Scanning X-ray Microdiffraction Research Articles

Characterization of morphology and hydration products of high-volume fly ash paste by monochromatic scanning x-ray micro-diffraction (μ-SXRD)

The present study focuses on identification and micro-structural characterization of the hydration products formed in high-volume fly ash (HVFA)/portland cement (PC) systems using monochromatic scanning x-ray micro-diffraction (μ-SXRD) and SEM-EDS. Pastes with up to 80% fly ash replacement were studied. Phase maps for HVFA samples using μ-SXRD patterns prove that μ-SXRD is an effective method to identify and visualize the distribution of phases in the matrix. μ-SXRD and SEM-EDS analysis shows that the C-S-H formed in HVFA system containing 50% or more of fly ash has a similar structure as C-S-H(I) with comparatively lower Ca/Si ratio than the one produced in PC system. Moreover, coexistence of C-S-H(I) and strätlingite is observed in the system containing 80% of fly ash, confirming that the amount of alumina and silicate phases provided by the fly ash is a major factor for the formation of C-S-H(I) and strätlingite in HVFA system.

Tissue specific specialization of the nanoscale architecture of Arabidopsis

The Arabidopsis stem is composed of five tissues - the pith, xylem, phloem, cortex and epidermis - each of which fulfills specific roles in support of the growth and survival of the organism. The lignocellulosic scaffolding of cell walls is specialized to provide optimal support for the diverse functional roles of these layers, but little is known about this specialization. X-ray scattering can be used to study this tissue-specific diversity because the cellulosic components of the cell walls give rise to recognizable scattering features interpretable in terms of the underlying molecular architecture and distinct from the largely unoriented scatter from other constituents. Here we use scanning X-ray microdiffraction from thin sections to characterize the diversity of molecular architecture in the Arabidopsis stem and correlate that diversity to the functional roles the distinct tissues of the stem play in the growth and survival of the organism.

Accelerating crystal–crystal transition in poly(1-butene) with two-step crystallization: An in-situ microscopic infrared imaging and microbeam X-ray diffraction study

The crystal–crystal transition of isotactic polybutene-1 (iPB-1) from form II to I at room temperature is investigated with in-situ Fourier transform infrared spectroscopy (FTIR), Fourier transformation infrared microspectroscopic imaging (FTIRI) and synchrotron radiation scanning X-ray micro-diffraction (SR-μSXRD). The transition rate from form II to I shows a non-monotonic correlation with crystallization temperature on samples isothermally crystallized at different single temperatures. An abnormal spatial distribution of transition rate is observed in samples prepared with a two-step crystallization approach, in which samples crystallized at high temperature and then were quenched to low temperatures for further crystallization. A maximum transition rate occurs around the edge of large spherulites formed at high temperature, which cannot be interpreted by the effect of crystallization temperature alone. The accelerated transition rate in this region is attributed to internal stress, where an intermediate state, revealed with SR-μSXRD, may be the structural origin for the fast transition rate from form II to I.

Understanding crystallization features of P(VDF-TrFE) copolymers under confinement to optimize ferroelectricity in nanostructures

The successful development of ferroelectric polymer devices depends on the effective fabrication of polar ferroelectric crystalline nanostructures. We demonstrate, by scanning X-ray microdiffraction using synchrotron light, the heterogeneous character of high aspect ratio one-dimensional nanoarrays of poly(vinylidene fluoride-co-trifluoroethylene) copolymers supported by a residual polymer film. They were prepared by melt and solution template wetting, using porous anodic aluminum oxide as a template. The spatial evolution of different polymorphs from the mixture of paraelectric and ferroelectric crystal forms (residual film) to the pure ferroelectric form (nanoarray) is evidenced for the samples prepared by solution wetting. However, for samples prepared by melt wetting the ferroelectric phase is exclusively obtained in both the residual film and nanoarray. The crystal nuclei formed in the polymer film connected to the nanoarray play a key role in determining the formation of a crystallinity distribution gradient, where the crystallinity decreases along the first 5-10 microns in the nanorods reaching a steady value afterwards. The minimum decrease in crystallinity is revealed for samples prepared by melt wetting. The results reported in this work endeavour to enhance the understanding of crystallization under confinement for ferroelectric copolymers and reveal the parameters for improving the ferroelectric character of polymer nanostructures.

