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Scientific reports 13(1), 318 (1-12) (2023). doi:10.1038/s41598-022-26877-6, Being able to observe the formation of multi-material nanostructures in situ, simultaneously from a morphological and crystallographic perspective, is a challenging task. Yet, this is essential for the fabrication of nanomaterials with well-controlled composition exposing the most active crystallographic surfaces, as required for highly active catalysts in energy applications. To demonstrate how X-ray ptychography can be combined with scanning nanoprobe diffraction to realize multimodal imaging, we study growing Cu$_2$O nanocubes and their transformation into Au nanocages. During the growth of nanocubes at a temperature of 138 °C, we measure the crystal structure of an individual nanoparticle and determine the presence of (100) crystallographic facets at its surface. We subsequently visualize the transformation of Cu$_2$O into Au nanocages by galvanic replacement. The nanocubes interior homogeneously dissolves while smaller Au particles grow on their surface and later coalesce to form porous nanocages. We finally determine the amount of radiation damage making use of the quantitative phase images. We find that both the total surface dose as well as the dose rate imparted by the X-ray beam trigger additional deposition of Au onto the nanocages. Our multimodal approach can benefit in-solution imaging of multi-material nanostructures in many related fields., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Nature Communications 13(1), 4971 (2022). doi:10.1038/s41467-022-32373-2, Understanding morphological changes of nanoparticles in solution is essential to tailor the functionality of devices used in energy generation and storage. However, we lack experimental methods that can visualize these processes in solution, or in electrolyte, and provide three-dimensional information. Here, we show how X-ray ptychography enables in situ nano-imaging of the formation and hollowing of nanoparticles in solution at 155 °C. We simultaneously image the growth of about 100 nanocubes with a spatial resolution of 66 nm. The quantitative phase images give access to the third dimension, allowing to additionally study particle thickness. We reveal that the substrate hinders their out-of-plane growth, thus the nanocubes are in fact nanocuboids. Moreover, we observe that the reduction of Cu$_2$O to Cu triggers the hollowing of the nanocuboids. We critically assess the interaction of X-rays with the liquid sample. Our method enables detailed in-solution imaging for a wide range of reaction conditions., Published by Nature Publishing Group UK, [London]

Raw data for "Imaging Cu2O nanocube hollowing in solution by quantitative in situ X-ray ptychography" Ptychographic data sets The file "raw_data_ptychography.zip" contains one HDF5 archive for each ptychographic scan. The archives are structured as follows: section experiment: identifiers of the lightsource, beamline, beamtime, session number, and scan number section measured: N diffraction patterns of size 512x512 px N scan positions in mm one detector mask of size 512x512 px slice separation in mm for multi slice reconstruction section parameters: distance between sample and detector in mm pixel size of detector in mm photon energy in keV cropping of diffraction patterns in px used during reconstruction The following list shows the scan numbers with their corresponding reaction times and slice separations for the in situ series measured at beamline P06 at 15.25 keV. scan number slice distance, mm reaction time, h 232 1 0.20 233 1 0.56 234 1 0.92 235 1 1.27 236 1 1.63 237 1 2.01 238 0.98 2.36 239 0.96 2.72 240 0.94 3.08 241 0.9 3.43 242 0.88 3.83 243 0.86 4.19 244 0.84 4.54 245 0.82 4.90 246 0.82 5.26 247 0.82 5.63 248 0.8 5.98 249 0.8 6.34 250 0.8 6.70 251 0.78 7.05 252 0.78 7.43 253 0.78 7.79 254 0.76 8.15 255 0.76 8.50 256 0.76 8.86 257 0.74 9.23 258 0.74 9.58 259 0.72 9.94 260 0.72 10.30 261 0.7 10.65 262 0.68 11.07 263 0.66 11.42 264 0.64 11.78 266 0.62 12.17 267 0.6 12.53 268 0.58 12.89 269 0.56 13.24 270 0.54 13.60 271 0.52 13.99 272 0.5 14.37 273 0.46 14.72 274 0.42 15.08 275 0.4 15.44 277 0.4 15.87 278 0.4 16.22 279 0.36 16.58 280 0.3 16.93 281 0.25 17.29 282 0.25 17.68 283 0.25 18.04 289 0.2 20.45 290 0.2 21.47 Ptychographic reconstructions The file "ptychographic_reconstructions.zip" contains the ptychographic reconstructions shown in the article and supplementary information in tiff format. Stacks of images corresponding to time series: P06_15.25_keV_scans_00232-00283_entrance_window_aligned.tif P06_15.25_keV_scans_00232-00283_exit_window_aligned.tif cSAXS_8.98_keV_scans_00200-00324_aligned.tif Single images (the file name indicates the respective figure): P06_15.25_keV_scan_00289_Figure_6_a.tif P06_15.25_keV_scan_00290_Supplementary_Figure_11.tif cSAXS_8.98_keV_scan_00347_Supplementary_Figure_13_d.tif cSAXS_8.98_keV_scan_00586_Supplementary_Figure_14_a.tif SEM images The file "SEM_images.zip" contains the SEM images shown in the article and supplementary information in tiff format. The file names indicate the respective figure: Figure_5_h.tif Figure_5_i.tif Figure_6_b.tif Supplementary_Figure_14_b.tif, Acknowledgements: This work was supported by the Bundesministerium für Bildung und Forschung (BMBF) within the Röntgen-Ångström-Cluster via the project 05K2020 - 2019-06104 XStereoVision (grant no. 05K20GUA), by the European Research Council within the project LINCHPIN (grant no. 818941), and by the Cluster of Excellence "CUI: Advanced Imaging of Matter" of the Deutsche Forschungsgemeinschaft (DFG) – EXC 2056 – project ID 390715994.

