Two years ago a paper on a new method of X-ray fluorescence analysis was presented. This method uses a variable take-off geometry and permits a quantitative analysis without calibration curves or the knowledge of the primary X-ray spectrum. As references either chemically analysed samples or pure elements are used. In case that only primary excitation exists, under the aspect, mentioned above, the method is to be regarded as “absolute”. For secondary excitation a simple parabolic approximation has been introduced, which requires a calibration. This paper gives an outline on the progress obtained during the last two years.

For time-resolved diffraction studies under high temperature and/or high pressure, we designed a new diffractometer incorporating a curved position sensitive detector and tested the rapid intensity measurement and the resolution of the angular dispersive diffraction. The diffraction profiles were compared with those from energy dispersive diffraction. Rapid intensity collection has been carried out with a CAMAC module. A curved position sensitive detector with a 120° working angular region was installed on the off-centered four circle diffractometer. Only a few seconds were needed to obtain a whole powder diffraction because of the extremely high counting efficiency due to the streamer mode.

Time-resolved observations of the dehydration reactions of Mg(OH)2 and Ca(OH)2, have been undertaken by angular dispersive and energy dispersive x-ray powder diffraction at high temperature. The in situ observations of the dehydration process provide kinetic information, such as the reaction rate, the apparent activation energy and the dehydration mechanism.

During recent years energy dispersive x-ray fluorescence (EDXRF) has been used to measure the elemental content of atmospheric aerosols. The code described here is used to reduce EDXRF data and determine the elemental composition of samples collected on membrane filters. The program has been specifically written for EDXRF analysis of size-fractionated aerosols collected by a dichotomous sampler.

The x-ray fluorescence spectrometer used in our laboratory employs a pulsed-mode x-ray tube and a lithium-drifted silicon detector. Pulse-height spectra are produced for elements ranging in atomic number from Z = 13 to Z = 82 (corresponding to an energy range from 1.4 to 32.1 keV). Approximately uniform x-ray production is attained by producing independent spectra from three secondary targets (Ti, Mo, Sm).

An unexplained anomalous sin2ψ split in x-ray stress measurements has consistently resulted from the use of Cr Kα radiation with nickel and austenitic stainless steels. Both, materials have diffraction peaks at low back-reflection angles for this radiation (nickel: 20 ⋍ 134°, austenitic stainless steel: 20 ⋍ 128°). The anomalous split is not evident when the measurements are made using Cr Kβ radiation, In an attempt to explain the errors produced by the Cr Kα radiation, focusing circle effects were analyzed and compared to experimental measurements made with both Cr Kα and Cr Kβ radiation on nickel-based samples,

We have recently described an automated powder diffractometer, the APD-3500, in which a small (4K x 18 bit) minicomputer is utilized for hardware control and data processing. Among the software programs developed for this system is a “Peak Search“ routine which is designed to record a diffraction pattern with optimum, use of scanning time and to give output directly in J.C.P.D.S. Powder Data File Format. Optimum use of scanning time is achieved by a double-pass System in which a first (rapid) pass is made to establish significant data.

A second routine is a “Line Profile” routine which gives the choice of rapid slewing or slow Step scanning of the goniometer between selected angular ranges. The routine thus allows the controlled stepping of the goniometer between selected angular ranges giving incremental and integral, background corrected counts. An automatic internal and/or external calibration capability makes this particular mode ideal for quantitative analysis.

The mass absorption coefficient (μ) of a weakly absorbing solid material may be measured by either the transmission or the reflection method. The latter typically employs a crystalline substrate and the diffraction method, measuring the transmission of the diffraction peak(s) of the substrate through the analyte. Compressing or compacting a powdered sample is not required when the reflection method is used.

Position-sensitive detectors (PSD's) are commonly available for X-ray diffraction, where they are used in the angle dispersive mode at fixed wavelength λ. They are sensitive to the scattering angle 2Θ. The resolution of such instruments is determined by the physical properties of the detector, and, of course, the distance from the sample. Using continuous radiation solid state detectors (Ge, Ge(Li), Si(Li)) are sensitive to energy (equivalent to λ) at fixed scattering angle 2Θo, They are being used for X-rays, especially with synchrotron radiation. Because X-rays travel with the speed of light, those two techniques cannot be combined. Thermal neutrons, on the other hand, are comparatively slowly traveling particles (2200 m/s at 300 K) and consequently time-of-flight (TOF) instruments with choppers at continuous neutron beams are known for a long time; they are being used as well for diff-actomet! y as for inelastic scattering.