Relationship between planar GaAs nanowire growth direction and substrate orientation

Planar GaAs nanowires are epitaxially grown on GaAs substrates of various orientations, via the Au-catalyzed vapor–liquid–solid mechanism using metal organic chemical vapor deposition. The nanowire geometry and growth direction are examined using scanning electron microscopy and x-ray microdiffraction. A hypothesis relating the planar nanowire growth direction to the surface projections of 〈111〉 B crystal directions is proposed. GaAs planar nanowire growth on vicinal substrates is performed to test this hypothesis. Good agreement between the experimental results and the projection model is found.

Conformational Ordering on the Growth Front of Isotactic Polypropylene Spherulite

The growth front of isotactic polypropylene (iPP) spherulites is studied with series of in-situ microanalyzing techniques: conventional source infrared microspectroscopic (CS-μIR), polarized infrared microspectroscopic imaging (SR-μPIR), and scanning X-ray microdiffraction (SR-μSXRD). By SR-μSXRD, the actual growth front boundary of spherulite was clearly defined, which is the boundary observed with an optical microscope. Measurements of CS-μIR and SR-μPIR on growing spherulites reveal that a growth front layer (GFL) with high content of conformational ordered long helices exists outside the growth front of spheurlite, which has a thickness up to 30 μm above 142 °C. These long helices preferentially orient perpendicular to the radial direction of spherulite, whose growth fashion seems correlating with the growth of spherulite.

Optimum inhomogeneity of local lattice distortions in La 2 CuO 4+ y

Electronic functionalities in materials from silicon to transition metal oxides are, to a large extent, controlled by defects and their relative arrangement. Outstanding examples are the oxides of copper, where defect order is correlated with their high superconducting transition temperatures. The oxygen defect order can be highly inhomogeneous, even in optimal superconducting samples, which raises the question of the nature of the sample regions where the order does not exist but which nonetheless form the "glue" binding the ordered regions together. Here we use scanning X-ray microdiffraction (with a beam 300 nm in diameter) to show that for La(2)CuO(4+y), the glue regions contain incommensurate modulated local lattice distortions, whose spatial extent is most pronounced for the best superconducting samples. For an underdoped single crystal with mobile oxygen interstitials in the spacer La(2)O(2+y) layers intercalated between the CuO(2) layers, the incommensurate modulated local lattice distortions form droplets anticorrelated with the ordered oxygen interstitials, and whose spatial extent is most pronounced for the best superconducting samples. In this simplest of high temperature superconductors, there are therefore not one, but two networks of ordered defects which can be tuned to achieve optimal superconductivity. For a given stoichiometry, the highest transition temperature is obtained when both the ordered oxygen and lattice defects form fractal patterns, as opposed to appearing in isolated spots. We speculate that the relationship between material complexity and superconducting transition temperature T(c) is actually underpinned by a fundamental relation between T(c) and the distribution of ordered defect networks supported by the materials.

Bacterially mediated mineralisation processes lead to biodeterioration of artworks in Maltese catacombs

