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Nuclear resonant reflectivity (NRR) from an Fe60Al40 film was measured using synchrotron radiation at several grazing angles near the critical angle of total external reflection. Using laterally resolved measurements after irradiation with 20 keV Ne+ ions of gradually varying fluence of 0–3.0 × 1014 ions cm−2, the progressive creation of the ferromagnetic A2 phase with increasing ion fluence was confirmed. The observed depth selectivity of the method has been explained by application of the standing wave approach. From the time spectra of the nuclear resonant scattering in several reflection directions the depth profiles for different hyperfine fields were extracted. The results show that the highest magnetic hyperfine fields (∼18–23 T) are initially created in the central part of the film and partially at the bottom interface with the SiO2 substrate. The evolution of the ferromagnetic onset, commencing at a fixed depth within the film and propagating towards the interfaces, has been directly observed. At higher fluence (3.0 × 1014 ions cm−2) the depth distribution of the ferromagnetic fractions became more homogeneous across the film depth, in accordance with previous results.

Porous silicon layers with different porosities were prepared by adjusting the anodization current density of the electrochemical etching process, starting from highly doped p-type crystalline silicon wafers. The microstructural parameters of the porous layers were assessed by high-resolution X-ray diffraction, total external reflection, scanning electron microscopy and nitrogen adsorption–desorption analysis. Furthermore, both the surface porosity and the mean porosity for the entire volume of the samples were estimated by employing total external reflection measurements and X-ray reciprocal-space mapping, respectively. The results clearly indicate that the surface porosity is different from the mean porosity, and the presence of a depth porosity gradient is suggested. To evaluate the porosity gradient in a nondestructive way, a new laboratory method using the grazing-incidence X-ray diffraction technique is reported. It is based on the analysis of the X-ray scattering profiles of the porous layers to obtain the static Debye–Waller factors. In this way, a description of the porosity gradient in a quantitative framework becomes possible, and, as a result, it was shown that the porosity increases exponentially with the X-ray penetration depth. Moreover, a strong dependence between the porosity gradient and the anodization current was demonstrated. Thus, in the case of the lowest anodization current (e.g.50 mA cm−2) a variation of only 15% of the porosity from the surface to the interface is found, but when applying a high anodization current of 110 mA cm−2the porosity close to the bulk interface is almost three times higher than at the surface.

A theoretical formalism for quantitative description of X-ray diffraction from Langmuir monolayers under conditions of total external reflection has been developed. The proposed approach, based on the distorted-wave approximation, allows to consider physical mechanisms for plotting diffraction curves and maps (in the reciprocal space) for real monolayers and describe self-consistently specific features of Bragg peaks. The resulting algorithm can easily be implemented on a personal computer, which provides the opportunities to carry out numerical simulation of experimental two-dimensional diffraction intensity maps and determine reliably both the mean values of structural parameters of layers and their rms deviations.

Glasslike dielectrics are investigated by methods of plasmon dispersion and asymmetry of the number of localized electrons in the region in which total external reflection of X-rays is formed and excitation of plasmon oscillations takes place. The internal mechanical stress and the related polarization of the studied dielectrics are determined. It is discovered that a lithium fluoride crystal lacks an internal mechanical stress and that the observed polarization in this single crystal is caused by a large macroscopic dipole moment.

We show how the combined use of the methods of Rutherford backscattering of ions and X-ray fluorescence analysis under conditions of total external reflection of the flow of exciting hard X-ray radiation and registration of the X-ray radiation output during ion excitation allows to effectively diagnose the elemental composition of thin-film coatings and films of dry residues of liquids. These methods and the features of their experimental application are briefly described. Examples of the complex methodological analysis of real objects are given. The possibility of increasing the efficiency of the methods of X-ray fluorescence analysis of materials due to the inclusion in the X-ray optical schemes of experimental measurements of flat X-ray waveguide resonators is indicated.

XANES spectra of protein films (hemoglobin and alkaline phosphatase) formed on the surface of a liquid subphase in a Langmuir trough have been obtained experimentally. The potential of X-ray absorption spectroscopy in the total external reflection geometry is demonstrated by the example of a protein film based on hemoglobin subjected to the action of urea. It is established that the presence of 0.09 M urea solution in the subphase enhances significantly the ability of hemoglobin to bind zinc and iron ions. Information about the local atomic environment of zinc ions bound with a hemoglobin molecule is obtained. It is shown that each zinc ion is coordinated by four ligands, two of which are amino acid residues of cysteine and histidine. The general concepts of the molecular mechanisms of accumulation of metal ions under the action of disturbing factors are formulated.

