Total reflection X-ray fluorescence—an efficient method for micro-, trace and surface layer analysis. Invited lecture

Abstract

Total reflection X-ray fluorescence spectrometry (TXRF) uses an ingenious excitation technique for energy-dispersive X-ray spectral analysis. A minute amount of sample is placed on an optically flat carrier and irradiated at a grazing incidence (an angle of only a few minutes) so that the carrier totally reflects the primary beam. The method is particularly suitable for micro-, trace and surface layer analysis. Microanalysis can be performed because <1 µg of a solid sample or <10 µl of a solution are required. Trace analyses are based on detection limits at the picogramme level and can be applied to aqueous solutions (1 pg ml–1), acids (10 pg ml–1), biological materials (10 ng ml–1) and ultra-pure metals (10 ng g–1) after matrix separation. A simple and reliable quantification can be carried out by the addition of an internal standard element. Surface and thin-film analyses are applied to semiconductor wafer materials. Contaminations at 1 × 1010 atoms cm–2 can be detected and even nanometre thick layers can be investigated by non-destructive depth profiling. For this latter purpose, the angle of incidence is continuously varied in the range of total reflection and an angle-dependent intensity profile is recorded.