arXiv subjects

Philipp Hönicke

Publications and source records attributed to Philipp Hönicke.

At least 19 recordsLinked to original sources

arXiv2025

Theoretical calculation of finite-temperature X-ray absorption fine structure: application to sodium K-edge in NaCl

We present a comprehensive computational framework for reproducing the full X-ray absorption fine structure (XAFS) through quantum-chemical simulations. The near-edge region is accurately captured using an efficient implementation of time-dependent density-functional perturbation theory applied to core excitations, while ab initio molecular dynamics provides essential sampling of core-excitation energies and interatomic distance distributions for interpreting extended X-ray absorption fine structure (EXAFS) features. Owing to the efficiency of the approach, the total spectrum can be decomposed into contributions from bulk, defective, and surface environments, which commonly coexist in experimental systems. The methodology is demonstrated for sodium at the Na K-edge in NaCl, where the predicted spectra show good agreement with experimental measurements on thin film samples. This strategy offers a practical route to generating chemically specific XAFS cross-section data for elements and species that remain challenging to characterize experimentally, thereby enabling deeper insights into materials of technological importance.

cond-mat.mtrl-sci↗

arXiv2025

Experimental determination of the sodium K-shell atomic fundamental parameters for X-ray spectroscopy

Reliable fundamental parameters are essential for accurate X-ray fluorescence analysis of sodium. This work presents updated experimental values with reliable uncertainties for sodium K-shell fundamental parameters such as: fluorescence yield, photoionization cross sections, and Auger yields. Using a physically calibrated setup and a thin NaCl layer on a silicon nitride membrane, a holistic determination approach was applied to reduce uncertainties. The new values represent a significant improvement on the ones widely used in databases. All data are available via Zenodo to support precise sodium quantification in scientific and industrial applications.

physics.atom-ph↗

arXiv2023

Titanium and titanium oxides at the K- and L-edges: validating theoretical calculations of X-ray absorption and X-ray emission spectra with measurements

Using well-calibrated experimental data we validate theoretical X-ray absorption spectroscopy (XAS) as well as X-ray emission spectroscopy (XES) calculations for titanium (Ti), titanium oxide (TiO), and titanium dioxide (TiO$_2$) at the Ti K- and L-edges as well as O K-edge. XAS and XES in combination with a multi-edge approach offer a detailed insight into the electronic structure of materials since both the occupied and unoccupied states, are probed. The experimental results are compared with ab initio calculations from the OCEAN package which uses the Bethe-Salpeter equation (BSE) approach. Using the same set of input parameters for each compound for calculations at different edges, the transferability of the OCEAN calculations across different spectroscopy methods and energy ranges is validated. Thus, the broad applicability for analysing and interpreting the electronic structure of materials with the OCEAN package is shown.

cond-mat.mtrl-sci↗

arXiv2023

Experimental determination of ruthenium L-shell fluorescence yields and Coster-Kronig transition probabilities

The L-shell fluorescence yields and the Coster-Kronig factors of ruthenium (and the corresponding uncertainty) were determined for the first time experimentally by applying radiometrically calibrated instrumentation of the Physikalisch-Technische Bundesanstalt. The resulting fluorescence yields ($ω_{L_3}=0.0459(20)$, $ω_{L_2}=0.0415(26)$, $ω_{L_1}=0.0109(9)$) and the Coster-Kronig factors ($f_{23}=0.177(32)$, $f_{13}=0.528(90)$, $f_{12}=0.173(73)$) agree reasonable well with parts of the data from the literature.

physics.atom-ph↗

arXiv2022

Experimental determination of tantalum L-shell fluorescence yields and Coster-Kronig transition probabilities

Using radiometrically calibrated instrumentation of Physikalisch-Technische Bundesanstalt, the L-shell fluorescence yields and Coster-Kronig factors of tantalum (including the uncertainty budget) were experimentally determined based on transmission and X-ray fluorescence experiments. The determined fluorescence yields ($ω_{L3} = 0.247(12)$, $ω_{L2} = 0.278(15)$, $ω_{L1} = 0.157(12)$) were independently validated trough XRR-GIXRF experiments. Both, the Coster-Kronig factors ($f_{23} = 0.123(84)$, $f_{13} = 0.328(152)$, $f_{12} = 0.14(11)$) as well as the fluorescence yields are in good agreement with the most established databases in the field of X-ray fluorescence.

physics.atom-ph↗

arXiv2022

Experimental determination of the gadolinium L subshells fluorescence yields and Coster-Kronig transition probabilities