—The kinetics of growth of a nanosized germanium film deposited by magnetron sputtering on the Si(001) surface is studied using a developed experimental X-ray reflectometry technique distinguished by the joint recording of specularly reflected and diffusely scattered radiation. By using this technique, it is possible to perform in situ both the analysis of the morphology of the growing film and the control of its thickness with an accuracy to 1 nm. Dependences of the intensity of specular reflection, diffuse scattering, rate of growth, and mean square roughness and density of the film on the deposition time are obtained. According to the results of the measurement of specularly reflected radiation, the film roughness increases with time according to a power law. However, at a thickness of the film of 4 nm, a clearly defined maximum of diffuse scattering is observed, the angular position of which corresponds to the critical angle of total external reflection of germanium of 0.31°. This pattern of distribution of scattered radiation is explained by the manifestation of the Yoneda effect that consists in the anomalous X-ray scattering, the maximum of which corresponds to the critical angle θC of total external reflection from the film. It is established experimentally that, at the initial stage of growth, the film is formed by the Volmer–Weber mechanism. It is found using in situ X-ray reflectometry that the formation of a continuous layer of a germanium film occurs at its thickness of 7 nm; the subsequent growth of the film proceeds according to the power law σf ~ tβ, where β = 0.23.

An approach for forming Langmuir monolayers of proteins is described, with lysozyme serving as an example. The essence of this approach is the deposition of a lysozyme solution containing a precipitant, KCl, onto the water surface in a Langmuir trough. The results of small-angle X-ray scattering indicate that the precipitant in the protein solution causes a significant fraction (>10%) of the protein molecules to assemble into dimers and octamers. Studying the formation of these monolayers by grazing-incidence X-ray standing waves (or X-ray standing waves under total external reflection conditions) showed that the thickness of the resulting protein layer was twice the diameter of an individual lysozyme molecule and matched the diameter of the octamer. Thin layers of precipitant ions (K and Cl) formed directly under the protein monolayer. Our results indicate that adding precipitant to the solution caused the formation of octamers with a retained structure that participated in Langmuir monolayer formation when the solution was applied to the water-subphase surface. Thus, the precipitant ions interacted with the protein monolayer. The proposed approach could facilitate the formation of ordered protein films in hybrid system design and in developing transition methods for nature-like technologies.

Multielement analysis of food products, including drinks, is important for an assessment of the content of the useful and toxic elements for the human body. In this paper, the main problems and their solutions in the analysis of sugar-containing drinks by Total Reflection X-ray Fluorescence Spectrometry ( TXRF ) method have been considered. The organic sucrose matrix causes certain difficulties both in the preparation of the samples and in the processing of measurement data for TXRF. The following most common sample preparation procedures for TXRF were considered: direct, based on the analysis of initial sample, dilution with water and acid digestion. In order to assess the fulfillment of the thin layer criterion, the physical characteristics of dried samples on the carriers were determined after applying each of the above-mentioned preparation procedures, and the corresponding surface density values were established. The obtained values were compared with the theoretical ones. Based on the calculation of mass absorption coefficients for C 12 H 22 O 11 matrix, it was found that the method of acid digestion was suitable for the quantitative determination of light (14 < Z < 20) elements. When analyzing the sample without the preliminary preparation or after diluting the sample with water, the influence of absorption effects was noted due to the mismatch of the surface density with the thin layer criterion. This mismatch of the samples in the direct analysis was confirmed by the measurements using a method based on an angle incidence scanning of the primary radiation on the sample, establishing a violation of the conditions for the effect of total external reflection. The detection limits were calculated for the considered sample preparation procedures, and it was concluded that the quantitative identification of Fe, Ni, Cu, Zn, Rb, Sr, and Pb trace elements at the level of tens of μg/l was possible by the acid digestion procedure. The application of the addition method to assess the trueness of elemental determination led to the conclusion that it was possible to use the direct analysis of sugar-containing drinks for the elements with Z ≥ 24 in the concentration ranges of 0.5–10 mg/l. Key words : X-ray fluorescence, TXRF, soft drinks, matrix effects, absorption effects, sucrose, multielement analysis, addition method (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.009 A.S. Maltsev 1, 2 , A. von Bohlen 3 , R.A. Yusupov 2 , S.A. Bakhteev 2 1 Institute of the Earth’s Crust, SB RAS, Lermontov st., 128, Irkutsk, 664033, Russian Federation 2 Kazan National Research Technological University, Marksa st., 68, Kazan, 420012, Russian Federation 3 Leibniz-Institut fur Analytische Wissenschften ISAS, Bunsen-Kirchhoff-Str. 11, Dortmund, 44139, Germany

The wave equation as derived in Section 7.1 and used so far in this book, is valid for sound propagation in lossless media. The Helmholtz form of this equation is

