TOTAL REFLECTION X-RAY-FLUORESCENCE - AN EFFICIENT METHOD FOR MICROANALYSIS, TRACE AND SURFACE-LAYER ANALYSIS

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-mu-g of a solid sample or < 10-mu-l of a solution are required. Trace analyses are based on detection limits at the picogram 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 x 10(10) 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.