A number of X-ray methods characterizing lattice defects are described. They were developed in response to a variety of challenging problems in materials science, A method based on a computer-aided rocking curve analysis, CARCA, was developed which offers a rapid mapping of the dislocation structure in an epitaxial film, as well as a tensor analysis of nonuniform elastic strains. Characterization methods were developed in an attempt at bridging, systematically, the gap between micro and macromechanics when the problem arose to clarify the distribution of elastic strains emanating from stress concentrators such as notches, cracks, holes and to elucidate strain interactions. Gradients of elastic strains were characterized by a method of local intensity measurements. For crystal with homogeneous elastic strain distribution a tensor analysis is described, based on precision measurements obtained by the backreflection divergent beam method. A direct linkage between the imaging of the micro structure by TEM and the macro-response of deformation and recovery of commercial alloys was achieved by a version of the CARCA method, designed to characterize the lattice defects in polycrystalline materials. Example applications of the methods are presented with the hope that their usefulness may find adaptations in other areas of investigation.

The total reflection x-ray fluorescence (TXRF) method of analyzing elemental contents Is based on the small angle irradiation of thin samples placed on a total reflecting backing with a narrow photon beam. Two instrumental problems are to be solved here. The first is to form the narrow beam with a small angular deviation. The usual way to solve this problem is to use collimators with small solid angles. These angles must be less than the critical angle for x-ray total reflection, which, in the energy range 10 - 20 keV has an order of magnitude around 10−3 rad.

The Total Reflection X-Ray Fluorescence method was used to detect low level (ppb) uranium concentration in water.

White beam transmission topography was used to image defect structures in gallium arsenide single crystal substrates representative of those used for microwave integrated circuit fabrication. A scanning topographic camera was developed for Beamline X-19C at the National Synchrotron Light Source. Acquiring film topographs within a particular range of scan rates and x-ray fluxes was found to produce distorted images. The distortions were shown to be thermoelastic, arising from inhomogeneous deposition of thermal energy through the absorption of residual x-rays. The problem could be circumvented using faster scans with some sacrifice in spatial resolution. Real time electrooptic topographs were recorded using x-ray fluxes about one percent of those used for the film topographs. The potential for reducing the flux requirement to even lower levels which would be accessible to flash x-ray generators is considered.

White beam synchrotron X-ray topography has been applied both to the characterization of two semiconductor heterostructures, GaAs/Si and InxGa1-xAs/GaAs strained layers, and a substrate to be used for growing semiconductor epilayers, Cd1-xZnxTe. In the case of the heterostructures, misfit dislocations were observed using depth sensitive X-ray topographic imaging in grazing incidence Bragg-Laue geometries. The X-ray penetration depth, which can be varied from several hundreds of angstroms to hundreds of micrometers by rotating about the main reflection vector, which in this specific case was (355), is governed by kinernatical theory. This is justified by comparing dislocation contrast and visibility with the extent of the calculated effective misorientalion field in comparison to the effective X-ray penetration depth. For the case of Cd1-xZnxTe, twin configurations are observed, and their analysis is presented.

A new procedure for indirect determination of pharmaceutical drugs is presented. The procedure consists of extracting ion pairs between organic basic compounds, that is, pharmaceutical drugs and cobalt tetrathiocyanate and of determining Co contents in the organic extraction phase using total reflection X-ray fluorescence spectrometry. Quinine, papaverine and pilocarpine are used as pharmaceutical drugs and 1,2-dichloroethane is adopted as extraction medium. Quinine cobalt tetrathiocyanate complex was isolated and was analyzed by FT-IR (Fourier Transform Infra-Red spectroscopy) suggested that approximately 4 ng of quinine could be detected by 1 μl of sampling of organic phase under ideal conditions using total reflection X-ray fluorescence spectrometry. These drugs have their own optimal pH for extraction. This technique can be applied to cocaine analysis.

Linear polarized x-rays are used as exciting radiation to reduce the background and to improve the detection limits in XRF. A combination of an x-ray tube and a measuring module realizing a compact cartesian geometry was constructed. An on-line adjustable Bragg-polarizer, a Barkla-polarizer or a secondary target can be used optionally. The anode material of the tube can be changed easily.

The characterization of defect configurations in various perovskite-like substrate materials for high Tc superconductor epitaxial films has been conducted using white beam synchrotron X-ray topography. The substrates were found to contain crystal lattice defects such as twins, dislocations and grain boundaries. It is shown that characterization of substrates can potentially afford insight into factors controlling the properties of the high Tc superconductor tilms supported on them. This can help in the selection of optimum substrate material. Defect formation mechanisms in individual materials as well as their respective influences on the films are discussed. Comparisons between the physical and chemical properties of several potential substrate materials are presented.

Polycrystalline materials may either be compact such as metals, ceramics, or some polymers or they may be powder samples. In both cases preferred orientation of the crystallites must be taken into account. In compact materials, texture formation by solid state processes and the texture-property relationship are the main purposes for texture investigations. In powder diffraction, texture correction can increase the accuracy of the results. Also strongly textured samples may be used in order to seperate diffraction peaks which are coincident in random powders.

The intensity performance of various common XRF crystals (LiF200, Ge, PET and LSM) has been investigated under fixed experimental conditions. Measured were the raw intensities of elements particularly suitable to a given crystal, and peak-to-background ratios at different elemental concentrations. Peak profiles for each crystal type were also recorded and analysed in terms of apparent crystallite size and mosaic spread. In general the LiF crystals showed least variability in performance, whereas the PET crystals demonstrated the most.