The possibilities are presented of X-ray diffraction methods for studying the propagation of surface acoustic waves (SAWs) in solids, including diffraction under total external reflection conditions and Bragg diffraction, using acoustically modulated X-ray multilayer mirrors and crystals. SAW propagation was studied using both meridional and sagittal diffraction geometries where the SAW wavevectors and X-ray photons are collinear or perpendicular, respectively. SAW propagation in a crystal leads to sinusoidal modulation of the crystal lattice and the appearance of diffraction satellites on the rocking curve. The intensities and angular positions of these diffraction satellites are determined by the SAW wavelength, amplitude and attenuation. Therefore, diffraction methods allow the analysis of the SAW propagation process and determination of SAW parameters. The influence of X-ray energy on diffraction by acoustically modulated crystals is studied for the first time. It is shown that changes in the X-ray energy can change the angular region where diffraction satellites exist under conditions of total external reflection. By contrast, in the Bragg diffraction region changes in the X-ray photon energy lead to changes in the X-ray penetration depth into the crystal and redistribution of the diffracted intensity among diffraction satellites, but do not change the angular divergence between diffraction satellites on the rocking curve. It is also shown that, in X-ray diffraction on acoustically modulated crystals on a number of successive reflections, a decrease in interplanar spacing leads to an increase in the number of diffraction satellites and a redistribution of diffracted radiation between them.

In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum–material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid–solid interfaces. The correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte–Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid–solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.

We consider the reflection from a random medium of light with short coherence length. We found that the second order correlation function of light can have a peak in a direction where the reflection angle is equal to angle of incidence. This occurs when the size of the region, from which light is collected, is larger than the coherence length., Comment: 5 pages, 2 figures

Hollow glass microcapillaries or x-ray waveguides very efficiently confine x-rays to submicron or nanospots, which can be used for point projection imaging. However, x-ray beams exiting from such devices have ultranarrow cones that are limited by the critical angle for the total external reflection to a few milliradians. Narrow cone beams result in small fields of view, and the application of multiple-reflection optics to cone beam tomography is challenging. In this work, we describe a new nonconventional tomographic geometry realized with multiple confocal ultranarrow cone beams. The geometry enables an increase in the effective radiation cone to over 10° without resolution reduction. The proposed tomographic scans can be performed without truncations of the field of view or limitations of the angular range and do not require sample translations, which are inherent to other multibeam x-ray techniques. Volumetric imaging is possible with a simultaneous iterative reconstruction technique or with a fast approximate noniterative two-step approach. A proof-of-principle experiment was performed in the multipoint projection geometry with polycapillary optics and a multi-pinhole mask inserted upstream of the optics. The geometry is suited for phase-contrast tomography with polychromatic laboratory and synchrotron sources.

Functional thin films are commonly integrated in electronic devices as part of a multi-layer architecture. Metal/oxide/metal structures e.g. in resistive switching memory and piezoelectric microelectrochemical devices are relevant applications. The films are mostly fabricated from the vapour phase or by solution deposition. Processing conditions with a limited thermal budget typically yield nanocrystalline or amorphous layers. For these aperiodic materials, the structure is described in terms of the local atomic order on the length scale of a few chemical bonds up to several nanometres. Previous structural studies of the short-range order in thin films have addressed the simple case of single coatings on amorphous substrates. By contrast, this work demonstrates how to probe the local structure of two stacked functional layers by means of grazing incidence total X-ray scattering and pair distribution function (PDF) analysis. The key to separating the contributions of the individual thin films is the variation of the incidence angle below the critical angle of total external reflection, In this way, structural information was obtained for functional oxides on textured electrodes, i.e. PbZr0.53O0.47O3 on Pt[111] and HfO2 on TiN, as well as HfO2-TiOx bilayers. For these systems, the transformations from disordered phases into periodic structures via thermal teatment are described. These examples highlight the opportunity to develop a detailed understanding of structural evolution during the fabrication of real thin film devices using the PDF technique.

Multilayer structures, consisting of successive lysozyme layers and layers of iodide and potassium ions, have been formed on a silicon substrate by the modified Langmuir–Schaefer method; the use of this technique implies preliminary preparation of a crystallization protein solution containing an oligomeric phase. The multilayer structure has been characterized by methods of X-ray reflectivity and total external reflection X-ray standing waves (TER XSW). The data obtained indicate the formation of a dense lysozyme film (3 nm thick) and layers of potassium and iodide ions, adjacent to this film.