The L subshell Coster Kronig (CK) transition factors of Gd have been experimentally determined by means of two different experimental approaches and compared to available literature data. On the one hand reference-free X-ray fluorescence (XRF) analysis using an energy-dispersive detector was applied. This method permitted in addition to determine the L subshell fluorescence yields since the absolute incident and emitted X-ray photon flux can be determined. On the other hand a wavelength dispersive spectrometer based on a modified von Hamos geometry using a full cylinder highly annealed pyrolithic graphite crystal for an experimental validation of the CK transition factors in an independent experiment. The use of this high energy resolution spectrometer allowed thanks to the capability to better discriminate the different X-ray emission lines to validate the reference-free XRF results. For both experiments the use of calibrated instrumentation enabled the provision a reliable uncertainty budget on the results obtained.

physics.atom-ph↗

arXiv2021

Experimental and theoretical approaches for determining the K-shell fluorescence yield of carbon

The knowledge of atomic fundamental parameters, such as the fluorescence yields with low uncertainties, is of decisive importance in elemental quantification involving X-ray fluorescence analysis techniques. However, especially for the low-Z elements, the available literature data are either of poor quality, of unknown or very large uncertainty, or both. For this reason, the K-shell fluorescence yield of carbon was determined in the PTB laboratory at the synchrotron radiation facility BESSY II. In addition, theoretical calculations of the same parameter were performed using the multiconfiguration Dirac-Fock method, including relativistic and quantum electrodynamics (QED) corrections. Both values obtained in this work are compared to the corresponding available literature data.

physics.atom-ph↗

arXiv2021

Peculiarities in quantification of airborne particulate matter by means of Total Reflection X-ray Fluorescence

Knowledge on the temporal and size distribution of particulate matter (PM) in air as well as on its elemental composition is a key information for source appointment, for the investigation of their influence on environmental processes and for providing valid data for climate models. A prerequisite is that size fractionated sampling times of few hours must be achieved such that anthropogenic and natural emissions can be correctly identified. While cascade impactors allow for time- and size-resolved collection of airborne PM, total reflection X-ray fluorescence (TXRF) allows for element-sensitive investigation of low sample amounts thanks to its detection sensitivity. However, during quantification by means of TXRF it is crucial to be aware of the limits of TXRF in order to identify situations where collection times or pollution levels were exceedingly long or high. It will be shown by means of grazing incidence X-ray fluorescence (GIXRF), where different reflection conditions are probed, that a self consistent quantification of elemental mass depositions can be performed in order to validate or identify issues in quantification by means of TXRF. Furthermore, monitors of validity for a reliable quantification of the elemental composition of PM by means of TXRF will be introduced. The methodological approach presented can be transferred to tabletop instrumentation in order to guarantee a reliable quantification on an element sensitive basis of the PM collected. This aspect is highly relevant for defining appropriate legislation and measures for health and climate protection and for supporting their enforcement and monitoring.

physics.ao-ph↗

arXiv2021

Laboratory grazing-incidence X-ray fluorescence spectroscopy as an analytical tool for the investigation of sub-nanometer CrSc multilayer water window optics

Efficient multilayer optics for radiation in the water window range are difficult to manufacture due to extremely small layer thicknesses and severe intermixing of elements between the layers. Therefore, adequate analytics and short feedback loops are of utmost importance for manufacturers to improve performance and efficiency. We show the possibility for non-destructive elemental depth profiling with commercial laboratory equipment using four real-life CrSc multilayer samples. Comparative measurements at the laboratory of PTB at the synchrotron radiation facility BESSY II confirm the results and prove the potential of laboratory equipment for the reliable analysis of stratified materials with sub-nanometer layer thicknesses.

physics.app-ph↗

arXiv2021

Towards a calibration of laboratory setups for grazing incidence and total-reflection X-ray fluorescence analysis

Grazing-Incidence X-ray fluorescence (GIXRF) analysis, which is closely related to total-reflection XRF, is a very powerful technique for the in-depth analysis of many types of technologically relevant samples, e.g. nanoparticle depositions, shallow dopant profiles, thin layered samples or even well-ordered nanostructures. However, the GIXRF based determination of the depth-dependent information about the sample is usually based on a modelling of the experimental data. This requires profound knowledge of the geometrical parameters of the setup employed, especially the incident beam profile as well as the detector aperture parameters. Together they determine the incident angle dependent so-called effective solid angle of detection which must be known in order to model any experimental data set. In this work, we demonstrate how these instrumental parameters, which are typically not known with sufficient accuracy, can be determined using dedicated experiments with a well-known calibration sample. In addition, this paves the way for a full calibration of the setup, as also information about other parameters, e.g. the incident photon flux is gained. Here, we are using a Bruker S4 T-STAR instrument for this demonstration but the principle can also be applied for other GIXRF setups.

physics.app-ph↗

arXiv2021

Grazing incidence X-ray fluorescence based characterization of nanostructures for element sensitive profile reconstruction

