Multiple X-ray Diffraction Research Articles

Characterization and Application of Bioactive Glass and Chitosan Nanoparticles for Tooth Enamel Remineralization

We investigated the remineralization of demineralized enamel surfaces through the application of bioactive glass (BG) and chitosan nanoparticles (CNPs). BG and CNPs were immersed in artificial saliva for 7 days. The resulting crystals were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Embedded enamel blocks were immersed in demineralization solution and then classified into five treatment groups: (1) No material applied; (2) toothpaste containing NaF (F); (3) CNP hydrogel; (4) distilled water slurry containing BG; and (5) CNP hydrogel containing BG (BG-CNP). The enamel blocks were immersed in an artificial saliva solution for 1 month; each material was applied twice per day. Nanoindentation testing of enamel surfaces was performed during the immersion period. We found that unidirectional rod-shaped crystals formed in the artificial saliva solutions treated with BG and BG-CNP, showing multiple XRD peaks for hydroxyapatite. The mechanical properties of enamel surfaces decreased markedly following immersion in the demineralization solution, and significantly recovered after 1 month of BG-CNP and BG treatment compared to other the specimens. Porous demineralized enamel surfaces were filled with a remineralization layer after immersion in saliva and application of NaF, BG, and CNP-BG. Thus, daily application of CNP-BG or BG facilitates enamel remineralization.

Environmentally stable lead-free cesium bismuth iodide (Cs3Bi2I9) perovskite: Synthesis to solar cell application

In this paper, we synthesized lead-free cesium bismuth iodide (Cs3Bi2I9) perovskite films by solution process using one-step spin-coating technique. Formation of Cs3Bi2I9 perovskite was confirmed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy analysis. The XRD analysis showed that all Cs3Bi2I9 perovskite films were polycrystalline in nature, with hexagonal crystal structure and preferred-orientation along (006) direction. The environmental stability of Cs3Bi2I9 perovskite was confirmed by XRD analysis and UV–visible spectroscopy. Multiple XRD and UV–Vis spectra taken after long time spans revealed the stable nature of Cs3Bi2I9 perovskite films. The UV–visible spectroscopy and photoluminescence analysis showed that the perovskite films absorbed strongly in the visible region and had an optical band gap of ~2.1 eV. Surface morphology of Cs3Bi2I9 perovskite over the entire substrate surface was investigated using scanning electron microscopy. Thermo-gravimetric analysis showed that Cs3Bi2I9 perovskite was thermally stable up to ∼ 420 °C. Finally, solar cells fabricated using Cs3Bi2I9 perovskite material showed maximum power conversion efficiency (PCE) of 0.17%, with short circuit current density of 1.43 mA/cm2, open circuit voltage of 0.37 V and fill factor of 32%. Applying compositional engineering and optimizing the device structure should further improve the PCE. These results are a significant step toward fabrication of Cs3Bi2I9 perovskite-based solar cells.

Assessment of phase transition and thermal expansion coefficients by means of secondary multiple reflections of Renninger scans

This paper reports the successful extension of the basis of the X-ray multiple diffraction phenomenon in the assessment of structural phase transitions and the determination of thermal expansion coefficients along three crystallographic directions, using synchrotron radiation Renninger scans. Suitable simultaneous four-beam cases have accurately resolved the lattice-parameter variation in a nearly perfect single-crystal Rochelle salt using a high-stability temperature apparatus. Secondary reflections observed in the Renninger patterns, chosen by their sensitivity to the shifts in angular position as a function of temperature, have allowed the detection of a monoclinic to orthorhombic phase transition, as well as subtle expansions of all the basic lattice parameters, i.e. without having to carry out measurements on each crystal axis. The thermal expansion coefficients have been estimated from the linear fit of the temperature dependence of the lattice parameters, and are in agreement with those reported in the literature.

