A technique has been developed for the interpretation of composition-depth profiles from angleresolved X-ray data using a Monte Carlo electron scattering simulation. This is a nondestructive depth profiling procedure. Software has been developed that uses a Monte Carlo scattering simulation to generate the signal intensity from a multilayer sample for any combination of primary beam angle of incidence and take-off angle to the X-ray detector. An interactive C++ application uses this simulation to interpret measured angle-resolved depth profiles. The method has been tested using a custom-made Ag/Al “staircase” sample containing two layers each of Ag and Al. Using the technique, it is possible to quantify the composition-depth profile for the two- and three-layer “steps” of the sample. Qualitative information may be gained about the four-layer area of the sample.

One of the atomic-focuser modes for ultra-high resolution electron microscopy is described theoretically and illustrated by the observation of images formed within the diffraction spots of nanodiffraction patterns of carbon nanoshells. In this mode, the specimen is illuminated by the focused probe of a scanning transmission electron microscope and is followed by a thin crystal at a Fourier-image distance. The theory shows that each diffraction spot of the crystal contains a magnified image of the illuminated area of the specimen, having a resolution depending on the width of the intensity peak of electrons channeled along atomic rows in the crystal. A thin graphite crystal, contained within one wall of a carbon nanoshell, can act as an atomic focuser to image part of the other wall of the nanoshell, or tungsten atoms deposited on this wall. Simulations of the transmission of electrons through graphite crystals show that the images formed should have a resolution of about 0.06 nm. Experimental images suggest that this resolution has been attained in the imaging of tungsten atoms or clusters of tungsten atoms.

In February 1999, the second Scanned Probe Microscopy conference (SPM II) of the Australian Scanned Probe Microscope Society was held in Sydney, Australia, in conjunction with the fifth biennial symposium of the Australian Microbeam Analysis Society (AMAS V). This issue of Microscopy and Microanalysis presents selected full-length papers arising from that meeting.

The preparation of frozen amorphous nano-meter thin films of solutions containing particles, and imaging with energy filtered TEM, opens for the first time the possibility to map the elemental distribution in solids interacting with liquids. The future possible areas of research in solution include: dynamic of crystal growth processes, adsorption mechanisms, ion exchange, structure determination of nano-sized solids in equilibrium with different solvents, etc.

The sample preparation uses a controlled-environment vitrification system. Solidification of the liquid phase was achieved by plunging the solution, suspended in the holes of a lacy carbon on a copper grid, into liquid ethane (-174 °C). The specimen was transferred into the microscope by an Oxford CT3500 cryo-holder. The specimen temperature in the microscope column can be kept at -183 °C. The thickness of the vitrified film's, including the particles, should be about 50-100 nm or preferably less. The Philips CM120 BioTWIN Cryo microscope, here used for cryo-EFTEM, has a focal length of 6 nun and a structural resolution of 0.4 nm.

Mammalian oocytes present challenges for optimal study by electron microscopy (EM) due to their high level of hydration, their large size, and their relatively undifferentiated cytoplasm. This is particularly true for immunoprobe localization which has led to a dependence on light microscopic (LM) techniques, such as immunofluorescence. This study presents correlative LM and EM data to describe an example of the failure of light microscopy to correctly predict the ultrastructure of one particular organelle. Immunoprobe localization of centrosome and microtubule organizing center (MTOC) antigens in the mammalian egg was made by immunofluorescence and post-embedding immuno-EM, with best EM results achieved in Lowicryl-embedded material. Centrosome and MTOC antigens were detected by 5051 and an antibody to gamma tubulin (γtubulin). Gamma tubulin is a highly conserved element of MTOCs in many species and, thus, is highly diagnostic for them; it is also considered essential for microtubule (MT) nucleation. Results indicate that prior to nuclear breakdown, 5051 antigens and γ-tubulin are found exclusively in a type of “organelle,” the multivesicular aggregate (MVA), that bears no resemblance to MTOCs at the ultrastructural level. Until recently, the MVA was considered an organelle without a known function, while standard MTOCs were presumed to be the entities that carry the proteins recognized by centrosome antibodies. LM localization of centrosomal antigens carried the presumption that standard MTOCs were the entities labeled. Whether or not other molecules are shown to co-localize to these MVA, the presence of γ-tubulin supports the contention that MVA, or their contents, serve as centrosomal precursors with a unique ultrastructure. Thus, dependence on LM techniques alone can lead to erroneous conclusions on organelle identity and function.

