Tetsuo Sakka

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Stratified optical filters with distinct spectral features and layered surface chemistry were prepared on silicon substrates with stepwise anodic porosification and thermal carbonization. The use of differing parameters for successive carbonization treatments enabled the production of hydrolytically stable porous silicon-based layered optical structures(More)
: Thermally promoted addition of undecylenic acid is studied as a method for modifying porous silicon optical reflectors that have been pre-treated with thermal hydrocarbonization. Successful derivatization of undecylenic acid is demonstrated and confirmed with Fourier transform infrared and X-ray photoelectron spectroscopies. The results indicate that the(More)
Macroporous structure of silicon can be obtained with anodization in hydrogen fluoride (HF) solution. The macropore formation in the presence of alcohol was studied. Macroporous layer formation in a low-concentration HF solution is stabilized with the increasing number of carbon in alcohol. The dissolution at the topmost part of the porous layer is observed(More)
Gold nanofibers have been found to be formed via a heterogeneous electron-transfer reaction at the ionic liquid|water interface. The tips of the nanofibers show a dendritic structure and the dendrites are bundled to nanofibers except around the tips. The roles of the ionic liquid for the dendritic nanofiber formation have been discussed.
The NaCl salt-solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt-solution interface system, and calculated the(More)
Different designs for producing multiple stopband mesoporous silicon rugate filters via electrochemical anodization are compared. The effects of light absorption and dispersion to visible range filter design are investigated. Thermal oxidation is applied for passivating the chemically reactive porous silicon surface, and the response of the passivated(More)
Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron microscope observation of the gold deposited porous silicon. Gold(More)
Spectroscopy is emerging as a technique that can expand the envelope of modern oceanographic sensors. The selectivity of spectroscopic techniques enables a single instrument to measure multiple components of the marine environment and can form the basis for versatile tools to perform in situ geochemical analysis. We have developed a deep-sea laser-induced(More)
We propose a technique of on-site quantitative analysis of Zn(2+) in aqueous solution based on the combination of electrodeposition for preconcentration of Zn onto a Cu electrode and successive underwater laser-induced breakdown spectroscopy (underwater LIBS) of the electrode surface under electrochemically controlled potential. Zinc emission lines are(More)