Characterization of the Structural Environment of Dithionate Ions Associated with Their Role in the Crystal Habit Modification of Sodium Chlorate

Sodium chlorate (NaClO3) crystals change from a cuboid to a tetrahedron of {111} morphology when crystallized in the presence of sodium dithionate (Na2S2O6) impurity. Polarized extended X-ray absorption fine structure at the S K-edge, used to probe the local structure around this impurity with respect to its orientation within the bulk crystal lattice, reveals that the S–S bond of the S2O62– ions is closely aligned along the / lattice direction. High resolution diffraction studies using X-ray multiple diffraction reveal growth-induced anisotropy in the doped crystals associated with subtle lattice distortions in the symmetry-independent {111} and {111} growth sectors. The data are consistent with a mechanistic model involving the creation of lattice vacancies and the substitution of one of the SO3 anionic groups of the dopant ion for a host ClO3 ion when incorporated at the {111} growth interface with the other SO3 group substituting for one or more anionic sites in the succeeding gr...

Structure diagnostics of heterostructures and multi-layered systems by X-ray multiple diffraction.

This article presents the results of research on multi-layered heterostructures by a modified calculation technique of multiple X-ray diffraction. The Al x In1-x Sb heterostructure and a Zn(Mn)Se/GaAs(001) multi-layered system were used as models to specify conditions for cases of coincidental coplanar three-beam or coincidental noncoplanar four-beam X-ray diffraction. These conditions provide the means for a high-precision determination of lattice parameters and strain anisotropy in layers.

Experimental evidence of transition between dynamical and kinematical diffraction regimes in ion-implanted Si observed through X-ray multiple-beam diffraction mappings

In this paper, the dependence of a Laue diffraction streak on the crystalline perfection of Xe-implanted Si(001) substrates is presented, based on the observation in the X-ray multiple diffraction (XRMD) mappings, as an experimental evidence of the transition between dynamical and kinematical diffraction regimes. A direct observation of the implanted region by transmission electron microscopy revealed an amorphous Si layer, which recrystallizes into a heavily twinned and faulted microstructure after thermal treatment at 800 °C. Besides the lattice damages, the annealing induces the formation of Xe bubbles. Both singularly affect the XRMD pattern, primarily the four-fold streaks profile of the (000)(002)(11¯1¯)(11¯3) four-beam simultaneous case when compared with the pristine Si pattern, highlighting the intra- and inter-block diffractions and the role played by the primary extinction effect. Such features provide information on the dominant diffraction regime. The findings are also discussed and compared to the conventional reciprocal space mappings via the asymmetric Si(113) reflection.

A study of X-ray multiple diffraction by means of section topography.

The results of theoretical and experimental study are presented for the question of how the X-ray multiple diffraction in a silicon single crystal influences the interference fringes of section topography for the 400 reflection in the Laue case. Two different cases of multiple diffraction are discovered for zero and very small values of the azimuthal angle for the sample in the form of a plate with the surface normal to the 001 direction. The cases are seen on the same topogram without rotation of the crystal. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. It is shown that the structure of interference fringes on the section topogram in the region of multiple diffraction becomes more complicated. It has a very sharp dependence on the azimuthal angle. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle. Nevertheless, the characteristic inclination of the interference fringes on the tails of the multiple diffraction region is easily seen. This phenomenon corresponds completely to the computer simulations.

X-ray n-beam diffraction to study nanodefects of Xe+ implantation in Si(001)

