Synchrotron radiation-induced total reflection X-ray fluorescence analysis

Abstract

Synchrotron radiation-induced total reflection X-ray fluorescence (SR-TXRF) analysis is a high sensitive analytical technique that offers limits of detection in the femtogram range for most elements. Besides the analytical aspect, SR-TXRF is mainly used in combination with angle-dependent measurements and/or X-ray absorption near-edge structure (XANES) spectroscopy to gain additional information about the investigated sample. In this article, we briefly discuss the fundamentals of SR-TXRF and follow with several examples of recent research applying the above-mentioned combination of techniques to analytical problems arising from industrial applications and environmental research. ª

High-energy-resolution grazing emission X-ray fluorescence applied to the characterization of thin Al films on Si

“…The resolution was found to be 0.17 mrad. This is better or comparable to the reported angular resolutions of other GEXRF setups which are of the order of 1 mrad or lower [49,74,76]. In the latter setups either an analyzer crystal or an energy-dispersive detector in combination with a collimator slit system was employed to define the grazing emission angle.…”

“…In most cases the assumption of a stratified model with homogeneous and discrete layers was made to fit the data by inverse modeling, the initial model needing to describe the probed sample already well enough for a reliable interpretation [55,57]. Also the surface roughness had to be considered [62,63] and the X-ray source coherence lengths were found to have a major impact on the extension of the standing wave-pattern [49,50]. A different grazing incidence technique is X-ray reflectometry (XRR) [64].…”

“…In the two former application domains the X-ray fluorescence intensity is detected at a fixed incidence or emission angle below the critical angle since the primary goal is to detect the presence of contaminants. In this case the grazing incidence geometry is commonly referred to as the total reflection of X-ray fluorescence (TXRF) technique [49][50][51]. TXRF has also been combined with sputter etching [52] to realize depth-profiling experiments.…”

Synchrotron X-ray fluorescence analysis in environmental and earth sciences

“…In total reflection X-ray fluorescence (TXRF), minute amounts of sample are excited at very low angle of incidence by the X-ray standing wave field generated above a reflector surface, due to interference of incoming and reflected beams [17,18]. An important attribute of this measurement condition is that the penetration depth of the X-ray field inside the sample substrate becomes very small thereby drastically reducing the spectral background, which in turn improves the detection sensitivities by several orders of magnitude.…”

Effect of synchrotron polarization on grazing incidence X-ray fluorescence analysis

“…Based on the classical dipole oscillator, it is well understood that the emission profile of scattered radiation is anisotropic in case of a polarized xray beam. Maximal signal to noise ratio can be realized if fluorescence signal is measured in a position, where the contribution of anisotropic scattered radiation is minimal 5 .…”