Mineral structures formed by bacterial and microalgal biofilms growing on the archaeological surface in Maltese hypogea were studied using Energy Dispersive X-Ray Spectroscopy (EDS) coupled to Environmental Scanning Electron Microscopy (ESEM), X-ray micro-diffraction (XRD) and X-ray fluorescence (XRF). These techniques have shown that mineral structures having different morphologies and chemical composition were associated with the microorganisms in the subaerophytic biofilm. Salt efflorescences and mineral deposits on the archaeological surface were often formed from gypsum (CaSO 4∙ 2H 2O), halite (NaCl) and calcite (CaCO 3). Biogenic carbonates produced by microbial activities were a common occurrence. These assumed different forms, such as the production of mineral coats around cyanobacterial sheaths and the occurrence of calcite fibres with different morphologies on the surface of the biofilms. Moreover, vaterite (CaCO 3) spherulites which appeared hollow in cross-section were observed. The presence of struvite was recorded from one catacomb site. These investigations have facilitated the study of the neoformation of metastable minerals by microbially mediated processes, which potentially contribute to a better understanding of the biodeterioration of artworks in Maltese palaeo-Christian catacombs.

Confinement-Induced One-Dimensional Ferroelectric Polymer Arrays

This work demonstrates the use of wetting nanoporous alumina template with polymer solution to produce arrays of isolated poly(vinylidene fluoride) (PVDF) ferroelectric gamma-type nanorods supported within a nonpolar alpha-structure film. The method is based upon a crystal phase transition which occurs due to PVDF confinement within alumina nanoporous. The system was studied using scanning X-ray microdiffraction (micro-XRD) that allows the solid-solid phase transition from the alpha-nonpolar crystal form (bulk) to the gamma polar ferroelectric form (nanorod array) to be spatially resolved, as well as providing crystallinity and orientation information. The results reveal that the interaction between polymer chains and the porous membrane's walls imposes a flat-on lamella growth along the nanorrods long axis, while improving crystal orientation.

Evolution of ferroelectric domain structures embedded inside polycrystalline BaTiO3 during heating

The evolution of ferroelectric domains inside a single grain of a polycrystalline BaTiO3 ceramic was investigated under quasistatic heating by using polychromatic scanning x-ray microdiffraction. Four domain orientations were observed, three of which exhibited a classic of ∼90° ferroelastic relationship. The fourth domain orientation was found to be crystallographically related with one of the other orientations by a rotation of either 180.47° or 0.47°. While heating the polycrystalline BaTiO3 from room temperature to above the Curie temperature (125 °C), all four ferroelectric domain orientations rotated toward a paraelectric cubic orientation which was found to be at an intermediate orientation relative to the four domain orientations. The crystallographic relationships of the domains with respect to paraelectric phase were explained using a domain structure model by Nepochatenko.

Keratin‐lipid structural organization in the corneous layer of snake

The shed epidermis (molt) of snakes comprises four distinct layers. The upper two layers, here considered as beta-layer, contain essentially beta-keratin. The following layer, known as mesos-layer, is similar to the human stratum corneum, and is formed by thin cells surrounded by intercellular lipids. The latter layer mainly contains alpha-keratin. In this study, the molecular assemblies of proteins and lipids contained in these layers have been analyzed in the scale of two species of snakes, the elapid Tiger snake (TS, Notechis scutatus) and the viperid Gabon viper (GV, Bitis gabonica). Scanning X-ray micro-diffraction, FTIR and Raman spectroscopies, thermal analysis, and scanning electron microscopy experiments confirm the presence of the three layers in the GV skin scale. Conversely, in the TS molt a typical alpha-keratin layer appears to be absent. In the latter, experimental data suggest the presence of two domains similar to those found in the lipid intercellular matrix of stratum corneum. X-ray diffraction data also allow to determine the relative orientation of keratins and lipids. The keratin fibrils are randomly oriented inside the layers parallel to the surface of scales while the lipids are organized in lamellar structures having aliphatic chains normal to the scale surface. The high ordered lipid organization in the mature mesos layer probably increases its effectiveness in limiting water-loss.

