Abstract. Measurements of X-ray fluorescence spectra versus grazing incident angles provide information on elemental composition as well as density and thickness of near surface layers. Calculations of fluorescence intensities are presented, which are used for the evaluation of data obtained by total reflection X-ray fluorescence (TXRF) spectrometry. The calculation is based on a matrix formalism to account for standing wave phenomena due to transmission and reflection in layered material. For the determination of concentrations the model makes additional use of the fundamental parameter technique in order to include absorption and enhancement effects of the fluorescence radiation. On the basis of experimental data some capabilities of this nondestructive and contactless probing technique are presented. PACS: 0%85, 68.35The production and application of thin films, single layers and layer systems on diverse substrates have reached a high degree of economic importance. It is widely appreciated that this technology will require further analytical techniques, especially those which can be employed in a production environment to support the increased requirements for contamination control and layer specification. In this paper we describe total reflection X-ray fluorescence (TXRF) spectrometry as a nondestructive and contactless probing technique for quantitative surface and layer analysis in the nanometer range.For X-rays striking a surface at grazing incidence, a critical angle exists below which total reflection occurs. Under total reflection conditions, the incident X-ray beam interacts, in contrast to conventional XRF, only with the near surface layers. Depending mainly on the density of the reflecting interface, the penetration depth of the primary X-ray beam is approximately 2-8 nm. In this mode of operation, the TXRF is an intrinsically surface sensitive as well as a proven method of trace element analysis [1]. Detection limits better than 10 l° atoms/cm 2 are obtained for metal impurities in the oxide layer of silicon wafers [2]. Moreover, it is possible to distinguish quantitatively between impurities which are embedded in a surface and those on a surface as particles or residues [3].* Author to whom correspondence should be addressed On exceeding a critical angle, the reflectivity decreases rapidly and the primary beam illuminates deeper parts of the material according to the angle of incidence. Therefore, X-ray fluorescence spectrometry in the critical angle regime offers the advantage of combining surface sensitivity with the analysis of stratified heterostructures [4,5]. We outline a procedure for the quantitative determination of elemental composition, density and thickness of layers: a calibrated instrument is used for measuring fluorescence intensities as a function of the incident angle. In order to deduce the layer parameters from the experimental data modelling calculations of the fluorescence intensities are compared with the measured data. By means of an iterative process that set of parameters ...

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Total Reflection X-ray Fluorescence Spectrometry (TXRF) has been used for the characterisation of a 20 nm thick Ni/Fe/Cr-layer on a silicon substrate. Instrumental aspects of the technique as well as the data evaluation procedure on the basis of modelling calculations are outlined in this paper. The effect of standing waves is discussed by means of the selected example. This particular layer serves also as an illustration of the capabilities and limitations of TXRF. At least three surface parameters are covered by the technique, elemental composition, density and layer thickness.

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