A radiofrequency gaseous detection device is proposed for use with instruments employing charged particle beams, such as electron microscopes and ion beam technologies, as well as for detection of ionizing radiations as in proportional counters. An alternating (oscillating) electromagnetic field in the radiofrequency range is applied in a gaseous environment of the instrument. Both the frequency and amplitude of oscillation are adjustable. The electron or ion beam interacts with a specimen and releases free electrons in the gas. Similarly, an ionizing radiation source releases free electrons in the gas. The free electrons are acted upon by the alternating electromagnetic field and undergo an oscillatory motion resulting in multiple collisions with the gas molecules, or atoms. At sufficiently low pressures, the oscillating electrons also collide with surrounding walls. These processes result in an amplified electron signal and an amplified photon signal in a controlled discharge. The amplified signals, which are proportional to the initial number of free electrons, are collected by suitable means for further processing and analysis.

The three-dimensional (3D) atom-probe technique produces a reconstruction of the elemental chemical identities and three-dimensional positions of atoms field evaporated from a sharply pointed metal specimen, with a local radius of curvature of less than 50 nm. The number of atoms collected can be on the order of one million, representing an analysis volume of approximately 20 nm × 20 nm × 200 nm (80,000 nm3). This large amount of data allows for the identification of microstructural features in a sample, such as grain or heterophase boundaries, if the feature density is large enough. Correlation of the measured atomic positions with these identified features results in an atom-by-atom description of the chemical environment of crystallographic defects. This article outlines a data compilation technique for the generation of composition profiles in the vicinity of interfaces in a geometrically independent way. This approach is applied to quantitative determination of interfacial segregation of silver at a MgO/Cu(Ag) heterophase interface.

From the late 1960s onwards the author embarked on a series of electron microscopic adventures using progressively more sophisticated techniques which yielded structural information and uncovered physics-chemical phenomena that would have been irretrievable by other methods. Illustrative examples include; (i) proof that photoreactivity and unexpected photoproducts of organic molecular crystals are governed by stacking faults, and that applied stress converts some photostable organic solid to photactive ones; (ii) elucidation of interdependence of photoluminesence and polymorphism in organic crystals; (iii) determination of surface pointdefect-concentration at, and discovery of catalytic channeling by metals in the oxidation of, graphite and molybdenite; (iv) establishing the mechanism of interconversion of “stages” in graphite intercalates, and the discovery of incommensurate guest-hosts-structures (with graphiteiron chloride); (v) rationalization of the structures of the many seemingly unrelated phases of bismuth molybdate catalysts (for oxidation) in terms of a common, defect-fluorite (Bi2O3) archetype;

The technique of atomic force microscopy (AFM) soft-imaging is outlined with respect to characterizing the adsorption of surfactants and polymers at the solid/liquid interface. This method utilizes the electrostatic and steric repulsion forces between the scanning probe and the sample to allow sensitive placement of the imaging probe near to the delicate surface layer. Specifically, the mixed adsorption of sodium dodecylsulfate (SDS) and poly(vinyl pyrrolidone) (PVP) on graphite is examined. Unlike the adsorbed layer in a solution of either component, the adsorbed layer in the mixture does not cover the substrate uniformly until equilibrium is reached (often hours later). The interesting kinetic and coverage effects observed are significant to the many applications reliant on adsorption from polymer-surfactant mixtures, especially to the flocculation of dispersions.

It is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated <100> split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.

Atherosclerotic lesions are heterogeneous in terms of their cellular and lipid composition. While heterogeneity can be the result of stochastic noise, an alternate hypothesis is that the differences observed among individual lesions arise from deterministic chaos. Five New Zealand white rabbits were fed a diet containing 0.15% cholesterol for 6 months. Segments of the aorta were fixed in formalin, stained en bloc with Nile red (NR) and filipin (F), and en face fluorescence microscopy was used to map the distribution of lipids in fatty streaks (FS). The smallest lesions detected stained only with filipin. Larger lesions stained with both Nile red and filipin and two distinct regions of Nile red staining, NR-orange (rich in polar lipids) and NR-yellow (rich in neutral lipids) were observed. Digital overlays revealed a “nested” arrangement of F, NR-orange, and NR-yellow. The lesions also showed marked heterogeneity in their lipid composition. Thus, although initially similar, as FS increased in size, their composition became divergent, suggesting that the ultimate composition of a FS was highly sensitive to its initial composition. Sensitivity to initial condition is one of the hallmarks of deterministic systems. To determine if FS were self-similar, another hallmark of deterministic chaos, the borders of the different regions defined by NR and F staining were subjected to fractal analysis. For each lesion, the borders of the F, NR-orange, and NR-yellow regions were found to be fractal. Return maps were constructed for the differently stained regions. Analysis of the entire 104-lesion data set showed that although the data could be described by a four-parameter logistic model, the population was not chaotic. However, return maps drawn for the maxima of the NR-orange stained regions demonstrated chaos. Taken together, the data suggest that deterministic chaos plays a role in the evolution of atheromatous disease but, in common with most biologic systems, as the lesions progress, chaotic behavior is dampened.

