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With the advent of both modern X-ray fluorescence (XRF) methods and improved analytical reliability requirements the demand for suitable reference samples has increased. Especially in nanotechnology with the very low areal mass depositions, quantification becomes considerably more difficult. However, the availability of suited reference samples is drastically lower than the demand. Physical vapor deposition techniques have been enhanced significantly in the last decade driven by the need for extremely precise film parameters in multilayer production. We have applied those techniques for the development of layer-like reference samples with mass depositions in the ng-range and well below for Ca, Cu, Pb, Mo, Pd, Pb, La, Fe and Ni. Numerous other elements would also be possible. Several types of reference samples were fabricated: multi-elemental layer and extremely low (sub-monolayer) samples for various applications in XRF and total-reflection XRF analysis. Those samples were characterized and compared at three different synchrotron radiation beamlines at the BESSY II electron storage ring employing the reference-free XRF approach based on physically calibrated instrumentation. In addition, the homogeneity of the multi-elemental coatings was checked at the P04 beamline at DESY. The measurements demonstrate the high precision achieved in the manufacturing process as well as the versatility of application fields for the presented reference samples.

Results of quantitative analysis of fluorescence x-ray absorption fine structure (XAFS) experiments at the FeK absorption edge are presented for a 6*(4.3 nm Fe/10.4 nm Al) multilayer prepared by pulsed laser deposition. Fluorescence XAFS experiments have been combined with excitation of prepared by pulsed laser deposition. Fluorescence XAFS experiments have been combined with excitation of x-ray standing waves. This combination in one experiment allowed for a depth-controlled excitation of Fe fluorescence and hence for a depth-resolved analysis of short-range order. Depth-resolved analysis showed that instead of sharp Fe/Al or Al/Fe interfaces extended interlayer regions exist. The structure retained that of bulk a-Fe. In the upper half of the Fe layer 37 at. % Al as nearest and next nearest neighbors of Fe were found, whereas in the lower half 80 at. % Al atoms occur. Thus the Fe/Al interface (deposition of Fe on Al)should be characterized by an intermixing zone significantly larger in comparison to that of the Al/Fe interface (deposition of Al on Fe).By conventional XAFS measurement carried out at a fixed angle of incidence of the exciting beam an average Fe neighborhood for the entire Fe layer of 58 at. % Al atoms was found. This value agrees with the average obtained when the analysis of the layer was performed separately for two sublayers by shifting the wave field through the layer.

To synthesize X-ray optical multilayers showing both high resolution and high reflectivity, spacer and absorber materials with low absorption coefficients for the desired spectral range are required. Beside the well-known candidates the material system Carbon / Carbon is interesting because of its low absorption coefficient over a wide spectral range and the opportunity, to deposit C-layers with different modifications, i.e. different optical properties. Simulations of C/C multilayers with different period thicknesses d and single layer densities ρ show, that reflectivities R (Cu Kα ) > 80% and a resolution ΔΘ≈0.002° can be achieved for C/C layer stacks with d= 3 nm and N= 1000 periods. An advanced large area Pulsed Laser Deposition (LA-PLD) technology was used to deposit C/C multilayers on Si-substrates up to 4" diameter. The carbon film growth conditions for the spacer and absorber layers were optimised by the variation of selected laser parameters like pulse energy and ablation wavelength, to achieve a sufficient density contrast and smooth interfaces. C/C multilayers with period thickness d= 1.1...7.0 nm and more than 500 periods were deposited. The X-ray optical performance of the C/C multilayers was characterized by means of X-ray reflectometry. A reflectivity R > 50 % (CuKα) was measured for C/C multilayers with d= 17.2 nm and N= 106 periods. A peak resolution (Δλ/λ) ≈ 1.1 % was obtained for a C/C multilayer structure with N= 80 periods and a period thickness d= 1.1nm. Results of TEM investigations indicate a regular morphology as well as smooth interfaces in the C-C layer stacks. Low compressive stresses were determined in C/C multilayers with different period thicknesses using X-ray diffraction techniques.

Performance of Ni/C, Ni/B4C, Mo/B4C and W/B4C multilayers in the energy range E > 8 keV is considered by simulation of x-ray reflectivity and resolution of 1st order Bragg reflection at three different photon energies. The results indicate, that Ni/C and Ni/B4C multilayers show highest theoretical reflectivities of R > 80% for Cu K(alpha) - radiation and also above the Mo K-edge (E equals 20.04 keV) at 30 keV. For Mo K(alpha) -radiation a reflectivity of R > 90% can be achieved by the use of Mo/B4C multilayers. For applications, where period thicknesses d < 3 nm and high reflectivities are required W/B4C multilayers can be used. Theoretical values are compared with X-ray reflectometry results, which were executed at 75 period Ni/C, Ni/B4C and Mo/B4C multilayers, fabricated by pulsed laser deposition (PLD) technology on Si substrates. Amorphous or nanocrystalline structures of single layers, smoothest interfaces and high reproducibility of single layer thickness across the entire layer stack are the results of this high precision PLD process.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.