We evaluate the usefulness of digital volume data produced with the high-resolution episcopic microscopy (HREM) method for visualizing the three-dimensional (3D) arrangement of components of human skin, and present protocols designed for processing skin biopsies for HREM data generation. A total of 328 biopsies collected from normally appearing skin and from a melanocytic nevus were processed. Cuboidal data volumes with side lengths of ~2×3×6 mm3 and voxel sizes of 1.07×1.07×1.5 µm3 were produced. HREM data fit ideally for visualizing the epidermis at large, and for producing highly detailed volume and surface-rendered 3D representations of the dermal and hypodermal components at a structural level. The architecture of the collagen fiber bundles and the spatial distribution of nevus cells can be easily visualized with volume-rendering algorithms. We conclude that HREM has great potential to serve as a routine tool for researching and diagnosing skin pathologies.

Properties of gold nanoparticles (AuNPs) are very different from bulk gold, in particular, highly dispersed AuNPs exhibit high catalytic activities on metal oxide supports. Catalytic activities of AuNPs are strongly dependent on: (i) size and morphology; (ii) synthesis methods; (iii) nature of the support; (iv) interaction between AuNPs and the support; and (v) oxidation state of AuNPs in the synthesized catalysts. A goal is to maintain the size and to prohibit aggregation of AuNPs, since aggregations deteriorate catalytic activities. Some strong interactions are therefore required between AuNPs and their supports to prevent the movement of AuNPs. SBA-15 is a promising material for the support of AuNPs since it has ordered two-dimensional hexagonal pore channels, uniform pore size ranging from 5 to 30 nm, narrow pore size distribution, thick amorphous walls ranging from 3 to 6 nm, and high surface area. In this study, SBA-15, TiO2-SBA-15 and TiO2-SBA-15-AuNP nanocomposites were synthesized by the sol-gel method and microstructural characterizations were carried out by both X-ray diffraction analysis and electron microscopy.

Magnetic nanocomposite materials consisting of 5 and 10 wt% CoFe2O4 nanoparticles in a silica aerogel matrix have been synthesized by the sol-gel method. For the CoFe2O4-10wt% sample, bright-field scanning transmission electron microscopy (BF STEM) and high-resolution transmission electron microscopy (HREM) images showed distinct, rounded CoFe2O4 nanoparticles, with typical diameters of roughly 8 nm. For the CoFe2O4-5wt% sample, BF STEM images and energy dispersive X-ray (EDX) measurements showed CoFe2O4 nanoparticles with diameters of roughly 3 ± 1 nm. EDX measurements indicate that all nanoparticles consist of stoichiometric CoFe2O4, and electron energy-loss spectroscopy measurements from lines crossing nanoparticles in the CoFe2O4-10wt% sample show a uniform composition within nanoparticles, with a precision of at best than ±0.5 nm in analysis position. BF STEM images obtained for the CoFe2O4-10wt% sample showed many “needle-like” nanostructures that typically have a length of ∼10 nm and a width of ∼1 nm, and frequently appear to be attached to nanoparticles. These needle-like nanostructures are observed to contain layers with interlayer spacing 0.33 ± 0.1 nm, which could be consistent with Co silicate hydroxide, a known precursor phase in these nanocomposite materials.

Magnetic nanocomposite materials consisting of 5.5 wt% Fe-Co alloy nanoparticles in a silica aerogel matrix, with compositions FexCo1−x of x = 0.50 and 0.67, have been synthesized by the sol-gel method. The high-resolution transmission electron microscopy images show nanoparticles consisting of single crystal grains of body-centered cubic Fe-Co alloy, with typical crystal grain diameters of approximately 4 and 7 nm for Fe0.5Co0.5 and Fe0.67Co0.33 samples, respectively. The energy dispersive X-ray (EDX) spectra summed over areas of the samples gave compositions FexCo1−x with x = 0.48 ± 0.06 and 0.68 ± 0.05. The EDX spectra obtained with the 1.5 nm probe positioned at the centers of ∼20 nanoparticles gave slightly lower concentrations of Fe, with means of ⟨x⟩ = 0.43 ± 0.01 and ⟨x⟩ = 0.64 ± 0.02, respectively. The Fe0.5Co0.5 sample was studied using electron energy loss spectroscopy (EELS), and EELS spectra summed over whole nanoparticles gave x = 0.47 ± 0.06. The EELS spectra from analysis profiles of nanoparticles show a distribution of Fe and Co that is homogeneous, i.e., x = 0.5, within a precision of at best ±0.05 in x and ±0.4 nm in position. The present microscopy results have not shown the presence of a thin layer of iron oxide, but this might be at the limit of detectability of the methods.

