S. Isoda

Utility test of imaging plate as a high-resolution image-recording material for radiation-sensitive specimens

Abstract The utility of an imaging plate in high-resolution electron microscopy for radiation-sensitive specimens was tested in terms of the quality factor in a range of accelerating voltages between 200 and 1000 kV. The sensitivity of an imaging plate decreases with increasing accelerating voltage in a manner similar to the case of electron microscopic films and is still higher at high accelerating voltages, although the resolution is much lower. As a whole, the quality factor F = S/δ2, where S is the sensitivity and δ the resolution of the imaging plate, takes its maximum value at an irradiated electron dose of 10-1 C/cm2 and is lower than that of the films.

A comparative study of the modulation transfer function of an imaging plate

Abstract An important factor to specify properties of an imaging plate (IP) is the modulation transfer function (MTF) which defines the resolving power of this recording material. The MTF of an IP was measured by comparing the shadow profile of a gold wire directly fixed on an IP with an ideal well-shaped profile, while, additionally, its dependence on the accelerating voltage and also on the irradiated electron dose was studied. The MTF was found not to depend on the accelerating voltage, but to be in close correlation with the irradiated dose. The practical resolution becomes worse with decreasing dosage. The resolving power determined from the MTF value of about 0.15 corresponded to the line resolution determined by the observation of lattice fringes.

Formation of ultrafine platinum particles in an aqueous solution with a surfactant

Abstract The formation process of ultrafine metal particles in water was examined with a cryogenic transmission electron microscope by using a rapid-freezing specimen-preparation technique. The particles were formed by hydrogen reduction in an aqueous solution of chloroplatinic acid with or without a surfactant. The ultrafine platinum particle was obtained with the surfactant, and they were concluded as formed not in a micelle as a nucleation site, but in arbitrary places in solution. During the formation process, the particles are coated and stabilized by surfactant molecules so as to not aggregate, when using the surfactant.

EELS study of radiation damage in chlorinated Cu-phthalocyanine and poly GeO-phthalocyanine

Abstract Electron energy-loss near edge structure (ELNES) was measured with parallel-EELS in the carbon and the nitrogen K-edges of the chlorinated Cu-phthalocyanine and poly GeO-phthalocyanine as a function of irradiation dose. The intensity of the first ELNES peak, which was attributed to the 1s → π ∗ transition peak in both edges, was decreased with an increase of irradiation dose. This fact clearly shows the unoccupied π ∗ molecular orbitals were changed in the course of electron irradiation. This 1s → π ∗ transition peak of the chlorinated Cu-Pc fades more slowly than that of the poly GeO-Pc, which can be understood by the “cage effect” of the atoms liberated from the molecules. Moreover, it was observed that the fading of the nitrogen 1s → π ∗ transition peak was rapid in comparison with that of the carbon peak in the poly GeO-Pc film. This suggests that the radiation damage may be a site-dependent process in the poly GeO-Pc.

A new 1000 kV HREM for organic crystal study

Abstract On the basis of the success in high-resolution observation at the atomic level with the previous 500 kV HREM, a new 1000 kV EM was constructed and installed at Kyoto University. The split-tank system was adopted for the HV supply to increase the potential stability. The objective lens system of high excitation was computer-designed to reduce the spherical aberration. A new image-recording system with highly sensitive imaging plate was attached in view of the quantitative measurements for the digital image processing and for the ED structure analysis. Some high-resolution images were obtained to be inspected by laser-optical diffraction which indicated the achievement of resolution better than 0.13 nm.

