Research team

Electron microscopy for materials research (EMAT)

Expertise

Transmission electron microscopy for materials science Development of novel measurement schemes with electron beams Adaptive optics with electron beams Electron energy loss spectroscopy

Electron beams enhancing analytical microscopy (EBEAM). 01/01/2021 - 31/03/2026

Abstract

Electron microscopy (EM) is a key technology to reveal the atomic structure and chemical composition of materials with (sub-)Ångström resolution. It is an essential technique to enable the breakthroughs that are needed to solve societal challenges in renewable energy technology, life sciences, and communication and quantum technology. To realize these breakthroughs, we require EM technology with ultrafast time scale, ultrahigh energy resolution, covering low-energy spectral ranges and several other capabilities, all of which are beyond the present state of the art. The EBEAM project brings together a proven consortium of EM experts that will integrate their complementary EM science and technology into completely new EM measurement modalities, exploiting the unique interactions between free electrons and optical light fields, and thereby combining ultrahigh spectral and temporal control with sub-Ångström spatial resolution. The project's ambition is to demonstrate <20 fs time resolution and <1 meV energy resolution, and to open up the 4-400 neV (1-100 MHz) energy range, all inaccessible in EM so far. Using new correlation and coincidence modalities that have never been used in EM before, we will unveil new methods to probe selection rules, low-energy band structures, trace elements, and more. We will demonstrate the broad applicability of the new EBEAM techniques by carrying out selected research projects that target key questions in energy conversion materials, opto-electronic materials and quantum technology. The consortium is composed of 8 EM groups in basic research and industry that represent a unique combination of EM instruments, knowledge and ideas that are well positioned to target the ambitious goals of the EBEAM project. It includes the world-leader in EM manufacturing and a successful SME. Together, the consortium will bring the EBEAM technology to a broad user community where it is expected to have strong scientific and economic impact.

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Strain to stabilize metal halide PERovSkites: an Integrated effort from fundamentalS toopto-electronic applicaTions (PERsist). 01/01/2021 - 31/12/2024

Abstract

Light detection and emission are crucial for displays, medical and security scanners. Given the societal relevance, there is an emerging need for novel opto-electronic materials with higher conversion effi-ciency and lower production cost. Metal halide perovskites are promising high-performance semicon-ductors due to their strong absorption and emission in a broad spectral range and their ease of manu-facturing. So far, integration in opto-electronic devices was hampered by inherent stability issues such as the degradation from the optically active "black" phase into an inactive phase. Based on our recent proof-of-concept, we will explore a fundamentally new paradigm to stabilize the black phase under ambient conditions. This innovative concept exploits strain engineering, with thin films fixed to sub-strates and/or patterned at the nano- to micrometer scale. PERsist builds on the synergy between leading experts in high-end micro/spectroscopy & modelling of nanomaterials.

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Automated Electron diffractometer for high throughput identification of nanocrystalline materials. 01/10/2020 - 30/09/2024

Abstract

The study of the structure of nanocrystalline materials is often difficult as standard X-ray diffraction techniques break down for sub micrometer particles, especially when occurring in a mixture. This is resolved by trying to crystallize specific compounds in larger crystals, but this is often problematic and time consuming. State of the art single crystal X-ray diffraction moreover requires a trip to a synchrotron which creates unnecessary long delays between growing a new structure and determining its structure. Electron diffraction provides an alternative for X-ray diffraction and excels especially for nanoscale crystals as it provides several orders of magnitude more information per volume for the same radiation damage. However, so far, electron diffraction is performed on expensive and difficult to handle transmission electron microscopes (TEM) requiring extensive interaction from highly trained researchers. This makes the technique rather unattractive for industrial demands where ease of use, high throughput, statistics and reproducibility are key concerns that don't fit well with the reality of TEM instruments in university labs. In this project, we propose to build a prototype electron diffractometer instrument on the basis of a modest Scanning Electron Microscope (SEM). The instrument will take a properly prepared nanocrystalline powder and automatically perform a full diffraction analysis on a very large number of particles without human interaction. This data is then fed into an automated structure refinement program and results in a full report on the structure and abundance of the particles found. An in house proof of concept shows that the obtained quality of diffraction data is excellent although several scientific issues will require attention. We propose to demonstrate this instrument on industry relevant materials in close interaction with several companies in Flanders that expressed strong interest in the capabilities of such instrument.

