Silicon‐doping induced strain of AlN layers: a comparative luminescence and Raman study

Si‐doped aluminum nitride layers show a shift of the near‐band‐edge luminescence at around 6 eV to lower energies for increasing Si concentration up to ≈(1–3) × 10¹⁹ cm^–3. For higher concentrations, the luminescence shifts back to higher energies. This behavior is compared to concomitant shifts of the Raman‐active E₂ vibrational mode and to X‐ray diffraction data. It can be explained in terms of increasing tensile strain which finally relaxes due to the formation of cracks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray‐excited optical luminescence and X‐ray absorption fine‐structures studies of CdWO4 scintillator

X‐ray‐excited optical luminescence (XEOL) emission and excitation spectra as well as the EXAFS signal of CdWO₄ were measured in the energy region of the Cd and W absorption edges. From EXAFS refinement, structural parameters such as number of atoms, distance from the absorbing atom and width of coordination shells in the W neighborhood were determined. The role of W–O interactions on the intrinsic luminescence of CdWO₄ is discussed. The efficiencies of conversion, transfer and emission processes involved in the scintillation mechanism showed to be high when self‐trapped excitons are formed locally by direct excitation of W ions. Annihilation of these excitons provides the characteristic scintillation of CdWO₄, a broad band emission with maximum at 500 nm. The presence of two energetically different O positions in the lattice gives rise to the composite structure of the luminescence band, and no influence of extrinsic defects was noticed. A mismatch between the X‐ray absorption coefficient and the zero‐order luminescence curves corroborates that the direct excitation of Cd ions induces secondary electronic excitations not very effective in transferring energy to the luminescent group, WO₆.     

Use of the CEARXRF GUI‐Based Monte Carlo–Library Least‐Squares (MCLLS) Code for the Micro‐Focused EDXRF analyzer

The CEARXRF GUI‐Based Monte Carlo–Library Least‐Squares (MCLLS) Code is demonstrated with results from a micro‐focused EDXRF analyzer, which can be used to calculate elemental weight fractions in metal alloys or rock samples accurately by library least‐squares regression of the measured X‐ray spectrum with computer‐generated elemental library spectra. An elemental stratified sampling variance reduction technique has been implemented in the CEARXRF5 code, which equalizes the statistical precision of the elemental libraries within the measured sample independent of the relative elemental amounts that are present. Also, an improved Si(Li) detector response function (DRF) has been obtained for micro‐focused X‐ray fluorescence (XRF) analyzers, and the DRF parameters are obtained based on regression from pure elemental experimental spectra. It is demonstrated that the resulting MCLLS approach can greatly improve the accuracy of elemental XRF analysis results. Copyright © 2011 John Wiley & Sons, Ltd.     

A simple calibration procedure of polycapillary based portable micro‐XRF spectrometers for reliable quantitative analysis of cultural heritage materials

Portable micro‐X‐ray fluorescence (micro‐XRF) spectrometers mostly utilize a polycapillary X‐ray lens along the excitation channel to collect, propagate and focus down to few tens of micrometers the X‐ray tube radiation. However, the polycapillary X‐ray lens increases the complexity of the quantification of micro‐XRF data because its transmission efficiency is strongly dependent on the lens specifications and the propagated X‐ray energy. This feature results to a significant and not easily predicted modification of the energy distribution of the primary X‐ray tube spectrum. In the present work, we propose a simple calibration procedure of the X‐ray lens transmission efficiency based on the fundamental parameters approach in XRF analysis. This analytical methodology is best suited for compact commercial and portable micro‐XRF spectrometers. The developed calibration procedure is validated through the quantitative analysis of a broad range of samples with archeological relevance such as glasses, historical copper alloys, silver and gold alloys offering an overall accuracy of less than 10%–15%. Copyright © 2015 John Wiley & Sons, Ltd.     