Investigations about the nanocavities/bubbles formation by inert gas ion implantation in Si matrix and its properties have constituted an ongoing challenge in material science. Dislocation/extended defects (likely the {113} defects) are produced by post-implant annealing, which affect directly the nanocavities/bubbles structural evolution. In this work, the formation of defects induced by Xenon gas ion implantation in a Si sample (#Si-pristine) was studied by high-resolution reciprocal space mappings (RSM) and non-conventional X-ray Multiple Diffraction (XRMD) using synchrotron radiation. For this, Xe+ ions (80 keV; 5x1015 cm-2) were implanted in Si(001) at room temperature. Subsequently, the as-implanted samples were thermally annealed in air atmosphere at 600, 700 and 800 °C for 30 min in order to nucleate Xe nanobubbles that were detected in annealed samples by TEM images. Differences in the diffracted intensity pattern, along the crystal truncation rod, were detected in the Si (113) asymmetrical RSM for as-implanted and annealed samples, in comparison to pristine Si, indicating defect contribution along in-plane an out-of-plane directions. The ω(incident):Φ(azimuthal) coupled scans of two XRMD cases: 3-beam Bragg-Surface-Diffraction (BSD) (000)(002)(1-11) and the 4-beam (000)(002)(1-1-1)(1-13) have shown expected broader peaks (as-implanted sample) in comparison to the pristine sample, besides the ω-axis intensity asymmetry (c-axis strain induced). Furthermore, the analysis of all BSD mappings has provided: i) the annealing effect of reducing the lattice strain (600 and 700 °C samples), and ii) a huge surface effect through the diffuse scattering (800 °C-sample). As to the 4-beam case, a strong streak (diffraction condition trace) was observed for annealed sample patterns. This remarkable effect can be associated to the {113} defects, which are in the same direction of the secondary/coupling diffracting planes (XRMD phenomenon). It is believed that these defects break the spatial coherence, increasing the streak intensity. On the other hand, the streak is suppressed by the primary extinction effect in the pristine-Si and as-implanted samples. Financial support by Brazilian Synchrotron Light Laboratory (LNLS), CAPES, CNPq and FAPEMA.

X-ray multiple diffraction of ZnO substrates and heteroepitaxial thin films

We investigate Umweganregung reflections (X-ray multiple reflections) for , (00.3), and (00.5) for a number of wurtzite structure ZnO samples, namely various bulk crystals (substrates), two ZnO thin films and a ZnO:Mg thin film, grown by pulsed laser deposition on a-plane sapphire. Using a low divergence setup, we achieve a high angular resolution of 0.1 or better. We derive an analytical formula for peak positions as a function of wavelength and the lattice parameters a and c. The three investigated ZnO substrates exhibit all expected (kinematically allowed) reflections for Cu Kα1, Kα2, and Kβ. A lineshape analysis of the multiple reflection peaks shows that the width of certain reflections is determined by the spectral linewidth of the exciting copper lines. The thin films exhibit only slight broadening of the peaks but disappearance of several reflections. The a lattice constant can be determined from the azimuthal peak positions. Umweganregung scan for () of a hydrothermally grown ZnO substrate, excited with Cu Kα1 radiation. The pattern is symmetric with respect to zero angle representing the (10.0) azimuth.

Analyzing structure factor phases in pure and doped single crystals by synchrotron X-ray Renninger scanning

X-ray multiple diffraction has been applied to study the substitutional incorporation of Mg2+ions into NSH crystals (nickel sulfate hexahydrate, NiSO4·6H2O). Intensity profiles provide information on invariant phases, while angular positions of the multiple diffractions allow accurate determination of lattice parameters. By increasing the atomic disordering only of O2−sites in model structures of doped NSH, the sense and magnitude of induced phase shifts match those necessary to justify the observed changes in the intensity profiles. Causes of disordering and lattice parameter variation are discussed. Although the amount of extra oxygen disordering is relatively large with respect to the small difference in the ionic radii of the metallic ions, this disordering is beyond the resolution power achievable by analyzing diffracted intensities of isolated reflections, such as in standard crystallographic techniques.