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Big data electron spectroscopy: electronic and optical properties of materials from large, momentum-resolved EELS datasets. 01/10/2020 - 30/09/2023

Abstract

We rely on materials science for progress in nearly every area of technology, to help us solve a variety of challenges. Materials science, in turn, relies the availability of characterisation techniques to help understand the behaviour and properties of materials, so that they can be engineered. Transmission electron microscopy is an important tool to this end, allowing us to probe the structure of materials and many of their properties with unrivalled resolution. Electron energy loss spectroscopy (EELS) is one of the most popular characterisation methods available in TEMs, allowing to investigate composition and much more by analysing the energy lost by the electrons in the beam by interacting with the sample. I want to broaden the scope of properties that can be measured with nanoscale resolution by analysing not only the energy loss but also the momentum exchange. In detail, I want to use momentum resolved EELS to measure the nanoscale fields in the optical resonances of nanoparticles more accurately and quantitatively than before, the bandgap and band structure of semiconductors and 2D materials with nanometer resolution and the bonding orientation of atoms in complex oxides. Separately, I want to develop a system to probe sub-THz spectroscopy at the nanoscale by using a sinusoidally pulsed electron beam to excite the sample with extreme spectral precision.

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AdaptEM: adaptive phaseplate for electron microscopy: phase 2, preparing for spin off. 01/09/2020 - 31/08/2022

Abstract

This project builds on the proof of concept technology of a programmable phase plate for electron optics developed during an earlier POC project (2018-2019) with the aim to develop it towards a spin off company. The unique and protected technology will lead to a disruptive step in the capabilities of electron microscopy. We singled out 8 different application domains that would critically benefit from this technology, each in a different phase of development. An in-depth market study is needed to prioritize these applications in terms of which ones should be started from. We aim to raise the TRL level from 5 to 7 by mastering the technological risks in order to sell a product to a selection of early adopters and thereby start the company. This envisioned path makes optimal use of the window of opportunity in the market and can transform the knowledge developed at UA into valorisable results that will lead both to a societal and economic added value for our university and region.

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Exploring adaptive optics in transmission electron microscopy. 01/01/2020 - 31/12/2023

Abstract

Adaptive optics, the technology to adapt the shape of lenses and mirrors to optimise the imaging capabilities, has sparked an avalanche of scientific discoveries in diverse areas of science that rely on light optics. Nowadays, optical waves can be dynamically programmed in terms of their phase profile, providing experimental research on exotic beam types and unprecedented control over the performance of optical instruments. Accelerated electron beams, on the other hand, as used extensively in e.g. electron microscopy, carry many similarities with light including the wave nature and the existence of (electron optical) lenses as well as a very similar mathematical description. The one part missing so far, is a generic programmable phase plate for electron waves allowing for similar flexibility as in state of the art light optics. The goal of this project is to explore the potential that a prototype generic phase plate, recently developed in my group and unique in the world, would bring to electron microscopy. Such a phase plate can dramatically increase the information obtained at a given electron dose, limiting the detrimental effect of beam damage that hinders the use of electron microscopy in e.g. life sciences or soft matter research. Specifically, it would enable the study of the structure and chirality of single molecules for e.g. drug discovery, insights in nanoplasmonic antennas for solar harvesting, improved precision in e-beam lithography and many more.

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Coincident event detection for advanced spectroscopy in transmission electron microscopy. 01/01/2020 - 31/12/2023

Abstract

Many materials around us show properties that depend in a sensitive way on small amounts of foreign atoms in an environment of majority atoms. Transmission electron microscopy is a very powerful method to study the atomic structure of materials down to the atomic scale, and spectroscopic methods allow to pinpoint the types of atoms present. Two spectroscopic methods, EELS and EDX, are commonly used and rely on the excitation of the atoms when interacting with a beam of accelerated electrons. Both methods however have significant shortcomings, especially when it comes to obtaining detailed information on these all-important minority atoms. In this project, we propose to make use of recent developments in detectors for electrons and X-rays that form the basis of these spectroscopic methods. We propose to collect atomic excitation events in a time resolved fashion, which allows us to select those events where both an electron and X-ray is detected at the same time. In doing so, we join the benefits of both EELS and EDX methods and dramatically improve the performance of these spectroscopic methods in cases where small amounts of atoms are present in an environment of a majority of other elements. We will test the benefits of a prototype setup on several types of materials that are relevant for society: modern engineering alloys, materials for future quantum computers and semiconductors for electronics and photovoltaic applications.

