Hatsujiro Hashimoto

High Temperature Gas Reaction Specimen Chamber for an Electron Microscope

High temperature gas reaction specimen chamber for an electron microscope has been constructed. The specimen under electron microscopic observation can be heated at about 1000°C in a gas layer at a pressure of about 300 Torr. The specimen is placed on a film covering the minute hole in the platinum ribbon and heated by an electric current sent through the ribbon. The gas is supplied around the specimen through a pipe and overflows into the vacuum of microscope column through the two platinum apertures on either side of the ribbon. The overflows gas from the specimen chamber is pumped out seperately from the evacuation system of main column. The minute hole in the ribbon and platinum apertures on either side of the ribbon are set to enable the passage of electron beams. The specimen stage can be taken out from the vacuum of electron microscope column through an air lock system without breaking down the vacuum. Some observations of gas reaction processes at elevated temperature by using the present device are presented.

Direct Observation of Fine Structure within Images of Atoms in Crystals by Transmission Electron Microscopy

Fine structure of the electron microscopic images of the atoms in crystals formed by the zero-aberration lens and a real lens is discussed by the theories of electron diffraction and image formation. The observed image of rows of gold atoms having such fine inner structure is shown,

Direct Observations of the Arrangement of Atoms around Stacking Faults and Twins in Gold Crystals and the Movement of Atoms Accompanying Their Formation and Disappearance

Two types of imaging methods in high resolution transmission electron microscopy, which give the images of atoms at the atomic positions in crystals containing defects, are presented. Using one of the methods, atomic arrangements of partial dislocations, intrinsic and extrinsic stacking faults, sessile dislocations formed by the interaction of two partial dislocations, and coherent and incoherent twin boundaries in gold thin crystals have been observed. Dynamic observations using TV systems have been carried out on the movement of atoms accompanying the formation, the movement and disappearance of stacking faults and twins, and their interaction.

β to ω phase transformation due to aging in a Ti-Mo alloy deformed in impact compression

Abstract We investigated the roles of vacancies and their clusters introduced in a Ti–20mass% Mo alloy by high-speed compression in the formation of aged ω-phase crystals. Specimens were deformed by a static compression mode and a high-speed compression mode, and were then aged. The relationships between morphology of aged ω-phase crystals and deformation modes are discussed along with the roles of vacancies and their clusters in the nucleation and growth of aged ω-phase crystals. Aged ω-phase crystals were found to be smaller but of higher density in a high-speed deformation specimen. These results suggest that vacancies and their clusters easily become nucleation sites of aged ω-phase crystals. Several aged ω-phase crystals in a high-speed deformation specimen were of string-like shape. High-resolution electron microscopy confirmed that the string-like crystals have the ω-phase crystal structure. One of the roles of vacancies of and their clusters introduced by high-speed deformation is considered to be relief of compressive stress, which is predicted to arise in the course of transformation.

Changes of Volume and Surface Compositions of Polymethylmethacrylate under Electron Beam Irradiation in Lithography

The change of the content of oxygen and carbon in Polymethylmethacrylate (PMMA) under electron beam irradiation is investigated by Auger electron spectroscopy (AES) whereby we estimate the characteristic energy deposition of the decrement of oxygen to be 0.8–1.2×103 eV/nm3. It is also confirmed that cooling of PMMA considerably reduces the elimination rate of oxygen and that the decrement of the thickness of PMMA film under electron beam irradiation is closely related to the change of oxygen content. Moreover, it is shown that the PMMA alters from the positive resist to the negative resist as determined by observing thickness changes.

Electron-Microscopic Study of Oxidation Processes by Metal Fine Particles

Fine aluminum, copper and iron particles are partly oxidized at temperatures between 200°C and 600°C in air, and studied by electron microscopy. Since the particles are of the order of 1000 A in size and transparent to 100 kV electrons, their cross sectional structures are observed clearly. An individual oxidized particle generally consists of two parts, metallic part in center and surface oxide layer, and shows the characteristic structures. In the case of iron particles, more than one circular vacant layers are produced concentrically beneath the surface oxide layer. Oxides on aluminum particles grow epitaxially and sometimes form spherical shell containing no inside metal aluminum. Oxides on copper particles grow as thin films nearly perpendicular to the particle surface. Mechanism of oxidation process and migration of metallic atoms based on the present observations are discussed.

Atomic Structure Images Formed by Plasma-Loss Electrons

Two kinds of energy filtered atomic structure images of Si crystal in (011) orientation formed by no-loss and plasma-loss electrons were photographed using the energy analyzer of a sector type magnet which was attached to the bottom of a high resolution electron microscope. The behavior of plasma-loss electrons in the crystal was discussed on the basis of the dynamical theory of electron diffraction. The contrast of the crystal lattice image formed by the plasma-loss electrons was calculated and compared with the observed image.

Electron beam irradiation of natural zeolites at low and room temperatures

Abstract Irradiation effects of a high energy electron beam to the particles of natural zeolites were investigated at low and room temperatures using a high resolution transmission electron microscope operated at 250 and 350 kV. The specimen zeolite crystals under electron beam irradiation changed from crystalline to amorphous structure (C-A transition), which was observed both in electron diffraction patterns and high resolution lattice images. Some parts of the specimens were sputtered and small holes were produced in the specimen. Total electron doses which produced the C-A transition were measured as a function of the crystalline particle size. The rate of C-A transition was constant and the total dose necessary for complete amorphization was proportional to the particle size. The C-A transition rate of the zeolite was accelerated maximum up to 500 times at 21 K than at room temperature (26°C). The time dependencies of elimination of the component elements were measured by EDX and EELS. By assuming the evaporation of water molecules from the crystal and a temperature dependence of displacement damage, a C-A transition mechanism by electron beam irradiation is proposed.

Formation of ω phase in Ti-Mo alloys after aging and deforming

AbstractInvestigations of ω phases formed by isothermal aging in Ti–20 wt-%Mo alloy and by deforming in tension in Ti–14 wt-% Mo alloy were carried out using transmission electron microscopy (TEM). Four ω phase variants in the same region of Ti–20Mo alloy single crystal aged at 623 K for 28·8 ks were observed using dark field TEM imaging. The microstructure of the ω particles was observed using high resolution electron microscopy (HREM). Dark field images were taken by using the diffraction spot due to respective ω phase variants and with the incident beams parallel to [l01], [313], and [311]. It was found that all ω particles grew in the 〈111〉 direction and were ellipsoids. The growth direction was the same as the direction of motion of atoms for forming ω particles according to a model proposed by previous authors. This result was confirmed by HREM images of the ω particles observed using dark field TEM. The volume fractions of respective ω phase variants were estimated using a conventional method. The ...

Investigation of omega-phase in Ti-Mo alloys by high resolution electron microscopy, image processing and dark-field methods

Abstract The microstructures of the omega phase in Ti-Mo alloy single crystals were investigated using high resolution electron microscopy (HREM), image processing and dark-field methods. By image processing, the assembly of linear defects which had been reported was revealed in the region of the superposition of two kinds of omega variant. The superpositions of these omega variants were observed in the dark-field images using two beams from each variant. HREM images of the particles corresponding to the omega phase, which is identified in the dark-field image, suggest that the omega phase is formed by atomic displacements in the four 〈111〉 directions as proposed by de Fontaine and Buck, and that omega phase particles grow parallel to the direction of atomic displacement.