Boron has many applications in science and industry yet there don't exist any easy-to-use X-ray fluorescence analysis techniques to detect low concentrations of boron in a sample. Wavelength dispersive X-ray spectrometry (WDX) after excitation by scanning electron microscope (SEM-WDX) combines high spatial resolution obtained with an electron microprobe and a spectrometer with sub-eV energy resolution, and high sensitivity in the soft X-ray range. The sensitivity necessary for low concentration boron detection is achieved by a wide sagittal acceptance, high diffraction efficiency and the focussing effect of the used reflection zone plate (RZP). The RZP and a CCD camera form a compact WDX spectrometer (309 × 156 × 165 mm3), suitable for tabletop laboratory setups and as an add-on to beamlines at large-scale facilities. In order to test the detection limit for boron, three samples were measured: Duran glass with ~ 9 at% boron, Si (55 %) / Ge (45 %) with 1 at% boron implantation and Si (55 %) / Ge (45 %) with 0.1 at% boron implantation. After optimising the setup, a signal to noise (S/N) ratio of 7.2 was achieved at 0.1 at% boron, indicating a detection limit of 500 ppm for the current setup. Effects of radiation damage and energy shifts depending on the boron binding state were observed as well.
Stoytschew et al. (2026) studied this question.