grazing-incidence x-ray scattering

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New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

A new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction 共SXRD兲 and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum 共UHV兲 and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1 – 1000 mbars and as a continuous flow cell for pressure lower than 10 −3 mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd 8 Ni 92 共110兲 surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules. © 2007 American Institute of Physics.
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X-ray reflectivity, diffraction and grazing incidence small angle X-ray scattering as complementary methods in the microstructural study of sol–gel zirconia thin films

X-ray reflectivity, diffraction and grazing incidence small angle X-ray scattering as complementary methods in the microstructural study of sol–gel zirconia thin films

zirconia phase and the SAXS signal in the transmission mode is recovered and exhibits a well defined scattered intensity peak at a non zero scattering vector. During the dipping, the liquid film runs out on the substrate, adheres to its surface and the evaporation of solvents leads to its rapid solidification. The as prepared layer could be considered as a xerogel obtained by a concentration effect. As for the bulk xerogel, we do not observe GISAXS signal for this raw layer even by using the synchrotron radiation facilities of LURE. At the beginning of the annealing, the correlation length corresponding to the appearing zirconia nanocrystals, about 4 nm at 300 -C, is in good agreement with the zirconium rich primary particle size present in the sol. During the temperature increase, the layer microstructure evolves by normal grain growth of the zirconia nanocrystals in agreement with the theoretical approach developed by Thompson [27] . For a given low temperature thermal treatment and whatever the substrate, the thin film GISAXS as well as the bulk xerogel SAXS patterns display quite similar feature in spite of very different experimental data recording ( Fig. 7 ). At this stage, the layer evolves as bulk xerogel and the film-substrate interface does not seem to influence its microstructural evolution. These results are in good agreement with the observations carried out on similar systems [28] .
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Two-dimensional resonant magnetic soft X-ray scattering set-up for extreme sample environment

Two-dimensional resonant magnetic soft X-ray scattering set-up for extreme sample environment

Our first test sample was a grating consisting of periodic Co lines with  = 300 nm spacing. It was elaborated using a nanoimprint technology, first presented by Chou et al. (1996), from a layered thin film structure of Ta(5 nm)/ Co(20 nm)/Ru(5 nm) deposited on a Si(100) substrate. Using this kind of lithographic process ensures large area samples are obtained, which is important when dealing with grazing- incidence measurement geometry. Fig. 4(a) shows an optical microscopy image of the sample. From this image we note that the sample shows several imperfections (line defects). Some domains thus appear to be shifted by half a period. Fig. 4(b) presents a SEM (scanning electron microscopy) image recorded on a defect region of the sample. The contrast occurs between alternate Co lines (bright regions) and etched Si substrate (dark regions). First, we can easily notice the absence of regular Co lines with fixed 300 nm width. Instead, alternate wide and narrow Co lines appear. Second, like in the highlighted area, we observe modulations in the lines width. Such modulations define the boundaries of the shifted domains appearing in the optical image (Fig. 4a). Most probably, during the nanoimprinting process, the lines were not transferred perfectly from the mask to the resist, owing to variation in processing parameters such as the pressure and the temperature. Therefore many defects occur prior to the sputtering of the metallic layers. As a direct consequence, in the scattered images we can identify two different scattered signal families, as shown in Fig. 4(c): the first, at q y = 4.72 
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Grazing Incidence X-ray Diffraction investigation of strains in silicon nanowires obtained by gold catalytic growth

Grazing Incidence X-ray Diffraction investigation of strains in silicon nanowires obtained by gold catalytic growth

mean thickness of about 1 to 2 nm. If this were the case, the contrast between the fringes would be less marked. We then performed Grazing Incident X-Ray Diffraction (GIXD) measurements. Typical diffraction profiles are shown in Figure 4. The diffracted intensity is plotted against the scattering vector q along the in-plane direction <300> (of the hexagonal system) for the <111> oriented silicon wafer. The profile reveals a narrow peak (Sub), arising from diffraction by the silicon substrate, and a broader one (SiNW) attributable to Bragg’s

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Morphological Component Analysis for the Inpainting of Grazing          Incidence X-Ray Diffraction Images Used for the Structural Characterization of Thin          Films

Morphological Component Analysis for the Inpainting of Grazing Incidence X-Ray Diffraction Images Used for the Structural Characterization of Thin Films