Optics express 30(18), 31519 - 31529 (2022). doi:10.1364/OE.454863, Diffraction-limited hard X-ray optics are key components for high-resolution microscopy, in particular for upcoming synchrotron radiation sources with ultra-low emittance. Diffractive optics like multilayer Laue lenses (MLL) have the potential to reach unprecedented numerical apertures (NA) when used in a crossed geometry of two one-dimensionally focusing lenses. However, minuscule fluctuations in the manufacturing process and technical limitations for high NA X-ray lenses can prevent a diffraction-limited performance. We present a method to overcome these challenges with a tailor-made refractive phase plate. With at-wavelength metrology and a rapid prototyping approach we demonstrate aberration correction for a crossed pair of MLL, improving the Strehl ratio from 0.41(2) to 0.81(4) at a numerical aperture of 3.3 × 10$^{−3}$. This highly adaptable aberration-correction scheme provides an important tool for diffraction-limited hard X-ray focusing., Published by Soc., Washington, DC

Scientific reports 12, 6203 (2022). doi:10.1038/s41598-022-09466-5, Imaging large areas of a sample non-destructively and with high resolution is of great interest for both science and industry. For scanning coherent X-ray diffraction microscopy, i. e., ptychography, the achievable scan area at a given spatial resolution is limited by the coherent photon flux of modern X-ray sources. Multibeam X-ray ptychography can improve the scanning speed by scanning the sample with several parallel mutually incoherent beams, e. g., generated by illuminating multiple focusing optics in parallel by a partially coherent beam. The main difficulty with this scheme is the robust separation of the superimposed signals from the different beams, especially when the beams and the illuminated sample areas are quite similar. We overcome this difficulty by encoding each of the probing beams with its own X-ray phase plate. This helps the algorithm to robustly reconstruct the multibeam data. We compare the coded multibeam scans to uncoded multibeam and single beam scans, demonstrating the enhanced performance on a microchip sample with regular and repeating structures., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Advances in X-Ray/EUV Optics and Components XVII : [Proceedings] - SPIE, 2022. - ISBN 97815106546489781510654655 - doi:10.1117/12.2633458 Advances in X-Ray/EUV Optics and Components XVII, San Diego, United States, 21 Aug 2022 - 26 Aug 2022; Proceedings of SPIE 12240, 122400J (2022). doi:10.1117/12.2633458 special issue: "SPIE Optical Engineering + Applications", While modern x-ray microscopes at synchrotron radiation sources and free-electron lasers require x-ray optics of highest quality, these optics often show aberrations due to limitations in fabrication technology. Based on ptychography, we determine these aberrations and fabricate tailor made refractive phase plates to compensate for them. Starting from the aberrated optics, diffraction-limited beams can be generated by introducing the phase plate behind these optics. In addition, the wavefront can be modified to generate custom beams for special needs, such as donut-shaped beams with orbital angular momentum or for structured-illumination microscopy. The nanofocused beam can be engineered in shape and phase by introducing specially designed phase plates. We introduce a general scheme for wavefront engineering and illustrate it with a numerical example., Published by SPIE, Bellingham, Wash.

