Individual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-modal images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. The sense of the Burgers vector can also be deduced from the abovementioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations.

Soft x-ray fluorescence spectroscopy provides an element and angular momentum selective measure of the valence band density of states in complex materials. Results are presented demonstrating the use of SXF both as a means of solving materials problems and as a means of increasing our fundamental understanding of low energy excitation processes in various types of materials. As examples of materials applications, we discuss the L2,3 spectra of Si in various environments, and describe radiation damage studies in Beryl. Fundamental new insights are provided by the study of SXF spectra excited near an x-ray threshold. For such excitation, recent work demonstrates that an electronic Raman scattering process can greatly modify the normal fluorescence spectrum. We discuss near threshold studies of graphite, h-BN and NiS to demonstrate that the nature of the electronic excitation processes differs dramatically in various classes of materials and provides important new insights into their properties.

The fluorescent CKα - spectra of ultra dispersed diamonds (UDD), separated into fractions by size, were obtained. The distinction between the spectra are more pronounced in the short-wave region. A quantum-chemical calculation of the C136 diamond cluster was performed using the MNDO method. Hydrogen atoms were placed on the broken bonds of the edge carbon atoms. According to the results of the calculation, the theoretical CKα- spectra of the cluster's surface and volume were simulated. In the theoretical and experimental spectra the same tendencies are reflected if the surface carbon atoms are linked to oxygen groups.

The CKα -emission spectra of the PdxC60 compounds were obtained. To interpret the spectrum and study the Pd - C60 chemical bond structure, the SCF Xα-SW calculations of the clusters simulating the bonding between two fullerene molecules and a Pd bridge atom were carried out. On the base of the obtained data, a diagram of the electron interaction between the Pd atoms and fullerenes was constructed.

The results of an Anomalous X-ray Scattering experiment performed on Sr(PO3)2 and Eu0.1Sr0.9(PO3)2.1 glasses are presented. These are the first measurements carried out on GILDA (General purpose Italian beamLine for Diffraction and Absorption) diffractometer, located at the European Synchrotron Radiation Facility (ESRF), Grenoble. To obtain detailed information about the local order on pure and Eu-doped Sr-metaphosphate glasses both samples were investigated near the Sr K-edge (16.107 KeV), while the latter was also studied near the Eu K-edge (48.517 KeV).

The local atomic structure of PbZrO3 (PZ) as a function of temperature has been examined using the atomic pair distribution function (PDF) analysis of the pulsed neutron powder-diffraction data. The local structure was found to be deviated significantly from the crystallographic average structure, and to vary less with the composition than the crystallographic average structure. Disordered oxygen octahedral rotations have been observed in the low-temperature antiferroelectric state. With heating the M-type rotation of octahedra becomes dominant and it persists through the intermediate phase into the high-temperature paraelectric state. The Pb displacements reflect these strong deviations, and locally have a large z-component. At room temperature, deviation of Pb displacements from the antiparallel [110] pattern was found. With increasing temperature disorder in the Pb displacement increases.

Half integer superlattice reflections characteristic of ordered structure in PMN (Pb(Mg1,3Nb2,3)O3) single crystal have been measured using resonant synchrotron x-ray scattering near the Pb LIII absorption edge. These superlattice peaks have been previously reported in PMN by electron diffraction, and were interpreted in the context of a two phase Nb/Mg ordering model to explain its relaxor ferroelectric behavior. Nevertheless, the microscopic origin of the superlattice peaks is controversial. Previous results have shown that the Nb atom contributes heavily to the superlattice peaks. However, the effective scattering factor for these peaks is significantly smaller than in the case of complete ordering. In addition, there is strong evidence that lead participates in the ordering.