CONCLUSIONS AND FUTURE WORK In this study, we exploited the efficiency of the recently introduced MCA algorithm for the decomposition of images in distinct morphological components, based on the achieved sparsity in appropriate over-complete redundant transform domains, with our objective being to solve the problem of recovering the missing information in corrupted GIXD images due to potential malfunction of the detectors. The experimental evaluation using high-resolution GIXD images of thin polythiophene-based films, showed that the proposed approach is highly efficient in recovering the miss- ing information in the form of either randomly burned pix- els, or whole burned rows, even at the order of 50% of the total number of pixels. This led to the derivation of accurate intensity 1-D plots (linecuts) from the recovered inpainted images, that will later allow for correct data interpretation. This result can be of high impact in scattering and imaging techniques applied for materials characterization, since it indicates that the proposed MCA-based inpainting approach weakens the necessity for long acquisition times or repeating experiments, especially in synchrotron-based experiments, related to inferior detector performance during the acquisi- tion process.
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Multireflection grazing incidence diffraction used for stress measurementsin surface layers

Multireflection grazing incidence diffraction used for stress measurementsin surface layers

1. Introduction The geometry based on the multire flection grazing incidence X-ray diffraction (named the MGIXD method) was applied to mea- sure the gradient of residual stresses in surface layers [1 –3] . When the non-symmetrical diffraction, with small incident angle ( α), is used the penetration depth of X ray radiation (limited by absorption) depends mostly on the long path of incident beam ( Fig. 1 ). However, to determine stresses it is necessary to measure interplanar spacing for different orientations of the scattering vector (characterized by ψ angle). In the case of MGIXD method, the incident angle (α) has to be constant, therefore the diffraction angle 2 θ has to be varied in order to collect data for different orientations of the scattering vector. It means, that for the same wavelength we have to measure diffrac- tion peaks for many re flections hkl.
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Neutron and X-ray Scattering for Biophysics and Biotechnology: Examples of Self-Assembled Lipid Systems

Neutron and X-ray Scattering for Biophysics and Biotechnology: Examples of Self-Assembled Lipid Systems

5 Conclusions Diffraction, scattering and reflectometry have become indis- pensable tools for the identification of lipid phases and measurement of their structural dimensions. In this brief review, we have highlighted the main scattering techniques employed in soft materials research. Lamellar ordering can be easily used to identify the length scales of the ordered system by diffraction, and with sufficient pseudo crystalline order. Even crystallo- graphic techniques can be used to determine structure on the nanometre scale. In the absence of order, small angle scattering can be employed, and with judicious use of contrast enhance- ment, it can identify the shapes and sizes of mesophases present in most lipid nanoparticles. Finally, lipids at surfaces can be studied by reflectometry and grazing incidence diffraction. We have illustrated each technique with some papers that have used scattering or diffraction as a matter of course in the last couple of years. These experiments cover a range of disciplines, from pure biophysics to applications of biotechnology affecting our daily lives.
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Multireflection grazing-incidence X-ray diffraction: A new approach to experimental data analysis

Multireflection grazing-incidence X-ray diffraction: A new approach to experimental data analysis

hkl 2 sin  sin 2 : ð5Þ The values of the XSFs or XECs can be evaluated experi- mentally by applying known external loads to the sample and measuring the lattice strains for different orientations of the scattering vector. Alternatively, the XSFs or XECs can be calculated from single-crystal elastic constants (SECs) using a chosen model of crystallite interaction (Do¨lle, 1979; Do¨lle & Cohen, 1980; Barral et al., 1987; Brakman, 1987; Baczman´ski et al., 1993, 2003; Matthies et al., 1994; Welzel et al., 2005). The Voigt (1928) and Reuss (1929) methods for calculation of the XECs or XSFs are based on the hypothesis of strain or stress homogeneity in the considered volume, respectively, and this assumption can be applied to quasi-isotropic and textured polycrystalline materials. However, in order to account for the interaction between grains in the calculations, it is necessary to use, for example, the Eshelby–Kro¨ner method (Kro¨ner, 1961), in which the grains are approximated by ellipsoidal inclusions (Eshelby, 1957) embedded in a homogeneous medium. In addition, to take into account the direction-dependent inter- action between grains, two approaches can be used. The first was given by Vook & Witt (1965) and developed by van Leeuwen et al. (1999) and Welzel & Mittemeijer (2003) for columnar grains in the surface layer. In this approach, grains having dimensions equal to the thickness of the film exhibit the same in-plane strain (a Voigt-type behaviour), whereas they can deform freely in the direction perpendicular to the surface (a Reuss-type behaviour). The second approach, called the free-surface model, was proposed by Baczmanski et al. (2008) for grains placed close to the sample surface. Simi- larly as in the Vook–Witt model, it was assumed that grains can freely deform in the direction normal to the surface (Reuss-type behaviour), while the in-plane interaction is Figure 1
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Characterizing plasma conditions in radiatively heated solid-density samples with x-ray Thomson scattering

