/0304-3991(92)90094-Z
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“Inelastic scattering of high-energy electrons in a crystal in thermal equilibrium with the environment: part 2: solution of the equations and applications to concrete cases”. Fanidis C, van Dyck D, van Landuyt J, Ultramicroscopy 48, 133 (1993)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.436
Times cited: 6
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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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“Introduction to a special issue in honour of W. Owen Saxton, David J. Smith and Dirk Van Dyck on the occasion of their 65th birthdays”. Dunin-Borkowski RE, Lichte H, Tillmann K, Van Aert S, Van Tendeloo G, Ultramicroscopy 134, 1 (2013). http://doi.org/10.1016/j.ultramic.2013.07.013
Keywords: Editorial; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 1
DOI: 10.1016/j.ultramic.2013.07.013
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“Is atomic resolution transmission electron microscopy able to resolve and refine amorphous structures?”.van Dyck D, Van Aert S, den Dekker AJ, van den Bos A, Ultramicroscopy 98, 27 (2003). http://doi.org/10.1016/S0304-3991(03)00023-8
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 26
DOI: 10.1016/S0304-3991(03)00023-8
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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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“Maximum likelihood estimation of structure parameters from high resolution electron microscopy images: part 1: a theoretical framework”. den Dekker AJ, Van Aert S, van den Bos A, van Dyck D, Ultramicroscopy 104, 83 (2005). http://doi.org/10.1016/j.ultramic.2005.03.001
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 70
DOI: 10.1016/j.ultramic.2005.03.001
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“Maximum likelihood estimation of structure parameters from high resolution electron microscopy images : part 2 : a practical example”. Van Aert S, den Dekker AJ, van den Bos A, van Dyck D, Chen JH, Ultramicroscopy 104, 107 (2005). http://doi.org/10.1016/j.ultramic.2005.03.002
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 37
DOI: 10.1016/j.ultramic.2005.03.002
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“Measurement of specimen thickness by phase change determination in TEM”. Croitoru MD, van Dyck D, Liu YZ, Zhang Z, Ultramicroscopy 108, 1616 (2008). http://doi.org/10.1016/j.ultramic.2008.06.002
Abstract: A non-destructive method for measuring the thickness of thin amorphous films composed of light elements has been developed. The method employs the statistics of the phase of the electron exit wave function. The accuracy of this method has been checked numerically by the multislice method and compared with that based on the mean inner potential.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 2
DOI: 10.1016/j.ultramic.2008.06.002
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“Measuring the absolute position of EELS ionisation edges in a TEM”. Potapov PL, Schryvers D, Ultramicroscopy 99, 73 (2004). http://doi.org/10.1016/S0304-3991(03)00185-2
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 29
DOI: 10.1016/S0304-3991(03)00185-2
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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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“A model based atomic resolution tomographic algorithm”. van den Broek W, Van Aert S, van Dyck D, Ultramicroscopy 109, 1485 (2009). http://doi.org/10.1016/j.ultramic.2009.08.003
Abstract: Tomography with high angular annular dark field scanning transmission electron microscopy at atomic resolution can be greatly improved if one is able to take advantage of prior knowledge. In this paper we present a reconstruction technique that explicitly takes into account the microscope parameters and the atomic nature of the projected object. This results in a more accurate estimate of the atomic positions and in a good resistance to noise. The reconstruction is a maximum likelihood estimator of the object. Moreover, the limits to the precision have been explored, allowing for a prediction of the amount of expected noise in the reconstruction for a certain experimental setup. We believe that the proposed reconstruction technique can be generalized to other tomographic experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 17
DOI: 10.1016/j.ultramic.2009.08.003
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“Model based quantification of EELS spectra”. Verbeeck J, Van Aert S, Ultramicroscopy 101, 207 (2004). http://doi.org/10.1016/j.ultramic.2004.06.004
Abstract: Recent advances in model based quantification of electron energy loss spectra (EELS) are reported. The maximum likelihood method for the estimation of physical parameters describing an EELS spectrum, the validation of the model used in this estimation procedure, and the computation of the attainable precision, that is, the theoretical lower bound on the variance of these estimates, are discussed. Experimental examples on An and GaAs samples show the power of the maximum likelihood method and show that the theoretical prediction of the attainable precision can be closely approached even for spectra with overlapping edges where conventional EELS quantification fails. To provide end-users with a low threshold alternative to conventional quantification, a user friendly program was developed which is freely available under a GNU public license. (C) 2004 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 147
DOI: 10.1016/j.ultramic.2004.06.004
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“Model-based quantification of EELS spectra: including the fine structure”. Verbeeck J, Van Aert S, Bertoni G, Ultramicroscopy 106, 976 (2006). http://doi.org/10.1016/j.ultramic.2006.05.006
Abstract: An extension to model-based electron energy loss spectroscopy (EELS) quantification is reported to improve the possibility of modelling fine structure changes in electron energy loss spectra. An equalisation function is used in the energy loss near edge structure (ELNES) region to model the differences between a single atom differential cross section and the cross section for an atom in a crystal. The equalisation function can be shown to approximate the relative density of unoccupied states for the given excitation edge. On a set of 200 experimental h-BN spectra, this technique leads to statistically acceptable models resulting into unbiased estimates of relative concentrations and making the estimated precisions come very close to the Cramer-Rao lower bound (CRLB). The method greatly expands the useability of model-based EELS quantification to spectra with pronounced fine structure. Another benefit of this model is that one also gets an estimate of the unoccupied density of states for a given excitation edge, without having to do background removal and deconvolution, making the outcome intrinsically more reliable and less noisy. (c) 2006 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 38
