Employing Synchrotron Radiation Research Articles

Amorphous Doped Indium Tin Oxide Thin‐Films by Atomic Layer Deposition.Insights into Their Structural, Electronic and Device Reliability

AbstractThin semiconducting films of magnesium doped indium‐ and tin oxide are prepared by thermal atomic layer deposition (ALD). The metal oxide films are deposited at 200 °C from the precursors trimethylindium, tetrakis(dimethylamido)tin, bis(ethylcyclopentadienyl)magnesium and water as oxidant. These thin‐films are observed to be amorphous by electron microscopy and X‐ray diffraction. However, they exhibited a near‐range atomic order with correlation lengths of up to 10 Å, as demonstrated by high energy total scattering at grazing incidence employing synchrotron radiation. Even minor alterations in composition reveal a significant impact on the thin‐film transistor (TFT) device parameters, due to magnesium's high oxygen binding capability and its ability to inhibit the formation of oxygen vacancies, resulting in a decrease of free charge carriers in the material. Stability tests indicate a device degradation after storage in ambient conditions due to water adsorption on the surface, which could be reversed by an additional annealing step which qualify the films as robust. This studie demonstrate the possibility of employing minor amounts of high band gap oxides such as MgO to manipulate and control the electric behavior of the active channel layer performance in inorganic TFT devices.

Synchrotron Micro-X-ray Diffraction in Transmission Geometry: A New Approach to Study Polychrome Stratigraphies in Cultural Heritage

In cultural heritage, paint stratigraphies are complex systems typically consisting of various paint layers with fine crystalline phases mixed with coarse pigment and filler grains. This complexity poses significant challenges for X-ray diffraction (XRD) analysis. In this work, we employed synchrotron radiation micro-X-ray diffraction in transmission geometry (SR-µTXRD) with linear mapping to develop a novel approach for studying the crystalline phases (pigments and fillers) in mock-up paint stratigraphies. A targeted approach was followed for qualitative, quantitative, and microstructural analysis, combining signals from micrometric crystallites and coarse single crystals as well as from randomly oriented and iso-oriented crystalline phases. This allows for identifying, localizing, and quantifying these phases even in low fractions and distinguishes the same phases across different layers with varying grain sizes or spatial orientations. Critical analysis of 2D XRD patterns, coupled with full-profile fitting performed by the Rietveld method, provides insights into material preparation (e.g., grinding), painting technique (e.g., color palette, use of fillers, brushing), and crystallo-chemical modifications over time. This analytical approach, integrating spatially resolved investigation with high-quality phase characterization, enhances the potential of specific XRD methodologies for a 2D investigation of multi-phase materials in cultural heritage, even without dedicated micro-mapping techniques.

In situ 3D crystallographic characterization of deformation-induced martensitic transformation in a metastable Fe–Cr–Ni austenitic alloy by X-ray microtomography

Excellent strength–ductility balance in metastable Fe–Cr–Ni austenitic alloys stems from phase transformation from austenite (fcc structure) to αʹ martensite (bcc structure) during deformation, namely deformation-induced αʹ martensitic transformation (DIMT). Here, DIMT in a metastable Fe–17Cr–7Ni austenitic alloy was detected in situ and characterized in three dimensions (3D) by employing synchrotron radiation X-ray microtomography. This technique utilizes refraction contrast, which is attributable to the presence of phase boundaries between the parent austenite and the newly formed αʹ martensite phase. By combining microtomography and position-sensitive X-ray diffraction, we succeeded in crystallographically identifying multiple αʹ martensite phases continuously transformed in four groups from a single parent austenitic phase.

