Yoshiyasu Harada

Development of a superfluid helium stage for high-resolution electron microscopy

The development of a new low-temperature stage for high-resolution electron cryo-microscopy is reported here. The stage is cooled down to 1.5 K by superfluid helium, and this cryo-microscope has enabled the authors to record images of chlorinated copper-phthalocyanine to a resolution of 0.26 nm at a stage temperature of 1.5 K. The low consumption rate of liquid helium of this cryo-stage has made possible the continuous operation of the cryo-microscope for more than 5 h without having to refill the cryo-stage tanks with liquid helium and liquid nitrogen. The stage has been tested for durability for more than 5 years. This electron cryo-microscope has also been equipped with an easily operated cryo-transfer device which has made possible the exchange of frozen-hydrated specimens under cryogenic conditions without any observable contamination.

Design and development of an ultrahigh vacuum high-resolution transmission electron microscope

Abstract A 200 kV ultrahigh vacuum high-resolution transmission electron microscope (UHV-HRTEM) for in-situ surface observation has been developed. With use of metal sealings, the vacuum at the specimen position was 2.6×10 −7 Pa without any cooling traps, and less than 1.5×10 −7 Pa with the built-in cooling traps cooled by LN 2 . A cantilever-type goniometer, a specimen holder and high-resolution objective lens were newly developed for high-resolution transmission (HRTEM) and reflection (HRREM) to observe surfaces with a point-to-point resolution of 0.21 nm. The specimen tilt is up to ±20°. Crucible-type and direct-heating-type specimen holders were constructed for in-situ experiments on thin films and small particles, and on bulk crystalline surfaces, respectively. The usefulness of the microscope for surface studies is shown by images of clean surfaces of Au and Si prepared in the microscope.

New Electron Diffraction Techniques Using Electronic Hollow-Cone Illumination

Two electron diffraction techniques using electronic hollow-cone illumination have been developed to improve the convergent beam electron diffraction method. One of them gives clear whole patterns of the higher order Laue-zone lines without diffraction disks. This technique also allows taking any higher order Laue-zone patterns. The other gives twice as large a convergent angle as that of the conventional convergent beam electron diffraction method and allows the combined use of high resolution electron microscopy and convergent beam electron diffraction.

The usefulness of a 400 kV high-resolution analytical electron microscope

Abstract In order to show the usefulness of a 400 kV high-resolution analytical electron microscope (JEM-4000EX), the accelerating voltage dependence of the peak-to-background ratio in both energy-dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) is studied. It is shown that the peak-to-background ratios increase continously with increase of the accelerating voltage from 100 to 400 kV. It is also shown that both crystal structure and chemical composition of 15R sialon polytype (SiAl4O2N4) may be determined on the basis of structure images and quantitative analysis of the corresponding EDXS and EELS spectra, demonstrating the capability of the combined techniques of high-resolution imaging and microanalysis.

A 400 kV High Resolution-Analytical Electron Microscope Newly Constructed

A resolution limit of 0.23 nm has been achieved successfully by a newly constructed 400 kV analytical electron microscope equipped with an energy dispersive X-ray spectrometer. The characteristic of the new microscope is briefly described and structure images of H-Nb2O5- and 6H-SiC crystals are obtained to show the observation capability of high resolution structure imaging.

The visibility of individual ferritin particles in a scanning electron microscope with a field emission gun

Ferritin particles on supporting materials — carbon films and bulk metals — were observed with a scanning electron microscope equipped with a field emission gun. Aggregated ferritin on both the supporting materials was successfully observed as individual particles in a high quality image. Both the contrast and size of a ferritin image increases with increasing diameter of the micelle. The ferritin image is formed by secondary electrons emitted due to the direct interaction between incident electrons and iron atoms of the micelle. An explanation has been given of the visibility of ferritin as it is related to the beam current and the micelle size, based on the signal-to-noise ratio which is approximately derived from experimental data of the secondary electron yield for bulk specimens.

Low-Temperature Electron Microscopy of a Bi2(Sr, Ca)3Cu2Ox Superconductor

A superconducting crystal Bi2(Sr, Ca)3Cu2Ox with Tc at 80 K has been examined by low-temperature electron microscopy, in which the specimen is cooled at a temperature lower than 10 K. High-resolution electron micrographs and electron diffractograms obtained at the low temperature are almost the same as those obtained at room temperature, suggesting that the crystal structure with the modulation along the b axis is not substantially changed on the transition to the superconducting state.

Electron Diffraction and Microscopy of the Structures of La-Ba(Sr)-Cu Oxides at Liquid Helium Temperature

Structural observation of the oxides, La1.9Ba0.1CuO4 (orthorhombic, Tc<4.2 K) and La1.8Sr0.2CuO4 (tetragonal, Tc=30 K: zero resistance), was made at liquid helium temperature by means of electron diffraction and microscopy, and the results were compared with those at room temperature. For the both oxides, no differences have been found in the crystal structure and morphology between 4.2 K and room temperature, although the lattice parameters changed as a result of thermal contraction.

The Latest Analytical Electron Microscope and its Application to Ceramics

We describe the general overview of the most advanced analytical electron microscope (AEM) first, and especially explain the electron gun and objective lens as well as the spherical aberration corrector, which relate to the AEM performance. Next, we describe the image formation in the transmission electron microscope and scanning transmission electron microscope and analysis methods with energy dispersive spectroscopy and electron energy loss spectroscopy , which are indispensable for applying AEM to material science field. Lastly, we introduce how the AEM is utilized in the research of ceramics material concretely based on several application examples.

Electron Diffraction and Microscopy of the Structures of La–Ba(Sr)–Cu–O and Ba–Y–Cu–O at Room and Liquid Helium Temperatures

Structural study of the superconducting oxides in the La–Ba (Sr)–Cu–O and Ba–Y–Cu–O systems has been made at room and liquid helium temperatures by electron diffraction and high resolution electron microscopy. La1.9Ba0.1CuO4, which is not superconductive down to 4.2 K, is orthorhombic and belongs to the space group pccm. La1.8Ba0.2CuO4 with Tc=28 K and La1.8Sr0.2CuO4 with Tc=36 K are tetragonal and belong to the space group 14/mnm. At liquid helium temperature, these oxides did not show any structural change. Oxides in the Ba–Y–Cu–O system with Tc=68 and 85 K are orthorhombic and belong to the space group Pmmm. (110) twins are formed in the structure. High resolution electron microscopy revealed the metal atom arrangement in these superconductive oxides.