High resolution X-ray diffraction, X-ray multiple diffraction and cathodoluminescence as combined tools for the characterization of substrates for epitaxy: the ZnO case

The goal of this work is to show the capability of X-ray multiple diffraction (XRMD) to be used in combination with high resolution X-ray diffraction (HRXRD) and cathodoluminescence (CL) as an easy and simple methodology to determine structural and surface defect-related characteristics of samples that could be used as substrates for epitaxial growth. For this study ZnO {0001}-oriented samples have been used in view of their use as substrates for homoepitaxy. The miscut and bending of the samples have been analyzed by measuring the position of the X-ray diffraction peaks. The presence of multiple crystallographic domains and their characteristics have been studied by HRXRD (from the allowed (0002) reflection) and XRMD (from the forbidden (0001) and (0003) reflections) through Renninger scans and omega-scans. Cathodoluminescence adds to the previous structural characterization the possibility of obtaining significant information on surface and bulk defect-related optical properties by means of probe depth modulation. Thus, the combined methodology using HRXRD, XRMD and CL shows its ability to assess the structural and surface defect-related properties of substrates, allowing an easy detection of subtle structural and surface defects that can affect the ulterior use of these substrates in epitaxial growth.

Assessment of the out-plane and in-plane ordering of high quality ZnO nanorods by X-ray multiple diffraction

ZnO nanorods grown on buffered and non buffered sapphire substrates have been investigated by X-ray multiple diffraction using Renninger scans of the ZnO(0001) and ZnO(0003) forbidden reflections. In this technique the diffracted X-ray beam is simultaneously diffracted by several sets of planes, providing information on the broadening in different directions, as well as from nanorods, and from the layer on which they grow. The intensities and angular widths of peaks obtained by azimuthal and omega scans have been analyzed, making a direct comparison with conventional measurements of the full width at half-maximum of symmetric and asymmetric reflections. The analysis leads to establish that the peaks of the Renninger scan are highly sensitive to structural characteristics, providing information related with both the out-plane and in-plane ordering of nanostructured samples with a single scan.

Mirror symmetries in multiple diffraction patterns of face-centred cubic crystals

In this work, a study of the mirror symmetries appearing in multiple diffraction patterns of face-centred cubic crystals is carried out. Several different X-ray and neutron multiple diffraction patterns have been simulated for different face-centred cubic structures. The patterns were plotted in circular plots which showed that two types of symmetry mirrors coexist in the patterns: isomorphic and anamorphic mirrors. The number and types of mirrors depend on then-fold symmetry of the scattering vector associated with the primary reflection. Forneven, onlynisomorphic mirrors appear in the patterns. Fornodd,nisomorphic mirrors are formed intercalated betweennanamorphic mirrors.

Growth of ZnGeP<sub>2</sub> Single Crystal by Three-Temperature-Zone Furnace

In order to meet the requirements of growing high-quality ZnGeP2, a crystal growth furnace with three-temperature-zone was designed and fabricated based on a conventional vertical two-zone tubular resistance furnace. Appropriate temperature gradients of 12~15°C/cm at the growth interface and stable thermal profile were obtained. A crack-free ZnGeP2 single crystal with size of Φ15mm×30mm was grown successfully in the furnace mentioned above. The as-grown crystal was characterized by X-ray diffraction (XRD) and Infrared (IR) spectrophotometers. It is found that there is a cleavage face of (101) and X-ray multiple diffraction peaks of the {101} faces are observed, The infrared transmission of a ZnGeP2 wafer of 3 mm thickness is about 50% in the region of 3~10μm. These results show the designed crystal growth furnace is suitable for growth of ZnGeP2 crystal, and the as-grown ZnGeP2 crystal has good structural integrity and high quality.

X-ray phase measurements as a probe of small structural changes in doped nonlinear optical crystals

X-ray multiple diffraction experiments with synchrotron radiation were carried out on pure and doped nonlinear optical crystals: NH4H2PO4and KH2PO4doped with Ni and Mn, respectively. Variations in the intensity profiles were observed from pure to doped samples, and these variations correlated with shifts in the structure factor phases, also known as triplet phases. This result demonstrates the potential of X-ray phase measurements to study doping in this type of single crystal. Different methodologies for probing structural changes were developed. Dynamical diffraction simulations and curve fitting procedures were also necessary for accurate phase determination. Structural changes causing the observed phase shifts are discussed.