We introduce a simple preparation method for ultrathin carbon support films that is especially useful for high-resolution electron microscopy (HREM) of nanoparticles. Oxidized iron nanoparticles were used as a test sample in a demonstration of this method. The film qualities are discussed on the basis of electron-energy-loss spectroscopy (EELS) and image analysis techniques such as thickness maps and histograms. We carried out a comparison between the homemade and commercial film qualities. The relative thickness of the homemade support films was 0.6 times less than that of the commercial films, which was calculated from the EELS analysis, whereas the thicknesses of both carbon support films varied within about 3%. The percentage of the observable area was about 67 ± 7.6% of the support film. This was about twice as large as the commercial film (32 ± 9.3%). The HREM image of the sample prepared with our support film improved 9% in brightness and 15% in contrast compared with images obtained with the commercial support.

Nanophase aluminum powder was characterized in a field-emission-gun transmission electron microscope (TEM). Different techniques were used to investigate the structure of the particles, including conventional bright-field and dark-field imaging, scanning transmission electron microscopy (STEM), high-resolution lattice imaging, diffraction studies, energy dispersive X-ray spectroscopy (EDS) analysis and mapping, and electron energy loss spectroscopy (EELS) analysis and mapping. It has been established that the particle cores consist of aluminum single crystals that sometimes contain crystal lattice defects. The core is covered by a passivating layer of aluminum oxide a few nanometers thick. The alumina is mostly amorphous, but evidences of partial crystallinity of the oxide were also found. The thickness of this layer was measured using different techniques, and the results are in good agreement with each other. The particles are agglomerated in two distinct ways. Some particles were apparently bonded together during processing before oxidation. These mostly form dumbbells covered by a joint oxide layer. Also, oxidized particles are loosely assembled into relatively large clusters.

John Cowley and his group at Arizona State University pioneered the use of transmission electron microscopy (TEM) for high-resolution imaging. Three decades ago they achieved images showing the crystal unit cell content at better than 4 Å resolution. Over the years, this achievement has inspired improvements in resolution that have enabled researchers to pinpoint the positions of heavy atom columns within the cell. More recently, this ability has been extended to light atoms as resolution has improved. Sub-Ångstrom resolution has enabled researchers to image the columns of light atoms (carbon, oxygen, and nitrogen) that are present in many complex structures. By using sub-Ångstrom focal-series reconstruction of the specimen exit surface wave to image columns of cobalt, oxygen, and lithium atoms in a transition metal oxide structure commonly used as positive electrodes in lithium rechargeable batteries, we show that the range of detectable light atoms extends to lithium. HRTEM at sub-Ångstrom resolution will provide the essential role of experimental verification for the emergent nanotech revolution. Our results foreshadow those to be expected from next-generation TEMs with CS-corrected lenses and monochromated electron beams.

Heterogeneous catalysis is one of the oldest nanosciences. Although model catalysts can be designed, synthesized, and, to a certain degree, characterized, industrial heterogeneous catalysts are often chemically and physically complex systems that have been developed through many years of catalytic art, technology, and science. The preparation of commercial catalysts is generally not well controlled and is often based on accumulated experiences. Catalyst characterization is thus critical to developing new catalysts with better activity, selectivity, and/or stability. Advanced electron microscopy, among many characterization techniques, can provide useful information for the fundamental understanding of heterogeneous catalysis and for guiding the development of industrial catalysts. In this article, we discuss the recent developments in applying advanced electron microscopy techniques to characterizing model and industrial heterogeneous catalysts. The importance of understanding the catalyst nanostructure and the challenges and opportunities of advanced electron microscopy in developing nanostructured catalysts are also discussed.

The structure of Xe precipitates with sizes in several nanometers embedded in Al is known to be stable and its structure is well confirmed. But knowledge about the structure of Xe precipitates with nanometer sizes is very limited. There are difficulties in observing such small structures embedded in a crystalline matrix. An off-Bragg condition is used to observe diffraction patterns, dark-field, and high-resolution transmission electron microscopy images. The structure of Xe precipitates with sizes of about 2 nm and smaller is observed and confirmed. They are in an fcc structure and their orientation relationship with the Al matrix is similar to that of larger crystalline Xe precipitates or in an undefined structure. The lattice spacing or atomic distance in such nanometer-sized Xe precipitates is smaller than those of larger Xe precipitates embedded in Al matrix. There is a trend that as the size becomes smaller, the precipitates are more likely to have an undefined structure.

The continuous displacement field within elastically relaxed GaInAs islands was calculated from digitized HREM images of {110} cross sections of In0.35Ga0.65As layers grown on GaAs by molecular beam epitaxy. Experimental maps of the deformations parallel to the interface (εx) and along the growth direction (εz) were drawn and compared with the ones calculated via the finite element method. It was found that εx exp was systematically higher than εx calc and the significant maximum observed for εz exp within the island could not be found for εz calc. These discrepancies were attributed to a variation of the chemical composition in the island. The maps showing the indium concentration gradient drawn from HREM and FE calculations were compared to quantitative profiles for indium concentration obtained by nanometric X-ray microanalysis in TEM. The measured gradient within the island backs our assumption.