At the species level, bryozoans (class Phylactolaemata) in the family Plumatellidae are difficult to organize taxonomically. Of principal concern is the absence of consistent distinguishing features due mainly to plasticity of the group, a common problem with soft-bodied invertebrates. Yet, within the last three decades, analysis of distinctive chitinous statoblasts—using scanning electron microscopy—has resolved certain taxonomic questions. I examined statoblasts from 30 similar collections, the majority from the midwestern United States, and identified four distinct subgroups. Also, nine new statoblast surface features were identified: fold, polar grooves, bead, cave, demarcation, parasutural zone, ridge, sutural band, and sutural knob. The surface features of floating statoblasts (floatoblasts) provide useful data for species identification. Most consistently useful in plumatellids is a suture which varies from one species to the next. Mound-like tubercles and net-like ridges are next in the extent of variability. Finally, folds and polar grooves are present but vary even within floatoblasts from the same colony. Analysis of the suture in Plumatella fungosa, over a 5-day germination period, reveals all features at the site remain intact regardless of the initial age of the floatoblast. Only the suture line itself splits lengthwise to permit emergence of the new animal.

In large bandgap semiconductors and insulators, the threshold energies for e–h pair production and ionization damage can lie above the vacuum level. For low energy imaging, a window is then opened whose width is potentially sensitive to local changes in work function, doping level, or acidity. Recent progress and future opportunities for damage-free imaging of these properties using low energy electrons are discussed in the light of the underlying physics, as well as of recent instrumental developments in low energy electron microscopy (LEEM), environmental scanning electron microscopy (ESEM), photoelectron emission microscopy (PEEM), scanned probe microscopy (SPM), and projection electron microscopy.

The reverse flow pressure limiting aperture is a device that creates and sustains a substantial gas pressure difference between two chambers connected via an aperture. The aperture is surrounded by an annular orifice leading to a third chamber. The third chamber is maintained at a relatively high pressure that forces gas to flow through the annular aperture into the first of said two chambers. The ensuing gas flow develops into a supersonic annular gas jet, the core of which is coaxial with the central aperture. A pumping action is created at the core of the jet and any gas molecules leaking through the aperture from the second chamber are entrained and forced into the first chamber, thus creating a substantial pressure difference between the first and second chamber.

The preparation of ultra flat gold surfaces for use in chemical force microscopy (CFM) has been studied. The surfaces were studied in terms of substrate effects by comparing mica, Si (110) wafer and glass slides. The effect of different annealing regimes was also investigated. Measurements on these surfaces were made by both atomic force microscopy (AFM) (in contact and tapping mode) and by scanning tunneling microscopy (STM). The films contain different morphologies with respect to grain size and topography. Calculations of surface roughness present values less than 2.5 nm for all surfaces studied, making the choice of the flattest surface difficult if based on criteria of surface roughness alone. Additionally, it is shown that different acquisition parameters can produce dissimilar images that have stability and reproducibility.

The results of a three-dimensional atom probe (3DAP) analysis, on a subnanometer scale, of a ceramic/metal heterophase interface, MgO/Cu, are presented. Segregation of Ag, from the Cu (Ag) matrix, at MgO/Cu interfaces is investigated and the Gibbsian interfacial excess of silver is determined; the range is 2.33 × 1018 to 5.81 × 1018 m−2. Also, silver segregation at the same MgO/Cu interfaces is analyzed employing a new approach that utilizes a proximity histogram or proxigram.

The production and characterization of NBS K-411 glass microspheres in the 2–40 μm range for certification as NIST Standard Reference Material® 2066 (SRM®) are described. Quantitative analysis and heterogeneity testing of the microspheres were done with an electron probe microanalyzer-X-ray energy dispersive spectrometry (EPMA-EDS) automated particle analysis procedure. Results for the trimmed and normalized data produced mean compositions for the elements Mg, Si, Ca, Fe, and O (calculated from stoichiometry) that are in good agreement with the certified values for the K-411 bulk glass (NBS SRM 470 Glasses for Mineral Analysis), but with uncertainties about twice as large as those for the bulk material. Differences from the bulk are attributable to microsphere geometry as well as mass and size effects.