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Trace Element Analysis using Total-Reflection X-Ray Fluorescence Spectrometry

Published online by Cambridge University Press:  06 March 2019

Andreas Prange  and
Heinrich Schwenke
Andreas Prange
Affiliation:
GKSS Research Centre, Institute for Physics, P.O. Box 1160 D-2054 Geesthacht, Germany
Heinrich Schwenke
Affiliation:
GKSS Research Centre, Institute for Physics, P.O. Box 1160 D-2054 Geesthacht, Germany
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Abstract

For the application of TXRF in trace element analysis, two characteristic features of the total reflection of X-rays are exploited. These are the high reflectivity on flat surfaces and the low penetration depth of the primary radiation. This allows the application of TXRF for both chemical trace and ultra-trace element analysis on the one hand and surface analysis on the other. For chemical trace clement analysis, total reflection on a highly polished substrate is characterized by a high reflectivity, which leads to a drastic reduction of the spectral background. The sample to be analyzed is prepared on the substrate as a residue of small quantities by evaporation from solutions or fine-grained suspensions. Instrumental detection limits of a few pg or sub-ng/ ml−1 arc state of the art for commercially available equipment. Besides the high detection power, internal standardization is another important feature of TXRF, enabling very simple quantification of the detected elements. The small sample mass required enables especially ultra-micro analytical questions to be tackled. For trace element analysis in surfaces the low penetration depth of the primary radiation under the conditions of total reflection is exploited. The penetration depth is in the range of a few nanometers, hence, TXRF is intrinsically surface sensitive. Detection limits better than 1010 atoms/cm2 are obtained for metal impurities on silicon wafers. For the examination of layered structures elemental composition, layer thickness, and density can be derived from die angle-dependent fluorescence intensities. The present paper describes the basic features of the total reflection of X-rays and gives some representative examples of the different uses of TXRF in trace element analysis.

Type
XII. Total Reflection XRS
Information
Advances in X-Ray Analysis , Volume 35 , Issue B: First Pacific-International Congress on X-ray Analytical Methods (PICXAM). Fortieth Annual Conference on Applications of X-ray Analysis, August 7-16, 1991 , 1991 , pp. 899 - 923
Copyright
Copyright © International Centre for Diffraction Data 1991

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