For the reliable fabrication of the current and next generation of nanostructures it is essential to be able to determine their material composition and dimensional parameters. Using the grazing incidence X-ray fluoresence technique, which is taking advantage of the X-ray standing wave field effect, nanostructures can be investigated with a high sensitivity with respect to the structural and elemental composition. This is demonstrated using lamellar gratings made of Si$_3$N$_4$. Rigorous field simulations obtained from a Maxwell solver based on the finite element method allow to determine the spatial distribution of elemental species and the geometrical shape with sub-nm resolution. The increasing complexity of nanostructures and demanded sensitivity for small changes quickly turn the curse of dimensionality for numerical simulation into a problem which can no longer be solved rationally even with massive parallelisation. New optimization schemes, e.g. machine learning, are required to satisfy the metrological requirements. We present reconstruction results obtained with a Bayesian optimization approach to reduce the computational effort.

physics.app-ph↗

arXiv2021

Time-frequency analysis assisted reconstruction of ruthenium optical constants in the sub-EUV spectral range 8nm-23.75nm

The optical constants of ruthenium in the spectral range 8 nm to 23.75 nm with their corresponding uncertainties are derived from the reflectance of a sputtered ruthenium thin film in the Extreme Ultraviolet (EUV) spectral range measured using monochromatized synchrotron radiation. This work emphasizes the correlation between structure modelling and the reconstructed optical parameters in a detailed inverse-problem optimization strategy. Complementary X-ray Reflectivity (XRR) measurements are coupled with Markov chain Monte Carlo (MCMC) based Bayesian inferences and quasi-model-independent methods to create a model factoring the sample's oxidation, contamination, and surface roughness. The sensitivity of the modelling scheme is tested and verified against contamination and oxidation. A notable approach mitigating the high dimensionality of the reconstruction problem is elaborated with the results of this work compared to two previously published datasets. The presented dataset is of high interest for the continuing development of Extreme Ultraviolet Lithography (EUVL) and EUV astronomy optical systems.

physics.optics↗

arXiv2021

Shape- and element-sensitive reconstruction of periodic nanostructures with grazing incidence X-ray fluorescence analysis and machine learning

The characterization of nanostructured surfaces with sensitivity in the sub-nm range is of high importance for the development of current and next generation integrated electronic circuits. Modern transistor architectures for e.g. FinFETs are realized by lithographic fabrication of complex, well ordered nanostructures. Recently, a novel characterization technique based on X-ray fluorescence measurements in grazing incidence geometry has been proposed for such applications. This technique uses the X-ray standing wave field, arising from an interference between incident and the reflected radiation, as a nanoscale sensor for the dimensional and compositional parameters of the nanostructure. The element sensitivity of the X-ray fluorescence technique allows for a reconstruction of the spatial element distribution using a finite-element method. Due to a high computational time, intelligent optimization methods employing machine learning algorithms are essential for a timely provision of results. Here, a sampling of the probability distributions by Bayesian optimization is not only fast, it also provides an initial estimate of the parameter uncertainties and sensitivities. The high sensitivity of the method requires a precise knowledge of the material parameters in the modeling of the dimensional shape provided that some physical properties of the material are known or determined beforehand. The unknown optical constants were extracted from an unstructured but otherwise identical layer system by means of soft X-ray reflectometry. The spatial distribution profiles of the different elements contained in the grating structure were compared to scanning electron and atomic force microscopy and the influence of carbon surface contamination on the modeling results were discussed.

physics.app-ph↗

arXiv2020

Speciation of FeS and FeS$_2$ by means of X-ray Emission Spectroscopy using a compact full-cylinder von Hamos spectrometer

We present Fe K$β$ X-ray emission (XES) and Fe K X-ray absorption spectra (XAS) of Iron(II)sulfide (FeS) and Iron(II)disulfide (FeS$_2$). While XES and XAS offer different discrimination capabilities for chemical speciation, depending on the valence states of the compounds probed, XES allows for using different excitation sources. The XES data was measured using polychromatic X-ray radiation with a full-cylinder von Hamos spectrometer being characterized by an energy window of up to 700 eV and a spectral resolving power of $E/ ΔE = 800$. The large energy window at a single position of the spectrometer components is made profit of to circumvent the instrumental sensitivity of wavelength-dispersive spectrometers to sample positioning. This results in a robust energy scale which is used to compare experimental data with ab initio valence-to-core calculations, which are carried out using the OCEAN package. To validate the reliability of the OCEAN package for the two sample systems, near edge X-ray absorption fine structure measurements of the Fe K absorption edge are compared to theory using the same input parameters as in the case of the X-ray emission calculations. Based on the example of iron sulfide compounds, the combination of XES experiments and OCEAN calculations allows unravelling the electronic structure of different transition metal sulfides and qualifying XES investigations for the speciation of different compounds.