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Towards improved high capacity layered electrode materials for Liion batteries through atomic-level understanding of the redox reactions. 01/01/2020 - 31/12/2022

Abstract

Rechargeable Li-ion batteries are a pillar of our current technology driven society. More energy per mass unit can be stored in layered high capacity cathodes but they suffer from the voltage fade and voltage hysteresis reducing their energy efficiency. These detrimental effects mainly originate from the structural changes in the cathode material during charge and discharge. Recent developments have led to a paradigm shift, by showing that in these promising cathodes the oxygen oxidation, contributing to high capacity, is inherently linked with transition metal cation migration upon cycling. Together, they cause the voltage hysteresis and voltage fade. Gaining understanding of the complex interplay and control over both is necessary to exploit the advantages while eliminating the detrimental effects. To monitor both effects systematically and separate from the influence of the microstructure, we will synthesize new model structures with dedicated structural variations of the initial crystal structure and microstructure. We will study their structural changes upon cycling with state-of-the-art structure characterization techniques, and relate them to the electrochemical properties. This project will thus result in new viable Li-ion battery cathodes and allow the comprehensive understanding of the role of the microstructure, local structure and local valence for the stability of Li-rich layered cathodes, major candidates for future advanced rechargeable Li-ion batteries.

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Enabling science and technology through European electron microscopy (ESTEEM3). 01/01/2019 - 30/06/2023

Abstract

ESTEEM3 is an integrating activity for electron microscopy providing access to the leading European state-of-the-art electron microscopy research infrastructures, facilitating and extending transnational access services of the most powerful atomic scale characterization techniques in advanced electron microscopy research to a wide range of academic and industrial research communities for the analysis and engineering of novel materials in physical, chemical and biological sciences. ESTEEM3 objective is to deliver more access to more users coming from a wider range of disciplines. Transnational Access to ESTEEM3 centres is obtained through a transparent, simple peer review process based on merit and scientific priorities. Optimum service to users is supported by networking and joint research activities, which address key issues such as specimen preparation, data interpretation, treatment and automation through theory and simulation, and standardization of protocols and methodologies. Innovative activities dedicated to the dissemination of expertise, education and training in cutting-edge quantitative transmission electron microscopy techniques, such as schools, advanced workshops and webinars, are offered to the European electron microscopy users from academia, research institutes and industry. Directed research programmes involving the academic and industrial partners of the consortium focus on the further methodology development in imaging and diffraction, spectroscopy, in-situ techniques and metrology, and on advancing applied research of materials related to ICT, energy, health, and transport for the benefit of European scientists and industry. Moreover, the definition of strategic roadmaps and open access data policies aims to ensure the long-term sustainability of the consortium. In all, ESTEEM3 establishes a strategic leadership in electron microscopy to guide future developments and promote electron microscopy to the widest research community at large.

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Plasma for environmental, medical, analytical chemistry and materials applications. 01/05/2018 - 31/12/2024

Abstract

Plasma is an ionized gas. It is the fourth state of matter, next to solid, liquid and gaseous state. It exists in nature, but it can also be generated in laboratories by applying electric fields or heat to a gas. It consists of gas molecules, but also many reactive species, like electrons, various types of ions, radicals and excited species. This highly reactive chemical cocktail makes plasma interesting for many applications. We are studying the underlying mechanisms in plasma, including the plasma chemistry, plasma reactor design and plasma‐surface interactions, by means of computer simulations and experiments, to improve the following applications: (1) in materials science (for nanotechnology and microchip fabrication), (2) for analytical chemistry, (3) in environmental/energy applications (i.e., conversion of greenhouse gases and nitrogen fixation), and (4) for medicine (mainly cancer research).

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Smart strategies to break the beam damage limits in transmission electron microscopy. 01/01/2018 - 31/12/2021

Abstract

The goal of this project is to develop and apply smart strategies, which are dedicated to characterise beam-sensitive nanostructures using quantitative scanning transmission electron microscopy imaging. This will allow one to use a minimum electron dose to detect single atoms, to determine their atom types and to precisely measure positions of atoms. In this manner, beam damage will be drastically reduced or will even be ruled out completely.

