Grazing Exit X-ray Fluorescence Research Articles

Exploring the Depths of Corrosion: A Novel GE-XANES Technique for Investigating Compositionally Complex Alloys.

In this study, we propose the use of nondestructive, depth-resolved, element-specific characterization using grazing exit X-ray absorption near-edge structure spectroscopy (GE-XANES) to investigate the corrosion process in compositionally complex alloys (CCAs). By combining grazing exit X-ray fluorescence spectroscopy (GE-XRF) geometry and a pnCCD detector, we provide a scanning-free, nondestructive, depth-resolved analysis in a sub-micrometer depth range, which is especially relevant for layered materials, such as corroded CCAs. Our setup allows for spatial and energy-resolved measurements and directly extracts the desired fluorescence line, free from scattering events and other overlapping lines. We demonstrate the potential of our approach on a compositionally complex CrCoNi alloy and a layered reference sample with known composition and specific layer thickness. Our findings indicate that this new GE-XANES approach has exciting opportunities for studying surface catalysis and corrosion processes in real-world materials.

Simultaneous Dimensional and Analytical Characterization of Ordered Nanostructures.

The spatial and compositional complexity of 3D structures employed in today's nanotechnologies has developed to a level at which the requirements for process development and control can no longer fully be met by existing metrology techniques. For instance, buried parts in stratified nanostructures, which are often crucial for device functionality, can only be probed in a destructive manner in few locations as many existing nondestructive techniques only probe the objects surfaces. Here, it is demonstrated that grazing exit X-ray fluorescence can simultaneously characterize an ensemble of regularly ordered nanostructures simultaneously with respect to their dimensional properties and their elemental composition. This technique is nondestructive and compatible to typically sized test fields, allowing the same array of structures to be studied by other techniques. For crucial parameters, the technique provides sub-nm discrimination capabilities and it does not require access-limited large-scale research facilities as it is compatible to laboratory-scaleinstrumentation.

Development of a portable grazing exit X-ray fluorescence system using a gold anode X-ray tube

A portable grazing exit X-ray fluorescence system (GE-XRF) composed of a low power X-ray tube (gold anode), a SiPIN detector, quartz reflector and an XY table plus rotary stage for positioning the reflector in grazing exit condition was developed in this work. The accuracy of the system was checked using a certified bovine liver sample (SRM 1577b, NIST). The relative errors between measured and certified values ranged from 2 to 22%, except P (39%) and S (26%). The absolute detection limits obtained with the portable system were in the range of 4–300 ng (15 ≤ Z ≤ 30). The portable GE-XRF system developed does not favor the detection of light elements since absorption effects were more critical (sample-to-detector distance ∼ 35 mm). Besides that, it was operated under room temperature and atmospheric pressure, 20 °C and 1.0 atm, respectively. The quantitative results of a multielement reference sample were compared with the results of a GI-XRF system. Both techniques were compatible and presented good accuracy with reference values. The portable GE-XRF system developed in this work was efficient, showing that it is possible to produce a grazing exit X-ray fluorescence system using a low power X-ray tube, a Si-PIN detector and quartz reflector.

Portable grazing exit X-ray fluorescence system using a low-power X-ray tube

In this work was developed a portable system of grazing exit X-ray fluorescence (geometric 90° - 0°) that can be applied in several areas science and technology. GE-XRF portable system is formed by a mini X-ray tube of low power (anode of Au) and a SiPIN detector. The reflectors used as sample support (sampler carrier) were quartz discs. The grazing exit angle was experimentally determined by measuring a cooper solution (10 μg.g-1). The accuracy of the system was checked using multielement reference solution as standard reference material. The relative errors between measured and certified values are in the range of 4 to 19%. The first results showed a background was drastically reduced at grazing exit angles, enabling trace elemental analysis. The system of GE-XRF proved to be quite stable and reproducible. This paper shows that it is possible to produce a portable system of grazing exit X-ray fluorescence compact, efficient, low-cost and easy-to-handle instrumentation using a low power X-ray tube and a SiPIN compact detector.

Development of a compact grazing exit X-ray fluorescence spectrometer for fast trace elemental analysis

A compact grazing exit X-ray fluorescence (GE-XRF) spectrometer was developed in the laboratory. An Al cylindrical collimator for the primary X-rays was placed just above the sample stage. This collimator also played the role of an exit slit to detect fluorescent X-rays at small grazing exit angles. Therefore, no additional exit slit was used in this setup, leading to a compact design. The entire size of the analysis equipment was 80mm×200mm×170mm (horizontal×vertical×height). The maximum exit angle was adjusted to the height of the sample stage. The background was drastically reduced at grazing exit angles, enabling trace elemental analysis. A calibration curve was obtained using 10μL Ga solutions. Accordingly, the detection limit for Ga was evaluated to be 20ppb.

