The use of Si carriers for aerosol particle collection and subsequent elemental analysis by total-reflection X-ray fluorescence spectrometry

The adoption of polished Si carriers was studied for the sensitive elemental analysis of aerosol particles using total-reflection X-ray fluorescence (TXRF) spectrometry. The surface roughness of the Si carrier measured by atomic force microscopy was found to be smaller than those of glassy carbon and quartz glass carriers, which are commonly used for TXRF analysis. The detection limits of elements for the Si carrier were superior to those for the glassy carbon and the quartz glass carriers, presumably due to its smaller surface roughness. For example, the detection limit of Sr for the Si carrier was 9 pg, which was 100 times and 3 times lower than those for the glassy carbon and the quartz glass carriers, respectively. The Si carriers could be successfully applied to the direct aerosol particle collection by impaction and the subsequent elemental analysis by TXRF. From the results of the elemental analysis of aerosol particles, the variations in the concentrations of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn Sr and Pb with time could be clarified.     

Design of a doubly-curved crystal to improve X-ray fluorescence analysis of aerosol particles

Doubly-curved crystals (DCCs) can be very useful devices to focus and monochromatize radiation from an X-ray tube or a synchrotron, especially for X-ray fluorescence analysis. However, production of a DCC is somewhat difficult. In this paper we will present some basic theory about DCC geometries, different ways of DCC production and methods to test the quality of the DCCs.     

Depth profiles of shallow implanted layers by soft ion sputtering and total-reflection X-ray fluorescence

A new method suitable for depth profiling of shallow layers on different materials is presented. It is based on a soft and planar ion sputtering combined with differential weighing, total-reflection X-ray fluorescence (TXRF) spectrometry and Tolansky interferometry. By means of a stepwise repetition of these techniques it is possible to determine both density/depth and concentration/depth profiles. The respective quantities are expressed in terms inherent only to the sample and traceable to the SI-units or subunits gram, nanometer and mole. It is a unique feature of this method that density/depth profiles can directly be obtained from measurements without any calibration or theoretical approximation. The method is applied to a Si wafer implanted with Co ions of 25 keV energy and a nominal dose of 1×10¹⁶ cm⁻². The depth resolution is shown to be <3 nm while a total depth of some 100 nm can be reached. The concentration/depth profile is compared with RBS measurements, wet-chemical etching plus TXRF and Monte Carlo simulations. In view of the fact that only similar but not exactly the same samples have been examined by these methods, a good correspondence can be noticed.     

Application of total-reflection X-ray fluorescence spectrometry in material analysis

X-ray fluorescence spectrometry with total reflection conditions is applied in the qualitative and quantitative determination of impurities in thin layers of Ti, TiO₂, and HfO₂ prepared by evaporation and of SiO₂, TiO₂, and Ta₂O₅ prepared by ion beam sputtering. The same method is used to examine stainless steel discs, which have to be used as reference materials,Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Evolution of anthropogenic aerosols in the coastal town of Salina Cruz,Mexico: part III size-segregated elemental composition analysed by total-reflection X-ray fluorescence spectrometry