The European physical journal / Plus 137(12), 1312 (2022). doi:10.1140/epjp/s13360-022-03517-6, PETRA III at DESY is one of the brightest synchrotron radiation sources worldwide. It serves a broad international multidisciplinary user community from academia to industry at currently 25 specialised beamlines. With a storage ring energy of 6 GeV, it provides mainly hard to high-energy X-rays for versatile experiments in a very broad range of scientific fields. It is ideally suited for an upgrade to the ultra-low emittance source PETRA IV, owing to its large circumference of 2304 m. With a targeted storage ring emittance of 20 × 5 pm2 rad2, PETRA IV will reach spectral brightnesses two to three orders of magnitude higher than today. The unique beam parameters will make PETRAIV the ultimate in situ 3D microscope for biological, chemical and physical processes helping to address key questions in health, energy, mobility, information technology, and earth and environment., Published by Springer, Heidelberg

Materials 14(1), 228 (tbd). doi:10.3390/ma14010228, Inhomogeneities and defects often limit the overall performance of thin-film solar cells. Therefore, sophisticated microscopy approaches are sought to characterize performance and defects at the nanoscale. Here, we demonstrate, for the first time, the simultaneous assessment of composition, structure, and performance in four-fold multi-modality. Using scanning X-ray microscopy of a Cu(In,Ga)Se$_2$ (CIGS) solar cell, we measured the elemental distribution of the key absorber elements, the electrical and optical response, and the phase shift of the coherent X-rays with nanoscale resolution. We found structural features in the absorber layer—interpreted as voids—that correlate with poor electrical performance and point towards defects that limit the overall solar cell efficiency., Published by MDPI, Basel

DESY, Helmholtz Zentrum Berlin/Dresden 33 pp. (2021)., Published by DESY, Helmholtz Zentrum Berlin/Dresden

International audience

Journal of synchrotron radiation 25(1), 1 - 8 (2018). doi:10.1107/S1600577517015272, Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) have been recovered for various lens sets and X-ray beam configurations. Due to manufacturing via an embossing process, aberrations of individual lenses within the investigated ensemble are very similar. By deriving a mean single-lens deformation for the ensemble, aberrations of any arbitrary lens stack can be predicted from the ensemble with \bar{\sigma} = 0.034λ. Using these findings the expected focusing performance of current Be CRLs are modeled for relevant X-ray energies and bandwidths and it is shown that a correction of aberrations can be realised without prior lens characterization but simply based on the derived lens deformation. The performance of aberration-corrected Be CRLs is discussed and the applicability of aberration-correction demonstrated over wide X-ray energy ranges., Published by IUCr, Chester

JoVE journal Biology [...] 150(150), 60001 (2019). doi:10.3791/60001, X-ray beam induced current (XBIC) measurements allow mapping out the nanoscale performance of electronic devices such as solar cells. Ideally, XBIC is employed simultaneously with other techniques within a multi-modal X-ray microscopy approach. An example is given herein combining XBIC with X-ray fluorescence to enable point-by-point correlations of the electrical performance with chemical composition. For the highest signal-to-noise ratio in XBIC measurements, lock-in amplification plays a crucial role. By this approach, the X-ray beam is modulated by an optical chopper upstream of the sample. The modulated X-ray beam induced electrical signal is amplified and demodulated to the chopper frequency using a lock-in amplifier. By optimizing low-pass filter settings, modulation frequency, and amplification amplitudes, noise can efficiently be suppressed for the extraction of a clear XBIC signal. A similar setup can be used to measure the X-ray beam induced voltage (XBIV). Beyond standard XBIC/XBIV measurements, XBIC can be measured with bias light or bias voltage applied such that outdoor working conditions of solar cells can be reproduced during in-situ and operando measurements. Ultimately, the multi-modal and multi-dimensional evaluation of electronic devices at the nanoscale enables new insights into the complex dependencies between composition, structure, and performance, which is an important step towards solving the materials’ paradigm., Published by JoVE410927, Cambridge, MA

Optics express 27(6), 8639 - 8650 (2019). doi:10.1364/OE.27.008639, The recent success in the development of high-precision printing techniques allows one to manufacture free-standing polymer structures of high quality. Two-photon polymerization lithography is a mask-less technique with down to 100 nm resolution that provides full geometric freedom. It has recently been applied to the nanofabrication of X-ray compound refractive lenses (CRLs). In this article we report on the characterization of two sets of CRLs of different design produced by two-photon polymerization-induced lithography., Published by OSA, Washington, DC