Approaches to solid sample preparation based on analytical depth for reliable X‐ray fluorescence analysis

In this paper, we discuss approaches to prepare solid samples for X‐ray fluorescence spectrometry (XRF). Although XRF can be used to analyze major and minor elements in various solid samples including powders and grains without dissolution techniques, to obtain reliable XRF results, the prepared sample must meet certain criteria related to homogeneity, particle size, flatness, and thickness. The conditions are defined by the analytical depth of fluorescent X‐rays from analytes, and the analytical depth can be estimated from the X‐ray absorption related to the energy of each X‐ray and the composition and density of the sample. For example, when the sample flatness and particle size are less than the analytical depth and the sample possesses homogeneity within a depth less than the analytical depth, the XRF results are representative of the entire sample. Furthermore, an appropriate sample thickness that is larger than the analytical depth or constant can prevent changes in fluorescent X‐ray intensity with variations in sample thickness. To obtain accurate and reproducible measurements, inhomogeneous solid samples must be pulverized, homogenized, and prepared as loose powder, powder pellets, or glass beads. This paper explains the approaches used to prepare solid samples for XRF analysis based on the analytical depths of fluorescent X‐rays. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of the detection limits in the analysis of some medium atomic number elements measured with a portable XRF and an external proton beam PIXE spectrometer system

A portable X‐ray fluorescence (XRF) spectrometer system was constructed using an Amptek Mini‐X X‐ray tube and an X‐123 compact spectrometer. The spectrometer is optimised for the best limits of detection. Its analytic properties are tested and compared with an analogous laboratory‐based instrument, an external beam proton‐induced X‐ray emission spectrometry (PIXE) setup. Depending on elements in question the thick target detection limits of this portable XRF device are comparable or even lower than the PIXE setup. Copyright © 2011 John Wiley & Sons, Ltd.     

Combined X‐ray microanalytical study of the Nd uptake capability of argillaceous rocks

Argillaceous rocks are considered as suitable host rock formation to isolate the high‐level radioactive waste from the biosphere for thousands of years. Boda Claystone Formation, the possible host rock formation for the Hungarian high‐level radioactive waste repository, has geologically and mineralogically been studied in detail, but its physico‐chemical parameters describing the retention capability of the rock needed further examinations. Studies were performed on thin sections subjected to 72 h sorption experiments using inactive Nd(III). Nd(III) has been used as a chemical analogue for transuranium elements of the radioactive waste to examine the ion uptake capability of the micrometre size mineral phases occurring in the rock. The elemental mapping of synchrotron radiation‐based microscopic X‐ray fluorescence (micro‐XRF) combined with scanning electron microscopy energy dispersive X‐ray analysis (SEM/EDX) has sufficient sensitivity to study the uptake capability of the different mineral phases on the microscale without the necessity of applying radioactive substances. Elemental maps were recorded on several thousand pixels using micrometre magnitude spatial resolution. By interleaving micro‐XRF and SEM/EDX data sets from the same sample area and applying multivariate methods, calcite and clay minerals could be identified as the main mineral phases responsible for Nd(III) uptake without using additional microscopic X‐ray diffraction mapping. It should be highlighted that the ion uptake capability of dolomite containing calcium and magnesium could be distinguished from the characteristics of calcite only by the interleaving of micro‐XRF and SEM/EDX data sets. The presence of minerals was verified by applying microscopic X‐ray diffraction point measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

Focus on sulfur count rates along marine sediment cores acquired by XRF Core Scanner

The aim of this study is to investigate the information provided by sulfur count rates obtained by X‐ray fluorescence core scanner (XRF‐CS) along sedimentary records. The analysis of two marine sediment cores from the Niger Delta margin shows that XRF‐CS sulfur count rates obtained at the surface of split core sections with XRF‐CS correlate with both direct quantitative pyrite concentrations, as inferred from X‐ray powder diffraction (XRD) and sulfur determination by wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry, and total dissolved sulfide (TDS) contents in the sediment pore water. These findings demonstrate the potential of XRF‐CS for providing continuous profiles of pyrite distribution along split sections of sediment cores. The potential of XRF‐CS to detect TDS pore water enrichments in marine sediment records, even a long time after sediment recovery, will be further discussed. Copyright © 2016 The Authors. X‐Ray Spectrometry Published by John Wiley & Sons Ltd.     

