This issue of Microscopy and Microanalysis contains contributions presented at the Frontiers of Electron Microscopy in Materials Science (FEMMS) meeting held in Kasteel Vaalsbroek, The Netherlands, on September 25–30, 2005. Tenth in the series of biennial conferences, the meeting focused on the latest developments in the field of advanced instrumentation and application of electron microscopy in materials science. The international character of this series of conferences was once again emphasized by the presence of over 140 delegates whose interests include academia, national laboratories, and industry from 16 countries representing all areas of the globe.

Aberration correctors using hexapole fields have proven useful to correct for the spherical aberration in electron microscopy. We investigate the limits of the present design for the hexapole corrector with respect to minimum probe size for the scanning transmission electron microscope and discuss several ways in which the design could be improved by rather small and incremental design changes for the next generation of advanced probe-forming systems equipped with a gun monochromator.

Initial results from an ultrahigh-vacuum (UHV) third-order spherical aberration (Cs) corrector for a dedicated scanning transmission electron microscopy, installed at the National Institute for Materials Science, Tsukuba, Japan, are presented here. The Cs corrector is of the dual hexapole type. It is UHV compatible and was installed on a UHV column. The Ronchigram obtained showed an extension of the sweet spot area, indicating a successful correction of the third-order spherical aberration Cs. The power spectrum of an image demonstrated that the resolution achieved was 0.1 nm. A first trial of the direct measurement of the fifth-order spherical aberration C5 was also attempted on the basis of a Ronchigram fringe measurement.

Methods for accurate and automated determination of the coefficients of the wave aberration function are compared with particular emphasis on measurements of higher order coefficients in corrected instruments. Experimental applications of aberration measurement to the determination of illumination isoplanicity and high precision local refinement of restored exit waves are also described.

Exit wave restoration using focus series of images has become a widely used technique to improve image resolution and interpretation. To understand the effects of the imaging approximations used, we have critically compared the specimen exit wave functions restored using the efficient linear Wiener filter, with a general nonlinear maximum likelihood method.

Structural features like defects or heterointerfaces in crystals or amorphous phases give rise to different local patterns in high-resolution electron micrographs or object wave functions. Pattern recognition techniques can be used to identify these typical patterns that constitute the image itself, as was already demonstrated for compositional changes in isostructural heterostructures, where the patterns within unit cells of the lattice were analyzed. To extend such analyses to more complex materials, we examined patterns in small circular areas centered on intensity maxima of the image. Nonsupervised clustering, namely, Ward's clustering method, was applied to these patterns. In two examples, a highly defective ZnMnTe layer on GaAs and a tunnel magneto resistance device, we demonstrate how typical patterns are identified by this method and how these results can be used for a further investigation of the microstructural properties of the sample.

The resolution-limiting aberrations of round electromagnetic lenses can now be successfully overcome via the use of multipole element “aberration correctors.” The installation and performance of a hexapole-based corrector (CEOS GmbH) integrated on the probe-forming side of a JEOL 2200FS FEG STEM/TEM is described. For the resolution of the microscope not to be severely compromised by its environment, a new, specially designed building at Oak Ridge National Laboratory has been built. The Advanced Microscopy Laboratory was designed with the goal of providing a suitable location for aberration-corrected electron microscopes. Construction methods and performance of the building are discussed in the context of the performance of the microscope. Initial performance of the microscope on relevant specimens and modifications made to eliminate resolution-limiting conditions are also discussed.

Planar defects in a polycrystalline diamond film were studied by high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy (STEM). In both modes, sub-Ångström resolution was achieved by making use of two aberration-corrected systems; a TEM and a STEM CS-corrected microscope, each operated at 300 kV. For the first time, diamond in 〈110〉 zone-axis orientation was imaged in STEM mode at a resolution that allows for resolving the atomic dumbbells of carbon at a projected interatomic distance of 89 pm. Twin boundaries that show approximately the Σ3 CSL structure reveal at sub-Ångström resolution imperfections; that is, local distortions, which break the symmetry of the ideal Σ3 type twin boundary, are likely present. In addition to these imperfect twin boundaries, voids on the atomic level were observed. It is proposed that both local distortions and small voids enhance the mechanical toughness of the film by locally increasing the critical stress intensity factor.

