Quantitative X-ray fluorescence analysis of boron in thin films of borophosphosilicate glasses

Abstract

X-ray fluorescence analysis of boron is complicated by the low atomic number and the low K shell energy of boron, and the effects of these on excitation, fluorescence yield, absorption and energy analysis. At present, acceptable energy resolution and sensitivity with small equipment dimensions and the capability of processing high photon counting rates can only be met by wavelength-dispersive energy analysis using synthetic multilayers as the diffraction device. These multilayers, compared with thallium acid phthalate and lead stearate, show a far increased reflectivity. They differ, however, from common analyser crystals in the marked appearance of higher order Bragg reflections. The analysis of boron in a matrix containing oxygen, for instance borophosphosilicate glass, is hampered by the overlap of B Kα in the first order and O Kα in the third order. It has been demonstrated that undesirable higher order Bragg reflections can be extinguished by employing multilayer structures with an appropriate thickness ratio of the layer pair. Thereby, it is possible to determine the mass content of boron in borophosphosilicate glass with an accuracy better than 0.2 wt.% B in a measuring time of 5 min.