Atom size differences induce static displacements from an average alloy lattice and play an important role in controlling alloy phase stability and properties. The details of this role however, are difficult to study; chemical order and displacements are strongly interrelated and static displacements are hard to measure. Diffuse x-ray scattering measurements with tunable-synchrotron radiation can now measure element-specific static displacements with an accuracy of ± 0.1 pm and can simultaneously measure local chemical order out to 20 shells or more. Ideal alloys for diffuse scattering analysis with synchrotron radiation, are those that have previously been the most intractable: alloys with small Z contrast, alloys with only local order and alloys with small size differences. The combination of precise characterization of local chemical order and precise measurement of static displacement provides new information that challenges existing alloy models. We report on an ongoing systematic study of static displacements in the Fe/Ni/Cr alloys and compare the observed static displacements to the static displacements predicted by current theories. The availability of more brilliant 3rd generation hard x-ray sources will greatly enhance these measurements.

We present a simplified model of electrons and phonons in a three-site cluster as a paradigm of a system exhibiting a lattice instability. We point out the utility of X-ray absorption fine structure (XAFS) in the study of materials where the coupling between electrons and phonons leads to the appearance of such lattice instabilities. As examples of these systems, we present X-ray absorption fine structure (XAFS) measurements on magnetic manganese oxide materials and II-VI semiconductors. Both of these systems exhibit local lattice instabilities which are reflected in the transport properties. In the case of the manganese oxide La0.67Ca0.33MnO3 we observe a change in the Mn-O local structure accompanying the ferromagnetic and metal-insulator transitions. For In doped CdTe we observe the appearance of a lattice distortion centered at the Cd atoms as the In concentration is increased. This distortion is associated with the trapping of free charge carriers, leading to the saturation of the conductivity as the In concentration increases.

In this paper, we discuss the use of x-ray absorption fine structure (XAFS) techniques for the determination of structure of metal complexes in fluid inclusions heated to elevated temperatures. Analysis of Zn K-edge XAFS spectra measured from a single hypersaline fluid inclusion in quartz shows that the ZnCl42- complex is dominant at all temperatures up to and including 430 °C. The Zn-Cl bond length was found to decrease uniformly with temperature, up to nearly 2% at 430 °C in comparison to the value at 25 °C. The Zn-Cl mean-square relative displacement increased linearly with temperature, from a value of 0.0043 Å2 at 25 °C to 0.0089 Å2 at 430 °C.

Near-edge x-ray absorption fine structure (NEXAFS) is used to examine the chemical bonding in boron and boron-nitride films sputter deposited from a fully-dense, pure boron target. Reactive sputtering is used to prepare the boron-nitride and multilayered films. Although the process of sputter deposition often produces films that lack long range order, NEXAFS reveals the distinguishing features of sp2 and sp3 hybridization that are associated with different crystalline structures. The sensitivity of NEXAFS to local order further provides details in bonding modifications that exist in these films.

Near-edge x-ray absorption fine structure (NEXAFS) and Raman spectroscopies have been used to characterize both nanocrystalline and faceted, microcrystalline diamond thin films grown by microwave plasma chemical vapor deposition under a variety of conditions. Raman spectroscopy is perhaps the most commonly used method of characterizing diamond film quality, whereas photoabsorption requires a synchrotron radiation source and is much less commonly used. Both methods characterize the sp2 (graphitic) /sp3 (diamond) electronic bonding character of the films, but Raman spectroscopy is considerably more sensitive to sp2 than sp3 bonded carbon. For nanocrystalline diamond, the use of a visible excitation source for Raman spectroscopy also gives rise to an intense fluorescence band which may completely mask the sp3 Raman line, even in films with negligible (<1%) sp2 bonding character. Near-edge x-ray absorption fine structure (NEXAFS) is a more localized measurement of the electronic bonding character, and does not have as large a variation in sensitivity between sp2 and sp3 phases.

