F29 Nanometer Multilayers as Monochromators for the X-ray Fluorescence Analysis

The principle of wavelength-dispersive X-ray fluorescence (WDXRF) analysis is based on the excitation of characteristic radiation of the chemical elements contained in the specimen under investigation. In order to separate the emission lines of the different elements, monochromators like crystals or multilayers are used. In this paper we will focus on the development and improvement of multilayer monochromators for the detection of light elements of the periodic table (Be – S). The photon wavelengths of the characteristic radiation of light elements are in the range of 0.711.4 nm. Correspondingly, the period thickness of the multilayers has to be in the same order. However with smaller period thicknesses the requirements for the interfaces between adjacent layers within the multilayer significantly increase. It has to be ensured that both interface roughness and interface diffusion has to be minimized at the same time. Additionally the stability of the deposition process must be extremely high since the multilayers consist of up to 1200 single layers. In this paper we will report about the improvement of different multilayer coatings (e.g. W/Si, W/B4C, Ni/C, Cr/C, Mo/B4C, Cr/Sc) in the period thickness range from 1.28.0 nm. We will present the improvement that was obtained and characterized by Cu-Kα reflectometry. Finally, we will show the performance of the multilayers at the working wavelengths.