Texture, i.e. preferred orientation (PO), of crystallites can cause serious systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. The singleparameter model of March (1932), proposed by Dollase (1986) for use in powder diffractometry is a promising mathematical formalism for correcting PO in XRPD analysis of uniaxially-oriented specimens. O'Connor et al. (1991) successfully applied the March formula in applying preferred orientation corrections for gibbsites, Al(OH)3, using Rietveld pattern-fitting and a line ratio method in which corrections are determined according to the intensity ratios of selected lines. The paper gives an appraisal of the general applicability of the methods considered by Li and O'Connor with particular reference to powder diffraction data for gibbsite, molybdite (MoO3), calcite (CaCO3) and kaolinite specimens. It is shown that some caution should be exercised when using the March formula to describe PO in Rietveld analysis.

An x-ray spectrometer has been designed for pixel by pixel analysis along lines or across selected areas of paintings and other art-objects. Characteristic technical data are: 0.8mm2 pixel size, 800mm (vert.) by 1000mm (horiz.) by 200mm (perpendicularly to object) motion distances, ±20μm precision in positioning the system, 2x3m maximum object size (mounted vertically); 2.8kW x-ray tube; Si(Li)detector. PC's are used for instrument control and new, complex data evaluation software.

Texture (of a polycrystalline sample) means the orientation distribution of the many crystallites in the sample with respect to a coordinate system on the sample, for example the rolling direction. Texture is responsible for many macroscopic properties of materials, for example in metals and alloys in the process of rolling or hot-pressing. It carries importance in many everyday production processes. Also in areas of geological science the texture of the sample, e.g. of the rocks should be known in order to explain geological processes.

It has been well established over recent years that synchrotron radiation possesses some unique features as a source of primary x-rays for x-ray fluorescence analysis. Advantage has been taken of the high intensity emanating from the bending magnets of storage rings to develop x-ray microprobes utilizing apertures or focussing optics, or both, to provide a beam spot at the specimen of the order of micrometers. The use of insertion devices wigglers and undulatora, can further increase the available intensity, especially for the high energy photons. Beam Line X-17C at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, accepts the unmodified continuum radiation from a superconducting wiggler in the storage ring. Some initial XRF measurements have been made on this beam line using apertures in the 10 to 100 micrometer range. The fluorescent radiation was measured by an intrinsic Ge detector having an energy resolution of 300 eV at 15 kev, and located at 90° to the incident beam in the plane of the electron orbit. In samples containing many elements, detection limits of a few ppm were achieved with 100 μm beams.

With a new irradiation chamber a comparison of three excitation modes under same conditions and with the same material has been done. The results of this comparison are presented in the following manner: - Barltla scattering (graphite) versus Bragg reflection (HOPS) - Bragg reflection (Mo) versus secondary target fluorescence (Mo) - secondary target fluorescence (Sn) versus Barkla scattering (graphite) Excitation spectra and detection sensitivities of a NBS standard will be discussed for the different modes. The Barkla scattering was found to be the best excitation mode for a wide elemental range.

Texture, by definition, is a description of the spatial arrangement of the polycrystalline grains in solids. For metals, the grain distribution is commonly presented in a pole figure in which the pole density of a set of crystallographic planes is plotted using standard stereographic projection techniques. In this paper, the pole figure is plotted such that the center of the pole figure coincides with the plate normal. A vertical line drawn in the equatorial projection corresponds to the rolling direction, while a horizontal line corresponds to the transverse direction. Consequently, the spatial arrangement of the grains in a given sample may be determined from an analysis of the pole figure.

Accurate diffraction intensity measurement from powder samples with a modern automatic x-ray diffractometer is nowadays a routine work. Most of the difficulties are caused because the samples are not the ideal ones. Especially, the effect of preferred orientation (or texture) may drastically distort the ratios of intensities in the collected data. To diminish these effects more careful preparation of the samples is needed. This is, however, often tedious and its success is not certain.

Two methods for improving the sensitivity of EDXRF will be presented. One method is to use a spherical geometry for the measurements. The analyzed specimen is made as a spherical layer (i.e., “orange rind”), with the exciting x-ray source and the detector being located in the inner surface of the specimen at opposite points on the diameter. The source radiation scattered into the detector is minimized by the 90° scattering angle at all points on the specimen. It has been shown that the sensitivity is improved by several times while earring out EDXRF measurements under conditions of spherical geometry as compared to the conventional flat arrangement.

The other method we have investigated makes use of polarized radiation. The source radiation is polarized by scattering from a thin, low atomic number material. Higher energy radiation from the x-ray tube passes through the polarizer, where it impinges on a secondary fluorescer. This secondary radiation is then polarized by the same scatterer as the primary radiation. A quasi-monoenergetic polarized source is produced with maximized intensity by these means. It has been shown experimentally that the use of this polarized source for excitation leads to detection limits which are several times lower in the whole range of moderate energy. It has further been shown that the use of the easily added secondary target to the standard orthogonal polarization geometry increases the polarized beam intensity by 10-15%.

For pole figure measurement the flat sample has to be tilted which leads to peak broadening and peak overlap in peak-reach diffraction spectra. Using a linear position sensitive detector /PSD/, complete diffraction spectra can be obtained in each sample orientation. Peak separation can then be done by Gaussian fitting. When measuring with a PSD, each diffraction peak corresponds to a particular diffraction vector. This has to be taken into consideration by a coordinate transformation. The PSD-method is the only practical method of texture measurement for materials with complex diffraction spectra.

X-ray micro analysis had suffered from the limited intensity of conventional X-ray sources like X-ray tubes etc. However, with the optical technique described in this paper, the so called “X-ray Capillary Optics” (XCO), it is possible to make X-Ray Fluorescence (XRF) analysis in micro-scale, down to a few μm2 still with conventional sources.