Determination of Work Functions in the $\hbox{Ta}_{1 - x}\hbox{Al}_{x}\hbox{N}_{y}/\hbox{HfO}_{2}$ Advanced Gate Stack Using Combinatorial Methodology

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Combinatorial methodology enables the generation of comprehensive and consistent data sets, compared with the “one-composition-at-a-time” approach. We demonstrate, for the first time, the combinatorial methodology applied to the work function <formula formulatype="inline"><tex Notation="TeX">$(\Phi_{m})$</tex></formula> extraction for <formula formulatype="inline"><tex Notation="TeX">$\hbox{Ta}_{1 - x}\hbox{Al}_{x}\hbox{N}_{y}$</tex></formula> alloys as metal gates on <formula formulatype="inline"><tex Notation="TeX">$\hbox{HfO}_{2}$</tex></formula>, for complementary metal–oxide–semiconductor applications, by automated measurement of over 2000 capacitor devices. Scanning X-ray microdiffraction indicates that a solid solution exists for the <formula formulatype="inline"><tex Notation="TeX">$ \hbox{Ta}_{1 - x}\hbox{Al}_{x}\hbox{N}_{y}$</tex></formula> libraries for <formula formulatype="inline"><tex Notation="TeX">$ \hbox{0.05} \leq x \leq \hbox{0.50}$</tex></formula>. The equivalent oxide thickness maps offer a snapshot of gate stack thermal stability, which show that <formula formulatype="inline"><tex Notation="TeX">$\hbox{Ta}_{1 - x}\hbox{Al}_{x} \hbox{N}_{y}$</tex></formula> alloys are stable up to 950 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}\hbox{C}$</tex> </formula>. The <formula formulatype="inline"><tex Notation="TeX">$\Phi_{m}$</tex></formula> of the <formula formulatype="inline"> <tex Notation="TeX">$\hbox{Ta}_{1 - x}\hbox{Al}_{x}\hbox{N}_{y}$</tex></formula> libraries can be tuned as a function of gate metal composition over a wide <formula formulatype="inline"><tex Notation="TeX">$(\hbox{0.05} \leq x \leq \hbox{0.50})$</tex></formula> composition range, as well as by annealing. We suggest that <formula formulatype="inline"><tex Notation="TeX">$\hbox{Ta}_{0.9} \hbox{Al}_{0.1}\hbox{N}_{1.24}$</tex></formula> gate metal electrodes may be useful for p-channel metal–oxide–semiconductor applica</para>

S25 The Reverse of Triaxial Strain Fields in a Multiferroic BiFeO3 Thin Film As Studied Using Scanning X-ray Microdiffraction

The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding micro-region. Here we report a 2D quantitative mapping of the grain orientation and the local triaxial strain-field in a 250nm-thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 5x10 and 6x10 and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region at room temperature. We have performed a 2D quantitative mapping of the grain orientation and the local triaxial strain-field in a BiFeO3 thin film at room temperature, 373K, 673K by using a synchrotron X-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is reversed with temperature raising, and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region.

Combinatorial Methodology for the Exploration of Metal Gate Electrodes on HfO2 for the Advanced Gate Stack

Combinatorial methodology offers an efficient platform to accelerate the exploration of new materials. We demonstrate the effectiveness of this technique on the study of new metal gates for the advanced gate stack. We report two examples, Ni-Ti-Pt ternary composition spreads, and Ta1-xAlxNy binary composition spreads, using a combinatorial sputtering tool. For the Ni-Ti-Pt library, wavelength dispersive spectroscopy (WDS), and scanning x-ray microdiffraction spectroscopy were used to determine compositions, and structures, respectively. Scanning Kelvin probe microscopy (SKPM) was used to measure work functions (Φm) directly. Our results show Φm variation is consistent with the variation for the corresponding bulk values. For the Ta1-xAlxNy metal gate electrodes, the extracted equivalent oxide thickness (EOT) map suggests thermal stability of the stack, and flat-band voltage shift (ΔVfb) varied systematically as per our expectation.

