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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.

Efficient soft X-ray spectroscopy in the laboratory is still a challenging task. Here, we report on new toroidal multilayer optics designed and applied with the laser-produced plasma (LPP) source of the Berlin Laboratory for innovative X-ray technologies. The optics are described and characterized, and the application of the updated source to scanning-free grazing emission X-ray fluorescence is demonstrated on thermoelectric gold-doped copper oxide nanofilms. The comparison with synchrotron measurements allows estimating a flux on the sample of approximately 7.5 × 109 photons/s in the 1 keV range on a 100 µm × 100 µm spot, emphasizing the suitability of the updated LPP source for the application in photon hungry experiments. K.B. is most grateful for the scholarship from the International Max-Planck Research School at the Fritz Haber Institute. J.B. would like to thank the Excellence Initiative of the Deutsche Forschungsgemeinschaft for financial support.

The European Integrated Activity of Excellence and Networking for nanoand Micro-Electronics Analysis (ANNA), www.ANNA-i3.net, has addressed the further development and assessment of methodologies for the detection of low concentration inorganic contaminants on and in silicon as well as for novel materials. The comparison of various analytical techniques available to the ANNA partners helped to identify the degree of comparableness of results revealed at different installations. The assessment of improved methodologies as well as the reliability of quantification and calibration procedures of specific analytical techniques such as Total-Reflection X-ray Fluorescence (TXRF) analysis has been of particular interest.

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.

The evolution of intrinsic stress in multilayers and its behavior with growing number of periods and/or during radiation exposure, i.e. thermal treatment, becomes important in many X-ray optical applications. In Ni/C X-ray optical multilayers fabricated by pulsed laser deposition (PLD) at room temperature with typical period thickness d approx. 4.0 nm microstructure and intrinsic stress are analyzed with growing period number up to the layer stack delamination. Microstructure of single layers and interfaces and morphology of the total layer stack were investigated by means of transmission electron microscopy (TEM), X-ray reflectometry and diffraction. A clear indication of nano-crystallites was found for the Ni-layers, whereas the carbon layers were always amorphous. The diffraction pattern of a 300 period Ni/C layer stack hint at a hexagonal structure of the Ni crystallites with the (011)-lattice plane parallel to the Si substrate surface. Thus the elastic misfit between the Ni- and C-layers seems to be minimized. To investigate the evolution of stresses in the growing up Ni/C multilayers depth dependent stresses in the Si (100) substrate were analyzed using X-ray results of the stress tensor for Si-crystal of the substrate averaged over different penetration depths (0.6 and 3.6 μm). The found dependence of the substrate stresses on the total layer thickness point at low compressive stresses in the PLD-fabricated Ni/C X-ray optics in the range below -100 MPa at least up to a total layer thickness of 1200 nm (300 periods). An increase of the compressive stresses was obtained only for stacks of more than 300 periods. A delamination of the layer stack in part was observed at 900 periods.

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.

Periodic multilayers are well known as Bragg reflectors for X- rays. A high reflectivity and a wide reflection width are their outstanding features. However, if multilayers shall be used as reflective coating for X-ray optics, especially for wide acceptance angles, uniform layer thicknesses cause chromatic aberrations. These aberrations can be overcome by laterally graded multilayer optics. Their Bragg angle is matched laterally to the incidence angle so that for all points on the reflector, Bragg reflection is obtained for the same wavelength. Three major types of laterally graded multilayer mirrors ('Gobel Mirrors') are applied in X-ray diffractometry: (1) parabolic, (2) elliptic and (3) planar. In this paper, we give design criteria and formulae for these mirrors. Furthermore, we discuss the requirements on the dimensions and the fabrication process. Two different processes suitable for the fabrication, sputter coating and pulsed laser deposition (PLD), are described. The X-ray optical parameters and their characterization are presented for various mirrors designed for Cu K(alpha) , Mo K(alpha) and Cr K(alpha) radiation. From Ni/C and Ni/B4C multilayers, high-photon-flux monochromators with a Cu K(beta) /K(alpha) intensity ratio of about 1:1000 have been realized. The divergence of the 'parallel' beam reflected from parabolic mirrors is about 0.02 degrees, which is one order of magnitude lower than the divergence of polycapillary optics, monocapillary optics and waveguides. Comparing the photon flux density in a high resolution diffraction setup with and without mirror optics a gain factor of 16 was achieved for parabolic Ni/B4C multilayer mirrors.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Pulsed laser deposition is described as a technique for the synthesis of multilayers showing X- ray optical quality. The state of the art is characterized by results that demonstrate a development of the instrument basis superior to that of conventional PLD systems. Multilayers of the Ni/C, Mo/Si- and W/C-types prove the versatility of the method and the output of layer stack characterization by HREM, SPM, XD, AES, XPS, ellipsometry and image processing ensures a high quality with regard to stack regularity, layer homogeneity and interface smoothness.