DOI: 10.1016/j.ultramic.2006.05.006
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“Model-based quantification of EELS spectra: treating the effect of correlated noise”. Verbeeck J, Bertoni G, Ultramicroscopy 108, 74 (2008). http://doi.org/10.1016/j.ultramic.2007.03.004
Abstract: Correlated noise is generally present in experimentally recorded electron energy loss spectra due to a non-ideal electron detector. In this contribution we describe a method to experimentally measure the noise properties of the detector as well as the consequences it has for model-based quantification using maximum likelihood. The effect of the correlated noise on the maximum likelihood fitting results can be shown to be negligible for the estimated (co)variance of the parameters while an experimentally obtained scaling factor is required to correct the likelihood ratio test for the reduction of noise power with frequency. Both effects are derived theoretically under a set of approximations and tested for a range of signal-to-noise values using numerical experiments. Finally, an experimental example shows that the correction for correlated noise is essential and should always be included in the fitting procedure. (c) 2007 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 16
DOI: 10.1016/j.ultramic.2007.03.004
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“A model based reconstruction technique for depth sectioning with scanning transmission electron microscopy”. van den Broek W, Van Aert S, van Dyck D, Ultramicroscopy 110, 548 (2010). http://doi.org/10.1016/j.ultramic.2009.09.008
Abstract: Depth sectioning in high angular annular dark field scanning transmission electron microscopy is considered a candidate for three-dimensional characterization on the atomic scale. However at present the depth resolution is still far from the atomic level, due to strong limitations in the opening angle of the beam. In this paper we introduce a new, parameter based tomographic reconstruction algorithm that allows to make maximal use of the prior knowledge about the constituent atom types and the microscope settings, so as to retrieve the atomic positions and push the resolution to the atomic level in all three dimensions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 16
DOI: 10.1016/j.ultramic.2009.09.008
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“Nonlinear imaging using annular dark field TEM”. Bals S, Kilaas R, Kisielowski C, Ultramicroscopy 104, 281 (2005). http://doi.org/10.1016/j.ultramic.2005.05.004
Abstract: Annular dark field TEM images exhibit a dominant mass-thickness contrast that can be quantified to extract single atom scattering cross sections. On top of this incoherent background, additional lattice fringes appear with a nonlinear information limit of 1.2 angstrom at 150 kV. The formation of these fringes is described by coherent nonlinear imaging theory and good agreement is found between experimental and simulated images. Calculations furthermore predict that the use of aberration corrected microscopes will improve the image quality dramatically. (c) 2005 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 15
DOI: 10.1016/j.ultramic.2005.05.004
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“On the interpretation of HREM images of partially ordered alloys”. De Meulenaere P, Van Tendeloo G, van Landuyt J, van Dyck D, Ultramicroscopy 60, 265 (1995). http://doi.org/10.1016/0304-3991(95)00065-9
Abstract: The ordering for 11/20 alloys has been studied by high-resolution electron microscopy (HREM). The distribution of the intensity maxima in the HREM image have been statistically examined, which provides a profound basis for the image interpretation. Processing of the HREM images allows ''dark-field'' images to be obtained, exhibiting a two-dimensional distribution of those columns which contain the most information in order to interpret the short-range order correlations. Pair correlations and higher cluster correlations between projected columns can be visualised, providing unique information about the ordering as retrieved from an experimental result without any other assumption. The method has been applied to Au4Cr and to Au4Mn to interpret the quenched short-range order state and the transition to long-range order.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.436
Times cited: 20
DOI: 10.1016/0304-3991(95)00065-9
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“Optimal aperture sizes and positions for EMCD experiments”. Verbeeck J, Hébert, Rubino S, Novák P, Rusz J, Houdellier F, Gatel C, Schattschneider P, Ultramicroscopy 108, 865 (2008). http://doi.org/10.1016/j.ultramic.2008.02.007
Abstract: The signal-to-noise ratio (SNR) in energy-loss magnetic chiral dichroism (EMCD)the equivalent of X-ray magnetic circular dichroism (XMCD) in the electron microscopeis optimized with respect to the detector shape, size and position. We show that an important increase in SNR over previous experiments can be obtained when taking much larger detector sizes. We determine the ideal shape of the detector but also show that round apertures are a good compromise if placed in their optimal position. We develop the theory for a simple analytical description of the EMCD experiment and then apply it to dynamical multibeam Bloch wave calculations and to an experimental data set. In all cases it is shown that a significant and welcome improvement of the SNR is possible.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 27
DOI: 10.1016/j.ultramic.2008.02.007
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“Optimal experimental design of STEM measurement of atom column positions”. Van Aert S, den Dekker AJ, van Dyck D, van den Bos A, Ultramicroscopy 90, 273 (2002). http://doi.org/10.1016/S0304-3991(01)00152-8
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 35
DOI: 10.1016/S0304-3991(01)00152-8
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