Valence shell electronically excited states of 1-phenylimidazole and 1-benzylimidazole

The valence shell electronically excited states of 1-phenylimidazole and 1-benzylimidazole have been studied by employing synchrotron radiation to measure the absolute photoabsorption cross-section of each molecule, from threshold up to an energy of 10.8 eV. Assignments have been proposed for some of the broad absorption bands using calculated transition energies and oscillator strengths. Natural transition orbital plots have allowed the Rydberg and/or valence character of the electronically excited states to be assessed. Some of the calculated transitions in 1-benzylimidazole and 1-phenylimidazole have initial and final orbitals that are analogous to those of transitions in the isolated constituent rings of imidazole and benzene. Other mixed Rydberg/valence transitions, especially those leading to some of the low energy electronically excited states in 1-phenylimidazole, have an initial orbital located on the imidazole ring while valence character in the final orbital is localised on the phenyl ring. Thus, photoexcitation results in charge transfer from the donor site (imidazole) to the acceptor (the phenyl ring) in the nascent ion core of the Rydberg state. In both 1-benzylimidazole and 1-phenylimidazole the lowest energy excited state arises from a transition analogous to the 1e1g → 1e2u 1B2u electric dipole-forbidden transition in benzene.

L-series X-ray fluorescence cross section measurements for 72Hf employing synchrotron radiation

In the present work, the Hf target was irradiated by tuning the energy (Ep) of synchrotron radiation across the Li (i = 1–3) edge-energies ranging from 9.6 keV to 14.0 keV in order to measure the cross sections for production of the fluorescent Lk X-rays (k = l, α, η, β1,6, β3, β4, β2,15, β5,7, β9,10, γ1,5, γ2,3,6,8, γ4). These measurements were performed with the aim to check the validity of independent particle approximation (IPA) models at incident photon energies in proximity to the Li absorption edges of a heavy transition element. The measured cross sections were compared with three sets of values calculated using the X-ray emission rates based on the Dirac-Fock model, the Li (i = 1–3) sub-shell photoionization cross-sections based on the non-relativistic Hartree-Fock-Slater model and three sets of the fluorescence (ωi) and Coster-Kronig (fji) yields.

Deep Reinforcement Learning Environment Approach Based on Nanocatalyst XAS Diagnostics Graphic Formalization.

The most in-demand instrumental methods for new functional nanomaterial diagnostics employ synchrotron radiation, which is used to determine a material's electronic and local atomic structure. The high time and resource costs of researching at international synchrotron radiation centers and the problems involved in developing an optimal strategy and in planning the control of the experiments are acute. One possible approach to solving these problems involves the use of deep reinforcement learning agents. However, this approach requires the creation of a special environment that provides a reliable level of response to the agent's actions. As the physical experimental environment of nanocatalyst diagnostics is potentially a complex multiscale system, there are no unified comprehensive representations that formalize the structure and states as a single digital model. This study proposes an approach based on the decomposition of the experimental system into the original physically plausible nodes, with subsequent merging and optimization as a metagraphic representation with which to model the complex multiscale physicochemical environments. The advantage of this approach is the possibility to directly use the numerical model to predict the system states and to optimize the experimental conditions and parameters. Additionally, the obtained model can form the basic planning principles and allow for the optimization of the search for the optimal strategy with which to control the experiment when it is used as a training environment to provide different abstraction levels of system state reactions.

Structural Properties of Metal-Organic Frameworks at Elevated Thermal Conditions via a Combined Density Functional Tight Binding Molecular Dynamics (DFTB MD) Approach.

The performance of different density functional tight binding (DFTB) methods for the description of six increasingly complex metal-organic framework (MOF) compounds have been assessed. In particular the self-consistent charge density functional tight binding (SCC DFTB) approach utilizing the 3ob and matsci parameter sets have been considered for a set of four Zn-based and two Al-based MOF systems. Moreover, the extended tight binding for geometries, frequencies, and noncovalent interactions (GFN2-xTB) approach has been considered as well. In addition to the application of energy minimizations of the respective unit cells, molecular dynamics (MD) simulations at constant temperature and pressure conditions (298.15 K, 1.013 bar) have been carried out to assess the performance of the different DFTB methods at nonzero thermal conditions. In order to obtain the XRD patterns from the MD simulations, a flexible workflow to obtain time-averaged XRD patterns from (in this study 5000) individual snapshots taken at regular intervals over the simulation trajectory has been applied. In addition, the comparison of pair-distribution functions (PDFs) directly accessible from the simulation data shows very good agreement with experimental reference data obtained via measurements employing synchrotron radiation in case of MOF-5. The comparison of the lattice constants and the associated X-ray diffraction (XRD) patterns with the experimental reference data demonstrate, that the SCC DFTB approach provides a highly efficient and accurate description of the target systems.

