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A method for taking electron holograms with a single crystal instead of an electron biprism is described. The method is so simple that only a single crystal needs to be placed on the specimen grid in the specimen holder. Then, the crystal lattice fringes are focused on the recording photographic film to form an off-axis Fresnel hologram. The procedures for both hologram formation and reconstruction are described. Experimental results show that holograms can also be achieved with a conventional transmission electron microscope having a low-coherence electron source.

Small angle electron diffraction patterns from vortex lattices in Nb thin films were observed using a field emission transmission electron microscope. It was possible to obtain diffraction patterns in magnetic fields of up to 1000 G, from selected areas of (1–10) μm in diameter, and in (1–30) s. The degree of order of the vortex lattice was determined from the fine structure of the diffraction pattern. We also demonstrated Foucault mode Lorentz microscopy by using a diffraction technique. Vortices appeared by diffraction contrast in a focused micrograph, and therefore both vortices and material defects were simultaneously observed.

Densely aggregated beta-amyloid peptides are believed to play a key role in the pathogenesis of Alzheimer's disease. Amyloid plaques are a potential target for molecular imaging to determine the clinical status of Alzheimer's disease. Phase-contrast X-ray imaging combined with computed tomography is a promising technique that can be used to visualize the physical density of structures in biological tissues non-invasively, and without the use of imaging agents. Using brain tissue isolated from a mouse model of Alzheimer's disease, we show that beta-amyloid 40-positive/beta-amyloid 42-positive amyloid plaques, but not beta-amyloid 40-negative/beta-amyloid 42-positive amyloid plaques, exist as high-density aggregates that can be specifically detected by phase-contrast X-ray computed tomography. The phase-contrast X-ray computed tomography detected beta-amyloid 40-positive/beta-amyloid 42-positive amyloid plaques in three-dimensions with an extremely high sensitivity comparable to that of histological analysis, and also enabled the load of amyloid plaques to be quantified. Furthermore, the use of phase-contrast X-ray computed tomography reveals that the physical density of beta-amyloid 40-positive/beta-amyloid 42-positive amyloid plaques increases with age, and that the large volume, high-density, amyloid plaques that are specifically observed in aged Alzheimer's disease mice are closely associated with neuritic dystrophy. These results demonstrate that phase-contrast X-ray computed tomography is a highly sensitive imaging technique for analyzing dense-cored amyloid plaques in postmortem samples, and is beneficial in elucidating amyloid pathophysiology in Alzheimer's disease.

Using a silicon fabricated slider, the output force and the maximum traverse velocity of a surface acoustic wave motor has been improved up to 12 times larger force and twice faster speed than the previous motor which used a multi contact points slider. To obtain the high output force, large contact area between the slider and the stator transducer is required. Therefore a silicon slider was developed and tested. As a result, the maximum output force of 3.5 N and the maximum traverse velocity of 0.65 m/s were obtained. The maximum output force of 3.5 N was 90 times of the transducer weight. Such a high output force performance is produced by high power density of surface acoustic wave devices and friction drive.

This paper describes the way of a miniaturization of a surface acoustic wave (SAW) linear motor and the first success of driving the miniaturized SAW linear motor. A problem which occurs with the miniaturization of the motor is also mentioned. The motor was operated at 50 MHz. The miniaturized motor could work at 0.7 m/s.

New applications of avalanche photodiodes as fast timing detectors for electrons ranging from 10 keV to 300 keV together with an analysis of the response of silicon avalanche photodiodes to the electrons are reported.

Using electron holography and coherent beam Lorentz microscopy, Akira Tonomura investigated the physics of magnetic flux lines, or vortices, in metal and high-temperature superconductors for more than 20 years. The methodology he developed for doing this made use of coherent electron waves from cold-emission (field-emission) sources and their quantum-mechanical phase shifts. Using 300-kV and 1-MV electron microscopes, Tonomura and his team clarified the dynamic behavior of magnetic flux lines in Pb and Nb superconductors and in high-temperature YBa2Cu3O7-δ and Bi2Sr2CaCu2O8 + δ superconductors. This memorial paper reviews the static and dynamic flux-line behaviors in superconductors as revealed by their results.