cond-mat.mtrl-sci↗

arXiv2020

Grazing incidence-X-ray fluorescence for a dimensional and elemental characterization of well-ordered nanostructures

The increasing importance of well-controlled ordered nanostructures on surfaces represents a challenge for existing metrology techniques. To develop such nanostructures and monitor complex processing constraints fabrication, both a dimensional reconstruction of nanostructures and a characterization (ideally a quantitative characterization) of their composition is required. In this work, we present a soft X-ray fluorescence-based methodology that allows both of these requirements to be addressed at the same time. By applying the grazing-incidence X-ray fluorescence technique and thus utilizing the X-ray standing wave field effect, nanostructures can be investigated with a high sensitivity with respect to their dimensional and compositional characteristics. By varying the incident angles of the exciting radiation, element-sensitive fluorescence radiation is emitted from different regions inside the nanoobjects. By applying an adequate modeling scheme, these datasets can be used to determine the nanostructure characteristics. We demonstrate these capabilities by performing an element-sensitive reconstruction of a lamellar grating made of Si$_3$N$_4$, where GIXRF data for the O-K$α$ and N-K$α$ fluorescence emission allows a thin oxide layer to be reconstructed on the surface of the grating structure. In addition, we employ the technique also to three dimensional nanostructures and derive both dimensional and compositional parameters in a quantitative manner.

physics.app-ph↗

arXiv2020

Interaction of nanoparticle properties and X-ray analytical techniques

In this work, Pt-Ti core-shell nanoparticles (NP) of 2 nm to 3 nm in size and 30000 u \pm 1500 u as specified single particle mass, deposited on flat silicon substrates by means of a mass-selected cluster beam source, were used for the investigation of the modification of the X-Ray Standing Wave (XSW) field intensity with increasing NP surface coverage. The focus of the investigation is on the determination of the range of validity of the undisturbed flat surface approach of the XSW intensity in dependence of the actual coverage rate of the surface. Therefore, the nanoparticles were characterized using reference-free grazing incidence X-ray fluorescence analysis (GIXRF) employing radiometrically calibrated instrumentation. In addition, near-edge X-ray absorption fine structure (NEXAFS) measurements were performed to investigate the binding state of titanium in the core-shell nanoparticles which was found to be amorphous TiO2. The combination of GIXRF measurements and of the calculated XSW field intensities allow for a quantification of the core-shell nanoparticle surface coverage. For six different samples, the peak surface coverage could be determined to vary from 7 % to 130 % of a complete monolayer-equivalent coverage. A result of the current investigation is that core-shell nanoparticles modify the intensity distribution of the XSW field with increasing surface coverage. This experimental result is in line with calculated XSW field intensity distributions at different surface coverages using an effective density approach.

physics.app-ph↗

arXiv2020

Validation of secondary fluorescence excitation in quantitative X-ray fluorescence analysis of thin alloy films

X-ray fluorescence (XRF) analysis is a widely applied technique for the quantitative analysis of thin films up to the $μ$m scale because of its non-destructive nature and because it is easily automated. When low uncertainties of the analytical results in the few percent range are required, the non-linear secondary fluorescence effect in multi-elemental samples may complicate an otherwise straightforward quantification, since it can easily exceed a relative contribution of 20%. The conventional solution, to rely on good performing reference samples, is hindered by their low availability, especially for thin film applications. To address this challenge, we demonstrate a flexible production method of multilayered, alloyed thin films with significant secondary fluorescence contributions. We use reference-free XRF analysis to validate the reliability of the physical model for secondary fluorescence, which includes a thorough uncertainty estimation. The investigated specimens are being qualified as calibration samples for XRF or other quantitative analyses.

cond-mat.mtrl-sci↗

arXiv2019

Experimental determination of line energies, line widths and relative transition probabilities of the Gadolinium L X-ray emission spectrum

In this work the complete L-emission spectrum of gadolinium with respect to line energies, natural line widths, and relative transition probabilities was investigated using monochromatized synchrotron radiation. The measurements were realized in the PTB laboratory at BESSY II by means of an in-house built von Hamos spectrometer based on up to two full-cylinder HAPG mosaic crystal. The von Hamos spectrometer is calibrated by means of elastically scattered photons from the employed synchrotron radiation beamline leading to a well-defined energy scale and an experimentally determined spectrometer response. A selective excitation of the gadolinium L subshells was carried out to ensure a robust deconvolution of neighboring emission lines of different L subshells. The experimental results are discussed in the context of existing data from common databases and published values since significant deviations, especially for the L$γ_2$ and L$γ_3$ emission lines, are observed. We further substantiate and discuss two satellite lines at the low-energy side of the L$β_{2,15}$ and L$γ_1$ emission lines arising from the N$_{4,5}$ subshell.

physics.atom-ph↗