Study of structures at the boundary and defects in organic thin films of perchlorocoronene by high-resolution and analytical transmission electron microscopy

Both the periodic and non-periodic structures of perchlorocoronene (C(24)Cl(12)) crystals were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), electron energy-loss spectroscopy (EELS), and energy-filtered transmission electron microscopy (EFTEM). The HRTEM images at the boundary of the C(24)Cl(12) crystals exhibit the flexibility of defect structures, where molecules align to compensate for the discontinuity between two different domains. Emphasized by the filtered images, it was found that the non-periodic regions are created everywhere with a small electron beam irradiation (∼ 10(6)electrons nm(-2)) and then spread over the entire regions to completely destroy the periodic structures after a higher electron dose (∼ 2 × 10(6)electrons nm(-2)). The effect of the electron beam irradiation was monitored by ED, EELS, and EFTEM, where periodic structures and content elements are well preserved up to 10(6)electrons nm(-2), but chlorine atoms decreased with a much higher electron dose. This is explained by the breakage of the C-Cl bond to detach chlorine atoms, confirmed by energy-loss near the edge structures (ELNES) of carbon π * peaks and chlorine loss at the edge of the specimen, as well as by theoretical simulation. The detachment of chlorine is localized at the peripheral edge around a hole confirmed by core-loss EFTEM imaging.

Replacement of molecules at liquid/solid interfaces

Perylene-3,4,9,10-tetracarboxylic-dianhydride (PTCDA) in a monomolecular layer was formed onto highly ordered pyrolytic graphite (HOPG) by vacuum deposition. After 17,19-dotetracontadiyne (DTDY) in phenyloctane solution was dripped on the above sample, the tip of a scanning tunneling microscope (STM) was inserted into the solution and scanned to scratch a part of the PTCDA monomolecular layer from the HOPG substrate. DTDY molecules were observed to be adsorbed on the scratched region of the PTCDA molecular layer to form a monomolecular layer. The orientation and size of the DTDY molecular layer could be controlled by selecting the scanning direction and area of the STM tip scratch.

Electron diffraction studies of stage-2 AlCl3GIC

Abstract The in-plane structure of the stage-2 binary AlCl3GIC was investigated by the electron diffraction method. The electron diffraction pattern from the intercalant layers of this GIC exhibits a two-dimensional ordering. The ordered structure of the intercalant layer has a rectangular lattice with unit cell dimensions of a = 1.628 nm and b = 1.402 nm which are about twice the dimensions of the lattice proposed previously.

Three-dimensional structure of AlCl3 in stage-1 AlCl3GIC

Abstract In stage-1 AlCl3GIC, a three-dimensional structure of intercalant AlCl3 was revealed by the tilt electron diffraction method. The unit cell is orthorhombic and its lattice constants are a = 1.619 nm, b = 1.397 nm and c = 1.908 nm. The ab-plane structure is not the same as the rectangular basal plane of the pristine AlCl3 crystal but has some structural correlation with it. The unit cell is commensurate-like to the graphite lattice, as one in the stage-2 AlCl3GIC. The lattice constant c corresponds to twice the repeat distance Ic determined by X-ray diffraction measurement, so that two crystallographically different AlCl3 layers (s1 and s2) in the unit cell stack alternate along the c-axis in the sequence of…, s1, s2, s1, s2, …

Thermal behavior of stage-2 FeCl3 graphite intercalation compound studied by analytical electron microscopy

The thermal behavior of stage-2 FeCl3-GIC in vacuum was investigated by in situ observation using an analytical electron microscope. Electron diffraction patterns and electron energy-loss spectra were obtained from the same specimen area during heating from room temperature to 400°C. The thermal behavior of FeCl3-GIC having hexagonal in-plane structure is characterized by the deintercalation and the decomposition of intercalant FeCl3. Below 250°C, about 40% of FeCl3 is deintercalated from graphite. The remaining FeCl3 between graphite layers begins to be decomposed into FeCl2 and Cl; at 250°C and this decomposition is completed at 300°C. The Cl2 gas thus produced is not incorporated with the two-dimensional FeCl2 structure. Above 250°C, the FeCl2 produced remains as hexagonal in-plane structure between graphite layers without deintercalation, but the Cl2 gas is slowly deintercalated from graphite up to 400°C. At 400°C, the atomic composition of the intercalant changes fully into FeCl2. The change of FeCl3 to FeCl2-GIC seems to progress as a direct solid-solid reaction without any intermediate or disordered state.