Hamburg : Deutsches Elektronen-Synchrotron DESY 259 pp. (2019)., Published by Deutsches Elektronen-Synchrotron DESY, Hamburg

Dissertation, Universität Hamburg, 2019; Hamburg : Staats- und Universitätsbibliothek Hamburg 1-127 (2019). = Dissertation, Universität Hamburg, 2019, Published by Staats- und Universitätsbibliothek Hamburg, Hamburg

The recent success in the development of high precision printing techniques allows one to manufacture free-standing polymer structures of high quality. Two-photon polymerization lithography is a mask-less technique with down to 100 {\mu}m resolution that provides full geometric freedom. It has recently been applied to the nanofabrication of X-ray compound refractive lenses (CRLs). In this article we report on the characterization of two sets of CRLs of different design produced by two-photon polymerization induced lithography.

Topics in Catalysis, 52 (10), ISSN:1022-5528, ISSN:1572-9028

Physical review applied 7(2), 024033(2017). doi:10.1103/PhysRevApplied.7.024033, Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In,Ga)N/GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80×90 nm$^2$, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finite-element method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs., Published by American Physical Society, College Park, Md. [u.a.]

At DESY the Synchrotron Light Source PETRA III offers scientists outstanding opportunities for experiments with hard X-rays of exceptionally high brilliance since 2009. Research activities have been started towards a future upgrade scenario of PETRA III which envisions the conversion of the PETRA ring into a ultra-low emittance hard X-ray radiation source: PETRA IV. The lattice design is aiming for a horizontal emittance in the range between 10 pm rad and 30 pm rad at a beam energy of 6 GeV. Two different approaches have been considered for the lattice design: a design based on a hybrid multibend achromat with an interleaved sextupole configuration based on the ESRF design, and a lattice with a non-interleaved sextupole configuration with a special phase space exchange configuration. We are reporting the current status of the design activities including studies related to the injector., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

21 pp. (2016).

Two different multilayer Laue lens designs were made with total deposition thicknesses of 48 mu m and 53 mu m, and focal lengths of 20.0 mm and 12.5 mm at 20.0 keV, respectively. From these two multilayer systems, several lenses were manufactured for one-and two-dimensional focusing. The latter is realised with a directly bonded assembly of two crossed lenses, that reduces the distance between the lenses in the beam direction to 30 mm and eliminates the necessity of producing different multilayer systems. Characterization of lens fabrication was performed using a laboratory X-ray microscope. Focusing properties have been investigated using ptychography.

PETRA III is the new 3rd generation hard X-ray synchrotron light source at DESY, operating at a beam energy of 6 GeV. Machine commissioning began in April 2009 and user operation starts in 2010. In order to achieve a high brilliance, damping wigglers with a total length of 80 m are installed to reduce the horizontal emittance down to an extremely low value of 1 nm rad. For a precise emittance online control, a dedicated diagnostics beamline was built up to image the beam profile with synchrotron radiation from a bending magnet in the X-ray region. The beamline is equipped with two interchangeable X-ray optical systems, a pinhole optic for standard operation and a high resolution compound refractive lens optic. In addition, the synchrotron radiation angular distribution can be exploited at high photon energies. In this presentation, first experience with the system will be reported., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

For investigations of ordered nanometre structures and for high-precision measurement of the atomic order in crystalline solids, X-ray diffraction is the most important tool. With the aid of X-ray microscopy, unordered and even living objects can also be imaged directly. The resolution of these images, applying different contrast techniques representing the state of the art, reaches the nanometre range. In the future, a synthesis of both methods could yield a shift of the spectral resolution down to the atomic level. Für die Aufklärung geordneter Nanometer-Strukturen und die hochpräzise Vermessung der Atomanordnung in kristallinen Festkörpern ist die Röntgenstrahlbeugung das wichtigste Werkzeug. Mit Hilfe der Mikroskopie mit Röntgenstrahlung können auch ungeordnete und sogar lebende Objekte direkt abgebildet werden. Die Auflösung dieser Abbildungen unter Nutzung verschiedener Kontraste erreicht nach dem Stand der Technik gerade die Grenze des Nanometerbereiches. Für die Zukunft wird eine Synthese beider Methoden und so auch die weitere Verschiebung der Grenze der erreichbaren Auflösung erwartet.

