SEM-XRF: Full Range EDS on large and irregular geological samples

Micro-X-ray fluorescence spectroscopy (XRF) represents a well-established and complementary analytical technique to electron beam energy dispersive spectroscopy (EDS) for the detailed characterization of elemental composition in samples. The integration of the X-ray source (namely XTrace) facilitates the application of XRF technology within a scanning electron microscope (SEM). Micro-XRF excitation analysis is a specialized small-area/volume technique, particularly suitable for beam-sensitive samples due to the absence of charging effects. The technique offers significant advantages, including enhanced sensitivity for trace element detection, the capability to excite higher energy X-ray lines (spanning a full spectral range to 40 keV), and the acquisition of information from greater sample depths even in centimeter level.

The deployment of advanced X-ray polycapillary optics enables the focal spot size of the X-rays to be reduced to 10 microns, all within an X-ray source compatible with SEM ports. X-ray energy detection is performed using the existing EDS detector integrated into the SEM system. Consequently, the SEM system attains dual-source capability, encompassing both electron and X-ray sources (as illustrated in Fig. 1), thereby expanding the possibilities for material characterization. This dual-source capability is termed "Full Range EDS," leveraging the novel analytical potential arising from the combined dual excitation of micro-XRF and electron beam sources alongside an EDS detector. This dual-beam system, allowing samples to interact with either the SEM's electron beam, the XTrace’s X-ray photons, or both simultaneously. Full Range EDS confers numerous advantages over traditional EDS, providing researchers with deeper insights into the elemental and compositional intricacies of their samples.