The Incorporation of Low-Molecular Weight Poly(Mannitol Sebacate)s on PLA Electrospun Fibers: Effects on the Mechanical Properties and Surface Chemistry.

We offer a report on the synthesis of low-molecular weight biobased poly(mannitol sebacate) (PMS) and its functionalization with acrylate groups (PMSAc). These synthesized polyesters were blended at a low level (10 wt%) with poly (lactic acid) PLA to prepare aligned fibers by electrospinning, coupled with a rotatory collector. The obtained fibers were extensively studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXS), employing synchrotron radiation. The incorporation of the PMSs on the PLA fibers did not significantly affect the fiber diameters, whereas the alignment was almost maintained. The crystallinity and thermal properties were also slightly modified with the addition of PMSs, and an increase in the degree of crystallinity and in the glass transition temperature of the blend compared to PLA was observed. Remarkably, the PLA/PMSs fibers were more ductile due to the elastomeric character of PMS, with higher values of elongation at break and tensile strengths, and a smaller Young modulus in comparison with the PLA fibers. These modifications of the properties were more noticeable in the case of the acrylated PMS, which also provided readily available functional groups at the surface for further chemical reactions, such as the Michael addition or crosslinking processes.

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

Deeper insights into the photoluminescence properties and (photo)chemical reactivity of cadmium red (CdS1\u2212xSex) paints in renowned twentieth century paintings by state-of-the-art investigations at multiple length scales

Cadmium red is the name used for denoting a class of twentieth century artists’ pigments described by the general formula CdS1−xSex. For their vibrant hues and excellent covering power, a number of renowned modern and contemporary painters, including Jackson Pollock, often used cadmium reds. As direct band gap semiconductors, CdS1−xSex compounds undergo direct radiative recombination (with emissions from the green to orange region) and radiative deactivation from intragap trapping states due to crystal defects, which give rise to two peculiar red-NIR emissions, known as deep level emissions (DLEs). The positions of the DLEs mainly depend on the Se content of CdS1−xSex; thus, photoluminescence and diffuse reflectance vis–NIR spectroscopy have been profitably used for the non-invasive identification of different cadmium red varieties in artworks over the last decade. Systematic knowledge is however currently lacking on what are the parameters related to intrinsic crystal defects of CdS1−xSex and environmental factors influencing the spectral properties of DLEs as well as on the overall (photo)chemical reactivity of cadmium reds in paint matrixes. Here, we present the application of a novel multi-length scale and multi-method approach to deepen insights into the photoluminescence properties and (photo)chemical reactivity of cadmium reds in oil paintings by combining both well established and new non-invasive/non-destructive analytical techniques, including macro-scale vis–NIR and vibrational spectroscopies and micro-/nano-scale advanced electron microscopy mapping and X-ray methods employing synchrotron radiation and conventional sources. Macro-scale vis–NIR spectroscopy data obtained from the in situ non-invasive analysis of nine masterpieces by Gerardo Dottori, Jackson Pollock and Nicolas de Staël allowed classifying the CdS1−xSex-paints in three groups, according to the relative intensity of the two DLE bands. These outcomes, combined with results from micro-/nano-scale electron microscopy mapping and X-ray analysis of a set of CdS1−xSex powders and artificially aged paint mock-ups, indicated that the relative intensity of DLEs is not affected by the morphology, microstructure and local atomic environment of the pigment particles but it is influenced by the presence of moisture. Furthermore, the extensive study of artificially aged oil paint mock-ups permitted us to provide first evidence of the tendency of cadmium reds toward photo-degradation and to establish that the conversion of CdS1−xSex to CdSO4 and/or oxalates is triggered by the oil binding medium and moisture level and depends on the Se content. Based on these findings, we could interpret the localized presence of CdSO4 and cadmium oxalate as alteration products of the original cadmium red paints in two paintings by Pollock.Graphical abstract