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Research in the field of Electron Microscopy for Material Sciences 01/01/2013 - 31/12/2022

Abstract

This project represents a research contract awarded by the University of Antwerp. The supervisor provides the Antwerp University research mentioned in the title of the project under the conditions stipulated by the university.

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Nanometre scale imaging of magnetic perovskite oxide thin films using scanning transmission electron microscopy (MAGIMOX). 01/04/2019 - 04/03/2020

Abstract

Magnetic materials are a vital part of modern society, being important components in technologies such as magnetic resonance imaging machines and hard disk drives. A common strategy to both improve existing technologies and develop new ones, is miniaturization. The most striking example being the billion-fold increase in silicon semiconductor transistor density, which fundamentally changed society since its invention in the 60ies. However, this miniaturization trend now seems to come to a slow-down as devices are shrinking to sizes where hard physical limits are setting in, and being able to image these nanoscale devices becomes ever more important. Scanning transmission electron microscopy (STEM) is a widely used imaging technique used to study such nanometre scale devices, however it does not readily provide imaging of the magnetic properties at this scale. The perovskite oxides form a materials family, which exhibits a wide range of properties including magnetism. A similar miniaturization process has been used for these materials, where making them as nanometre thick films revealed new phenomena. The most exciting being multiferroics, where an applied electric field can change the magnetic structure, and vice versa. This has attracted much interest in both making and studying these oxide materials, especially their magnetic properties, due to the great potential for new device concepts. However, due to the small sizes of these films they're often very hard to study, especially when it comes to their nanoscale magnetic structure. This action will take advantage of recently developed fast electron STEM detectors to image the nanometre scale magnetic structures of these materials directly with unprecedented resolution. Using a high-end STEM equipped with such a detector, both the magnetic and crystal structure will be studied in the same microscope. This will enable highly correlated studies of the perovskites, giving a deeper understanding of these new phenomena.

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Preparation Vortex/Bessel beam apertures for TEM experiments. 14/01/2019 - 31/12/2019

Abstract

Application of an in-house Focused Ion Beam (FIB) protocol for preparation of TEM apertures developed during the ERC-project "Vortex". These specialized apertures can be used for generation of vortex and/or Bessel beams for analysis of e.g. electromagnetic properties, strain and plasmonics.

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Development of a programmable phase plate for electron microscopy. 01/05/2018 - 31/10/2019

Abstract

This project aims at developing a prototype of a programmable electrostatic phase plate that allows the user to freely change the phase of electron waves. The target of this POC project is the realization of a tunable easy-to-use 5x5-pixel prototype that will demonstrate the potential of adaptive optics in electron microscopy. Its realization will be based on lithographic technology to allow for future upscaling. It is expected that such a phase plate can dramatically increase the information obtained at a given electron dose, limiting the detrimental effects of beam damage that currently hinders the use of electron microscopy in e.g. life sciences. As such, it has the potential to disrupt the electron microscopy market with novel applications while at the same time reducing cost and complexity and increasing the potential for fully automated instruments.

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Nanoscale imaging of magnetic structures using scanning transmission electron microscopy (NanoMagSTEM). 01/05/2018 - 31/03/2019

Abstract

Modern society relies on materials which exhibits or are influenced by magnetic fields, such as functional materials used in electronic devices. In the last decades the performance of such devices have been greatly improved though miniaturization, however at some point the size of the these devices cannot be reduced further due to physical limits. To continue the advances in electronics, new materials with novel properties must be utilized. This requires a deep insight into the coupling between structural and functional properties, with nanometre resolution. An understanding of how the magnetic microstructure at the nanoscale is affected by the atomic and electronic structure of materials will help researchers in the design of functional materials with tailored-made properties. The hypothesis of this proposal is that "Magnetic fields in functional materials can be characterized at nanometre length scales by using scanning transmission electron microscopy combined with fast pixelated detectors. This enables correlated characterization of both functional and structural properties and improved understanding of materials." With the recent development of fast pixelated electron detectors, the whole electron beam in a scanning transmission electron microscope (STEM) can be imaged. This enables imaging of magnetic fields in materials using differential phase contrast (DPC), and coupled with an aberration corrected microscope this can be done at an unprecedented resolution of 1 nm. Perovskite oxide heterostructures are receiving great interest due to the many ways magnetic properties can be altered through structure engineering. The goals of this proposal is to extend the DPC method to imaging of static and dynamic magnetic properties of such materials with nanometre resolution. Adjoined with conventional high quality STEM data of the atomic and orbital structure of the materials, our understanding of structure-function coupling in perovskite thin films will be improved.