The features of the analysis of thin films by small-angle X-ray reflectometry and grazing incidence X-ray diffractometry are considered by the example of tantalum films. In particular, it is shown that a substantial shift of the diffraction peak at small angles of incidence is associated with the refraction of X-rays near the angle of total external reflection. The results of the measurements are in good agreement with calculations. These factors should be considered in grazing incidence X-ray diffractometry to obtain a correct description of the distribution of the properties of thin films over their depth. It is demonstrated that the approach proposed in this paper can be used to determine the material constants (δ, β) and the thickness of tantalum films.

The phenomenon of total external reflection (TER) of quasi-monochromatic X-ray radiation fluxes on a material interface and the effect of waveguide–resonator propagation of these fluxes in nanosize extended slit clearance, as well as a device operating on the basis of this effect—a planar X-ray waveguide–resonator—are briefly described. Experimental data on the formation of an X-ray flux by a composite X-ray waveguide–resonator are presented, and a model describing the decrease in the angular divergence of the formed flux without a decrease in the integral intensity is proposed. The model is based on the conception of partial angular tunneling of the radiation flux in the gap between two consequently mounted and mutually adjusted waveguide–resonators; the tunneling is implemented due to the interaction between interference fields of standing X-ray waves excited by the radiation transported by the slit clearance of these waveguide–resonators.

We investigate electric field standing wave effects in the system semiinfinite incidence medium with high index of refraction/layer/vacuum, the latter being the semiinfinite exit medium. If the layer has a lower index of refraction than the incidence medium, then very strong resonances occur between the two critical angles of the system defined by the systems incidence medium/layer and incidence medium/vacuum, as the layer is then a cavity. In particular close to the lower critical angles, the evanescent fields extend strongly into the exit medium. Based on this effect we suggest two new spectroscopic modalities, namely interference-enhanced internal reflection Raman spectroscopy and interference-enhanced attenuated total reflection infrared spectroscopy.

Thermal waves are of great significance as non-Fourier effects arise with ultrafast heating rates and small system length. This study analytically and numerically investigated the behavior of thermal waves based on the Cattaneo-Vernotte model at an ideal interface. A stable, fast algorithm based on the alternative direction implicit method is introduced to solve the two-dimensional heat conduction problem. When thermal waves meet with an ideal interface, some energy is reflected back while the rest is conveyed across the interface, which are called the reflection and refraction of thermal waves. The changes of the profile and direction and the energy distribution between the reflection and refraction of the thermal waves are studied both analytically and numerically. Regardless of the boundary conditions imposed on the interface, the reflection angle is always identical to the incident angle, and the ratio of the sine of the refraction angle of the thermal waves to that of the incident angle is equal to the ratio of the thermal wave speeds in the two material layers. A theoretical equation to describe the relationships between the energy distribution and the material thermal properties shows that the thermal wave speeds in the materials, the specific heat and the incident angle determine the thermal energy transmittance ratio. Total reflection can occur for some conditions, and the nature of the energy conveyed by thermal waves is interesting and instructive.

In this paper, a method for measuring the continuous dispersion spectrum of nonlinear refraction coefficients of materials based on complex refractive index dispersion (CRID) measurement is proposed. This method involves measuring internal reflection spectra with a lab-made apparatus. From the determined CRIDs of a material with and without exciting light, the changes in refractive index over a wide spectral range can be obtained, from which the nonlinear refraction coefficients can be deduced. In addition, the RI changes at wavelengths far from the nonlinear range can be used to monitor the thermal effects. In this study, a methyl-red-doped poly(methyl methacrylate) (MR-PMMA) sample was investigated. A large nonlinear refraction coefficient on the order of 10 −1 cm 2 /W was observed. The results also show that the absolute value of nonlinear refraction coefficient of the MR-PMMA sample decreases with the increase of excitation intensity. Consequently, this study provides a powerful approach that has the potential to be applied in the study of the nonlinear properties of materials.

Journal of synchrotron radiation 25(1), 77 - 84 (2018). doi:10.1107/S1600577517017362, The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface., Published by IUCr, Chester

A method to determine plasma oscillations in metals with the aid of total external reflection (TER) of X-rays is proposed. It is shown that the plasmon energy, concentration of conduction electrons, and Fermi energies can be calculated using experimentally measured grazing angles of X-rays after TER. Such characteristics depend on crystallographic directions and may depend on the TER depth.

Total external reflection of X rays from surfaces of several polycrystalline metals is analyzed. The roentgenograms of total reflection and X-ray diffraction are comprehensively studied for nickel, copper, silver, platinum, and bismuth. Theoretical processing of experimental roentgenograms is used to calculate Xray refractive indices, number of surface crystallites, interplane distances, and remaining quantities for polycrystalline metals. It is shown that the refractive index inversely depends on the interplane distance in crystallites of polycrystalline solids. Total reflection of X rays from the lead zirconate titanate ferroelectric film is studied.