X‐ray spectrometry applied for characterization of bricks of Brazilian historical sites

This paper presents the results of X‐ray fluorescence (XRF) analysis of bricks sampled from historical places in Pernambuco, a state in the northeastern region of Brazil. In this study, twenty bricks found in historical sites were analyzed. Two bricks made in the 17th century, presumably used as ballast in ships coming from Holland, five locally manufactured bricks: one from 18th century, three from 19th century, and one from 20th century, and thirteen bricks collected from a recent Archeological investigation of Alto da Sé, in the town of Olinda. Qualitative determination of the chemical elements present in the samples was undertaken using a self‐assembled portable XRF system based on a compact X‐ray tube and a thermoelectrically cooled Si‐PIN photodiode system, both commercially available. X‐ray diffraction analysis was also carried out to assess the crystalline mineral phases present in the bricks. The results showed that quartz (SiO₂) is the major mineral content in all bricks. Although less expressive in the XRD patterns, mineral phases of illite, kaolinite, anorthite, and rutile are also identified. The trace element distribution patterns of the bricks, determined by the XRF technique, is dominated by Fe and, in decreasing order, by K, Ti, Ca, Mn, Zr, Rb, Sr, Cr, and Y with slight differences among them. Analyses of the chemical compositional features of the bricks, evaluated by principal component analysis of the XRF datasets, allowed the samples to be grouped into five clusters with similar chemical composition. These cluster groups were able to identify both age and manufacturing sites. Dutch bricks prepared with different geological clays compositions were defined.     

Investigation of cadmium accumulation mechanism in hepatopancreas of Patinopecten yessoensis by synchrotron radiation X‐ray absorption fine structure and synchrotron radiation X‐ray fluorescence analyses

Chemical state of cadmium in a hepatopancreas of a scallop (Patinopecten yessoensis) was studied by means of synchrotron radiation‐based X‐ray analytical techniques. X‐ray absorption fine structure (XAFS) and X‐ray fluorescence (XRF) imaging were used to identify the chemical state and the distribution of cadmium in the hepatopancreas, respectively. The results of in vivo Cd K‐edge XAFS suggested that the neighboring atoms of the cadmium in the hepatopancreas are of sulfur. Therefore, we propose that cadmium was accumulated by a metalloprotein with sulfur. Micro XRF imaging of thin sections of the hepatopancreas showed that cadmium is distributed on the surface of intestinal epithelia and concentrated in the internal tissue of the hepatopancreas. These results indicated that scallops accumulate cadmium inside the hepatopancreas through the intestinal epithelium.     

A sub‐micrometer resolution hard X‐ray microprobe system of BL8C at Pohang Light Source

A microprobe system has been installed on the nanoprobe/XAFS beamline (BL8C) at PLS‐II, South Korea. Owing to the reproducible switch of the gap of the in‐vacuum undulator (IVU), the intense and brilliant hard X‐ray beam of an IVU can be used in X‐ray fluorescence (XRF) and X‐ray absorption fine‐structure (XAFS) experiments. For high‐spatial‐resolution microprobe experiments a Kirkpatrick–Baez mirror system has been used to focus the millimeter‐sized X‐ray beam to a micrometer‐sized beam. The performance of this system was examined by a combination of micro‐XRF imaging and micro‐XAFS of a beetle wing. These results indicate that the microprobe system of the BL8C can be used to obtain the distributions of trace elements and chemical and structural information of complex materials.     

A critical analysis of the application of EDXRF spectrometry on complex stratigraphies

In this work, the potentialities and limits of the investigation by portable energy‐dispersive X‐ray fluorescence (XRF) of complex polychrome stratigraphies are discussed. Data are affected by the mutual influence effects of the chemical elements that characterize mineral pigments, by the sequence and the thickness of the paint layers in the stratigraphies and by the size of pigment grains. Sequences of pictorial layers, which produce the typical stratigraphy of cold‐painted terracotta and wooden sculptures, have been prepared and then analysed by means of two portable X‐ray spectrometers: Innov X Systems Alpha 4000 (Tantalum X‐ray tube, 40 kV and 7 µA) and Assing Lithos 3000 (Molybdenum X‐ray tube, 25 kV and 300 µA). For each layer of pigment, the XRF spectrum was acquired and the areas of K and L peaks of characterizing elements were calculated. Moreover, the thickness of the layers was determined using XRF data following an algorithm already shown and the values have been compared with those measured on polished cross sections observed by optical microscope in reflected light. Copyright © 2011 John Wiley & Sons, Ltd.     