RWTH-Themen : Berichte aus der Rheinisch-Westfälischen Technischen Hochschule Aachen 2002(2), 64-64(2002). special issue: "Life Sciences / hrsg. im Auftr. d. Rektors von d. Presse- und Öffentlichkeitsarbeit der RWTH Aachen", Published by RWTH, Aachen

A novel complementary approach of electron microscopy/environmental TEM and in situ hard X-ray ptychography was used to study the thermally induced coarsening of nanoporous gold under different atmospheres, pressures and after ceria deposition. The temperature applied during ptychographic imaging was determined by IR thermography. While using elevated temperatures (room temperature – 400 °C) and realistic gas atmospheres (1 bar) we achieved for the first time a spatial resolution of about 20 nm during hard X-ray ptychography. The annealing of pure and ceria stabilized nanoporous gold in different atmospheres revealed that the conditions have a tremendous influence on the coarsening. The porous structure of the samples was stable up to approximately 800 °C in vacuum, whereas pronounced changes and coarsening were observed already at approximately 300 °C in oxygen containing atmospheres. A layer of ceria on the nanoporous gold led to an improvement of the stability, but did not alleviate the influence of the gas atmosphere. Different behaviors were observed, such as coarsening and even material loss or migration. The results suggest that additional mechanisms beyond surface diffusion need to be considered and that microscopic studies aimed at more realistic conditions are important to understand the behavior of such materials and catalysts.

ACS nano 10(3), 3553 - 3561(2016). doi:10.1021/acsnano.5b07871, In recent years, X-ray imaging of biological cells has emerged as a complementary alternative to fluorescence and electron microscopy. Different techniques were established and successfully applied to macromolecular assemblies and structures in cells. However, while the resolution is reaching the nanometer scale, the dose is increasing. It is essential to develop strategies to overcome or reduce radiation damage. Here we approach this intrinsic problem by combing two different X-ray techniques, namely ptychography and nanodiffraction, in one experiment and on the same sample. We acquire low dose ptychography overview images of whole cells at a resolution of 65 nm. We subsequently record high-resolution nanodiffraction data from regions of interest. By comparing images from the two modalities, we can exclude strong effects of radiation damage on the specimen. From the diffraction data we retrieve quantitative structural information from intracellular bundles of keratin intermediate filaments such as a filament radius of 5 nm, hexagonal geometric arrangement with an interfilament distance of 14 nm and bundle diameters on the order of 70 nm. Thus, we present an appealing combined approach to answer a broad range of questions in soft-matter physics, biophysics and biology., Published by Soc., Washington, DC

Journal of synchrotron radiation 28(1), 52 - 63 (2021). doi:10.1107/S160057752001557X, X-ray free-electron lasers (XFELs) have opened up unprecedented opportunities for time-resolved nano-scale imaging with X-rays. Near-field propagation-based imaging, and in particular near-field holography (NFH) in its high-resolution implementation in cone-beam geometry, can offer full-field views of a specimen's dynamics captured by single XFEL pulses. To exploit this capability, for example in optical-pump/X-ray-probe imaging schemes, the stochastic nature of the self-amplified spontaneous emission pulses, i.e. the dynamics of the beam itself, presents a major challenge. In this work, a concept is presented to address the fluctuating illumination wavefronts by sampling the configuration space of SASE pulses before an actual recording, followed by a principal component analysis. This scheme is implemented at the MID (Materials Imaging and Dynamics) instrument of the European XFEL and time-resolved NFH is performed using aberration-corrected nano-focusing compound refractive lenses. Specifically, the dynamics of a micro-fluidic water-jet, which is commonly used as sample delivery system at XFELs, is imaged. The jet exhibits rich dynamics of droplet formation in the break-up regime. Moreover, pump–probe imaging is demonstrated using an infrared pulsed laser to induce cavitation and explosion of the jet., Published by Wiley-Blackwell, [S.l.]