Characterizing plasma conditions in radiatively heated solid-density samples with x-ray Thomson scattering

over-predict the temperatures reached in the centers of the cylinders. This platform can be extended to understand better the mechanism of radiative heating, as well as the properties of warm dense matter. Systematic studies could be performed to determine how parameters such as x-ray converter foil thickness, x-ray converter foil material, laser drive-time, and laser intensity affect the temperatures reached in the sample. In addition, temperatures in the sample could be increased to measure properties such as the onset of K-shell ioniza- tion in warm dense matter. The radius of the cylinder could be decreased to increase the sample temperature, or more beams used to heat the x-ray converter foil. Future exper- iments will further improve the error bars on the returned plasma parameters by increasing the signal-to-noise ratio of the measurement, presumably by adding more lasers to heat the x-ray backlighter or by summing repeated measurements. In addition, measurements at higher temperatures will be more accurate as the width of the inelastic Compton feature becomes more sensitive to electron temperature when the temperature exceeds the Fermi temperature.
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TiC-carbide derived carbon electrolyte adsorption study by ways of X-ray scattering analysis

TiC-carbide derived carbon electrolyte adsorption study by ways of X-ray scattering analysis

Barbara Daffos 1,2 • Pierre-Louis Taberna 1,2 • Patrice Simon 1,2 Abstract Understanding ion adsorption in nanoporous carbon electrodes is of great importance for designing the next-generation of high energy density electrical double- layer capacitors. In this work, X-ray scattering is used for investigating the impregnation of nanoporous carbons with electrolytes in the absence of applied potential. We are able to show that interactions between the carbon surface and electrolytes allow adsorption to take place in sub-nano- pores, thus confirming experimentally for the first time the results predicted by molecular dynamic simulations.
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The X-ray universe

The X-ray universe

THE X-RAY UNIVERSE Ken Tapping, 7 th February, 2017 There is a really interesting astronomical video circulating around the research community. It was obtained using the Chandra orbiting observatory, and shows a piece of sky as we would see it if we had X-ray eyes. It comprises a sequence of images accumulated over three months and is presented as a one-minute time-lapse movie. It shows what looks like a piece of starry sky about a third the size of the Full Moon. Some of the “stars” shine steadily; others twinkle and flash. However, the twinkling of the stars we see in the night sky is due to turbulence in the atmosphere. The Chandra observatory lies out in space, well above the atmosphere, so those dots are truly flashing. Moreover, we are looking at the X-ray sky, and those dots are not stars.
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Low-angle neutron and x-ray scattering of hydrogenated and deuterated Mo/V superlattices

Low-angle neutron and x-ray scattering of hydrogenated and deuterated Mo/V superlattices

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Chemical composition of nano-phases studied by anomalous small-angle X-ray scattering (ASAXS)

Chemical composition of nano-phases studied by anomalous small-angle X-ray scattering (ASAXS)

MAUGIS, Sébastien JEGOU, Laurent BARRALLIER - Chemical composition of nano-phases studied by anomalous small-angle X-ray scattering (ASAXS) - 2014.. Any correspondence concerning this se[r]

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Magnetic spectral response and lattice properties in mixed-valence Sm1-x Yx S solid solutions studied with x-ray diffraction, x-ray absorption spectroscopy, and inelastic neutron scattering