Nondestructive elemental depth profiling of Japanese lacquerware ‘Tamamushi‐nuri’ by confocal 3D‐XRF analysis in comparison with micro GE‐XRF

AbstractWe have applied recently two XRF (micro x‐ray fluorescence) methods [micro‐Grazing Exit XRF (GE‐XRF) and confocal 3D‐XRF] to Japanese lacquerware ‘Tamamushi‐nuri.’ A laboratory grazing‐exit XRF (GE‐XRF) instrument was developed in combination with a micro‐XRF setup. A micro x‐ray beam was produced by a single capillary and a pinhole aperture. Elemental x‐ray images (2D images) obtained at different analyzing depths by micro GE‐XRF have been reported. However, it was difficult to directly obtain depth‐selective x‐ray spectra and 2D images. A 3D XRF instrument using two independent polycapillary x‐ray lenses and two x‐ray sources (Cr and Mo targets) was also applied to the same sample. 2D XRF images of a Japanese lacquerware showed specific distributions of elements at the different depths, indicating that ‘Tamamushi‐nuri’ lacquerware has a layered structure. The merits and disadvantages of both the micro GE‐XRF and confocal micro XRF methods are discussed. Copyright © 2009 John Wiley & Sons, Ltd.

Grazing exit versus grazing incidence geometry for x-ray absorption near edge structure analysis of arsenic traces

In the presented study the grazing exit x-ray fluorescence was tested for its applicability to x-ray absorption near edge structure analysis of arsenic in droplet samples. The experimental results have been compared to the findings of former analyses of the same samples using a grazing incidence (GI) setup to compare the performance of both geometries. Furthermore, the investigations were accomplished to gain a better understanding of the so called self-absorption effect, which was observed and investigated in previous studies using a GI geometry. It was suggested that a normal incidence-grazing-exit geometry would not suffer from self-absorption effects in x-ray absorption fine structure (XAFS) analysis due to the minimized path length of the incident beam through the sample. The results proved this assumption and in turn confirmed the occurrence of the self-absorption effect for GI geometry. Due to its lower sensitivity it is difficult to apply the GE geometry to XAFS analysis of trace amounts (few nanograms) of samples but the technique is well suited for the analysis of small amounts of concentrated samples.

A micro X-ray fluorescence analysis method using polycapillary X-ray optics and grazing exit geometry

Grazing exit X-ray fluorescence (GE-XRF), which has unique advantages in surface and film analysis, is a development of XRF related to total reflection XRF. The combination of polycapillary X-ray optics with total reflection geometry in the detection path allows micro analysis in thin layer characterization. This technique was applied to analyze a series of titanium and iron layers which were deposited on GaAs single crystal by metal vapor vacuum arc ion sources. Thickness and density of the layers result from fitting the experimental data to model calculations, and the information of layer uniformity can be acquired by two-dimensional scan analysis. The GE-XRF method has application for complete layer characterization and process control during the layer deposition.

Numerical approach for depth profiling with GE‐XRF

AbstractThe atomic percentage of implanted particles on the sample surface was estimated from the peak position of angle dependency of the experimental grazing exit X‐ray fluorescence (GE‐XRF) intensity profile. An algorithm for constructing three‐parametric Gaussian‐type depth profiles of atoms implanted in a substrate was developed. The position of the maximum and its value of the implanted particles distribution as well as a dispersion of that distribution were considered in the calculations. The model was applied to the intensity of the As Kα line emitted from As atoms implanted in a Si wafer. The least‐square method was used to minimize the overall difference between experimental and calculated GE‐XRF intensity. Optimum parameters of the particle distribution were determined in this procedure. Using that profile, the depth dependencies of effective real and imaginary parts of atomic scattering factor and complex index of refraction of the sample material were evaluated. Copyright © 2006 John Wiley & Sons, Ltd.

Grazing-Exit and Micro X-ray Fluorescence Analyses for Chemical Microchips

Grazing-exit x-ray fluorescence (GE-XRF) and micro x-ray fluorescence (micro-XRF) methods were applied to chemical microchips as a detection method. Since an energy-dispersive x-ray detector was used, the simultaneous detection of multiple elements was possible. An analyzing region was especially designed on the microchip so that a sample solution could be dried and concentrated in a suitable area corresponding to the size of the primary x-ray beam. Finally, it was confirmed that both analytical methods could be combined well for use with a microchip. In GE-XRF, the background intensity in the XRF spectrum was reduced at grazing-exit angles. In addition, a good relationship between the x-ray fluorescence intensities and the concentrations of standard solutions that were introduced into the microchip was obtained. This indicates that the GE-XRF method is feasible for trace elemental analysis in chemical microchip systems. In micro-XRF, an attempt was made to concentrate and dry the analyte within a small analyzing region. The preliminary results indicated that the micro-XRF method could be applied for the analysis of microchips.