The need for reliable standards for the characterization of x-ray powder diffraction (XRD) instruments has been well documented. As a result of the round robin study, of various candidate standard materials, described by Fawcett et al., the National Institute of Science and Technology has made the SRM-660, lanthanum hexaboride, XRD peak width standard available. It has been normal practice to use powder sample standards for XRD powder diffraction studies. Powder standards have been justified on the principle that standards should be as much as possible like the unknowns to be analyzed; however, standards must be quite different from the unknowns because their peak profiles must be as narrow as possible for deconvolution from sample peak profiles. It would seem most advantageous to use standards of the highest degree of crystallinity so that they would be useful over the maximum number of applications. Single crystals, with their extremely high crystallinity, offer that advantage.

Preliminary study of performance of an HPGe detector with an ion implanted entrance window in the spectrometry of the ultralowenergy x-rays is presented.

For the first time it has been shown that almost symmetric photopeaks and absence of low energy tailing can be obtained in this region from HPGe detectors.

Residual stress measurements were made on a ground rail steel (0.75 %C) using the newly developed ϕ-integral method and the conventional ψ-differential method. The strains <εϕψ> were measured as a function of the azimuth angle ϕ, the angle of rotation about an axis perpendicular to the specimen surface, from 0° to 360° in steps of 15°, at fixed tilt angles ψ, the angle between the normals to the specimen surface and the reflecting planes (hkl), set between 0° and 45° in steps of 9°.

It was found that <εϕψ> plotted as a function of ϕ is not periodic with the period of 180° and consequently exhibits the so-called ψ-splitting when plotted as a function of sin2ψ at constant ϕ. The Fourier coefficients of the function <εϕψ> plotted versus ϕ were used to evaluate the strain tensor <εij> in the integral method. Assuming that isotropic elasticity theory is applicable, the stress tensor <σij> was calculated, and excellent agreement was found between the values determined with the ϕ integral and ψ-differential methods.

It is necessary to know the orientation of thin surface layers for the electronic industry as well as for different studies on interphases (epitaxy, topotaxy, phase transformation, reactivity of solids).

It is difficult to obtain information with a conventional Schulz goniometer (Bragg-Brentano geometry) because of the insufficient amount of diffracting material.

Metallic filaments with sub-micrometer diameters have recently been fabricated using novel materials fabrication techniques at NRL. The specimens are enshrouded in a glass sheath and all efforts to obtain structural information from these samples with conventional x-ray sources have been negative. By using synchrotron radiation on a wiggler beam line, x-ray diffraction data have been obtained from samples with diameters of 0.22, 0.09, 0.07, and 0.04 μm. The two thicker samples were found to be single crystals with a structure consistent with that of normal Bi. Single crystal diffraction peaks obtained from the 0.07 μm sample are incompatible with the Bi-1 or any other known structure of Bi. We have provisionally identified this as Bi-X.

The behavior of charged dislocations in alkali-halide crystals has been drawing attention in connection with the charge transfer which occurs during plastic deformation.1-9 Recently, Itagaki proposed a charged dislocation mechanism to account for the dielectric properties of ice.10 His theory is in part supported by the dielectric measurements o f strained ice made by Ackley and Itagaki.11 Brantley and Bauer12 derived similar equations for the dielectric constant based on charged dislocation motion. They also proposed a new mechanism for apparent piezoelectricity based on moving charged dislocations in an electric field .

The excitation efficiencies for K- and L- x-ray fluorescence by a Mo transmission tube operated at 30 kV have been measured. K x-ray excitation efficiencies for 14 elements ranging from A1 to Y and L x-ray excitation efficiencies for 12 elements ranging from Br to U are presented. The K x-ray excitation efficiencies are compared to those predicted from theoretical photoionization cross sections and empirical fluorescence yields, and the L x-ray excitation efficiencies are used in conjunction with theoretical photoionization cross sections to derive average L-shell fluorescence yields.

A simple method for high-resolution measurement of surface misorientation in electronic materials is introduced. The technique combines laser optical alignment with double-crystal x-ray diffraction to yield a typical sensitivity of better than 1-2 arc sec. The technique can also be used to make corrections in spectrometric measurements in which commonly ignored rocking - curve errors may be significant.