Scanning x-ray microdiffraction of optically manipulated liposomes

We show optical tweezers manipulation of individual micron-sized samples investigating at the same time their inner nanostructure by synchrotron diffraction experiments. The validity of this technique is demonstrated for clusters of multilamellar liposomes trapped in single and multiple positions in the optical path of a microfocused x-ray beam and analyzed in a microscanning mode. The signal to background ratio of the first order peak shows that single liposome measurements are feasible. Multiple trapping by means of diffractive optical elements is demonstrated as an effective manipulation tool for future x-ray diffraction studies of the interaction between different sample entities.

Skin-core structure and bimodal Weibull distribution of the strength of carbon fibers

The bimodal Weibull parameters of polyacrylonitrile-based carbon fibers were obtained from the fiber-bundle tension test. The bimodality increases with increasing high temperature treatment up to 2100 °C and then decreases for the highest temperature treatment of 2400 °C. The local structure of the fibers was investigated by scanning X-ray microdiffraction using synchrotron radiation. This enables the mapping of the atomistic structure across the fiber with a position resolution of 100 nm. The mechanical bimodality is attributed to a reversal of the observed skin structure from less orientation to higher orientation as compared to the core.

Two-dimensional mapping of triaxial strain fields in a multiferroic BiFeO3 thin film using scanning x-ray microdiffraction

The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding microregion. Here the authors report a 2D quantitative mapping of the grain orientation and the local triaxial strain field in a 250nm thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 5×10−3 and 6×10−3 and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region.

Mapping fibre orientation in complex-shaped biological systems with micrometre resolution by scanning X-ray microdiffraction

A fully automated procedure to extract and to image local fibre orientation in biological tissues from scanning X-ray diffraction is presented. The preferred chitin fibre orientation in the flow sensing system of crickets is determined with high spatial resolution by applying synchrotron radiation based X-ray microbeam diffraction in conjunction with advanced sample sectioning using a UV micro-laser. The data analysis is based on an automated detection of azimuthal diffraction maxima after 2D convolution filtering (smoothing) of the 2D diffraction patterns. Under the assumption of crystallographic fibre symmetry around the morphological fibre axis, the evaluation method allows mapping the three-dimensional orientation of the fibre axes in space. The resulting two-dimensional maps of the local fibre orientations – together with the complex shape of the flow sensing system – may be useful for a better understanding of the mechanical optimization of such tissues.

A new batch-processing data-reduction application for X-ray diffraction data

Modern synchrotron radiation facility beamlines offer high-brilliance beams and sensitive area detectors. Consequently, experiments such as scanning X-ray microdiffraction can generate large data sets within relatively short time periods. In these specialist fields there are currently very few automated data-treatment solutions to tackle the large data sets produced. Where there is existing software, it is either insufficiently specialized or cannot be operated in a batch-wise processing mode. As a result, a large gap exists between the rate at which X-ray diffraction data can be generated and the rate at which they can be realistically analysed. This article describes a new software application to perform batch-wise data reduction. It is designed to operate in combination with the commonly usedFit2Dprogram. Through the use of intuitive file selection, numerous processing lists and a generic operation sequence, it is capable of the batch-wise reduction of up to 60 000 diffraction patterns during each treatment session. It can perform automated intensity corrections to large data series, perform advanced background-subtraction operations and automatically organizes results. Integration limits can be set graphically on-screen, uniquely derived from existing peak positions or globally calculated from user-supplied values. The software represents a working solution to a hitherto unsolved problem.

Application of the White/Monochromatic X-Ray μ-Diffraction Technique to the Study of Texture and Triaxial Strain at the Submicron Level

A scanning X-ray microdiffraction beamline using white or monochromatic beam has been recently made available to the user’s community at the Advanced Light Source, Berkeley, USA. Samples are scanned under an X-ray beam with size ranging from 15 microns down to less than a micron, and 2D diffraction patterns are collected at each step. A specifically written software allows for the full treatments of these patterns to obtain as outputs high spatial resolution grain orientation, strain/stress or mineral species distribution maps. The range of applications of this technique goes from the study of the mechanical properties of thin films to the understanding of trace elements speciation in environmental sciences.