Si PIN X‐ray photon counter

A Si PIN detector for visible light detection, instead of a Geiger‐Müller tube, is applied to X‐ray photon counting. We counted radiation from a checking source of a Geiger‐Müller counter with a Si PIN counter and with a Geiger‐Müller counter. White X‐ray of energy up to 20 keV emitted from a pyroelectric X‐ray emitter was also counted, and the Si PIN X‐ray counter showed a similar curve of count rate versus source distance in both measurements. Pulse counting was performed by spectroscopy circuits. An audio digitizer with computer software for signal processing was also used to simplify the photon counter. A plot of count rate versus time was obtained with this setup. With simple pulse counting circuits, Si PIN X‐ray counters have advantages such as compact structure, low cost and easy application. Copyright © 2011 John Wiley & Sons, Ltd.     

Ca_(1-x)Al_2Si_2O_8∶Eu_x表面结构与荧光强度相互关系的研究

采用固相法分别在1 150,1 250,1 350,1 450℃下制备了Ca_(1-x)Al_2Si_2O_8∶Eu_x(x=0,0.01,0.05,0.15)系列微晶材料。通过X射线衍射仪(XRD)、拉曼光谱仪(Raman)、光致发光光谱仪(PL)和X射线荧光光谱仪(XRF)研究了CaAl_2Si_2O_8表面结构与荧光强度之间的相互关系。XRD和Raman结果表明:在制备CaAl_2Si_2O_8材料的过程中,随着温度不断升高,原材料逐渐结晶形成结构较为完整的CaAl_2Si_2O_8相;并且从拉曼光谱可以清晰看出,当Eu掺杂量相同时,随着烧结温度的升高,Si—O非晶相逐渐减少,硅氧四面体逐步形成,其振动峰位置逐渐向低波数移动,但当温度过高时硅氧四面体破坏形成宽化的的非晶峰;Eu的掺杂阻碍了Al取代Si位置的过程,因此在1 620波数处振动峰先增强后减弱。这种材料表面结构的变化与Eu的掺杂密切相关,影响着材料表面Eu原子数量分布。PL和XRF结果表明:相同Eu掺杂量时,温度越高越有利于Eu原子扩散到样品表面,从而使样品的荧光强度更强。因此样品的荧光强度和样品单位表面积Eu原子数量存在正比关系。     

The first microbeam synchrotron X‐ray fluorescence beamline at the Siam Photon Laboratory

The first microbeam synchrotron X‐ray fluorescence (µ‐SXRF) beamline using continuous synchrotron radiation from Siam Photon Source has been constructed and commissioned as of August 2011. Utilizing an X‐ray capillary half‐lens allows synchrotron radiation from a 1.4 T bending magnet of the 1.2 GeV electron storage ring to be focused from a few millimeters‐sized beam to a micrometer‐sized beam. This beamline was originally designed for deep X‐ray lithography (DXL) and was one of the first two operational beamlines at this facility. A modification has been carried out to the beamline in order to additionally enable µ‐SXRF and synchrotron X‐ray powder diffraction (SXPD). Modifications included the installation of a new chamber housing a Si(111) crystal to extract 8 keV synchrotron radiation from the white X‐ray beam (for SXPD), a fixed aperture and three gate valves. Two end‐stations incorporating optics and detectors for µ‐SXRF and SXPD have then been installed immediately upstream of the DXL station, with the three techniques sharing available beam time. The µ‐SXRF station utilizes a polycapillary half‐lens for X‐ray focusing. This optic focuses X‐ray white beam from 5 mm × 2 mm (H × V) at the entrance of the lens down to a diameter of 100 µm FWHM measured at a sample position 22 mm (lens focal point) downstream of the lens exit. The end‐station also incorporates an XYZ motorized sample holder with 25 mm travel per axis, a 5× ZEISS microscope objective with 5 mm × 5 mm field of view coupled to a CCD camera looking to the sample, and an AMPTEK single‐element Si (PIN) solid‐state detector for fluorescence detection. A graphic user interface data acquisition program using the LabVIEW platform has also been developed in‐house to generate a series of single‐column data which are compatible with available XRF data‐processing software. Finally, to test the performance of the µ‐SXRF beamline, an elemental surface profile has been obtained for a piece of ancient pottery from the Ban Chiang archaeological site, a UNESCO heritage site. It was found that the newly constructed µ‐SXRF technique was able to clearly distinguish the distribution of different elements on the specimen.     

