Atomic structures of iron-silicide ultra-thin films epitaxial grown on Si(111) were investigated by x-ray crystaltruncation-rod scattering measurements. Two films, each of them respectively exhibited 1×1 and 2×2 periodicities in ultra high vacuum, were measured with the x-ray diffraction under ambient air. Both of the films showed essentially the same Laue peaks. The Laue peaks directly indicate that both films have the CsCl-type (so-called c-FeSi) structure whose stacking orientation is rotated by 180 • with respect to the substrate. Quantitative structural analysis, which includes degree of the film roughness as fit parameters, reveals that the interfacial Fe atom is 8-fold coordinated to Si atoms (so-called B8 model). The determined interlayer spacing in the silicide film and the Fe-Si bond length at the interface are respectively ∼6 % and ∼9 % larger than those in the hypothetical c-FeSi.

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An X-ray holographic method that reconstructs a single layer of atoms at the interface between ultra-thin film and substrate crystal is studied. We applied the method to the analysis of the interface structure of iron-silicide grown on the Si(111) surface, the structure of which is considered to be the CsCl-type FeSi. First we confirmed by simulations that the method is useful to discriminate whether an additional layer at the interface exists or not, using calculated X-ray intensities. Next we applied the method to the analysis of experimental data obtained for Si(111)-2×2-Fe. The result indicated the existence of the interface atoms, corresponding to the B8 model for CsCl-type FeSi.

A perforated caisson breakwater with wave-dissipating blocks, which has passage holes in the caissons, was developed for the purpose of maintaining a superior water quality environment in the landward area of a port. This structure allows permeability of tides and permanent currents, and uses wave energy to introduce seaward water into the landward water area of the port.In order to examine the wave force characteristics on perforated caisson breakwaters with wavedissipating blocks, a, two-dimensional hydraulic model experiment was conducted. Based on the results, a method of structurally resistive design against wave action was proposed. This method is an expansion the general design method for breakwaters covered with wave-dissipating blocks, upon which the Goda's method had been applied. It is believed that general horizontal wave forces and uplift pressure, which were obtained by introducing the wave pressure reduction coefficient to the Goda's method, are applied to the front and bottom surfaces of the caisson. The horizontal wave force, however, was not applied because there were no pressure receiving surfaces at the openings of the passage holes, but inner-hole uplift pressure was applied onto the upper surface in the passage holes. Appropriateness of this method was confirmed in sliding tests.Keyword ; sea water exchange, structurally resistive design against wave action, hydraulic model experiment

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