Microscopy and microanalysis 24(S2), 268 - 269 (2018). doi:10.1017/S1431927618013673, Published by Cambridge University Press, New York, NY

RSC Advances 6(86), 83031 - 83043(2016). doi:10.1039/C6RA12853J, A novel complementary approach of electron microscopy/environmental TEM and in situ hard X-ray ptychography was used to study the thermally induced coarsening of nanoporous gold under different atmospheres, pressures and after ceria deposition. The temperature applied during ptychographic imaging was determined by IR thermography. While using elevated temperatures (room temperature – 400 °C) and realistic gas atmospheres (1 bar) we achieved for the first time a spatial resolution of about 20 nm during hard X-ray ptychography. The annealing of pure and ceria stabilized nanoporous gold in different atmospheres revealed that the conditions have a tremendous influence on the coarsening. The porous structure of the samples was stable up to approximately 800 °C in vacuum, whereas pronounced changes and coarsening were observed already at approximately 300 °C in oxygen containing atmospheres. A layer of ceria on the nanoporous gold led to an improvement of the stability, but did not alleviate the influence of the gas atmosphere. Different behaviors were observed, such as coarsening and even material loss or migration. The results suggest that additional mechanisms beyond surface diffusion need to be considered and that microscopic studies aimed at more realistic conditions are important to understand the behavior of such materials and catalysts., Published by RSC Publishing, London

Nature Communications 10(1), 2600 (2019). doi:10.1038/s41467-019-10670-7, Reaching the full potential of X-ray nanotomography, in particular for biological samples, is limited by many factors, of which one of the most serious is radiation damage. Although sample deformation caused by radiation damage can be partly mitigated by cryogenic protection, it is still present in these conditions and, as we exemplify here using a specimen extracted from scales of the Cyphochilus beetle, it will pose a limit to the achievable imaging resolution. We demonstrate a generalized tomographic model, which optimally follows the sample morphological changes and attempts to recover the original sample structure close to the ideal, damage-free reconstruction. Whereas our demonstration was performed using ptychographic X-ray tomography, the method can be adopted for any tomographic imaging modality. Our application demonstrates improved reconstruction quality of radiation-sensitive samples, which will be of increasing relevance with the higher brightness of 4th generation synchrotron sources., Published by Nature Publishing Group UK, [London]

Dissertation, University of Hamburg, 2021; Hamburg : Staats- und Universitätsbibliothek Hamburg 119 pp. (2022). doi:10.3204/PUBDB-2022-01190 = Dissertation, University of Hamburg, 2021, X-ray fluorescence tomograms of large or highly absorbing samples often suffer from self-absorption effects. For qualitative and quantitative results, it is necessary to correct these effects.In this thesis, a fully 3D self-absorption corrected reconstruction algorithm for X-ray fluorescence tomography datasets is presented. As an extension of the tomographic maximum-likelihood expectation-maximization algorithm, it is an iterative algorithm that reconstructs the density volumes of all measured elements in parallel. The algorithm includes multiple optional parts to aid its convergence, including density and background constraints. Noise may be reduced by using a priori information of the sample to introduce a weighted penalty term. All calibration parameters are derived from experimental measurements and small inconsistencies in those values may be corrected by a rudimentary adaptive calibration. Parallel calculations on CPU and GPU as well as downscaling approximations are used to assure high performance of the algorithm and to allow for online reconstruction during experiments.Numerical simulations of multi-element phantoms without and with added noise confirmed the qualitative as well as quantitative properties of the self-absorption correction. Additionally, tomographic STXM and XRF measurements of a barred olivine micrometeorite were performed at beamline P06 of the PETRA III synchrotron storage ring at DESY in Hamburg, Germany. Although the algorithm was able to correct parts of the self-absorption effects in the micrometeorite data, the qualitative and quantitative properties of the final reconstructions were severely limited by inconsistencies in the experimental calibration, mainly the deadtime and pile-up corrections., Published by Staats- und Universitätsbibliothek Hamburg, Hamburg

Dissertation, University of Hamburg, 2021; 244 pp. (2022). doi:10.3204/PUBDB-2022-01017 = Dissertation, University of Hamburg, 2021, The present thesis is focused on the extensive analysis of statistical properties of modern X-ray sources at Large Scale Facilities, such as the 4th generation high-energy storage ring PETRA IV, European XFEL (EuXFEL), and XFEL at Pohang Accelerator Laboratory (PAL-XFEL). Special attention is paid to the effects that may decrease coherence characteristics and impact source properties at these facilities. The present thesis is divided into two parts, where a comprehensive analysis of the coherence properties of the DLSR radiation is presented in the first part. Attention is paid to the optics effects on the photon beam transported through the beamline, electron beam energy spread effects on coherence and brightness of a DLSR photon source, and resonant energy detuning effects. A method in the framework of statistical optics is proposed as an adequate approach for the characterization of photon beamproperties at DLSR facilities. The analysis is backed up with semi-analytical simulations based on the proposed model and specialized software. The second part of the thesis is devoted to photon source diagnostics and precise determination of the statistical parameters at the high-energy XFEL facilities. Results of experiments performed at EuXFEL and PAL-XFEL are discussed in this part of the thesis. The method within the framework of statistical optics for the EuXFEL photon beam characterization is described, where special attention was paid to the monochromator resolution and interplay between the resolution and the size of the exit slits of the monochromator. The method was applied to the three different regimes of the XFEL operation and was checked with simple analytical simulations. The influence of the energy chirp effect on the analysis results was considered as well. Further, the photon source diagnostics is presented for the PAL-XFEL facility, operating in a Self-Amplified Spontaneous Emission regime with the wide bandwidth beam and filtered monochromatic beam, as well as in the regime of Self-Seeding with highly intense radiation.

