Pressure is an important thermodynamical variable. It provides the most efficient means of altering interatomic distances while leaving the thermal energy of a system invariant. It therefore provides an important mechanism for testing theoretical models that are based upon atomic separations and crystallographic configurations. Like its counterpart, temperature, pressure can be used to assist chemical reactions or to bring about crystallographic phase transformations. New allotropes, formed under conditions of extreme pressure and/or temperature, may have physical properties that are significantly different from those of the material formed under normal conditions. A classic example is that of carbon: the hardness, electrical and thermal conductivities, transparency, and cost of graphite, the normal phase of carbon, are significantly different from those of diamond, the phase formed at elevated pressures and temperatures. In the quest for higher static pressures, researchers have been reducing the size of the pressure chamber, and hence the sample, to microscopic dimensions; this, in turn, necessitates the use of brighter light sources to "see" the sample in a reasonable time period.

This plenary paper is intended to be an introduction to the capabilities and limitations of analytical electron microscopy (AEM). The description to be given assumes no prior knowledge of AEM or any other electron microscopy, scanning or transmission. However, a basic understanding of x-ray generation and detection will be assumed.

The most familiar result from X-ray analysis is a spectrum (on a chart recording or on film), or perhaps a short list of values (concentrations, d-spacings, etc.) taken from such a spectrum. X-ray pictures are usually associated in our minds with the hospital emergency room or the dentist's office. But images formed by X-rays are also an important tool to study materials' structures. Both conventional and unconventional uses of X-rays to study structural and compositional inhomogeneities find widespread application to materials. Applications include characterization of surface topography and composition variation, as well as internal structure. The methods make use of all types of X-ray interaction with materials, including Bragg diffraction and the fluorescence of characteristic X-rays, as well as simple X-ray attenuation due to absorption and scattering.

There is a veritable renaissance occurring in x-ray imaging. X-ray imaging by radiography has been a highly developed technology in medicine and industry for many years. However, high resolution imaging has not generally been practical because sources have been relatively dim and diffuse, optical elements have been nonexistant for most applications, and detectors have been slow and of low resolution. Materials analysis needs have therefore gone unmet. Rapid progress is now taking place because we are able to exploit developments in microelectronics and related material fabrication techniques, and because of the availability of intense x-ray sources.

Secondary ion mass spectrometry (SIMS) Is a well established technique for the microcharacterization of solid samples. SIMS is able to detect all the elements in the periodic table, from H to U, and their isotopes. It Is unique among the common surface analytical techniques in its ability to detect H directly. SIMS has high sensitivity, ppm to ppb, for most elements. It has good depth and lateral resolution, 5-10nm and 1-2µ, respectively. Sample preparation is minimal and almost any sample oan be accommodated. In addition, molecular SIMS offers the chance to obtain chemical information about the sample. As a result of these features, SIMS has found applications in many fields; The techniques related to SIMS that will be described at the end of this paper differ primarily in their methods of generating secondary ions. This leads to differences in the information obtained and the types of samples which can be analyzed. This paper will be a brief introduction to the field of SIMS. Several reviews and a recently published text are available in the literature.

X-ray microscopy is a field that has developed rapidly in recent years. Two different approaches have been used. Zone plates have been employed to produce focussed beams with sizes as low as 0.07 pm for x-ray energies below 1 keV. Images of biological materials and elemental maps for major and minor low Z have been produced using above and below absorption edge differences. At higher energies collimators and focussing mirrors have been used to make small diameter beams for excitation of characteristic K— or L-x rays of all elements in the periodic table.

Spectroscopic data from a var iety of analyt ical techniques such as x-ray diffraction (XRD), infrared (IR) and Raman spectroscopies, secondary ion mass spectrometry (SIMS) and energy dispersive X-ray analysis (EDX) can be obtained from small areas of samples (< 1 mm2) through the use of microscope sampling accessories. If provisions are made to scan or translate the sample, then a spectrum that is characteristic of each region of interest can be obtained. Alternatively, selective area detectors eliminate the requirement for scanning the sample. Extract ion of information about a specific energy band from each spectrum allows elucidat ion of the spatial distribution of the feature giving rise to that band. For example, the distribution of a compound could be imaged by extracting the intensity of an IR band or XRD peak due to that compound. Peak posit ion and peak width are other parameters that can be extracted as a function of posit ion. Similarly, elemental distributions could be obtained using SIMS and EDX.