Magnetic spectral response and lattice properties in mixed-valence Sm1-x Yx S solid solutions studied with x-ray diffraction, x-ray absorption spectroscopy, and inelastic neutron scattering

involve the p orbitals from boron. In the following, we report a detailed INS study of Sm 1−x Y x S (0 ≤ x ≤ 0.45) performed on both pow- der and single-crystal samples, covering a wide tempera- ture range, and including measurements under an applied pressure. We also present x-ray diffraction data on the temperature dependence of the lattice constant, the ther- mal expansion coefficient, and the Sm mean-square dis- placements, as well as the temperature evolution of the Sm valence obtained by x-ray absorption (XAS) spec- troscopy. A comprehensive analysis of these different re- sults allows us to make a connection between dynamical characteristics of the material and its valence state, and provides clear evidence for the major role played by ex- change interactions in the properties of the ground state.
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Small-angle X-ray scattering and small-angle neutron scattering studies of liquid-crystalline halato(semi)telechelic polymers

Small-angle X-ray scattering and small-angle neutron scattering studies of liquid-crystalline halato(semi)telechelic polymers

systematic observation of a greater dIP in the Pis (7.57 and 8.48 nm) relative to the PSs (6 44 and 6.83 nm). These experimental observations suggest that, all other conditions being constant, polyisoprene chains yield a greater dIP than the corresponding polystyrene, whatever the functionality of the chain. In all cases, dIP is greater than the observed value for the PIS2Xs. Combining all the previous results shows that the greater distance between the ionic aggregates in the present study results from the replacement of the metallic cations, as previously investigated, by the mesogenic cation. The layer spacing of the mesogenic cation can be valued at about 3.2 nm, in agreement with the data published by Ujiie & Iimura (1992) on the same pure mesogenic ion analysed by wide-angle X-ray scattering.
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Applications of Neutron and X-ray Scattering to the Study of Biologically Relevant Model Membranes

Applications of Neutron and X-ray Scattering to the Study of Biologically Relevant Model Membranes

where the constants A fl and  fl are derived from the osmotic pressure dependence of the line-shape parameter  (Eq. (1) ) through high-resolution X-ray diffraction experiments. It is clear, therefore, that even for neutral multibilayer systems, there are a number of parameters that need to be determined from pressure isotherms. Membrane thickness and bilayer separation are derived from the scattering length density profiles. Fortunately, d B remains essentially constant up to osmotic pressures of ∼20 atm. Thus, d W can be inferred directly from the lamellar repeat distance once d B is known for a given ˘. The constants P h and  h are best determined at intermediate osmotic pressures (i.e. in the approx- imate range of 10–20 atm), which is where the hydration force dominates the repulsive interactions, and the applied ˘ modulates the attractive interactions. van der Waals interaction and fluctua- tion forces are prominent at low ˘’s, and there are basically two strategies used to elucidate them. One is to fix the Hamaker con- stant and fit for the bending rigidity ( Pabst et al., 2007a, 2009 ), while
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Coupling high throughput microfluidics and small-angle x-ray scattering to study protein crystallization from solution

Coupling high throughput microfluidics and small-angle x-ray scattering to study protein crystallization from solution

In order to gather high quality data (by acquiring only the SAXS data inside the droplets) and to reduce radiation damage of the oil and the protein, the X-ray beam, the CCD detector, and the droplets were synchronized. The synchronization is based on real time image processing (developed in OpenCV and Matlab). Brie fly, the template matching algorithm detects the front of the droplet flowing in the capillary and sends a TTL signal to the beamline shutter and the Pilatus camera to trigger the acquisition. Depending on the size and the speed of the droplets, this results in the acquisition of one to three SAXS signals per droplet. In addition, this approach allows us to avoid shooting droplet interfaces which produces a huge SAXS signal at very low angles and can cause miss interpretations of the data.
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Scattering density profile model of POPG bilayers as determined by molecular dynamics simulations and small-angle neutron and x-ray scattering experiments

Scattering density profile model of POPG bilayers as determined by molecular dynamics simulations and small-angle neutron and x-ray scattering experiments