Experimental results from the first monochromated and aberration-corrected scanning transmission electron microscope operated at 200 kV are described. The formation of an electron probe with a diameter of less than 0.2 nm at an energy width significantly under 0.3 eV and its planned application to the chemical analysis of nanometer-scale structures in materials science are described. Both energy and spatial resolution will benefit from this: The monochromator improves the energy resolution for studies of energy loss near edge structures. The Cs corrector allows formation of either a smaller probe for a given beam current or yields, at fixed probe size, an enhanced beam current density using a larger condenser aperture. We also point out another advantage of the combination of both components: Increasing the convergence angle by using larger condenser apertures in an aberration-corrected instrument will enlarge the undesirable chromatic focus spread. This in turn influences spatial resolution. The effect of polychromatic probe tails is proportional to the product of convergence angle, chromatic aberration constant, and energy spread. It can thus be compensated for in our new instrument by decreasing the energy width by the same factor as the beam convergence is increased to form a more intense probe. An alternative in future developments might be hardware correction of the chromatic aberration, which could eliminate the chromatic probe spread completely.

We report on the sub-electron-volt-sub-angstrom microscope (SESAM), a high-resolution 200-kV FEG-TEM equipped with a monochromator and an in-column MANDOLINE filter. We report on recent results obtained with this instrument, demonstrating its performance (e.g., 87-meV energy resolution at 10-s exposure time, or a transmissivity of the energy filter of T1 eV = 11,000 nm2). New opportunities to do unique experiments that may advance the frontiers of microscopy in areas such as energy-filtered TEM, spectroscopy, energy-filtered electron diffraction and spectroscopic profiling are also discussed.

A Nion spherical-aberration (Cs) corrector was recently installed on Lehigh University's 300-keV cold field-emission gun (FEG) Vacuum Generators HB 603 dedicated scanning transmission electron microscope (STEM), optimized for X-ray analysis of thin specimens. In this article, the impact of the Cs-corrector on X-ray analysis is theoretically evaluated, in terms of expected improvements in spatial resolution and analytical sensitivity, and the calculations are compared with initial experimental results. Finally, the possibilities of atomic-column X-ray analysis in a Cs-corrected STEM are discussed.

Two recent developments in X-ray spectrometer technology provide dramatic improvements in analytical capabilities that impact the frontiers of electron microscopy. Silicon drift detectors (SDD) use the same physics as silicon (lithium) energy dispersive spectrometers [Si(Li) EDS] but differ in design: only 10% of the thickness of the Si(Li) EDS with an anode area below 0.1 mm2 and a complex rear surface electrode pattern that creates a lateral internal charge collection field. The SDD equals or betters the Si(Li) EDS in most measures of performance. For output versus input count rate, the SDD exceeds the Si(Li) EDS by a factor of 5 to 10 for the same resolution. This high throughput can benefit analytical measurements that are count limited, such as X-ray mapping and trace measurements. The microcalorimeter EDS determines the X-ray energy by measuring the temperature rise in a metal absorber. Operating at 100 mK, the microcalorimeter EDS achieves resolution of 2–5 eV over a photon energy range of 200 eV to 10 keV in energy dispersive operation, eliminating most peak interference situations and providing high peak-to-background to detect low fluorescence yield peaks. Chemical bonding effects on low energy (<2 keV) peak shapes can be measured.

Multivariate statistical analysis methods have been applied to scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectral images. The particular application of the multivariate curve resolution (MCR) technique provides a high spectral contrast view of the raw spectral image. The power of this approach is demonstrated with a microelectronics failure analysis. Specifically, an unexpected component describing a chemical contaminant was found, as well as a component consistent with a foil thickness change associated with the focused ion beam specimen preparation process. The MCR solution is compared with a conventional analysis of the same spectral image data set.

A new TEM sample preparation technique using electron-beam-induced deposition combined with low-energy ion milling was used to fabricate for two different shapes of sample, conical and plate. High-quality HREM images can be obtained from samples prepared by this technique. A desired sample position can be obtained with high accuracy, and the total sample preparation time can be much less than conventional techniques. Because the gas deposition system used can easily be integrated in a conventional SEM, the method can be performed in any laboratory equipped with a SEM and an ion milling machine.

The process of electron-beam-induced deposition (EBID) was simulated with a dynamic Monte Carlo profile simulator, and the growth of carbon, silver, and tungsten supertips was investigated to study the dependence of material composition on the spatial resolution of EBID. Because light atoms have a smaller scattering angle and a longer mean free path, the carbon supertip has the smallest lateral size and the highest aspect ratio of a bottom tip compared to silver and tungsten supertips. Thus the best spatial resolution of EBID can be achieved on materials of low atomic number. The calculation also indicated a significant contribution of primary electrons to the growth of a supertip in EBID, which is consistent with the experimental observations. These results lead to a more comprehensive understanding of EBID, which is a complex interaction process between electrons and solids.

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 Nestor Zaluzec, zaluzec@aaem.amc.anl.gov.