Multilayer X-ray optics with single layers of a few nanometers thickness can be obtained nowadays. These optics are used in X-ray diffractometers (XRD), X-ray fluorescence spectrometers (XRF) and at synchrotron sources. A detailed description of the production of multilayer X-ray optics using sputter deposition methods is presented and the simulation of X-ray optics and characterization with X-ray analytical measurements are explained. Finally, the advantages of multilayer X-ray optics in typical X-ray analytical applications are summarized.
An EUV reflectometer for the analysis of surfaces and thin films regarding refractive index, surface roughness, and mass density at the wavelength of 12.98 nm was developed. The setup uses a laser produced plasma source with an oxygen gas puff target for the generation of narrow-band EUV radiation and a flexible Kirkpatrick-Baez optics for focusing. We present EUV reflectometry (EUVR) measurements conducted on a series of carbon thin films to determine thickness and mass density of the coatings. In case of the thickness measurements results are compared to data obtained from nondestructive standard methods, i.e., grazing incidence X-ray reflectometry and spectroscopic ellipsometry. In addition, we propose a method to deduce the mass density of a sample directly from the fitted index of refraction obtained from EUVR measurements.
A high‐performance W/B4C multilayer mirror with 80 periods of nominally 1.37 nm was measured by grazing‐incidence small‐angle X ray scattering (GISAXS) in order to analyse the lateral and vertical correlations of the interface roughness within the framework of a scaling concept of multilayer growth. A dynamic growth exponent z = 2.19 (7) was derived, which is close to the value predicted by the Edwards–Wilkinson growth model. The effective number of correlated periods indicates a partial replication of the low interface roughness frequencies. A simulation of the GISAXS pattern based on the Born approximation suggests a zero Hurst fractal parameter H and a logarithmic type of autocorrelation function. The as‐deposited mirror layers are amorphous and exhibit excellent thermal stability up to 1248 K in a 120 s rapid thermal vacuum annealing process. At higher temperatures, the B4C layers decompose and poorly developed crystallites of a boron‐rich W–B hexagonal phase are formed, and yet multilayer collapse is not complete even at 1273 K. Ozone treatment for 3000 s in a reactor with an ozone concentration of 150 mg m−3 results in the formation of an oxidized near‐surface region of a thickness approaching ∼10% of the total multilayer thickness, with a tendency to saturation.
X-ray mirrors are needed for beam shaping and monochromatization at advanced research light sources, for instance, free-electron lasers and synchrotron sources. Such mirrors consist of a substrate and a coating. The shape accuracy of the substrate and the layer precision of the coating are the crucial parameters that determine the beam properties required for various applications. In principal, the selection of the layer materials determines the mirror reflectivity. A single layer mirror offers high reflectivity in the range of total external reflection, whereas the reflectivity is reduced considerably above the critical angle. A periodic multilayer can enhance the reflectivity at higher angles due to Bragg reflection. Here, the selection of a suitable combination of layer materials is essential to achieve a high flux at distinct photon energies, which is often required for applications such as microtomography, diffraction, or protein crystallography. This contribution presents the current development of a Ru/C multilayer mirror prepared by magnetron sputtering with a sputtering facility that was designed in-house at the Helmholtz-Zentrum Geesthacht. The deposition conditions were optimized in order to achieve ultra-high precision and high flux in future mirrors. Input for the improved deposition parameters came from investigations by transmission electron microscopy. The X-ray optical properties were investigated by means of X-ray reflectometry using Cu- and Mo-radiation. The change of the multilayer d-spacing over the mirror dimensions and the variation of the Bragg angles were determined. The results demonstrate the ability to precisely control the variation in thickness over the whole mirror length of 500 mm thus achieving picometer-precision in the meter-range.
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