Dissertation, University of Hamburg, 2022; Hamburg 182 pp. (2023). = Dissertation, University of Hamburg, 2022, Colloidal crystals are ordered arrays of colloidal particles forming a superlattice similar to that in conventional crystals. In recent decades, the research on colloidal crystals has blossomed due to their fascinating structure-related properties such as diffraction of light at optical wavelengths, high porosity, etc. Moreover, colloidal crystals are often viewed as a model system for conventional crystals since their larger dimensions allow easier tracing of changes in structure. Mesocrystals are a special subclass of colloidal crystals in which the crystalline nanoparticles constituting the crystal are mutually oriented. Such highly ordered nanocrystal superlattices can display functional collective properties distinct from those of conventional colloidal сrystals and individual nanoparticles. These collective properties are conditioned by the interparticle interactions which are highly dependent on the structural features of the mesocrystals. Even though colloidal crystals and mesocrystals have already found many practical applications, the structure-property relationships are still poorly understood due to the lack of suitable methods of structural investigations.This cumulative Thesis is based on six publications and is devoted to the development of X-ray methods for the structural study of colloidal crystals and mesocrystals.In the first three publications, the structure of colloidal crystals and mesocrystals is revealed by analysis of the measured two-dimensional (2D) scattering patterns. The first publication addresses the structural evolution of a thermoresponsive colloidal crystal consisting of gold–poly(N-isopropylacrylamide) core–shell nanoparticles during cooling and heating. The Bragg peak analysis of the data obtained in Ultra-Small-Angle X-ray Scattering (USAXS) experimental geometry provided a unique insight into the processes of crystallization and melting of such colloidal crystals. The second and third publications deal with mesocrystals consisting of inorganic lead sulfide or lead halide perovskite semiconductive nanoparticles stabilized by organic copper tetraaminophtalocyanine (Cu4APc) or oleic acid (OA) ligands. The experimental geometry allowed the simultaneous registration of both Small-Angle X-ray Scattering (SAXS) from the superlattice structure and Wide-Angle X-ray Scattering (WAXS) from the atomic lattices of the constituting nanoparticles. Analysis of the Bragg peaks registered at both small and wide angles at different spatial points of the sample allowed spatially-resolved structural mapping of the mesocrystals. The extracted superlattice unit cell parameters were combined with the angular orientation of the nanoparticles inside the superlattice to obtain the complete structure of the mesocrystal on both length scales. The revealed structures were then correlated with the measured functional properties of the mesocrystals such as conductivity and photoluminescence.In the other three publications, the structural information is extracted by application of Angular X-ray Cross-Correlation Analysis (AXCCA) to the measured intensity distributions in three-dimensional (3D) reciprocal space. The fourth publication contains the details of adapting this method for application to 3D intensity distributions instead of common 2D scattering patterns. In this work, AXCCA was shown prospective for qualitative structure determination in close-packed colloidal crystals using an exemplary sample consisting of spherical silica particles. In the fifth and sixth publications, AXCCA was successfully applied to the measured 3D scattered intensity distributions to reveal the structure of mesocrystals composed of gold and magnetite nanocubes.The proposed approaches to structural studies of colloidal crystals and mesocrystals can be further extended to other materials. The obtained results on the structure of colloidal crystals and mesocrystals and their correlations with the functional properties are highly novel and are of great interest to the materials science community., Published by Hamburg

