This issue of Microscopy and Microanalysis contains a selection of invited papers from the topical symposium, Thirty Years of Energy-Dispersive Spectrometry in Microanalysis, sponsored by the Microbeam Analysis Society (MAS) at the Microscopy & Microanalysis (M&M) '98 meeting, held July 12-16 in Atlanta, Georgia. This was the second MAS topical symposium held in conjunction with the annual M&M meetings, the first being at the meeting in Minneapolis, Minnesota, in 1996. The MAS topical symposia are part of an initiative to provide venues for in-depth study of topics of special interest to the microbeam analysis community. The next MAS topical symposium is planned as part of M&M '99 and will celebrate Fifty Years of the Electron Microprobe.

The energy-dispersive Si(Li) X-ray spectrometer, introduced 30 years ago into electron probe mi-croanalysis (EPMA) by R. Fitzgerald et al., has profoundly affected the development of microanalysis. It offers many advantages over the wavelength-dispersive crystal spectrometer. It has no moving parts and covers the full energy range of interest in EPMA. There is no defocusing over large distances on the specimen, the efficiency of the device is high, varies slowly and continuously with atomic number, and can be predicted fairly accurately, and, most importantly, all emission lines are detected and can be observed simultaneously. The one remaining disadvantage of the Si(Li) spectrometer is its poorer energy resolution. Solid-state detection devices now under development promise to achieve resolution comparable to that of the crystal spectrometer.

As part of the Microbeam Analysis Society (MAS) symposium marking 30 years of energy-dispersive spectrometry (EDS), this article reviews many innovations in the field over those years. Innovations that added a capability previously not available to the microanalyst are chosen for further description. Included are innovations in both X-ray microanalysis and digital imaging using the EDS analyzer.

X-ray microanalysis of materials using energy-dispersive spectrometry (EDS) has made the greatest impact in studies of compositional changes at atomic-level interfaces. The small physical dimensions of the silicon detector make EDS the X-ray analyzer of choice for analytical transmission electron microscopy (AEM). X-ray analysis of thin foils in the AEM has contributed to our understanding of elemental segregation to interphase interfaces and grain boundaries, as well as other planar defects. Measurement of atomic diffusion on a small scale close to interphase interfaces has permitted determination of substitutional atomic diffusivities several orders of magnitude smaller than previously possible and has also led to the determination of low-temperature equilibrium phase diagrams through the measurement of local interface compositions. Elemental segregation to grain boundaries is responsible for such deleterious behavior as temper embrittlement, stress-corrosion cracking, and other forms of intergranular failure. On the other hand, segregation can bring about improvement in behavior: sintering aids in ceramics and de-embrittlement of intermetallics. EDS in the AEM has been responsible for quantitative analysis of all aspects of the segregation process and, more recently, in combination with electron energy-loss spectrometry (EELS) has given insight into why boundary segregation results in such significant macroscopic changes in properties.

Low-voltage energy-dispersive X-ray microanalysis has a number of distinct advantages for measuring the concentration of light elements (Z = 11−20) in a largely organic matrix. Between 10 and 4 kV, there is a 50-fold decrease in the size of the incident beam-specimen interaction volume which enables discrete subcel-lular compartments to be analyzed. Experiments with mineral and organic samples of known chemical composition show that two of the most widely used analytical algorithms are capable of providing quantitative data at accelerating voltages as low as 5 kV. This technique is used at 5 kV to analyze frozen hydrated fracture faces of leaves of the tea plant which are known to contain aluminium. Higher levels of aluminium are found in the cell walls and are associated with increased levels of silicon and magnesium. The advantages and disadvantages of the experimental approach are discussed in relation to analysis carried out at higher voltages.

Electron beam X-ray microanalysis with semiconductor energy-dispersive spectrometry (EDS) performed with standards and calculated matrix corrections can yield quantitative results with a distribution such that 95% of analyses fall within ±5% relative for major and minor constituents. Standardless methods substitute calculations for the standard intensities, based either on physical models of X-ray generation and propagation (first principles) or on mathematical fits to remotely measured standards (fitted standards). Error distributions have been measured for three different standardless analysis procedures with a suite of microanalysis standards including metal alloys, glasses, minerals, ceramics, and stoichiometric compounds. For the first-principles standardless procedure, the error distribution placed 95% of analyses within ±50% relative, whereas for two commercial fitted standards procedures, the error distributions placed 95% of analyses within ±25% relative. The implication of these error distributions for the accuracy of analytical results is considered, and recommendations for the use of standardless analysis are given.

X-ray counting statistics plays a key role in establishing confidence limits in composition determination by X-ray microanalysis. The process starts with measurements of intensity on one or more samples and standards as well as related background determinations. Since each individual measurement is subject to variability associated with counting statistics, it is necessary to combine all of the counting variability according to established mathematical procedures. The next step is to apply propagation of error calculations to equations for quantitative analysis and determine confidence limits in reported composition. Similar concepts can also be applied to trace element determination. This approach can then be combined with spectral simulation modeling, making it possible to predict detectability limits without additional measurements.

As Si(Li) detector technology has matured, many of the fundamental problems have been addressed in the competition among manufacturers and there is now an expectation, implied by many textbooks, that all energy-dispersive X-ray (EDX) detectors are made and will perform in the same way. Although there has been some convergence in Si(Li) systems and these are still the most common, manufacturing recipes still differ and there are many alternative EDX devices, such as microcalorimeters and room temperature detectors, that have both advantages and disadvantages over Si(Li). Rather than emphasizing differences in technologies, performance measures should reveal benefits relevant to the intended application. The instrument is inevitably going to be a “black box” of integrated components; this article reviews some of the methods that have been applied and introduces some new techniques that can be used to assess performance without resorting to complex software or sophisticated mathematical algorithms. Sensitivity, resolution, artefacts, and stability are discussed with particular application to compositional analysis using electron beam excitation of X-rays in the 100-eV to 10-keV energy region.