Studying defect structure of GaN epilayers by means of three-beam X-ray diffraction analysis

X-ray multiple diffraction in epitaxial films of GaN with various densities of dislocations has been measured using Renninger scans for a primary forbidden (0001) reflection. The angular widths of three-beam diffraction peaks measured in both φ scans (rotation about the normal to the sample surface) and θ scans (rotation about the Bragg angle) have been analyzed. It is established that the three-beam Renninger diffraction peaks exhibit splitting due to a large-block structure of epilayers. For some three-beam combinations, the half-width (FWHM) of θ scan peaks is highly sensitive to the dislocation density.

Experimental Evidence for the Influence of Mn3+ Concentration on the Impurity Incorporation and Habit Modification Mechanism of Potassium Dihydrogen Phosphate

High resolution X-ray diffraction is applied to study Mn3+ doped potassium dihydrogen phosphate (KDP) single crystals as a function of dopant concentration with quantitative dopant composition within the crystals being assessed using Rutherford backscattering spectroscopy (RBS). Synchrotron radiation high resolution X-ray multiple diffraction studies using both the Renninger scanning and two-dimensional angular mapping techniques are consistent with the Mn3+ ionic complex entering the crystal lattice via a substitutional incorporation mechanism for Mn3+ at a concentration of 0.1 wt %. For a higher Mn concentration of 0.9 wt %, the data indicate incorporation via an interstitial mechanism associated with a decrease in lattice perfection (an increased mosaic spread). This analysis is supported through X-ray powder diffraction studies which reveal lattice contraction for lower dopant levels with lattice dilation for the higher dopant levels. The potential impact of this observation on the associated crystal growth habit modification process is discussed.

Synchrotron x-ray multiple diffraction in the study of Fe+ ion implantation in Si(0 0 1)

In this work, x-ray multiple diffraction has been used as a three-dimensional high-resolution probe to study the Fe+ ion implantation process in Si(0 0 1). The semiconducting β-FeSi2 crystallographic phase has been synthesized by Fe ion co-implantation in Si(0 0 1) followed by ion-beam-induced epitaxial crystallization (IBIEC) and thermal treatment. This phase was clearly detected by the conventional techniques, micro-Raman scattering spectroscopy, transmission electron microscopy (TEM) and grazing incidence x-ray diffraction. Synchrotron radiation rocking curves (ω-scans) and mapping of the Bragg surface diffraction (BSD) of the Si matrix, as-implanted, after the IBIEC process and thermally treated, have enabled the detection of co-implanted regions formation that present distinct lattices in comparison with the matrix one clearly observed by TEM. Also, the compressive strain of both regions in depth by rocking curve and in-plane has been determined by using BSD, which is one order of magnitude smaller.

An instrument for combining x-ray multiple diffraction and x-ray topographic imaging for examining crystal microcrystallography and perfection

Diffraction imaging using x-ray topography (XRT) and x-ray multiple diffraction (XRMD) provide valuable tools for examining the growth defects in crystals and the distributions from ideal lattice symmetry (microcrystallography). The topographic x-ray multiple diffraction microprobe (TMDM) combines the complementary aspects of both techniques enabling XRT and XRMD studies within the same instrument providing a useful resource for the structural characterization of materials that are not very stable in vacuum and electron beam environments. The design of the TMDM instrument is described together with data taken on GaAs (001) and potassium dihydrogen phosphate (001).

Effect of Ni(II) doping on the structure of L-histidine hydrochloride monohydratecrystals

In this paper, we study the effect of Ni(II) doping on the structure of L-histidinehydrochloride monohydrate crystals using x-ray diffraction and Raman spectroscopy.X-ray powder diffraction shows no significant change in the unit cell parameters ofthe doped single crystal, whereas x-ray multiple diffraction using synchrotronradiation indicates that the Ni ions are located in interstitial positions in the crystallattice. The temperature-dependent Raman spectra reveal a structural phasetransition in the 10–300 K temperature range. The proposed mechanism of this phasetransition supports the suggestion that the Ni ions occupy interstitial positions.