Heavy metals in various size modes of the atmospheric aerosol are a concern for human health. Their and other elements’ concentrations are indicative for anthropogenic and natural aerosol sources. Si, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Hg, and Pb were determined as a complementary contribution to a study on aerosol cycling during the wet season, June 2004, in a humid, subtropical climate, i.e. in the city of Salina Cruz, situated on the Pacific coast of the Isthmus of Tehuantepec (16.2°N, 95.2°W), Mexico. For mass (gravimetry) and elemental analyses, particles were collected by a Berner low-pressure round nozzle cascade impactor using four stages corresponding to 0.1–0.25, 0.25–1.0, 1.0–4.0, and 4–16?µm of aerodynamic particle size. The impaction plates were modified such that approx. 1/6 consisted of a plastic support (Persplex®) for total reflection X-ray fluorescence spectrometry (TXRF). The elements’ total content was determined by TXRF without any further sample pretreatment. Limits of quantification (LOQ) for elemental content in individual impactor stages corresponded to 25–60?ng?m^?3 for Si; 0.8–4?ng?m^?3 for Cl, K, Ca, Ti, and V; 3–20?pg?m^?3 for Cr, Mn, Fe, Cu, Ni, and Zn; and 7–50?pg?m^?3 for As, Se, Br, Rb, Sr, Hg, and Pb. In some samples, however, high blank values for the supports gave an LOQ?=?6–19?ng?m^?3 for Cl; 3--7?ng?m^?3 for Ca; 3–7?ng?m^?3 for Fe, Ni, Cu, and Zn; and 60–70?ng?m^?3 for Pb. The influence of local natural, industrial, and vehicle traffic sources for heavy-metal mobilization was obvious. Heavy-metal abundances did not coincide with regionally distributed pollutants. V and Ni were found at particularly elevated levels advected with the sea breeze, which points to ships as sources. Br and Pb were found at particularly low levels. The concentrations of Br, Rb, Sr, and Pb were found below LOQ at least in some, As, Co, Se, and Hg in all of the samples. The elements’ characteristic differences in mass size distributions were obvious despite the coarse size resolution. During the cycling of air masses from land to sea and back again, enrichment of super-micrometre particles in the near ground aerosol was observed under dry weather conditions. Rain preferentially removed the large particles with which heavy metals have been associated.     

Total-reflection X-ray fluorescence analysis for semiconductor process characterization

Semiconductor process characterization techniques based on total-reflection X-ray fluorescence (TXRF) analysis are reviewed and discussed. One of the most critical factors in obtaining reliable determinations by TXRF is the reliability of the standard samples that are used. Conventional physisorption standard samples such as spin coat wafers have two potential drawbacks: reproducibility of depth profile and stability. A method of chemisorption called ‘immersion in alkaline hydrogen peroxide solution (IAP)’ was proposed that provides answers to these two problems. IAP standard samples were used to experimentally examine three methods of TXRF application: Straight-TXRF, VPD-TXRF, and Sweeping-TXRF. In the application of Straight-TXRF, the linearity of Cu at a level of 10⁹ atoms cm⁻² is examined. In the application of VPD-TXRF, test results of VPD-TXRF for both transition metals and light elements are shown. Finally, a new measurement protocol called Sweeping-TXRF is proposed to conduct whole-surface analysis without chemical preconcentration.     

Study of biofilm formation by total-reflection X-ray fluorescence spectrometry

A total reflection X-ray fluorescence spectrometric method was developed for elemental analysis of natural biofilms grown on polycarbonate substrates in the Lake Velence. For the duration of 9 weeks long growing period, two substrates were removed weekly from the lake and investigated by analytical and algological methods. The total biomass production achieved its highest value after 7 weeks. Ca, Sr and Ti, as well as Fe, Mn, K and Zn showed their maximum concentrations in the biofilms after 5 and 6-7 weeks, respectively. The enrichment factors of the 6 weeks old biofilm for the detected seven elements amounted to 10³-10⁴. The recommended colonization time for biomonitoring of the Lake Velence is 6 weeks applying polycarbonate substrates.     

Identification of steel by X-ray fluorescence analysis with a pyroelectric X-ray generator

An application of X-ray fluorescence analysis with a pyroelectric X-ray generator is presented. Steel standard samples were identified by X-ray fluorescence analysis with this novel X-ray generator to check its capability for performing qualitative and quantitative analysis as an X-ray source for X-ray fluorescence spectrometers. Cr, Ni, V, Co, and W were detected in steel standard samples. V and Cr can be detected even when the content is below 1%. Although it is difficult to detect minor elements because of the low power of the excitation X-rays, it is possible to identify the analyzed samples on the basis of major elements at the percentage level. The pyroelectric X-ray generator is very suitable for portable X-ray fluorescence spectrometers.     