Raman spectra measured using 632.8 nm light exhibit a sharp diamond phonon peak at 1332 cm−1 for faceted, large grain diamond films, and no obvious diamond phonon peak for the nanocrystalline diamond films. However, Raman spectra excited by 228.9 nm light exhibit a sharp diamond phonon peak for both nanocrystalline and large grain, faceted diamond films. The UV Raman results are consistent with the C(ls) NEXAFS measurements which show clear bulk diamond excitonic and sp3 features, with little evidence of sp2 character for all of the tested films. We conclude that the use of visible excitation Raman spectroscopy as the sole criterion for the assessment of quality in nanocrystalline diamond films is misleading, but that UV Raman spectroscopy and NEXAFS provide a consistent and reliable characterization. Nanocrystalline films grown using a fullerene precursor in an Ar microwave plasma with very low levels of hydrogen (2%) are found by both of the latter methods to consist almost entirely of sp3-bonded carbon with ˜2% non-tetrahedral bonding.

Synchrotron radiation soft x-ray photoelectron and photoabsorption spectroscopy was used to characterize commercially obtained SiC fibers, which were produced by chemical vapor deposition (CVD) of SiC on a W core, followed by a carbon passivating layer. Depth profiling of the fiber through the carbon/SiC interface was done by making Si 2p and C ls core level PES and PAS, as well as scanning Auger microscopy, measurements following Ar+ sputtering. No significant changes in either photoemission or absorption or Auger line shapes were observed as a function of the depth, which indicates that there is no significant interfacial reaction. The line shapes of the carbonaceous coatings are predominately graphite-like and those of the CVD SiC coatings are microcrystalline, with presence of disorder to some extent in both cases.

We present results of Si K-edge XANES-investigations for novel Si-C-N containing solid phases prepared by annealing of Si(NCN)2 at temperatures between room temperature (RT) and 1600°C. The chemical equivalence of the NCN-group arid oxygen as a ligand of silicon is confirmed. The spectra show the presence of an intermediate crystalline phase and its decomposition. Furthermore the recrystallisation of a Si3N4/SiC composite material and its dependence on temperature can be seen.

We report on XANES-investigations at the nitrogen and carbon K-edge of Si-C-N containing solid phases prepared by the reaction of silicon tetrachloride with bis(trimethylsilyl)carbodiimide and annealing the reaction product at temperatures between room temperature (RT) and 1600°C. From the spectra it is possible to evidence the evolution of four phase regions and their different structural increments. We can relate the observed changes of atomic excitations to chemical and structural effects. By that means proposed structural models for the different phases are testified.

Electroplating is a key technology in the LIGA process (German acronym for Lithographie (Lithography), Galvano (Electroplating) and Abformung (Moulding)). The electroplating process determines the physical, chemical, and mechanical properties of a device. In the macro environment, the process is empirically understood arid electroplating results are fairly well predictable. For use in the micro environment, in particular in microfabrication of LIGA components with high-aspect-ratios, effects like delamination from the substrate, inhomogeneous material distribution, pores in the material and large grain sizes have to be avoided. It is, therefore, important to investigate the structure and composition of such materials. Various electroplated Permalloy foils have been prepared, which are of interest because of their soft magnetic behaviour and use as materials for microsensors and microactuators. X-ray absorption fine structure (XAFS) and x-ray absorption near edge structure (XANES) have been recorded at the Nickel and Iron K-edges (8333 and 7112 eV respectively) for electroplated Permalloy.

Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy of polymers performed in a scanning transmission X-ray microscope (STXM) can provide chemical speciation with <0.1 gm spatial resolution in imaging mode. The core excitation spectra of molecular compounds that are structural analogues of polymers help interpret the NEXAFS spectra of polymers. The effect of nt-delocalization on polymer NEXAFS is discussed and illustrated by comparison to molecular spectra. Extended Htickel calculations are particularly useful for providing insight into the relationship between chemical structure and the molecular and polymer spectra. We report the interpretation of experimental NEXAFS spectra of polyethylene terephthalate (PET). Molecular models indicate that NEXAFS will be sensitive to structural isomerization in polyester polymers. We demonstrate the capability of NEXAFS to distinguish hard-segment and soft-segment phase segregation in polyurethanes.