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Larger spectral bandwidth and higher photon flux density are the major advantages of multilayer monochromators over crystal-based devices. Especially for synchrotron-based hard X-ray microimaging applications the increased photon flux density is important in order to achieve high contrast and resolution in space and/or time. However, the modifications on the beam profile induced by reflection on a multilayer are a drawback which can seriously harm the performance of such a monochromator. A recent study [A. Rack, T. Weitkamp, M. Riotte, D. Grigoriev, T. Rack, L. Helfen, T. Baumbach, R. Dietsch, T. Holz, M. Krämer, F. Siewert, M. Meduna, P. Cloetens, E. Ziegler, J. Synchrotron Radiat. 17 (2010) 496510] has shown that the modifications in terms of beam flatness and coherence preservation can be influenced via the material composition of the multilayer coating. The present article extends this knowledge by studying further material compositions used on a daily basis for hard X-ray monochromatization at the beamline ID19 of the European Synchrotron Radiation Facility.
The results of an interlaboratory comparison of energy dispersive X-ray microanalysis of TiN0.84 and ZrN were presented. The microprobe group of the German Physical Society (DPG) and the Federal Institute for Materials Research and Testing (BAM) had initiated the interlaboratory comparison. The primary aim was to test modern EDX systems equipped with ultrathin windows concerning the accuracy and reliability of the analysis of compounds containing light elements. The participants from 23 laboratories performed the analysis at different primary energies, in the standard-less mode as well as on the base of own standards, and considering Ti-K or Ti-L in case of TiN0.84. The results show a slight overestimation of the nitrogen content and a large standard deviation from the mean value. Reasons for the scattering of the results are discussed.
Electron probe microanalysis (EPMA) measurement of thin-film thickness in the nanometre range
(2002)
The thickness of thin films of platinum and nickel on fused silica and silicon substrates has been determined by EPMA using the commercial software STRATAGEM for calculation of film thickness. Film thickness ranged in the order 10 nm. An attempt was made to estimate the confidence range of the method by comparison with results from other methods of analysis. The data show that in addition to the uncertainty of the spectral intensity measurement and the complicated fitting routine, systematic deviation caused by the underlying model should be added. The scattering in the results from other methods does not enable specification of a range of uncertainty, but deviations from the real thickness are estimated to be less than 20%.
One of the crucial characteristics of functionalized thin films is their porosity (i.e., the ratio between the pore volume and the volume of the whole film). Due to the very low amount of material per coated area corresponding to thin films, it is a challenge for analytics to measure the film porosity. In this work, we present an Approach to determine the porosity of thin films by means of electron probe microanalysis (EPMA) either by wavelength-dispersive X-ray spectrometry (WDX) or by energy-dispersive X-ray spectrometry (EDX) with a scanning electron microscope (SEM). The procedure is based on the calculation of the film mass deposition from electron-excited X-ray spectra. The
mass deposition is converted into film density by division of measured film thickness.
Finally, the film porosity is calculated from the measured film density and the density of bulk, nonporous film material. The general applicability of the procedure to determine the
porosity is demonstrated on thin templated mesoporous TiO₂
films, dip-coated on silicon
wafer, with controlled porosity in the range of 15 to 50%. The high accuracy of the mass deposition as determined from X-ray spectra was validated with independent methods (ICP-OES and weighing). Furthermore, for the validation of the porosity results, ellipsometry, interference fringes method (IFM), and focused ion beam (FIB) cross sectioning were employed as independent techniques. Hence, the approach proposed
in the present study is proven to be suited as a new analytical tool for accurate and relatively fast determination of the porosity of thin films.
Controlling the level of mostly detrimental residual stresses already during the welding process would be highly attractive as time and cost consuming post processing may be prevented. Therefore, in this study, the approach using suitable alloy concepts with reduced phase transformation temperatures has been evaluated concerning the interactions between transformation temperature, transformation kinetics and resulting residual stresses. Ideal tools for observing these phenomena in-situ are diffraction techniques. For that purpose, a special setup was developed allowing for localized observation of phase transformation kinetics during a real welding process by energy dispersive synchrotron diffraction (EDXRD). In the present work, this setup was successfully applied for the first time in order to characterize a selection of alloys especially designed for residual stress control. The results demonstrate that in-process observation is highly suitable for characterizing and discussing phase transformation sensitive phenomena like residual stress formation. Furthermore, it was proven that residual stresses can be effectively controlled by means of an adjusted alloy design.
X-ray backscatter imaging is a promising NDT technique to inspect complex objects using only a single-sided access. In difference to conventional transmission X-ray radiography, the X-ray backscatter imaging utilizes the scattered radiation caused by the Compton scattering effect. In order to achieve high backscatter intensities from a test object, it is necessary to optimize the backscatter system parameters namely the angle between source and slit camera, the slit-collimator system, the shielding between the source and scatter camera, and the type of detector. Here a single-slit as well as a multi-slit camera are considered. For the multi-slit camera several twisted slits were parallel arranged in a metal block. This camera generates a set of similar projections per slit overlaying each other. Afterwards, the image is corrected based on a de-convolution algorithm to focus the overlaying projections into a single representation of the object.
The scatter phenomena in the object under inspection are investigated. In this contribution, the Monte Carlo model McRay is discussed, which considers all relevant single and multiple interactions of photons and electrons. This model can be used to simulate back scatter techniques. Simulations are important to describe the imaging process, to interpret the results, and to optimize the backscatter camera investigated here. Experimental results will be presented and compared with simulations.
Ionic liquids (ILs) are proposed as simple and efficient test materials to evaluate the performance of energy dispersive X-ray spectrometers (EDS) in the low energy range below 1 keV. By only one measurement, C Kα, N Kα, O Kα, and F Kα X-ray lines can be excited. Additionally, the S Kα line at 2.3 keV and, particularly, the S L series at 149 eV complete the picture with X-ray lines offered by the selected ILs. The well-known (certifiable) elemental composition of the ILs selected in the present study can be used to check the accuracy of results produced with the available EDS quantification routines in the low energy range, simultaneously, for several low atomic number elements. A comparison with other reference materials in use for testing the performance of EDS in the low energy range is included.
An energy dispersive X-ray spectrometer operating with a semiconductor detector should be specified in compliance with the ISO standard 15632 [1]. Requirements for specification are: a) a general description of the spectrometer to evaluate its performance, b) the energy resolution with corresponding dead time, c) the P/B ratio in the Fe55 spectrum and, finally, d) the L/K intensity Ratio in a Ni or Cu spectrum to estimate spectrometer efficiency at low energies. Items b) to d) can be easily checked by the user. Related procedures are recommended in the annexes of the standard.
As one of the widely used analytical methods for the analysis of elemental composition of solid matter, energy dispersive X-ray spectroscopy (EDS) has recently gained significant importance regarding its application to the chemical analysis of nanoparticles, especially in conjunction with the use of a scanning electron microscope (SEM) and the use of the transmission operation mode of SEM (STEM-in-SEM). This development was mainly driven by the technological progress with highly sensitive EDS detectors, such that individual nanoparticles can be quickly inspected with EDS at a SEM. Qualitative information on elemental composition with about 10 nm spatial resolution can be achieved complementary to the high-resolution information of the sample surface morphology within the same scanned area as provided by the electron microscope. Representative examples with successful EDS analysis on nanoparticles are presented, but also limitations of the method are described.