Toshikazu Honda

Surface observation of Mo nanocrystals deposited on Si (111) thin films by a newly developed ultrahigh vacuum field-emission transmission electron microscope

Abstract An ultrahigh vacuum field-emission transmission electron microscope (UHV-FE-TEM) has been newly developed for the observation of semiconductor surfaces. It provides ultrahigh vacuum environment of 2.0×10 −8 Pa for surface studies, in addition to high contrast electron probe with large beam current for high-resolution transmission electron microscopy (HRTEM). Nanometric surface analysis using energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) can be carried out simultaneously with HRTEM. Deposition of Mo onto both as-prepared and cleaned Si (111) TEM samples was performed at room temperature. HRTEM and EDS analysis suggest the formation of Mo nanocrystals. The size of the nanocrystals was about 2–3 nm on as-prepared sample, and 10–15 nm on cleaned sample. Electron beam irradiation resulted in the formation of Mo-related compound in as-prepared sample case, and sputtering or sublimation of Mo and Si in cleaned sample case.

Observation of lattice fringes in convergent-beam electron diffraction patterns

Abstract Mirror symmetry, no symmetry and glide symmetry of crystals are displayed using interference (lattice) fringes appearing in overlapping disks of convergent-beam electron diffraction (CBED) patterns. The lattice fringes with a spacing of 2.7 A of the 200 reflection of FeS 2 have been observed in coherent CBED patterns with use of a JEM2010F electron microscope equipped with a field-emission gun. Two-dimensional interference fringes are shown in three overlapping disks taken from FeS 2 at [111] electron incidence. It is demonstrated that such lattice fringes can be obtained even by an LaB 6 electron source when using imaging plates.

Performance of a Monochromator for a 200 kV Analytical Electron Microscope

We have been developing a 200 kV analytical electron microscope, which is equipped with a monochromator [1]. The target performance of the microscope is to achieve an energy resolution of 0.2 eV with a smaller than 2 nm diameter probe on a specimen plane. Though the ultimate energy resolution of 0.14 eV was obtained with our first monochromator, the shape of the beam on the specimen plane was oval [2]. The new monochromator consists of two dodecapole-type Wien-filters (Fig. 1) of 30 mm length and a slit on the symmetric plane of the two filters [2], [3]. The upper (1st) filter and the electro-static round lens at the entrance of the monochromator make an energy-dispersed focus on the slit. The lower (2nd) filter cancels the energy dispersion and makes an achromatic and stigmatic focus at the exit of the monochromator. We obtained the energy dispersion of 19.5 μm/eV on the slit experimentally, which is sufficient to obtain the energy resolution of 0.2 eV using the slit. Figure 2 shows the shape of a 200 keV electron beam on the specimen plane with the new monochromator. It shows that an almost round shaped beam or a better achromatic beam of a 4 nm (FWHM) was obtained. A smaller beam than a 2 nm diameter on the specimen plane at the achromatic condition of the monochromator will be obtained by using a higher excitation condition of the probe forming lens system. We have succeeded in obtaining an energy-dispersed beam on the slit and a stigmatic and achromatic beam at the exit of the monochromator.

Design of omega mode imaging energy filters

Abstract Optical properties of two types of omega filter, A-type and B-type, are compared. The A-type has three focuses in the magnetic field direction ( y ), while the B-type has two. The latter gives a smaller total tilting angle at the entrance and the exit edges and a shorter drift length between the deflection magnets. The effect of the length L L between the window and the pupil planes on the non-isochromaticity is examined under two conditions of a fixed post-filter lens magnification M PL =100 and the optimum magnification M PL (opt). Longer L L is better for isochromatic imaging under the fixed magnification condition M PL =100 times. However, the selection of L L is not so important when the optimum M PL (opt) is used. Three-dimensional field distribution and ray trajectory calculations are made to show the effects of misalignment of the optical axis and mistake of the tilting angle at the entrance and exit edges of the deflection magnets.

Field emission ultrahigh-resolution analytical electron microscope

Abstract This paper reports the present situation of the ultrahigh-resolution analytical electron microscope (UHRAEM) and the new technology introduced into the JEM-2010F. By adding an FEG to the TEM, not only does the image contrast greatly improve through its high coherency and low energy spread of electrons, but also sensitivity for nanometer area analysis improves substantially. Particularly, due to the probe current about 100 times larger than LaB6, it is possible to do high-sensitivity analysis with a sub-nanometer probe. With the UHRAEM, some of the difficulties in the new developments of materials science are being solved.

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.

Scattering angle dependence of signal/background ratio of inner-shell electron excitation loss in eels

Abstract Scattering angle dependence of the signal/background ratio of Si K-shell and A1 K-shell electron excitation losses has been measured for single crystals and evaporated films. The ratio changed periodically with the scattering angle, and maxima were found to be located between Bragg reflections including the center beam. Thus the ratio is improved between the Bragg reflections and just outside the incident beam, which is very important as a practical technique for elemental analysis in the higher energy loss region in EELS.

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.

A Newly Developed 300 kV Field-Emission Analytical Transmission Electron Microscope

In order to carry out high-spatial-resolution analysis at the nanometer level, a 300 kV analytical transmission electron microscope with a field-emission gun has been developed. Some characteristic features of the new microscope are described and the results of the nanometer-level analysis are shown for silicon nitride and indium iron zinc oxide.