Determination of thickness and composition of thin films by x-ray fluorescence spectrometry using theoretical influence coefficient algorithms

摘要

X-ray fluorescence radiation intensity from analyte in thin film is a complex function of matrix composition and film thickness. Nevertheless, the complicated problem of matrix correction in XRF analysis of these materials can be simply solved by using the concept of theoretical influence coefficients. In this article, two algorithms based on the previous published equation for intermediate-thickness samples are proposed. In the first algorithm, the coefficients are treated as constants; in the second one, the coefficients are linear functions of sample thickness and concentration of all matrix elements. The coefficients are calculated from composition and relative radiation intensity (calculated from theory) of hypothetical pure element films and binary films. The calculations are presented in detail on Fe-Cr-Ni ternary films as an example. The capability of the algorithms is demonstrated with hypothetical Fe-Cr-Ni ternary systems and binaries Fe-Cr, Fe-Ni and Cr-Ni of thickness from 0.01 to 2 mg cm(-2). Diverse compositions of these specimens are in the range 5-95% (m/m) of each element. The algorithms are also verified using experimental data of Fe-Ni binary system films and Cu films taken from literature. Obtained results indicate the usefulness of the proposed algorithms for simultaneous and accurate determination of the chemical composition and thickness of thin film materials. Moreover, the calibration procedure is very clear and interpretation of the data is easy for the analyst, which is a serious advantage of the proposed algorithms over fundamental parameters methods. Copyright (C) 2008 John Wiley & Sons, Ltd.