Angle-resolved photoemission spectroscopy study of the (101) surface of the Kondo insulator CeNiSn

The electronic structure of CeNiSn, which is considered a possible topological Kondo insulator, has been investigated by employing synchrotron radiation excited angle-resolved photoemission spectroscopy (ARPES). We have found that the easy cleavage plane in CeNiSn is (101), for which we have investigated the Fermi surface (FS) and band structures. The measured FS and ARPES for the (101) plane are described well by the calculated FS and band structures, obtained from the DFT calculations. The measured ARPES bands and photon energy map show that the metallic states crossing the Fermi level have the 3D nature, casting a negative suspicion for the existence of the topological surface states of the 2D character in CeNiSn. The Ce 4f Kondo resonance peak is observed in Ce 4d → 4f resonant photoemission spectroscopy, suggesting the importance of the Ce 4f electrons in determining the temperature-dependent topological electronic structure of CeNiSn.

Synchrotron spectroscopy of the CSH-bending and CH3-rocking bands of methyl mercaptan

The CSH-bending and CH3-rocking infrared bands of CH3SH have been investigated in Fourier transform spectra recorded at 0.001 cm−1 resolution employing synchrotron radiation at the Canadian Light Source in Saskatoon. The relative band strengths and structures are quite different from those of the CH3OH methanol analogue, with the CSH bend being very weak and both the in-plane and out-of-plane CH3 rocks being strong with intensities greater than the C–S stretch. The CSH bend has parallel a-type character with no detectable b-type component. The out-of-plane CH3 rock is a purely c-type perpendicular band, whereas the in-plane rock is of mixed a/b character. Sub-bands have been assigned for A and E torsional species up to about K = 10 for each vibrational mode, providing upper-state term values from which K-reduced substate origins were determined. For the CSH bend, the origins follow the customary oscillatory torsional pattern as a function of K with a sharply reduced amplitude of 0.362 cm−1 compared to the 0.653 cm−1 for the ground state. The torsional energy curves for the out-of-plane rock are also well-behaved but have inverted ordering of the A–E torsional splitting components and a larger amplitude of 1.33 cm−1. In contrast, the substate origins for the in-plane rock are scattered over a range of about 2 cm−1 without clear oscillatory structure. Several instances of coupling among the lower modes and the ground state via resonances between accidentally near-degenerate levels have been observed and characterized. Ab initio calculations are found to give a good representation of the frequency and relative intensity patterns for the lower vibrational modes.

Structure Development in Polymers during Fused Filament Fabrication (FFF): An in Situ Small- and Wide-Angle X-ray Scattering Study Using Synchrotron Radiation

Microstructure formation in individual layers during fused filament fabrication (FFF) of a Π-shaped multilayer single-walled polymer sample was studied by simultaneous measurement of small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) methods employing synchrotron radiation. We investigated individual layers and the welding zone between individual layers. As a model material, we used isotactic polypropylene (iPP), which is a commodity semicrystalline polymer and has a strong potential as a feedstock material for additive manufacturing. The layers were deposited by an FFF three-dimensional (3D) printer that was custom-built to fit into the synchrotron beamline. WAXS data were utilized to determine the temperature of the irradiated volume. The polymer microstructure was characterized in terms of crystallinity and long-spacing. Avrami analysis indicates that the crystallization behavior of iPP in thin layers is rather similar to that observed in quiescent crystallization of bulk iPP, suggest...

A guide to sample delivery systems for serial crystallography.