We have developed 100-kV, 200-kV, and 350-kV cold-field-emission transmission electron microscopes (FE-TEMs) successively up to this time. Using these instruments, we have been studying the magnetic structure of materials, high-resolution imaging by electron holography, and dynamic observation of the vortex in superconductors by Lorentz microscopy. To make more progress in our research, we need a better electron beam in terms of coherency, beam brightness, and penetration. Here, we report a new lMV-cold-field-emission transmission electron microscope we have developed. Historically, the pioneering projects on a lMV-field-emission scanning transmission electron microscope (FE-STEM) (Zeitler and Crewe, 1974) and a 1.6MV FE-STEM (Jouffrey et al., 1984) have been reported. In 1988, Maruse and Shimoyama obtained a lMV-field-emission beam using their 1.25MV-STEM connected to a field-emission gun. Since then, continuous improvements in beam brightness has been made.The target specifications of our 1 MV-cold-field-emission TEM (H-1000FT) are as follows: Acceleration voltage: 1MV, high-voltage stability

Electron holography has been applied to a variety of field, in which the reconstructed phase information was effectively used to elucidate many important natures of materials. Applications of electron holography to biological specimen, however, has not been developed yet. We report here an application of electron holography of frozen-hydrated biological specimen, which is observed by electron holography for the first time.An electron microscope(Hitachi HU-12A) equipped with a 100-kV cold field emission gun was used for the experiment. Catalase crystals were embedded in amorphous ice by quick-freezing and the grids were transferred to the microscope using Gatan cryo transfer system. A specially designed low-dose imaging system for the microscope was devised and used to record holograms.

A Magnetic flux quantum (fluxon) penetrating a superconductor plays an important role in both fundamental and practical applications of superconductivity. However, the fluxon has evaded direct observation, because it is shaped like an extremely thin filament in addition to its small flux value, h/2e (=2x10−15Wb). Several methods have already been developed to indirectly observe each filament of flux. One method is Bitter's [1], in which magnetic powder is sprinkled on the superconductor surface. The powder accumulates at the fluxons, and the image is observed by electron microscopy.We have observed the magnetic field of a single fluxon using holographic electron interferometry [2], in which the phase distribution of an electron beam can be measured to a precision of 2Π/50. The schematic diagram of the experiment is shown in Fig. 1. A weak magnetic field is applied perpendicularly to a superconducting lead film. Fiuxons penetrating the film are observed as phase contour fringes through the electron holography process. The sample is prepared by evaporating lead on one side of a thin tungsten wire, which is shown in Fig. 2.

Magnetization patterns recorded on Co thin films prepared by oblique incidence vacuum deposition were directly observed by electron holography. Complicated ellipse-like interference fringes were observed along the sawtooth-like walls in the transition regions. Stray magnetic flux was observed in empty space beyond the edge of the film. The following results were obtained from analysis of these interference images. The smaller the product of the remanence and the film thickness, and the higher the coercivity, the narrower is the transition length that determines the limit of the recording density of a medium. It was confirmed that longitudinal magnetic recording of a density of up to 170 kBPI is attainable using Co film 30 nm thick and with coercivity of 112 kA/m. It was quantitatively proven that the intensity of the recorded magnetization in a medium is equal to its remanence when the magnetized area is distinguishable from the transition region.

An anomalous surface superstructure along 〈110〉 of a clean (111)Au surface and two-dimensional nucleus formation of Pd on an atomically flat (111)Ag surface have been observed by an UHV electron microscope.

In 1975, Blakemore found aquatic bacteria that swim along earth's magnetic lines of force [1]. They have permanent magnets of iron-rich fine particles within them. Such particles were found by Mössbauer analysis to consist of magnetite in the case of magnetospirilla [2]. In addition, Towe et al confirmed by electron diffraction that the particles were crystalline [3]. The purpose of the present investigation is to determine the crystal and magnetic structure of these particles by both high-resolution lattice imaging and electron holography; however only the former is reported here.Magnetotactic bacteria were gathered in a fresh-water pond. The specimens were peanut-shaped, and approximately 3um in length. Transmission electron micrographs, such as that shown in Fig. 1, reveal that approximately 30 fine particles are aligned within each bacterium.