A Σ = 5 (310)[001] tilt grain boundary in molybdenum has been annealed at high temperature in the presence of carbon and observed in high-resolution electron microscopy. The carbon is located at the grain boundary in a 1-nm slab. Two different morphologies coexist. The first one is a grain boundary precipitation while the second one can be considered as a segregation.

Structures of Pt-nanowires, synthesized in channels of silica mesoporous materials MCM-41, SBA-15 and MCM-48, were investigated by transmission electron microscopy. One dimensional (1D) Pt-nanowires were formed inside the channels of the MCM-41, and were single crystals with a length of several tens to several hundreds nanometers and a diameter of ca. 3 nm Pt-nanowires synthesized in SBA-15 formed a new 3D-network following 3D-pore geometry of SBA-15; that is, the main 1D-channels are interconnected to each other through randomly distributed tunnels. These Pt-nanowires showed a well single crystalline. MCM-48 has two non-intersecting chiral channels, and Pt-networks were mostly formed in one of the two channels. Therefore the networks were also chiral; however, the chirality of Pt-networks remained to be determined. It was shown that all Pt-nanowires were formed following the channel geometries of silica mesoporous materials used.

We investigated the structural evolution of the Ni/Au contact on GaN(000l) during annealing in N2, using in-situ x-ray diffraction, anomalous x-ray scattering, and high resolution electron microscopy. GaN decomposition occurred mostly along GaN dislocations at temperature higher than 500°C. The decomposed Ga diffused into Au and Ni substitutional positions, and the decomposed nitrogen reacted with Ni, forming Ni4N. Interestingly, Ni4N was grown epitaxially. The epitaxial relationship of the Ni4N, Au, and Ni was identified as M(111)//GaN(0002) and M[1 −1 0]//GaN[1 1 −2 0] (M= Ni4N, Au, and Ni). At dislocation free regions, however, the atomically smooth interface remained intact up to 700 °C. Remarkable improvement of device reliability is expected in the contact on dislocation free regions compared with the contact on dislocations.

Conventional MOCVD method has been explored to prepare Pd supported catalysts. Pd and PdO phases were found on the surface of the support. Small Pd particles about 1 to 3 nm and dispersions up to 19%were obtained by MOCVD. TPR results indicated that several surface Pd compounds are reduced. At temperatures below 25°C, PdO, the main compound, is completely converted to metallic Pd which forms hydrides. At higher temperatures, between 500 to 800°C, the reduction peaks could be attributed to Pd-support interactions and a strong support dehydroxylation. All catalysts were inactive in benzene hydrogenation and a significant conversion was only detected a temperatures above 100 °C. This was explained by the reduced accessibility of Pd sites imposed by the carbon contamination and by the Pd-Al2O3 interactions.

An horizontal hot-wall MOCVD reactor was used to prepare palladium and platinum catalysts supported on alumina. A conventional impregnated Pt on alumina catalyst was prepared as comparison. The solids were characterized by XRD, Auger spectroscopy, HREM and H2 -TPR. The operation conditions of the MOCVD reactor were fixed preparing several Pd catalysts until to find the appropriate deposition zone. The particle size of Pt catalysts prepared by MOCVD was at about 7 nm compared with 6 ran obtained with the Pt impregnated catalyst, measured by XRD. The HREM image of the Pt MOCVD catalyst showed a narrower particle size ranging from 1 to 4 nm. After calcination three Pt compounds were detected by TPR, which were attributed to PtO, PtO2 and Pt-Al2O3 interaction in MOCVD preparation. Additionally, a clear reduction of surface oxygens of alumina was also observed.

In N-rich growth conditions, prismatic domains were formed in the initial stage of a cyclotron assisted MBE of GaN over 6H-SiC (0001). They exhibit {10 0} facets and are either voids or amorphous phase. Their density is of a few 109 cm−2 and they are located in a 50 nm layer closest to the substrate surface.

A 1/2[0001](0001) stacking fault and a planar 60° rotational domain boundary on the (0001) plane in as-grown CVD α-Si3N4 crystals have been characterized by high-resolution electron microscopy and image simulation. As reported previously, two types of coherent boundaries have been observed in this material, namely, stacking faults and rotational domain boundaries. The former involves only a translational displacement, while the latter separates two grains by a 60° rotation in addition to a translation. Inasmuch as the difference resulting from the rotational component can hardly be detected by high-resolution electron microscopy, care must be taken to analyze them first by analytical electron microscopy. In this paper, these two types of boundaries are studied and structural models are constructed that give simulated images in satisfactory agreement with observed images.