Cryogenic energy-dispersive X-ray detectors are being developed because of their superior energy resolution (10 eV FWHM for keV X-rays) compared to that achieved in semiconductor energy-dispersive spectrometry (EDS) systems. So far, their range of application is limited because of their comparably small size and low count rate. We present data on the development of superconducting tunnel junction (STJ) detector arrays to address both of these issues. A single STJ detector has a resolution of around 10 eV below 1 keV and can be operated at count rates of the order 10,000 counts/sec. We show that the simultaneous operation of several STJ detectors does not dimish their energy resolution significantly, and it increases the detector area and the maximum count rate by a factor given by the total number of independent channels.

Originally designed as position-sensitive detectors for particle tracking, silicon drift detectors (SDDs) are now used for high-count rate X-ray spectroscopy, operating close to room temperature. Their low-capacitance read-node concept places them among the fastest high-resolution detector systems. They have been used in a new spectrum of experiments in the wide field of X-ray spectroscopy: fluorescent analysis, diffrac-tometry, materials analysis, and synchrotron experiments such as X-ray holography and element imaging in scanning electron microscopes. The fact that the detector system can be used at room temperature with good spectroscopic performance and at −10°C with excellent energy resolution, avoiding liquid nitrogen for cooling and high-quality vacuum, guarantees a large variety of new applications, independent of the laboratory environment. A brief description of the device principles is followed by basics on low noise amplification. The performance results of a complete detector system are presented as well as some dedicated applications already realized, including use in a surface mapping instrument and use of a “mini-spectrometer” for the analysis of works of art. Fully depleted pn-charge-coupled devices (pn-CCDs) have been fabricated for the European X-ray Multi-Mirror mission (XMM) and the German X-ray satellite ABRIXAS, enabling high-speed, low-noise, position-resolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm2. At −70°C it has a noise of 4 e- rms, with a readout time of the total focal plane array of 4 msec. The maximum count rate for single photon counting was 105 cps under flat field conditions. In the integration mode, more than 109 cps can be detected at 6 keV. Its position resolution is on the order of 100 μm. The quantum efficiency is higher than 90%, ranging from carbon K X-rays (277 eV) up to 10 keV.

X-ray optics have been used in X-ray analytical instruments for several years. Applications of X-ray optics have been reported in X-ray diffraction, X-ray fluorescence, and wavelength dispersive spectroscopy. X-ray optics have been used to increase the X-ray flux incident on the sample or to direct and focus emitted X-rays from a sample. We report here the use of a grazing incidence optic (GIO) as a flux-enhancing collimator for use with an energy-dispersive (ED) detector used to perform electron beam microanalysis. We found that the GIO in combination with an ED spectrometer (EDS) provides substantial intensity gain for X-ray lines with energy below 1 keV. The GIO is also found to provide a modest focus effect, and introduces minimal spectral artifacts.

This issue brings my first full year as editor of the News and Commentary to a close—a year of evolution from “making up it as we go along” to a position where there are regular features that provide consistency and a theme to the News and Commentary. The Calendar of Meetings and Courses continues. Most notable has been the introduction of a feature entitled “The Life and Achievements of …” in which such scientists as Albert Prebus, John Reisner, and Raymond Castaing have been profiled by individuals who knew them and who have generously agreed to write about them. This feature will be continued and any suggestions for individuals to be profiled are welcome.

The International Federation of Societies for Electron Microscopy (IFSEM) was established in the mid-1950s out of a postwar desire to foster communications and collaboration among electron microscopists around the world and, to some extent, in response to growing recognition of the need for formal endorsement of an expanding calendar of meetings featuring foreign speakers and soliciting attendance from the rapidly swelling international community of electron microscopists. The present oversight function, pertaining to the scientific program, adequacy of the budgets, capacity of the facilities, and special amenities of the setting, came later. It must be said that the international ”Olympic Committee” system has worked well with an admirable string of successful meetings and no major problems. This short account deals primarily with the early IFSEM period. Developments during the middle and more recent IFSEM years have been described in a joint publication by Arvid Maunsbach and Gareth Thomas (1996)—both past Presidents of IFSEM. A subsequent account of the present structure, membership, and functions of IFSEM will also appear in a later issue of the Journal.

The 14th and last International Congress of Electron Microscopy (ICEM) of the century was held in Cancun, Mexico on August 31-September 4, 1998 under the chairmanship of Dr. Miguel José Yacaman. Held every 4 years in a different international location, these ICEMs are renowned for the science presented, the state-of-the-art instrumentation exhibited, and the mix of international scientists in attendance. They are also made memorable by the unique scientific and cultural contributions from the host country. This Congress was no exception and the 14th ICEM in Cancun, Mexico, characterized by all of these features, was further augmented by the intrinsic beauty and archaeological interest of the Yucatan Peninsula region.

Following is a list of microscopy-related meetings and courses. The editors would greatly appreciate input to this list via the electronic submission form found in the MSA World Wide Web page at http://www.msa.microscopy.com/. We will gladly add hypertext links to the notice on the Web and insert a listing of the meeting in the next issue of the Journal. Send comments and questions to Barbara Reine, reine@u.washington.edu or Nestor Zaluzec, zaluzec@aaem.amc.anl.gov.