Total-Reflection X-ray fluorescence analysis of elements in size-fractionated particulate matter sampled on polycarbonate filters — Composition and sources of aerosol particles in Göteborg,Sweden

This is the first study applying the technique of cold plasma ashing on polycarbonate filters as a preparative step for subsequent elemental analysis of aerosol particles by Total-Reflection X-ray fluorescence. The procedure has been validated by analyzing blanks of the filter material, chemicals used as additives as well as certified standard reference material. The results showed that cold plasma ashing is superior to conventional digestion methods with regard to the ease of sample preparation and contamination. A PIXE cascade impactor was used to collect size-fractionated aerosol particles in 9 size classes ranging from 16 to 0.06 µm aerodynamic diameter at an urban and a suburban site in Göteborg, Sweden. Filter segments loaded with the aerosol particles were cut out and fixed on Quartz carriers. After adding 10 ng of Ga as internal standard the samples were dried, digested by cold plasma ashing and analyzed by Total-Reflection X-ray fluorescence. The analysis of aerosol particles showed that elemental concentrations at both the urban and the suburban site in Göteborg were low compared to central Europe. More and concurrent sampling of size-fractionated particles is required to identify local sources of trace elements in the urban area of Göteborg.     

Development of vapor phase decomposition-total-reflection X-ray fluorescence spectrometer

A total reflection X-ray fluorescence spectrometer integrated with vapor phase decomposition, VPD-TXRF, was newly developed. This instrument was designed to achieve a minimum footprint, to avoid cross contamination during operation, and to protect people and instruments from HF gas. Comparisons between analysis by VPD-TXRF and by atomic absorption spectrometry (AAS) indicated very good agreement in a wide range, from 10⁸ to 10¹² atoms/cm². The lower limits of detection (LLDs) were improved by two orders of magnitude compared with straight TXRF. For 300-mm Si wafers, the LLDs were 5×10⁸ atoms/cm² and 1×10⁷ atoms/cm² for Al and Ni, respectively. VPD-TXRF was able to perform ultra-trace analysis at the level of 10⁸ atoms/cm².     

Development of an X-ray fluorescence spectrometric method for the analysis of atmospheric aerosol samples

A simple, rapid method was developed for the analysis of aerosol samples by X-ray fluorescence spectrometry. Aerosol measurements were made using various sample supports (Whatman and Teflon filters, Prolene® foil). The calibration procedure was carried out by dripping 500 μl of a gradually diluted multi-elemental standard solution (CertiPUR® 11355) onto the top of the sample supports, which were then dried at ambient temperature. Thirteen elements, namely Na, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr and Pb were calibrated and quantified. The optimal measurement parameters (excitation conditions, measuring times for each element) were determined on the basis of blank values and the amplitude of the signals. The filters were covered with Ta or Re plates to ensure infinite thickness for the penetration depth of the primary X-ray beam. It was also demonstrated that these plates served as a secondary target. The accuracy, precision and detection limits (0.01–0.18 mg/kg) were calculated. All the analytical parameters were better when Teflon filters and Prolene® foil were used than in the case of Whatman quartz fibre filters.     

X射线荧光光谱分析

本文评述了我国在2005年至2006年X射线荧光光谱,包括粒子激发的X射线光谱的发展和应用,内容包括仪器研制、激发源、探测器、软件、仪器改造、仪器维护和维修、样品制备技术、分析方法研究和应用.     

X射线荧光光光谱分析

评述了我国在2007～2008年X射线荧光光谱,包括质子激发的X射线光谱的发展和应用,内容包括仪器、软件、仪器改造、仪器维护和维修、基础研究和分析方法研究及其应用.     

X-ray Peltier cooled detectors for X-ray fluorescence analysis

The recent results on development of X-ray Si(Li), Si-planar and CdTe p-i-n detectors cooled by Peltier coolers for fabrication of laboratory and portable XRF analysers for different applications are discussed.

Low detection limits of XRF analysers are provided by increasing of detectors sensitive surface; improvement of their spectrometrical characteristics; decreasing of front-end-electronics noise level; Peltier coolers and vacuum chambers cooling modes optimization.

