Kaoru Tamada

A novel method for creation of free volume in a one-component self-assembled monolayer. Dramatic size effect of para-carborane

We fabricated the self-assembled monolayers (SAMs) composed of 4-(12-(10-mercaptodecyl)-1,12-dicarba-closo-dodecaborane)-4′-octyloxy azobenzene and 4-(10-mercaptodecyloxy)-4′-octyloxyazobenzene on a gold surface, and performed photoswitching experiments. The SAM including p-carborane exhibited a much higher and more reversible photochemical response in comparison with the SAM in the absence of the p-carborane. This result suggests that the free volume of the azobenzene moiety to change its conformation is increased due to the size effect of the p-carborane.

Two-dimensional thickness measurements based on internal reflection ellipsometry

An imaging ellipsometer technique on internal reflection geometry that can measure the thickness distribution of a thin film possessing an assumed refractive index is described. Because a prism is used for the internal reflection geometry, it was theoretically predicted that angular derivation from the normal incidence on the prism surface affects only the psi value by a factor of 0.97 at maximum. Measurements were carried out for an optical system of silica substrate-TiO2 layer-silica layer-protein film-air, with a thin-film array of dried protein as the sample film. Thickness of the protein films was two-dimensionally estimated only from the measured map of the delta value by use of the simulated relationship between the thickness and the delta value. The thickness map obtained was coincident on the whole with the results according to a mechanical scanning. The detection limit was approximately +/- 0.2 nm. These findings validate the optical effect of a high-index additional layer to improve the sensitivity and precision of thickness measurements of the sample film on transparent substrates.

Intercalation Effect of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimetane Having Strong Electron Affinity in Self-Assembled Monolayers Composed of Charge Transfer Complex Prepared by Coadsorption and Layer-by-Layer Adsorption Methods

Charge transfer (CT) complex self-assembled monolayers (SAMs) on a gold substrate are prepared using layer-by-layer adsorption and coadsorption methods with mercapto-methyl-tetrathiafulvalene (TTF-CH2SH) and strong acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4), in comparison with TTF-CH2SH/TCNQ SAMs consisting of moderate acceptor TCNQ. The layer-by-layer method yields TTF-CH2SH/TCNQF4 SAMs with the coexistence of neutral TCNQF4 and anionic TCNQF4-, where the TCNQF4- anions are laid on the TTF layer with the TTF-CH2SH molecules standing perpendicular to the gold substrate. The neutral TCNQF4 molecules are stacked above the TCNQF4- anion layer. This is in contrast to the fact that TCNQ having intermediate strength of acceptor character does not yield any CT SAMs when using the layer-by-layer technique. In the coadsorption method, TTF-CH2SH/TCNQF4 SAMs are formed, where all the TCNQF4 molecules are completely reduced as TCNQF4- anions, similar to those in bulk TTF-TCNQF4 crystals. Taking into account that TTF-CH2SH/TCNQ SAMs have the same fractional value (0.6) of the degree of charge transfer to that of bulk TTF-TCNQ crystal, the coadsorption technique can reproduce the electronic structure of the bulk CT complex in the 2D SAMs. The coadsorbed SAMs have an intercalation structure, where acceptor molecules are intercalated into the interstitials of TTF-CH2SH/Au units with the molecular axes of both acceptor and donor molecules parallel to each other. Such a donor/acceptor molecular arrangement can provide a favorable situation in the charge transfer between the two ingredients, resulting in the similar electronic structure to that of bulk CT crystals.

Photo-induced surface relief on Azo polymer for optical component fabrication

With respect to the manufacturing of optical elements, facile and effective fabrication method is proposed. It is developed in connection with photo-induced surface relief (PSR)formation phenomenon that occurs on the azobenzene functionalized polymer film. Purely optically inscribed surface relief structures have been used as a plastic mold for manufacturing of its replica. At least a hundred times replication process has been achieved using thermosetting resin without any deterioration. This method has many merits not only from a technical viewpoint but also from a economical efficiency. In this report,first the PSR phenomenon is explained and then several examples for optical component fabrication are demonstrated.

Submicron-Wide Pattern of Silver Wire Stabilized on Functionalized Substrates

A stable submicron-wide electric conductive pattern consists of silver nanoparticles/polymer composite is established via photolithographic procedure, in which the introduction of furan-functionalized surface for the chemical anchoring of the pattern was a significant contrivance. Due to the strong anchoring between narrow-patterned film and the treated substrate, submicron-wide patterns stands up well against the development and annealing process. Approximately 180 nm-wide nanopattern has been achieved by the irradiation of 488 nm light. The width is well below the dimension of the incident light wavelength. Time dependence of the electric resistance of the composite thin film during annealing process has been measured at 200°C, and an optimum annealing time was found. The achieved volume resistivity after the optimum annealing was evaluated as∼8 × 10−4 Ohm · cm that was determined by four-probe measurements.