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Adaptive transmission electron microscopy: development of a programmable phase plate (ADAPTEM). 01/03/2018 - 31/08/2019

Abstract

Adaptive optics, the technology to dynamically program the phase of optical waves has sparked an avalanche of scientific discoveries and innovations in light optics applications. Nowadays, the phase of optical waves can be dynamically programmed providing research on exotic optical beams and unprecedented control over the performance of optical instruments. Although electron waves carry many similarities in comparison to their optical counterparts, a generic programmable phase plate for electrons is still missing. This project aims at developing a prototype of a programmable electrostatic phase plate that allows the user to freely change the phase of electron waves and demonstrate it to potential licensees for further upscaling and introduction to the market. The target of this POC project is the realization of a tunable easy-to-use 5x5-pixel prototype that will demonstrate the potential of adaptive optics in electron microscopy. Its realization will be based on lithographic technology to allow for future upscaling. It is expected that such a phase plate can dramatically increase the information obtained at a given electron dose, limiting the detrimental effects of beam damage that currently hinders the use of electron microscopy in e.g. life sciences. As such, it has the potential to disrupt the electron microscopy market with novel applications while at the same time reducing cost and complexity and increasing the potential for fully automated instruments.

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All optical, high resolution, non-invasive, quality control of crystalline GRMs via imaging of their non-linear optical properties (GRAPH-EYE) 01/01/2018 - 31/12/2019

Abstract

In this project, we propose a fast, high-resolution non-linear optical method for the ex-situ and potentially upgradable to in-situ quality control of as-grown GRMs and their heterostructures. Polarization resolved Second Harmonic Generation (PSHG) imaging microscopy will reveal detailed information of the crystal orientation, thickness inhomogeneities and nanoscale defects. Pixel-by-pixel information of the atomic structure of 2D nanosheets will be extracted from PSHG data with a spatial resolution of ~50 nm in two measuring modes: First, the number of atomic layers for each pixel will be precisely estimated by imaging the SHG intensity. Secondly, the polarization of the pixel-by-pixel SHG signal will reveal high-resolution details of the crystallographic axis orientation. Preliminary results show that defects of the crystal structure create a sharp contrast in the PSHG image. To further analyze the experimental findings, a theoretical model will be developed to accurately predict and explain the PSHG data. The interpretation of the PSHG signal by the theoretical predictions will be utilized as a "second order filter" which will further enhance the optical contrast attained. Due to the small dimensions of the pixel (~50nm) compared to the diameter of the excited volume (~500nm), the extracted optical information goes beyond the diffraction limit. This technique is being developed at the Foundation for Research and Technology- Hellas (FORTH). Towards the accurate validation and quantitative evaluation of the PSHG observations, the crystallographic orientation, specimen thickness, strain and doping/impurity levels, stacking sequence and twist, chemical composition, electric fields and charge densities will be probed on the same samples, via atomic-resolution scanning transmission electron microscopy (STEM) imaging at the Electron Microscopy for Materials Science group of the University of Antwerp (UA) and via high resolution Raman spectroscopy at the Graphene Centre (CGC) of UCAM. The CVD test-case samples will be provided by the CGC and the AIXTRON company. This project introduces for the first time an all-optical, fast and high-throughput, high-resolution, non-invasive, non- linear optical technique for the evaluation of the crystal quality of as-grown GRMs and their heterostructures. This technique can be readily upgradable for the in-situ monitoring of the 2D crystals' quality during growth. We envizage that the results obtained will have significant impact in the field of GRMs' and will be proved useful towards the development of defect-free GRMs with excellent optoelectronic properties.

