Various porous titania photocatalysts are analyzed three-dimensionally in real space by electron tomography. Shapes and three-dimensional (3D) distributions of fine pores and silver (Ag) particles (2 nm in diameter) within the pores are successfully reconstructed from the 3D data. Electron tomography is applied for measuring the specific surface area of the porous structures including open and closed porosity. Calculated specific surface areas of 22.8 m2/g for a conventional sol-gel TiO2 sample and 366 m2/g for a highly porous TiO2 sample prepared using the Pluronic P-123 self-assembly process are compared with those measured by the general BET method. The real-space surface measurement indicates that the highly porous TiO2 produced by the present method using block copolymers has a greater number of effective reaction sites for the degradation of methylene blue. Electron tomography shows a great potential to contribute considerably to the nanostructural analysis and design of such catalyst materials for photocatalysis.

We propose a simple and practical solution to remove artificial contrast inhibiting direct interpretation of atomic arrangements in aberration-corrected TEM. The method is based on a combination of “image subtraction” for elimination of nonlinear components in images and newly improved “image deconvolution” for proper compensation of nonflat phase contrast transfer function. The efficiency of the method is shown by experimental and simulation data of typical materials such as gold, silicon, and magnesium oxide. The hypothetical results from further improvements of TEM instruments are also simulated. It is concluded that we can approach actual atomic structures by using the present method, that is, a proper combination of a Cs corrector, image subtraction, and image deconvolution processes.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

InxGa1−xAs quantum dots in GaP(100) crystals prepared by the OMVPE technique are observed along the [011] direction with a newly developed 200-kV spherical aberration(Cs)-corrected HRTEM, a 200-kV annular dark-field (ADF)-STEM, and a 200-kV conventional HRTEM equipped with a thermal field-emission gun. The dots are 6–10 nm in size and strongly strained due to the misfit of about 9% with the GaP substrate and GaP cap layer. All of the cross-sectional high-resolution electron micrographs show dumbbell images of Ga and P atomic columns separated by 0.136 nm in well-oriented and perfect GaP areas, but the interpretable images are limited to those taken with the Cs-corrected HRTEM and ADF-STEM with Fourier filtering of the images. The Cs-corrected HRTEM and ADF-STEM are comparable from the viewpoint of interpretable resolution. A detailed comparison between the Cs-corrected HRTEM images and the simulated ones with electron incidence tilted by 1° to 5° from the [011] zone axis gives information on local lattice bending in the dots from the images around 0.1 nm resolution. This becomes one of the useful techniques newly available from electron microscopy with sub-Ångstrom resolution.

Three-dimensional (3D) observation is one of the important trials of future TEM and STEM methods. in the field of biological science, 3D-observation has already become general because the biological materials are usually amorphous and computed tomography (CT) routines can be effectively used. The CT assumes that the image intensity is linearly proportional to the projection of material density. in a crystalline specimen, however, this linearity does not hold due to the dynamical diffraction effect depending on spepimen thickness and incident directions of electron beam. High-angle annular-darkfield STEM (HAADF-STEM) and EDX mapping images could meet this requirement of the linearity because their image intensity are little affected by the dynamical diffraction effect.

Our 3D-STEM is based on a 300 kV FE-TEM/STEM(Hitachi HF-3000) equipped with a specially designed eucentric specimen stage with double spherical fulcra, a newly developed dark/bright field STEM detectors, a 3D-sampling system and a 3D-imaging processor for 3D topography and tomography.

Time-resolved high-resolution transmission electron microscopy at a spatial resolution of 0.2 nm and a time resolution of 1/60 sec using a piezo-driving specimen holder is reported here. Various types of atomic processes in mechanical interaction, such as contact, bonding, deformation, and fracture, in nanometer-sized gold crystallites and carbon nanotubes are demonstrated.

Nanoscale materials show a variety of interesting physical and chemical properties. Since the properties are mostly determined by mesoscopic- and atomicscale areas of the materials, characterization of nanoscale materials at the atomic level is crucial for understanding the origin of their properties as well as for tailoring them to industrial needs. High-resolution electron microscopy (HREM) is an effective method to observe atomic structures in nanophase materials. The “structure-imaging technique,” originated by Ueda et al., and Cowley and Iijima, contributed much to the development of the method. Innovations are anticipated in (1) three-dimensional analysis of nanophase materials in real space, (2) observation of dynamic phenomena, and (3) extraction of compositional and physical information from nanometer-sized areas. Using the structure-imaging technique, one can observe directly nanometer-scale particles and defect structures such as voids and line and plane defects in crystals, including surfaces and interfaces. There were previously some limitations on the study of the dynamic process on the atomic level since images were captured on films. The recent development of high-sensitivity silicon-integrated-target-television (SIT-TV) cameras has initiated a new stage of HREM.

Our time-resolved-high-resolution-electron-microscopy (TRHREM) system is composed of a 200-kV HREM (JEOL: JEM-2010) equipped with a high-sensitivity SIT-TV camera, various types of dedicated sample holders, an ultrahigh-vacuum (UHV) sample-preparation chamber, and a digital videotape recorder, as partly illustrated in Figure 5. The HREM images at 0.8–1.0-million magnification are recorded on the videotape recorder. In the U.S.-Japan TV system, one “frame image” of 1/30-s time resolution is composed of two interlaced “field images” of 1/60-s time resolution. The digital videotape recorder enables us to output the two “field images” separately from two frame memories.

Both YBa2Cu4O8 and (Y0.95Ca0.05)Ba2Cu4O8 were successfully prepared by firing for 160 h at 850 °C and at oxygen partial pressure of 3 atm without using any catalysts. These samples were characterized in terms of the crystallographic structure and thermal and superconducting properties. The x-ray powder diffraction patterns and superconducting properties for these samples were little changed after post-annealing for 6 h at 1070 °C and at oxygen partial pressure of 400 atm. However, when heat-treated at 700 °C in air and then quenched into liquid nitrogen, samples without post-annealing showed broader superconducting transitions than those post-annealed. Actually, the sharpness of the superconducting transition for a post-annealed sample was little affected by quenching. These observations were in agreement with the results of both transmission electron microscopy and thermal analyses.