Dissertation, University of Hamburg, 2021; Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky 145 pages: illustrations, diagrams (2020). = Dissertation, University of Hamburg, 2021, With the fast technological developments of our time often new possibilities arise to gain a deeperscientific understanding of complex processes, may these be of biological, chemical or physicalnature, and materials. In natural sciences, X-ray and electron microscopy is indispensable tohelp uncovering these scientific backgrounds. Sophisticated microscopy methods with spatialresolutions in the nanometer range allows us to gains new insights about relations and functionprinciples.One example in this regard is nanotechnology continuously pushing the physical limits to buildsmaller structures such as transistors in microchips, thereby enhancing computing power whilesimultaneously lowering energy consumption of current devices. Without microchips, all thesepossibilities just as much as the many everyday things and gadgets of the modern life would beunthinkable. Therefore, in the manufacture of these semiconductor products troubleshootingand controlling of the manufacturing processes and the resulting structures gain great attention.With the continuously decreasing structure sizes, the analysis options of these factories reachtheir limits in some aspects.Examinations using high-brilliance X-rays offer a variety of complementary analysis opportunities.Electron microscopy is commonplace in semiconductor factories, but it only images surfaces ortransmits thin samples, partially demanding for precise preparation including destruction. Due tothe high penetration depth of X-rays in matter, the usage of X-ray ptychography provides newinsights into the produced microchips as comparably thick samples can be investigated withresolutions in the nanometer range.In this thesis, the potential of imaging even the smallest structures inside a microchip is demonstratedon the example of a test chip. In addition, X-ray fluorescence helps determine theelemental composition and X-ray diffraction provides information about the crystalline states ofvarious components. These procedures were all applied in a multimodal experiment. Throughthe evaluation of X-ray diffraction data using powder X-ray diffraction methods, the phases ofcrystalline materials are precisely determined. The diffraction data is furthermore used to determinethe position, size and orientation of single grains inside the microchip. The combinationwith computed tomography allows for spatial assignment of these information to the internalstructures and can thus point to function and structure relations.The interplay of the various X-ray techniques provides a complementary picture of the inside ofa microchip, the spatial resolution of structures, their composition, crystalline phase and orientation.It opens up new perspectives for both the investigation and development of microchips aswell as of other composite solids made of different materials and crystalline states. It also offersprospects for the expansion of these investigations for example by additional contrasts, such asX-ray ptychography or visualizing active conduction., Published by Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, Hamburg

Dissertation, University of Hamburg, 2021; Hamburg : Staats- und Universit��tsbibliothek Hamburg 168 pp. (2021). = Dissertation, University of Hamburg, 2021, X-ray microscopy is characterized by its high spatial resolution, exceeding that ofvisible light microscopy, while also being able to penetrate thick samples and sample enclosures that are inaccessible to electron microscopy. With these characteristics, x-ray microscopy excels in in-situ imaging of nanoscopic sample systems that are highly relevant in fields such as chemistry and life sciences.Ptychography is a lensless, computational microscopy technique in which the objective lens of the microscope is replaced with an algorithm to retrieve the phases of the coherent wave field. With this approach, the spatial resolution achieved in a ptychographic microscope can widely exceed that of the used x-ray focusing optics.One of the limiting factors of current ptychographic microscopes are nanopositioning errors and vibrations. Using laser-interferometry, these factors are studied in this thesis at the Ptychographic Nano-Analytical Microscope (PtyNAMi, P06, PETRA III) with particular attention to the occurring measurement uncertainties. In addition, an ultra-stable setup for two-dimensional measurements, that exhibits isotropic vibrations in the order of 1nm rms, is presented.Further improvement of the instrumentation is achieved by placing the area detector into a windowless and evacuated detector device, thereby suppressing the incoherent scattering background. With both of these instrumentational optimizations, ptychographic imaging with 10nm resolution is demonstrated.A distinct advantage of ptychography is the high degree of overdetermination in the data set that permits extensions of the ptychographic model to describe experimental imperfections. For samples that extent along the optical axis beyond the depth-offield of the microscope, several independent virtual object planes can be modeled, reconstructing all of them from a single measurement.This multi-slice ptychography is required when imaging the synthesis of nanoparticles in solution in cases in which the forming particles adhere to both windows of the in situ cell. Such an in situ cell, that is designed to be compatible with hard x-ray ptychographic imaging, is designed and commissioned.In a first demonstration, the nucleation and growth of copper and copper oxidenanoparticles in heated benzyl alcohol is imaged. For a period of 20 h, the growth of individual nanoparticles was imaged with a spatial resolution of 70nm and a temporal resolution of 22 minutes in two image planes. The observed imaging artifacts are part of an overarching discussion about the disadvantages of multi-slice ptychography., Published by Staats- und Universit��tsbibliothek Hamburg, Hamburg