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Probing localised surface plasmon resonances in the TEM: overcoming the limitation of time-averaged intensity mapping with novel beam shaping methods. 01/10/2017 - 30/09/2020

Abstract

Small (submicron) metal particles interact with light in a peculiar way. Their optical properties (i.e. the colours of light they absorb or reflect) are determined by their size and shape, like the harmonics that define the sound of an organ pipe. The "harmonics" of a metal particle are called surface plasmon resonances (SPR). If SPRs can be correctly understood and harnessed, they offer the possibility to manipulate light as effectively as is done now with radio waves, allowing to produce (among others) better photovoltaics and LEDs, better chemical sensors, and integrated optical devices of much smaller size. An instrument often used to study SPRs is the transmission electron microscope (TEM). TEMs allow to observe phenomena at the nanoscale by passing a beam of high energy electrons through a sample and can achieve atomic scale resolution. The TEM is of great use to study metal particles: besides visualising their shape and structure, it allows to study the electromagnetic fields related to the SPRs. However, while this allows to visualise the harmonics, it doesn't provide all information about them. Using conventional methods, we only obtain a time-averaged view of their amplitude. With this project we want study an entirely new setup that we have recently demonstrated. It is based on altering the "quantum wave function" of a TEM's electron beam to selectively detect SPRs of a chosen shape and symmetry, helping determine their exact properties.

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Compressed sensing enabling low dose imaging in transmission electron microscopy. 01/01/2017 - 31/12/2020

Abstract

Transmission electron microscopy (TEM) has provided scientists with a view on the atomic structure of materials for many decades. As instruments improved dramatically, the damage incurred by bombarding the material with electrons has become a major obstacle in the quest for more information from ever smaller nanomaterials. In short, the material rather than the microscope has become the limiting factor to further progress. In this project we propose to apply recent insights from the field of data compression to overcome this hurdle. In essence, we will develop the instrumentation for the recording of a subset of a microscopy image while still being able to reconstruct the whole image. We use the fact that images, unlike random signals, possess a level of predictability. The reason this works is the same as why holiday pictures can be compressed for storage without losing their information content. The difference between compression algorithms and this so-called compressed sensing approach is that rather than storage space reduction, we gain a reduction in the electron dose needed to obtain an image, reducing the damage that is blocking further progress in TEM. The project builds on the recent implementation of a prototype and will explore the benefits of this approach from both a theoretical and experimental point of view with the aim to demonstrate a significant improvement in the performance of TEM on materials that previously were damaged before an image could be taken.

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Direct electron detector for soft matter TEM. 01/05/2016 - 30/04/2020

Abstract

Modern materials are made to perform a certain task very well at a low (energy) cost of production. This drive towards more efficient materials has shifted the attention from making e.g. the strongest material to making a sufficiently strong material at an acceptable use of natural resources. Combining this trend in materials science with the nano revolution where properties of materials depend increasingly on their structure at the nanoscale, requires scientific instruments that study these so-called soft materials on the nanoscale. Typically, this is a task for transmission electron microscopy (TEM) offering a look inside materials down to the atomic structure. A drawback of TEM however is that this process can destroy soft materials while viewing, making the analysis unreliable or impossible. In order to overcome this issue, we propose to acquire a so-called direct electron detector which efficiently detects every electron that interacts with a given material reducing the required electron dose by up to a factor of 100. This considerably shifts the field of applicability of TEM into the range of soft materials allowing us to resolve their structure down to the atomic level.

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Nano consortium of excellence. 01/01/2015 - 31/12/2019

Abstract

The NANO consortium of excellence represents the internationally renowned expertise in nanoscience at the University of Anwerp. It consists of three participating groups that are international leaders in their subfield: EMAT, CMT and PLASMANT. The consortium joins forces towards a uniform communication and collaboration in order to further strengthen the international position of the nanosciences at the University of Antwerp.

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SOLARPAINT: Understanding the durability of light sensitive materials: transferring insights between solar cell physics and the chemistry of paintings. 01/01/2015 - 31/12/2018

Abstract

When light interacts with matter, it responds to this external stimulus in ways that depend on macroscopic properties but also on the microscopic details of the material. Pigments for instance, have a wavelength dependent reflection and absorption that causes the appearance of color in e.g. oil paintings. The absorption of light can also be used to capture the energy stored in solar light for use in photovoltaic solar cells. Perhaps surprisingly, the microscopic function of solar cells and pigments have a lot in common. Both absorb light and suffer from deterioration upon prolonged illumination and environmental conditions. This leads to chemical degradation (and altered colors) in historical paintings and to gradually reducing efficiencies in organic solar cells. In order to better understand their function and alteration behaviour, in this project, we propose to study in detail the microscopic origins of the capturing of light in heterogeneous materials found in oil paints and organic solar cells by combining state of the art experimental techniques based on synchrotron radiation and electron microscopy with advanced quantum mechanical models. This multidisciplinary approach will enable to improve the function and durability of future organic solar cells and will help to preserve and restore historical paintings from our cultural heritage.