Because the cost of the large number of standards required for quantitative X-ray fluorescence analysis is prohibitive, a mathematical procedure, the “fundamental parameters method” is gaining popularity. A major problem in using the method is the limited knowledge of the spectral distribution of the primary radiation from the X-ray tube, the need for a large computer memory which makes it difficult to use with minicomputers and uncertainties in the basic parameters. A monochromatic X-ray source was developed to avoid the problem of the spectral distribution. This permitted simple calculations for the calibration and a simple algorithm to transform the intensities to mass fraction or coating thickness. The calculations were made with a slide rule calculator.

Plastic deformation of metals produces a state characterized by the presence of residual elastic strains, small domains which diffract X-rays coherently, and often stacking faults; these effects may be studied with X-ray diffraction techniques. Changes in the lattice parameter, shifts in the relative positions of diffraction lines, and the broadening of diffraction lines were used to study the state of coldwork resulting in Cu-6.6 at.%Si-1.2 at.%Mn after deformation by filing, wiredrawing, and uniaxial tension at room temperature.

Both filing and wire-drawing produce large root-mean-square strains and stacking faults, whereas deformation by tension up to 22% extension fails to produce any clear evidence of faulting or root-mean-square strains. Tensile deformation causes fragmentation of coherent domains to an average dimension of 250 Å after 22% extension, and results in a radial, tensile, residual macrostrain arising from a smaller rate of work hardening in the surface layers than in the interior. Wire drawing also results in a residual macrostrain system. Deformation appears to enhance diffusion and promote solute clustering at room temperature.

This is a review of Total reflection X-Ray Fluorescence (TXRF) applications for semiconductors. This review is limited to surface analysis of contamination for semiconductors and does not include chemical analysis in semiconductor processing. TXRF for surface analysis is a relatively new technology. One of the first publications occurred in 1986 using synchrotron radiation. Publications using commercially available TXRF instruments for semiconductor applications began in 1988. Today there are on the order of 100 TXRF instruments worldwide in the semiconductor industry. Since 1988 there have been about 100 publications in this field, but this number does not include numerous abstracts and publications in Japan where the majority of the commercial instruments are found today. The commercial instruments were developed for the primary application of characterizing the cleaning of planar silicon wafers, however, numerous unforeseen applications were developed by users and many of those applications are reported here. In essence TXRF has much broader application today in the semiconductor industry than supporting the cleaning of silicon wafers.

Calculations carried out to investigate the van Cittert iterative deconvolution method and the effects of random noise and truncation errors on its convergence behavior are presented. Gaussian functions are used for "both the true function W and the system, response function A. The model "observed" function S is generated from W and A. Both rms differences between the result of n iterations Wn and the true function, and between Wn*A and S are used to measure convergence. The effects of introducing errors can be measured against standards set by the convergence without such errors. These "no-error" calculations make use of true functions with widths from 2.0 to 0.67 times the response function width. The effects of random noise are investigated by adding noise to W*A before deconvolution. A small amount of random noise initially added builds up rapidly in amplitude during the iterative process and eventually dominates the rms difference calculations. To suppress the effects of random noise build-up; smoothing techniques are applied, the best of which involved smoothing both the noisy observed function, S, and the system response function, A, before deconvolution. The smoothing operation is thus taken as part of the measurement and. the divergence resulting from, the noise build-up is avoided. The results depend strongly upon, the -width of the smoothing function. Uhsymmetric system response functions, similar' to those encountered in soft x-ray appearance potential spectroscopy and in x-ray continuum, isochromat measurements, are used in investigations of truncation errors. Abrupt cut-offs of the model S and A functions before deconvolution result in the build-up of large fluctuations in W . These truncation errors become increasingly localized with continued iterations and make only minor contributions to the errors in Wn in the vicinity of the real peak if the truncations are made sufficiently far from the peak location. Alternatively, the truncation errors can be avoided by analytical continuation.

The high-temperature continuous X-ray diffraction technique has been used at the University of Illinois for several years in our investigation of structural transformations and the development of phase minerals as natural materials are heated. Of particular interest are the effects which chemical impurities have on predicted structural transformations at elevated temperatures.

The formation of mullite and beta-cristobalite as they develop from the clay mineral kaolinite is examined by continuous X-ray diffraction up to 1450°C, and the influence of added impurities either to enhance or to retard nucleation of these phase minerals is shown. The 2θ range containing diagnostic peaks of both the initial material and of the transition and phase minerals which develop on heating was continually traversed, thus providing a constant record for comparing structural changes vs. temperature.

The furnace used is described in detail, and the effects of added impurities on kaolinite transformations are evaluated to show their importance in controlling the thermal history of a natural material under nonequilibrium conditions.