Comparison of grazing-exit particle-induced X-ray emission with other related methods

Particle-induced X-ray emission (PIXE) is recognized as a trace analysis method; the Bremsstrahlung background, however, still limits the detection power in the low-energy region of spectrum. The grazing-incidence or grazing-exit arrangements are considered to be useful in order to reduce the background intensity. We measure grazing-incidence PIXE (GI-PIXE) and grazing-exit PIXE (GE-PIXE) using an identical sample vacuum chamber to evaluate the performance of both methods. The sample used is a standard sample (Ca, Fe, Ni and Zn) prepared on Si wafer by the spin-coating method. In GI-PIXE mode, a collimated 2.5 MeV proton beam irradiates the surface of the sample at grazing incident angles. However, it was difficult to reduce sufficiently the background intensity in the GI-PIXE spectra because of the Bremsstrahlung background induced by secondary electrons. In the GE-PIXE mode, proton-induced X-rays are measured at grazing-exit angles. The background intensity is reduced, because only the X-rays emitted from the near-surface layer can be detected in the grazing-exit arrangement. Furthermore, the result obtained for an Au–Cu thin film sample by GE-PIXE method was compared with the result obtained by other related methods: grazing-exit X-ray fluorescence and grazing-exit electron probe microanalysis. Similar results were obtained by different methods, indicating that the same phenomena occur in all grazing-exit X-rays measurements. One of the merits of the grazing-exit microprobe analysis method is in microanalysis using a small diameter electron probe; however, the damage by electron irradiation is more severe than that in GE-PIXE.

Mathematical model for evaluation of surface analysis data by total reflection XRF

The general problem of an electromagnetic wave moving through a stratified medium appears naturally in all the techniques associated with surface analysis by total reflection. It is a consequence of the theoretical models that describe that describe the physical processes involved in these techniques. This problem has been extensively studied owing to its importance in optics. The mentioned techniques are known as grazing incidence x-ray fluorescence (GIXRF) and grazing exit x-ray fluorescence (GEXRF). In this work, the electric field in a stratified medium was calculated using basic mathematical tools. The model uses a matrix approach to take advantage of well-known mathematical results (such as Hessenberg's matrix properties). In this way, the model optimizes and facilitates the data analysis in GIXRF measurements and GEXRF experiments. The simplicity of the formalism admits approximations of the electric field, which allow a better understanding of the experimental data in both techniques. The model was used to analyze experimental data on silicon wafers with surface layers of different elements, showing excellent results. Copyright © 1999 John Wiley & Sons, Ltd.

Mathematical model for evaluation of surface analysis data by total reflection XRF

The general problem of an electromagnetic wave moving through a stratified medium appears naturally in all the techniques associated with surface analysis by total reflection. It is a consequence of the theoretical models that describe that describe the physical processes involved in these techniques. This problem has been extensively studied owing to its importance in optics. The mentioned techniques are known as grazing incidence x-ray fluorescence (GIXRF) and grazing exit x-ray fluorescence (GEXRF). In this work, the electric field in a stratified medium was calculated using basic mathematical tools. The model uses a matrix approach to take advantage of well-known mathematical results (such as Hessenberg's matrix properties). In this way, the model optimizes and facilitates the data analysis in GIXRF measurements and GEXRF experiments. The simplicity of the formalism admits approximations of the electric field, which allow a better understanding of the experimental data in both techniques. The model was used to analyze experimental data on silicon wafers with surface layers of different elements, showing excellent results. Copyright © 1999 John Wiley & Sons, Ltd.

New spectrometer for grazing exit x-ray fluorescence

Among the x-ray fluorescence techniques using energy dispersive systems, the excitation in the total reflection regime is becoming widespread. This technique may be applied to surface analysis if the fluorescent radiation emitted by the sample is measured as a function of the grazing incidence angle. The main limitation in performing this sort of analysis is the need to use a monochromator, which notably reduces the incident flux of radiation. Besides, the method requires the radiated surface to be perfectly smooth and polished and to have a total length of some centimeters. A similar technique known as grazing exit x-ray fluorescence presents certain advantages and is easier to implement. By this method, fluorescent photons in terms of the grazing exit angle are detected. In this work, a spectrometer for performing surface analysis at grazing exit is described, the different experimental situations are analyzed, and some measurements performed with this device are shown.