Crystallography has made a notable contribution to our knowledge of structural biology. For traditional crystallography experiments, the growth of crystals with large size and high quality is crucial, and it remains one of the bottlenecks. In recent years, the successful application of serial femtosecond crystallography (SFX) provides a new choice when only numerous microcrystals can be obtained. The intense pulsed radiation of X-ray free-electron lasers (XFELs) enables the data collection of small-sized crystals, making the size of crystals no longer a limiting factor. The ultrafast pulses of XFELs can achieve 'diffraction before destruction', which effectively avoids radiation damage and realizes diffraction near physiological temperatures. More recently, the SFX has been expanded to serial crystallography (SX) that can additionally employ synchrotron radiation as the light source. In addition to the traditional ones, these techniques provide complementary opportunities for structural determination. The development of SX experiments strongly relies on the advancement of hardware including the sample delivery system, the X-ray source, and the X-ray detector. Here, in this review, we categorize the existing sample delivery systems, summarize their progress, and propose their future prospectives.

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

In this work the most intense x-ray lines of the L-emission spectrum of gadolinium with respect to line energies, natural line widths, and relative transition probabilities were 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 crystals. 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 and L emission lines, are observed. We further substantiate and discuss two satellite lines at the low-energy side of the L and L emission lines arising from the N4,5 subshell.

N'-(1,3-Benzo-thia-zol-2-yl)benzene-sulfono-hydrazide: crystal structure, Hirshfeld surface analysis and computational chemistry.

The asymmetric unit of the title compound, C13H11N3O2S2, comprises two independent mol-ecules (A and B); the crystal structure was determined by employing synchrotron radiation. The mol-ecules exhibit essentially the same features with an almost planar benzo-thia-zole ring (r.m.s. deviation = 0.026 and 0.009 Å for A and B, respectively), which forms an inclined dihedral angle with the phenyl ring [28.3 (3) and 29.1 (3)°, respectively]. A difference between the mol-ecules is noted in a twist about the N-S bonds [the C-S-N-N torsion angles = -56.2 (5) and -68.8 (5)°, respectively], which leads to a minor difference in orientation of the phenyl rings. In the mol-ecular packing, A and B are linked into a supra-molecular dimer via pairwise hydrazinyl-N-H⋯N(thiazol-yl) hydrogen bonds. Hydrazinyl-N-H⋯O(sulfon-yl) hydrogen bonds between A mol-ecules assemble the dimers into chains along the a-axis direction, while links between centrosymmetrically related B mol-ecules, leading to eight-membered {⋯HNSO}2 synthons, link the mol-ecules along [001]. The result is an undulating supra-molecular layer. Layers stack along the b-axis direction with benzo-thia-zole-C-H⋯O(sulfon-yl) points of contact being evident. The analyses of the calculated Hirshfeld surfaces confirm the relevance of the above inter-molecular inter-actions, but also serve to further differentiate the weaker inter-molecular inter-actions formed by the independent mol-ecules, such as π-π inter-actions. This is also highlighted in distinctive energy frameworks calculated for the individual mol-ecules.

Total cross-section for low-energy and very low-energy electron collisions with O2

An absolute total cross-section for electron scattering from O2 is obtained in the energy range from 20 eV down to 16 meV with a very narrow electron energy width of 7 meV, using the threshold-photoelectron source employing synchrotron radiation. The total cross-section obtained in the present study generally agrees well with those obtained in previous experimental works in the energy region where the previous experimental total cross-sections agree with each other. At lower energies, several features are found, including the very large contribution of the resonance to the total cross-section. The resonance energies and the resonance widths of the individual vibrational states of the resonance are determined from the analysis of the measured absolute total cross-section. The resonance width of the resonance of O2 is found to be much narrower than the value estimated from previous high-resolution experiments and theoretical calculations.

Multiparameter High-Throughput and in Situ X-ray Diffraction Study of Six New Bismuth Sulfonatocarboxylates: Discovery, Phase Transformation, and Reaction Trends.