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Topological effects in the diffraction of waves. 01/10/2014 - 30/09/2016

Abstract

In this project, we propose to extend this concept to waves with a so-called topological charge. Such waves behave similar to a tornado as they have a component of velocity around a central axis. The mathematical description of such waves is fundamentally distinct from 'normal' waves, as they cannot be transformed into one another by a smooth deformation of the wave fronts. This difference is called a topological difference and it can be shown that this property of the wave is quite robust against scattering to objects. This means that in most cases a wave with vortex character will keep this character after scattering. There are important exceptions however, as the scattering object itself possesses a 'handedness', i.e. when left and right hand variants of an object exist. Such objects are called chiral and we will demonstrate that one can distinguish between left and right handed variants making use of electron vortex waves.

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Theoretical study of relativistic electron vortex waves. 01/10/2014 - 31/12/2015

Abstract

The goal of this FWO Aspirant proposal is to contribute to the theoretical and conceptual understanding of these newly created vortex beams and their interaction with matter. With this proposal we want to complement the experimental capabilities with a solid foundation of theoretical understanding in order to stay at the forefront of electron vortex research.

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Development of the prototype device for generation of electron vortex beams. 01/11/2013 - 31/10/2014

Abstract

The project aims at developing a prototype device for generation of vortex electron beams (VEBs). VEBs enable probing magnetic state of matter down to atomic scale, manipulate nanoparticles or determine chirality of crystals. The major valorization tracks are seen as licensing production of VEB-generating devices and through bilateral contractual research with the industrial parties in Flanders and abroad.

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Research in the field of imaging. 30/09/2013 - 13/07/2016

Abstract

This project represents a formal research agreement between UA and on the other hand Erasmus Mundus. UA provides Erasmus Mundus research results mentioned in the title of the project under the conditions as stipulated in this contract.

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Revealing the source of emergent properties in complex oxides via direct imaging of charge/orbital/spin ordering. 01/01/2013 - 31/12/2016

Abstract

Oxides form a challenging subgroup of materials for tomorrow's technology and can be applied in fuel cells for greener cars, as faster nonvolatile memory that can reduce power consumption in computers, as ultrasensitive magnetic sensors for medical applications and many more. The range of physical properties of oxides is enormous and can even be expanded by bringing different oxides in contact with each other where so-called emergent properties occur at the interface. The reason why this happens is still heavily debated but naturally occurring ordering phenomena play an important role. In this project we propose to study such ordering of e.g. local atomic charges or atomic orbitals or the spin of atomic electrons with transmission electron microscopy. This is a fundamentally more direct method of studying this topic as compared to commonly used techniques which only give information on the average ordering over large volumes of material. It is exactly this direct visualization that will allow us to study the ordering phenomena near interfaces and defects in crystals in order to better understand the physics and properties of oxide devices.

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Topological affects in the diffraction of waves. 01/10/2012 - 30/09/2014

Abstract

In this project, we propose to extend this concept to waves with a so-called topological charge. Such waves behave similar to a tornado as they have a component of velocity around a central axis. The mathematical description of such waves is fundamentally distinct from 'normal' waves, as they cannot be transformed into one another by a smooth deformation of the wave fronts. This difference is called a topological difference and it can be shown that this property of the wave is quite robust against scattering to objects. This means that in most cases a wave with vortex character will keep this character after scattering. There are important exceptions however, as the scattering object itself possesses a 'handedness', i.e. when left and right hand variants of an object exist. Such objects are called chiral and we will demonstrate that one can distinguish between left and right handed variants making use of electron vortex waves.

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Theoretical study of relativistic electron vortex waves. 01/10/2012 - 30/09/2014

Abstract

The goal of this FWO Aspirant proposal is to contribute to the theoretical and conceptual understanding of these newly created vortex beams and their interaction with matter. With this proposal we want to complement the experimental capabilities with a solid foundation of theoretical understanding in order to stay at the forefront of electron vortex research.