Methodological challenges of optical tweezers‐based X‐ray fluorescence imaging of biological model organisms at synchrotron facilities

Recently, a radically new synchrotron radiation‐based elemental imaging approach for the analysis of biological model organisms and single cells in their natural in vivo state was introduced. The methodology combines optical tweezers (OT) technology for non‐contact laser‐based sample manipulation with synchrotron radiation confocal X‐ray fluorescence (XRF) microimaging for the first time at ESRF‐ID13. The optical manipulation possibilities and limitations of biological model organisms, the OT setup developments for XRF imaging and the confocal XRF‐related challenges are reported. In general, the applicability of the OT‐based setup is extended with the aim of introducing the OT XRF methodology in all research fields where highly sensitive in vivo multi‐elemental analysis is of relevance at the (sub)micrometre spatial resolution level.     

Confocal macro X‐ray fluorescence spectrometer on commercial 3D printer

Novel confocal X‐ray fluorescence (XRF) spectrometer was designed and constructed for 3D analysis of elementary composition in the surface layer of spatially extended objects having unlimited chemical composition and geometrical shape. The main elements of the XRF device were mounted on a moving frame of a commercial 3D printer. The XRF unit consists of a silicon drift detector and a low‐power transmission‐type X‐ray tube. Both the excitation and secondary X‐ray beams were formed and regulated by simple collimator systems in order to create a macro confocal measuring setup. The spatial accuracy of the mechanical stages of the 3D printer achieved was less than 5 μm at 100‐μm step‐size. The diameter of the focal spot of the confocal measuring arrangement was between 1.5 and 2.0 mm. The alignment of the excitation and secondary X‐ray beams and the selection of the measuring spot on the sample surface were ensured by two laser beams and a digital microscope for visualization of the irradiated spot. The elements of the optical system together with the XRF spectrometer were mounted on the horizontal arm of the 3D printer, which mechanical design is capable of synchronized moving the full spectroscopic device within vertical directions. Analytical capability and the 3D spatial resolution of the confocal spectrometer were determined. Copyright © 2017 John Wiley & Sons, Ltd.     

Synchrotron XANES and ED‐XRF analyses of fine‐paste ware from 13th to 14th century maritime Southeast Asia

The combination of energy dispersive X‐ray fluorescence (ED‐XRF) and synchrotron X‐ray absorption near‐edge structure (XANES) provides the detailed composition of fine‐paste ware (FPW) kendis, dated back to 13th–14th century maritime Southeast Asia. Sources of clay and production sites were classified according to Al₂O₃, SiO₂, α‐Fe₂O₃ and γ‐Fe₂O₃ as well as trace elements. The similarities based on these components provided another evidence of a trade route between Kota Cina in North Sumatra of Indonesia and Kok Moh on Satingphra Peninsula, a well‐known production area in present‐day Thailand. In additions, the uniquely large contribution of α‐Fe₂O₃ in XANES spectra suggests that Nakhon Si Thammarat province of Thailand could also be one of FPW production areas in maritime Southeast Asia. Copyright © 2017 John Wiley & Sons, Ltd.     

ED‐XRF set‐up for size‐segregated aerosol samples analysis

The knowledge of size‐segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi‐stage cascade impactors. In this work, samples were collected using a low‐pressure 12‐stage Small Deposit Impactor and a 13‐stage rotating Micro Orifice Uniform Deposit Impactor^?. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set‐up for X‐ray analysis. This work aims at setting up an energy dispersive X‐ray fluorescence (ED‐XRF) spectrometer to analyse quantitatively size‐segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED‐XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle‐induced X‐ray emission (PIXE), which is more frequently applied to size‐segregated samples characterised by small PM quantities. A very good agreement between ED‐XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter‐comparability proves that our methodology is reliable for analysing size‐segregated samples by ED‐XRF technique. The advantage of this approach is that ED‐XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi‐stage impactors. Copyright © 2011 John Wiley & Sons, Ltd.