With the employment of high-throughput methods, the system Bi3+/4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H4DSNDC)/H2O/additive (HNO3 or NaOH) was systematically investigated under hydrothermal reaction conditions. The influence of the molar ratio of the starting materials, pH, and reaction temperature and time was investigated in more than 500 reactions. The product formation is highly sensitive toward small changes of the synthesis parameters, but six new bismuth sulfonatocarboxylates were reproducibly obtained starting from clear solutions of the reactants. All compounds were structurally characterized from single-crystal X-ray diffraction data. Fully deprotonated linker ions are found in [Bi6O6(OH)2(H2O)4(DSNDC)] (1), [Bi2(OH)2(DSNDC)] (2), [Bi8O7(OH)2(H2O)2(DSNDC)2] (3), and [Bi7O5(OH)3(H2O)4(DSNDC)2]·4H2O (4), while the presence of larger amounts of acid or short reaction times leads to compounds with noncoordinating -COOH groups, [Bi2(OH)2(H2O)2(DSNDC)(H2DSNDC)] (5) and [Bi6O4(OH)4(H2O)12(H2DSNDC)3]· xH2O (6), respectively. The inorganic building units (IBUs) in all six structures differ substantially from each other; the IBUs found in 2 ({Bi2(OH)2}), 5 (BiO8 polyhedron), and 6 ({Bi6O4(OH)4} cluster) have been reported in the literature, while new IBUs are observed for 1 (chains of composition {Bi3O3(OH)}∞), 3 ({Bi16O14(OH)4} cluster), and 4 ({Bi7O5(OH)3} cluster). Systematic variation of the reaction temperature and time indicated their distinct influence on product formation. Hence, in situ powder X-ray diffraction measurements at Deutsches Elektronen-Synchrotron, Hamburg, Germany, employing synchrotron radiation were carried out. In all studied in situ reactions, compound 6 is first observed and subsequently transformed to 1, 2, 4, and 5, depending on the reaction time and temperature as well as concentration of the starting materials.

The optical stretcher as a tool for single-particle X-ray imaging and diffraction.

For almost half a century, optical tweezers have successfully been used to micromanipulate micrometre and sub-micrometre-sized particles. However, in recent years it has been shown experimentally that, compared with single-beam traps, the use of two opposing and divergent laser beams can be more suitable in studying the elastic properties of biological cells and vesicles. Such a configuration is termed an optical stretcher due to its capability of applying high deforming forces on biological objects such as cells. In this article the experimental capabilities of an optical stretcher as a potential sample delivery system for X-ray diffraction and imaging studies at synchrotrons and X-ray free-electron laser (FEL) facilites are demonstrated. To highlight the potential of the optical stretcher its micromanipulation capabilities have been used to image polymer beads and label biological cells. Even in a non-optimized configuration based on a commercially available optical stretcher system, X-ray holograms could be recorded from different views on a biological cell and the three-dimensional phase of the cell could be reconstructed. The capability of the setup to deform cells at higher laser intensities in combination with, for example, X-ray diffraction studies could furthermore lead to interesting studies that couple structural parameters to elastic properties. By means of high-throughput screening, the optical stretcher could become a useful tool in X-ray studies employing synchrotron radiation, and, at a later stage, femtosecond X-ray pulses delivered by X-ray free-electron lasers.

Photoionization mass spectrometry of ω-phenylalkylamines: Role of radical cation-π interaction

Linear ω-phenylalkylamines of increasing alkyl chain length have been investigated employing synchrotron radiation in the photon energy range from 7 to 15 eV. These molecules have received considerable interest because they bear the skeleton of biologically relevant compounds including neurotransmitters and because of the possible interaction between the amino moiety and the phenyl ring. Recently, the contribution of this interaction has been assayed in both neutral and protonated species, pointing to a role of the polymethylene chain length. In this work, the ionization energy (IE) values of benzylamine (BA), 2-phenylethylamine (2-PEA), 3-phenylpropylamine (3-PPA), and 4-phenylbutylamine (4-PBA) were investigated in order to ascertain the impact of the different alkyl chain lengths and to verify an amino radical cation-π interaction. The IEs obtained experimentally, 8.54, 8.37, 8.29, and 8.31 eV for BA, 2-PEA, 3-PPA and 4-PBA, respectively, show a decreasing trend that is discussed employing calculations at the CBS-QB3 level. Moreover, the appearance energy values for major fragments produced by the photofragmentation process are reported.