Theoretical Considerations about Total Reflection X-Ray Fluorescence for Light Element Analysis at Various Excitation Energies and Experimental Results

TXRF with a special energy dispersive spectrometer is well suited for analyzing light elements, such as C, N, O, F, Na, Mg and Al. The elemental sensitivity is mainly influenced by the energy of the exciting radiation. Different excitation energies from 1.7 to 17.5 keV and the resulting background due to scattering on the reflector substrate under total reflection conditions were studied theoretically. The angular dependence of the fluorescence signal from low-Z atoms implanted in Si, excited by monoenergetic radiation of various energies, was calculated. The same was also done for Ti atoms implanted in Si, and compared with the measured results. The excitation energy in the experiments was monochromatized Cr-Kα radiation. In addition, results obtained with synchrotron radiation as the excitation source are presented. A detection limit of 200 fg for Mg has been obtained.