| Research Abstract |
This project aimed to develop new methods of morphological analysis by using electron holography. The results are summarized as follows.
The hardware of electron holography studies was constructed by installing a platinum wire of 0.6μm φ, as a biprism, and a TV camera into our transmission electron microscope with a field emitter. This equipment has enabled us to observe electron holograms of various materials owing to the bright illumination from the field emitter, and to record the holograms quantitatively, which is necessary to carry out a precise morphological analysis.
We also developed a computer program that could evaluate the phase shift of holograms with high precision. The holograms are obtained as two-dimensional digital data if they are recorded by using the system as described above. It is possible to know the phase shift by Fourier transformations of the digitized holograms. This program can be applied to evaluations of specimens with complicated shapes, as well as analyzes
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of magnetic domain structures of various materials.
By using the methods developed in this project, some precise morphological analyzes were carried out with shape controlled SiO_2 particles etc. As a way of thickness measurement, electron energy-loss spectroscopy (EELS) has been widely accepted because of the simplicity of measurements and analyzes. However, this method cannot be applied to extremely thin specimens. It was shown in the present work that the minimum thickness, to which EELS could be applied, was about 30nm, while the electron holography can evaluate the thickness less than 10 nm. As another application, we have accurately determined the magnitude of charging, which is a troublesome phenomenon in observations of insulators. The magnitude of charging in SiO_2 particles was determined by evaluating the residual index between the simulated hologram and the observation.
The electron holography has been used to discuss some peculiar phenomena of physics to date. The present work has established useful methods of morphological analyzes based on the electron holography, which can be applied to many advanced materials. Less
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