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Exploring electron vortex beams (VORTEX). 01/01/2012 - 31/12/2016

Abstract

In this project I will exploit new possibilities opened up by the recent succesful demonstration of our ability to create electron vortex beams in a transmission electron microscope. Electron vortex beams carry a helical phase and angular momentum around their propagation axis. They form the counterpart of optical vortex beams that were invented almost 20 years ago and have lead to many exciting new applications in optics.

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Project website

Electronic and structural properties of complex oxide multilayer systems at the atomic scale: a (S)TEM and EELS investigation. 01/10/2011 - 30/06/2012

Abstract

During this project novel oxide materials (layered systems) will be characterized to provide insight in their macroscopic properties. The techniques used, (scanning) transmission electron microscopy (S/TEM) and electron energy loss spectroscopy (EELS), will provide chemical and structural information down to the atomic scale due to the improved resolution of the QU-Ant-EM microscope. Several data analysis techniques will be compared and adapted in order to maximize the output of information obtained in these experiments.

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Optimising the photoluminescence in scheelite-based materials through the incommensurate modulation of the cations. 01/01/2011 - 31/12/2014

Abstract

We will study the structure and optical properties of suitable new and old incommensurate scheelite based structures to determine this relation and optimize the optical properties by achieving the optimal cation arrangement.

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Study of mechanisms for diamond nucleation in the presence of a metal based interlayer. 01/01/2010 - 31/12/2013

Abstract

The project aims to achieve original, in-depth insights into the nucleation mechanisms of nanocrystalline diamond films in the presence of metal containing interlayers with different compositions, deposited by means of aqueous CSD. Through the obtained understanding, the nucleation ¿ growth mechanism can be controlled with positive effect, leading to the growth of uniform NCD materials by means of MWPECVD onto a wide variety of substrates. In this way, fundamental research in new areas of application will become possible.

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Quantitative electron microscopy: from experimental measurements to precise numbers. 01/01/2010 - 31/12/2013

Abstract

The aim of this research project is to determine unknown structure parameters such as atom positions, concentrations of atoms, atom types, and energy levels of inelastic excitations, in a quantitative way from experimental measurements obtained by means of electron microscopy. Therefore, use will be made of statistical parameter estimation theory which is expected to provide a considerable improvement in accuracy, precision and reproducibility in comparison to conventional ad-hoc methods which are currently used to extract parameters from experimental measurements.

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XANES meets ELNES: a study of heterogeneous materials at different length scales. 01/01/2009 - 31/12/2012

Abstract

The project aims to confront and compare the results of two related techniques for obtaining information on the structural environment of metals in solid materials: X-ray absorption near-edge spectroscopy (XANES) and electron loss near-edge spectroscopy (ELNES). Both probe the density of unoccupied electron states in atoms and the manner in which this distribution is influenced by the neighbours of these atoms. Both methods employ different primary projectiles (resp photons and electrons) and different ways modes of detection; as a result they operate on different length scales.

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    Plasmon Holography 01/01/2006 - 31/12/2009

    Abstract

    This project aims to measure inelastic interactions of fast electrons with plasmons in order to obtain phaserelations. It combines two well known techniques in electron microscopy: electron energy loss spectroscopy and electron holography. Traditional electron holography operates with elastically scattered electrons to obtain phase information of the exit wave near the object. In this project, we will use holography to obtain the phase relations in experiments with inelastic electrons. In this case, the reference wave traditionally used in holography needs to be replaces by a beam which underwent the same inelastic excitation in order to still have some coherence between reference wave and exit wave near the sample. In the theoretical part of this project we study the inelastic interaction of electrons with plasmon and how this can be linked to the experiments. We make use of the time dependent Hartree Fock aproach. This theory uses the equations of motion aproach of the general density matrix (essentially the Fourier transform of the MDFF). Special attention is put to the off-diagonal elements of the density matrix that contain information on correlation and coherence which can be closely linked to the experimental results.

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    Characterisation and correction of electronic instabilities in TEM . 01/05/2003 - 30/04/2005

    Abstract

    This project will measure the short and long term stabilities of the electrical sources in a tranmission electron microscope, in order to optimise their performance. With an active feedback loop, the instabilities will be reduced. The project will focus on the high tension source, which is directly related to the stability of the energy axis in EELS mode, but the equipment is chosen to be flexible enough to study other sources of instabilities like lens current sources and temperature.

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