The semiconductor industry is continually striving'for smaller, denser devices. Microdiffractometry is an analytical technique which endeavors to apply x-ray diffraction techniques for measuring strain and phase information to areas approaching 50 micrometers diameter or less.

This study extends the work of Goldsmith and Walker in the measurement of strain using the lattice distortion or sin2(ψ) plot method.

The systematic errors arising from both sample and beam displacement relative to the center of rotation of the cample ie examined. A relationship is derived which predicts the influence of these displacements upon the slope of a stress plot. The predictions are compared to experiment.

The influence of random errors arising from particle size and photon counting statistics will also be discussed. Guidelines will be presented which will minimize both systematic and random errors.

In this article, we demonstrate that the combination of elemental and phase mapping is a very powerful tool for characterizing sputtered, binary plutonium alloys.

A specially designed energy-dispersive spectrometer equipped with an automated x-y translational stage was used to measure elemental differences in several disks sputter-coated with binary plutonium alloys. Automated diffractometer scans were obtained from selected areas on the disks by using specially designed sample holders. The elemental differences were then correlated with the phases present and the observed corrosion resistance. The elemental spectra and diffractometer scans were analyzed using a modified version of the SPECPLOT program. This program enables the user to analyze both energy-dispersive elemental data and diffractometer data using a single program.

Recently there has been a growing interest in the field of X-Ray MicroFluorescence (XRMF) for analyzing small areas (with sizes greater than about 10 microns diameter). Several recent papers have described prototype systems for this kind of analysis, with particular emphasis on the elemental imaging applications. However, the technique of small-area XRF analysis is not new. For example, Bertin gives an excellent review of much of the earlier work (up to the late 1960s), which used a variety of focusing (with curved crystals) or collimation techniques. Several wavelength dispersive spectrometer systems were modified for small-spot analysis. One of the earliest spectrometers was the X-ray Milliprobe developed by Adler and Axelrod, which employed curved crystals.

Computed tomography (CT), commonly known as CAT scanning (computerized axial tomography), is a technology that produces an image of the internaI structure of a cross sectional slice through an object via the reconstruction of a matrix of X-ray attenuation coefficients. This non-destructive method is fast (50 ms to 7 min per image depending on the technological generation of the instrument) and requires minimal sample preparation. Images are generated from digital computations, and instruments essentially have a linear response. This allows quantitative estimations of density variations, dimensions and areas directly from console displays.

Thin film structures determined by X-ray reflection and transmission diffractometer methods has been used to co rrelate with th e magnetic p roperties of CoCrTa thin films. Well-crystallized CoCrTa alloy particles with strong h.c.p. c-axis preferred oriented normal to the film surfaces were found to be mainly responsible for the perpendicular magnetic anisotropy observed in specimens IL and 8L, whereas poorly crystallized CoCrTa particles in the 150Å thick magnetic layers of a third specimen 33L have led to an observed longitudinal magnetization. Microstrains generated by the crystalline - amorphous interface stresses induced an enhanced perpendicular magnetic anisotropy in specimen 8L. Values of crystallite size D determined from the Warren-Averbach analysis were correlated with the coercivities He. Analysis of the He vs. D curve indicated th a t the critical particle size for a magnetic multi- to single-domain transition was 270± 25Å. The retention in coercivity (Hc=175 Oe) at a small particle size (D=75Å) in specimen 8L suggested that strong interparticle interactions existed among the wellcrystallized CoCrTa particles. A much smaller retention in coercivity (Hc=90 Oe) at D=70Å of specimen 33L indicated the inter particle interactions in poorly crystallized CoCrTa layers were relatively weak.

This paper examines the relationship between the lattice defects and crystallization process of synthetic diamonds. Diamonds synthesized by high pressure, high temperature methods as well as diamonds vapor deposited under metastable conditions are considered. High pressure crystals precipitated from Ni or Co solutions contain inclusions of metastable carbides and metal atoms distributed throughout a small fraction of the octahedral holes in the diamond lattice.