Solution of all mentioned tasks allowed to develop Peltier cooled detectors with the following performances:

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Advantages and disadvantages of all types of detectors for X-ray fluorescence analysis are compared. Spectra are presented. Application of different XRF analysers based on developed detectors in medicine, environmental science, industry, cryminalistics and history of art are demonstrated.     

X射线荧光光谱分析

作为《分析试验室》定期评述“X射线荧光光谱分析”系列评论第八篇,本文收集国内学者在1998年7月至2000年6月期间公开发表在国内外期刊和国际会议文集上的129篇论文,并对此期间对我国X射线荧光光谱分析的概况、发展和国际上的地位进行了讲述,内容包括仪器及维修、基体校正、数据处理方法、谱分析方法的研究、标样及样品制备、全反射X射线荧光光谱、同步辐射光源X射线荧光光谱、粒子激发X射线发射、X射线荧光光谱分析方法研究及其应用。     

X射线荧光光谱分析

本文评述了我国在2002年7月～2004年6月间X射线荧光光谱, 包括粒子激发的X射线光谱的发展和应用, 内容包括仪器的研制、维护和维修、样品制备技术、 X射线荧光光谱基础研究、谱处理、分析方法研究和应用.     

Electro-deposition as a sample preparation technique for total-reflection X-ray fluorescence analysis

A one-step sample preparation by electro-deposition for total-reflection X-ray fluorescence (TXRF) analysis has been developed using a common three-electrode arrangement with a rotating disc as the working electrode. Several elements such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Pb, As and U have been determined simultaneously in saline matrix. A special electrode tip has been constructed as a holder for the TXRF sample carrier, which consists of polished glassy carbon. The influence of parameters such as time, pH value, and trace element concentration on the deposition yield has been examined for 14 elements. From repeatability studies, the uncertainty in deposition yields at the 95% confidence level has been found to be less than 20% for most of these elements. Typical detection limits range from 5 to 20 ng/l under the experimental conditions applied here. By an appropriate choice of the reference element and by calculation of yield factors, reliable quantification can be achieved directly by internal standardization. First results obtained for the standard reference material CRM 505 are presented.     

Sapphire sample carriers for silicon determination by total-reflection X-ray fluorescence analysis

Sapphire is presented as a new sample carrier material for total-reflection X-ray fluorescence spectrometry (TXRF). A comparison with conventional sample carrier materials such as quartz glass, Perspex®, glassy carbon and boron nitride demonstrates that sapphire has all the physical and chemical properties required for TXRF micro and trace analysis. Moreover, sapphire sample carriers allow the determination of silicon in many matrices in a comparatively simple way. Especially for airborne particulate matter, acid digestion can be avoided by cool-plasma ashing of suitable filter materials directly on the sample carrier. This technique has been successfully applied to environmental samples.     

X-ray fluorescence imaging with polycapillary X-ray optics

X-ray fluorescence spectrometry imaging is a powerful tool to provide information about the chemical composition and elemental distribution of a specimen. X-ray fluorescence spectrometry images were conventionally obtained by using a μ-X-ray fluorescence spectrometry spectrometer, which requires scanning a sample. Faster X-ray fluorescence spectrometry imaging would be achieved by eliminating the process of sample scanning. Thus, we developed an X-ray fluorescence spectrometry imaging instrument without sample scanning by using polycapillary X-ray optics, which had energy filter characteristics caused by the energy dependence of the total reflection phenomenon. In the present paper, we show that two independent straight polycapillary X-ray optics could be used as an energy filter of X-rays for X-ray fluorescence. Only low energy X-rays were detected when the angle between the two optical axes was increased slightly. Energy-selective X-ray fluorescence spectrometry images with projection mode were taken by using an X-ray CCD camera equipped with two polycapillary optics. It was shown that Fe Kα (6.40 keV) and Cu Kα (8.04 keV) could be discriminated for Fe and Cu foils.