Small-Angle X-ray Scattering. X-ray data were taken at the G-1 station located at the Cornell High Energy Synchrotron Source (CHESS). A 1.18 Å wavelength (λ) X-ray beam of dimensions 0.24  0.24 mm 2 was detected using a 1024  1024 pixel array FLICAM charge-coupled device (CCD) with 71 μm linear dimension pixels. The sample-to-detector distance (SDD) was 423.6 mm, as determined using silver behenate (d-spacing of 58.367 Å). Samples were contained in 1.5 mm quartz capillaries placed in a temperature-controlled, multiple position sample holder. Two-dimensional (2D) images were dezingered using two consecu- tive 10 s exposures and corrected using calibration files supplied by CHESS. Data sets were normalized using the incident beam intensity as measured by an ion chamber. Background scattering resulting from water and air was subtracted according to the procedure described in ref 21. An additional linear function was used to correct for an unaccountable rise in background scattering, most likely due to an increase in the sample-to-detector path length at higher angles, while an absorption correction was found unnecessary. 4 Finally, the experi- mental scattering form factor moduli were obtained using
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Structural analyses by advanced X-ray scattering on GaP layers epitaxially grown on silicon for integrated photonic applications

Structural analyses by advanced X-ray scattering on GaP layers epitaxially grown on silicon for integrated photonic applications

au-dessus de 500°C qui confirme ce qui a été reporté dans la litérature 7,8 Un scénario de formation des micro-macles est proposé via la formation de lacunes ainsi qu’une énergie d’activation mise en jeu pour éviter ce phénomène. Cependant, la croissance à haute température génère une surface très rugueuse qui ne peut être utilisée ensuite pour la réalisation de dispositifs. Une procédure de croissance dite « MEE » (Migration Enhanced Epitaxy qui consiste à déposer de manière alternée Ga et P) a été développée et optimisée par caractérisation DRX et AFM. Les échantillons « MEE » présentent après optimisation et pour une même épaisseur déposée, un volume maclé beaucoup plus faible et une surface beaucoup plus lisse que les meilleurs échantillons réalisés par MBE classique à même température de croissance. Enfin, la structure de la couche GaP/Si a été optimisée par une séquence de croissance de deux étapes: une première croissance de 40 monocouches de GaP à 350 °C (basse température) par la MEE suivie d’une deuxième croissance de 40 nm de GaP à 500 °C (haute température) par la MBE. La figure 2 a) représente la figure de pôle de cet échantillon (S1330), où l’intensité de micro-macles est très faible. La faction volumique de micro-macles est évalué à inférieur à 1% (la limite de résolution de ces méthodes par diffraction des rayons X à base résolution). La rugosité surfacique de cet échantillon est mesurée à 0.3 nm (la limite de sensibilité de cette technique d’AFM est de l’ordre de 0.15 nm) par l’image d’AFM comme présenté dans la figure 2 b).
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Structural analyses by advanced X-ray scattering on GaP layers epitaxially grown on silicon for integrated photonic applications

Structural analyses by advanced X-ray scattering on GaP layers epitaxially grown on silicon for integrated photonic applications

au-dessus de 500°C qui confirme ce qui a été reporté dans la litérature 7,8 Un scénario de formation des micro-macles est proposé via la formation de lacunes ainsi qu’une énergie d’activation mise en jeu pour éviter ce phénomène. Cependant, la croissance à haute température génère une surface très rugueuse qui ne peut être utilisée ensuite pour la réalisation de dispositifs. Une procédure de croissance dite « MEE » (Migration Enhanced Epitaxy qui consiste à déposer de manière alternée Ga et P) a été développée et optimisée par caractérisation DRX et AFM. Les échantillons « MEE » présentent après optimisation et pour une même épaisseur déposée, un volume maclé beaucoup plus faible et une surface beaucoup plus lisse que les meilleurs échantillons réalisés par MBE classique à même température de croissance. Enfin, la structure de la couche GaP/Si a été optimisée par une séquence de croissance de deux étapes: une première croissance de 40 monocouches de GaP à 350 °C (basse température) par la MEE suivie d’une deuxième croissance de 40 nm de GaP à 500 °C (haute température) par la MBE. La figure 2 a) représente la figure de pôle de cet échantillon (S1330), où l’intensité de micro-macles est très faible. La faction volumique de micro-macles est évalué à inférieur à 1% (la limite de résolution de ces méthodes par diffraction des rayons X à base résolution). La rugosité surfacique de cet échantillon est mesurée à 0.3 nm (la limite de sensibilité de cette technique d’AFM est de l’ordre de 0.15 nm) par l’image d’AFM comme présenté dans la figure 2 b).
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