In Müllverbrennungsanlagen versagten nach relativ kurzer Zeit die feuerfesten Zustellungen aus Si3N4-gebundenen SiC-Platten. Anhand von Untersuchungen mittels Rasterelektronenmikroskopie, Diffraktographie und Raman-Spektroskopie konnte gezeigt werden, dass in Rückstellproben relevante Mengen an Cristobalit vorhanden waren, was das Ausdehnungsverhalten der SiC-Platten beeinflusst. Diese Platten verformen sich während des Betriebs und werden dadurch thermisch höher beansprucht.

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.

X-ray Bragg diffraction profiles of epitaxial layers of A1N and GaN grown onc-plane sapphire were measured with a novel triple-axis diffractometer using a parabolically curved, graded multilayer mirror in the diffracted beam instead of an analyzer crystal. In addition, the intensity of the incident beam is enhanced by a parabolically graded multilayer mirror acting as condensor for a Ge(022) channel-cut monochromator. This novel diffractometer configuration provides a clear improvement in intensity at sufficiently high resolution for the study of angular peak broadening and peak shape functions of weak reflections from samples of poor structural quality and from thin layers. For AlN and GaN, the reason for peak broadening of symmetric rocking curves was found to be small coherence lengths parallel to the substrate surface and not distinct out-of-plane misorientations. Additionally, different peak broadenings of asymmetric reflections due to edge dislocations were observed for AlN and GaN.

X-ray Bragg diffraction profiles of epitaxial layers of AIN and GaN grown on c-plane sapphire were measured with a novel triple-axis diffractometer using a parabolically curved, graded multilayer mirror in the diffracted beam instead of an analyzer crystal. In addition, the intensity of the incident beam is enhanced by a parabolically graded multilayer mirror acting as condenser for a Ge(022) channel-cut monochromator. This novel diffractometer configuration provides a clear improvement in intensity at sufficiently high resolution for the study of angular peak broadening and peak shape functions of weak reflections from samples of poor structural quality and from thin layers. For AIN and GaN, the reason for peak broadening of symmetric rocking curves was found to be small coherence lengths parallel to the substrate surface and not distinct out-of-plane misorientations. Additionally, different peak broadenings of asymmetric reflections due to edge dislocations were observed for AlN and GaN.

It is shown in this paper that the reflectivity of X-rays at smooth and flat surfaces gives the dispersive correction f'(E) to the atomic form factor with an accuracy comparable to that obtained by X-ray interferometry. A detailed set of values of f'(E) in the energy range 7-27 keV is given for Ni, Cu, CuO, Ta, LiTaO3, Pt and Au, together with the corresponding linear absorption coefficients mu/rho. Whenever comparison is possible the values of f'(E) agree very well with those obtained by interferometry or by Kramers-Kronig transformation. Data calculated according to Cromer & Liberman [J. Chem. Phys. (1970). 53, 1891-1898] agree well with our data far from absorption edges. At the edges there are substantial differences because the calculations do not take into account the structure of the edges, their chemical shift in compounds and the EXAFS structure above the edges. Below absorption edges the values of f'(E) for metals and their oxides are equal, provided the chemical shift in the position of the edges is taken care of. This feature is interesting in anomalous scattering experiments, where the variation of f' with energy is used to vary the scattering contrast of a given atomic species. Once f'(E) is known, X-rav reflectivity measurements can be used to determine the density and the thickness of layers on flat substrates. In addition, the roughness of the air-layer and layer-substrate interfaces have been determined with high precision in the metals and oxides mentioned above.

A total reflection X-ray fluorescence spectrometer with monochromatic excitation for trace-element analysis on semiconductor wafers is presented. Using a multilayer monochromator intense monochromatic and tunable excitation is provided. The monochromatic excitation brings about a clear background reduction and produces an excitation spectrum of inherent spectral purity. Even with a low power Mo fine-focus tube, detection limits of 10(10) atoms/cm2 are attainable. The tunability of the excitation conditions allows selective excitation, which is especially advantageous for light elements. The in-line capability of the method lends itself to process control in semiconductor fabrication.

Silicon pin photodiodes from different manufacturers were tested with synchrotron radiation and found to be excellently suited as detectors for the X-ray range between 5 and 25 keV. They have a high dynamical range (more than 6 decades) and a high degree of linearity. They can be used in the current mode down to 100 photons/s. This corresponds to a photocurrent of 50 fA. The performance of the signal processing (current-voltage amplifier, voltage-frequency converter, frequency counter) is of great importance. The Keithley current-voltage amplifier 18000-20, whose range can be switched electronically, is superior in performance to the Keithley amplifier 427, when the intensity range exceeds 4 decades.

X-ray fluorescence analysis of boron is complicated by the low atomic number and the low K shell energy of boron, and the effects of these on excitation, fluorescence yield, absorption and energy analysis. At present, acceptable energy resolution and sensitivity with small equipment dimensions and the capability of processing high photon counting rates can only be met by wavelength-dispersive energy analysis using synthetic multilayers as the diffraction device. These multilayers, compared with thallium acid phthalate and lead stearate, show a far increased reflectivity. They differ, however, from common analyser crystals in the marked appearance of higher order Bragg reflections. The analysis of boron in a matrix containing oxygen, for instance borophosphosilicate glass, is hampered by the overlap of B Kα in the first order and O Kα in the third order. It has been demonstrated that undesirable higher order Bragg reflections can be extinguished by employing multilayer structures with an appropriate thickness ratio of the layer pair. Thereby, it is possible to determine the mass content of boron in borophosphosilicate glass with an accuracy better than 0.2 wt.% B in a measuring time of 5 min.

In surface channeling, fast ions are incident at a grazing angle upon a crystal surface along a low index surface direction. Surface channeled ions are used as versatile probes for surface analysis. The atomic structure of crystal surfaces, especially surface reconstructions and positions of adsorbed atoms, can be analyzed by ions channeled at the crystal surface in combination with appropriate detection reactions. We review the application of ion surface channeling to surface structure analysis. The principles of surface channeling are outlined. Several detection reactions, such as backscattering, nuclear reactions, X-ray emission. Auger electron emission, forwardscattering, light emission and secondary electron emission, are discussed with respect to surface channeling. Finally, some recent experiments are given as examples: (2 × 1)-O/Ni(110), steps on Ni0.6Fe0.4(110) and (2 × 2)-In/Si(100).