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.

Recent advances of UHV techniques, LEED, RHEED and AES, arose a surge of interest on the surface of solids. These techniques reveal structures and chemical compositions at the mono-atomic or mono-molecular level. All of them, however, are devoid of detailed topographic informations, although some efforts to introduce the scanning techniques have been done[l]. Transmission electron microscopy of high resolution should play a complementary role to these techniques. No attempt, however, has been done previously to use it to such a purpose. This was because it was difficult to get and keep clean surfaces in the poor vacuum at 1x10-5Torr level of the conventional electron microscope.The present paper reports observations of surface phenomena of one or two atomic layer level using a UHV JEM 100B electron microscope (10-8-10-10Torr), recently developed for insitu thin film growth studies[2]. Atomically flat (111) surfaces of Ag, Pd, Au and Cu were prepared by in- situ deposition at 150-350°C on M0S2, graphite and MgO. Air Cleaved thin films of MoS2 and graphite were preheated to 800°C to get clean surfaces[3].

Reflection electron microscopy in ultra high vacuum has been performed during the process of thermal cleaning which converts the dirty (111) silicon surface of the 1 × 1 structure to the clean surface of the 7 × 7 structure, and during the transformations of the 7 × 7 structure to the 5 × 1, √3 × √3 and 6 × 6 structures produced by deposition of gold up to a few monatomic layers. The reflection images showed the microtopographical aspects of the process and of the transformations to be in close correlation with the structural information given by the reflection diffraction patterns observed simultaneously.

Interference electron microscopy by holographic reconstruction has been applied to many fields: An interferogram of a specimen having nonunifom thickness can be interpreted as a thickness contour map. In case of a ferromagnetic thin film, contour lines in an interferogram follow the magnetic lines of force. The contour interval of a phase-shift ƛ (ƛ is an electron wave length) correspons to a thickness of 2 ϕ0 ƛ/V0 (V0 is the mean inner potential and ϕ0 is the accererlating voltage) and a magnetic flux of h/e (= 4.1X10—15 Wb) respectively. For detailed observation such as that of atomic scale thickness variation or weak magnetic fields from single domain fine particles, electron phase shifts recorded in a hologram has to be amplified. In recent experiment conducted by authors, interferograms phase amplified 10 times were obtained. The method employed a higher-order diffracted beam and its conjugate utilizing the film's nonlineality. However the phase amplification of factor 10 is not sufficient for the above purposes. In the present experiment, successful attempt to detect an electron phase shift of order ƛ /100 was made using another phase-amplification technique introduced by Bryngdahl and improved by Matsuda.

Using electron holography, information about a specimen, such as distributions of magnetization and thickness, can be revealed by investigating the shape of reconstructed wavefronts of the laser beam. These distinctive features can be utilized in investigations in the fields of superconductivity and biology. Therefore, we have developed a low temperature specimen stage which is reguired for superconducting specimens and to decrease the radiation damage in biological specimens. Using this cold stage, we have observed magnetic flux quantization in superconductors.

The phase transition process of clean (111) silicon surfaces between the (7 × 7) and (1 × 1) structures at about 830°C was directly observed by reflection electron microscopy, which had been briefly reported in a previous short communication (Osakabe et al., Japan. J. Appl. Phys, 19 (1980) L309). Smooth atomic steps, whose shapes change spontaneously and continually in a microscopic scale at high temperature of the (1 × 1) structure, transform into zig-zag steps at low temperature of the (7 × 7) structure, where the changes of the step shape stop. On cooling, domains of the (7 × 7) structure nucleate preferentially on upper terraces along the steps and expand on the terraces to the neighbouring steps. Out of phase boundaries with phase differences of 2πn/7 are seen to be formed. On heating the reversed process takes place. The out of phase boundaries are easy places to transform to the (1 × 1) structure. The observations clearly suggest the phase transition of the first order and the models of the (7 × 7) structure of ordered vacancies or adatoms rather than of static displacements of surface atoms.