Diamonds are grown metastabily by a chemical vapor deposition process in which CH4 and H2 are excited by a microwave plasma. Such diamonds are deposited as individual micro-monocrystals or as solid poly crystalline films. The defects in such crystals are related to impurities such as Si and H which produce point defects and tend to nucleate graphite, which can generate planar defects. Nucleation of a diamond phase on β-SiC is also considered, because of the lattice matching between them.

Diamond structure is a prototype of a family of related phases such as cubic BN (sphalerite structure) and solid solutions of diamond and cubic BN, Cubic BN-diamond solid solutions (BN)x(C2)1-x,0<x<l are, in turn, a prototype of AIIIBV-CIV phases, of which (GaP)x(Si2)1-x,0<x<l is an example. Substitution of B-N (or Ga-P) by C-C (or Si-Si) atom pairs at lattice sites is characteristic of these solid solutions.

The Fourier analysis of the broadened profiles in a powder pattern allows the determination of the effective particle or domain size and the microstrains within each domain in polycrystalline materials. In order to apply this method to the diffraction patterns of thin films and coatings, deposited on crystalline or amorphous substrates, special diffraction techniques must be employed for the registration of the relatively weak intensities. The fitting of the experimental profiles to pseudo-Voigt functions permits the recovery of the peak tails and a precise determination of the background. The positions of the peak maxima or centroids yield information about any compositional variations, and about the occurrence of stacking faults and residual stresses in thin films and coatings.

There is considerable interest in the microelectronics industry to obtain high-resolution images, as well as precise measures of defect densities in “ device quality” thin films and substrates. In the field of x-ray diffraction, research groups worldwide are intensely pursuing the relevant applications of computerized x-ray rocking curve analysis and topography. Production-type, on-site rocking curve instrumentation has already been introduced into the market, and potential uses of x-ray topography are also under consideration.

In the present study, the merits and limitations of these two techniques are critically evaluated. Possible pitfalls of automated data collection are pointed out and conditions under which meaningful measurements may be made are explored. It is shown that reliable results may nearly always be obtained with reasonable care when each method is applied subject to its own mode of operation. However, extreme caution is needed when digitized data initially collected for topography is subsequently used for rocking curve analysis; otherwise, the correspondence between the interpretation and actual defect configuration may be vitiated. Thus, additional tests will be necessary to ensure the validity of the results.

X-ray scattering techniques at grazing incidence have been used to characterize single quantum well hetero–structures. Double–and triple-axis diffractometry has been used to determine lattice mismatch and layer thickness of a 250Å thick layer of AlInAs grown by MBE on an InP substrate and capped by a 45Å GaAs layer. Reflectivity measurements in the triple – crystal mode permit accurate measurement of individual layer thicknesses, relative electron density and interface roughnesses on the Angstrom level.

A very accurate 8X8 matrix approach to dynamical theory of X-ray diffraction in which fewer approximations are made than in the classic vonLaue approach, is described here. The method is related to the very general matrix method of Kokushima and Yamakito, and is particularly suited to numerical solution with a computer. It can be used to solve problems in ideal, undistorted crystals with high precision even at near grazing incidence without special consideration of refraction or external reflection. It is also easy to apply to problems where periodicity of oblique Bragg planes varies in the direction normal to the surface. Such strain may be induced, for example, by variation of composition with depth. Certain problems wherein simultaneous diffraction by two sets of Bragg planes occurs can also be treated by this approach.

A new matrix representation of the dynamical theory of x–ray diffraction which treats asymmetric reflections of coherent (i.e., pseudomorphic) epitaxial single crystal structures has been applied to III–V semiconductor multilayer structures. The laminar approximation is made, and Maxwell‘s equations are integrated in a 8 x 8 matrix form for the sublayers. Diffraction profiles from any multilayer can be obtained by multiplying the sublayer matrices. The method was used to simulate on a computer the intrinsic reflecting power of hypothetical structures in order to probe theoretical sensitivity limits for thin layers. We investigated [100] oriented structures consisting of single In ( l–x )Ga (x)As(l–y)P(y) quaternary (Q) layers on InP substrates as well as double heterostructures (DH‘s) consisting of a thin Q layer sandwiched between an InP substrate and an InP cladding layer.