Tatsuro Kawamura

Tuning plasmonic interaction between gold nanorings and a gold film for surface enhanced Raman scattering

We investigate the plasmonic properties of gold nanorings in close proximity to a gold film. The rings have been fabricated using nanosphere lithography and are optimized to boost their near-infrared surface enhanced Raman scattering (SERS) effects. A SERS enhancement factor as large as 1.4×107 has been achieved by tuning the separation between the gold nanorings and the gold film. In addition, we have numerically and experimentally demonstrated an enhanced tunability of the plasmon resonance wavelength and a narrowing of the plasmon linewidth for increasing ring-film interaction.

A CMOS imager hybridized to an avalanche multiplied film

A highly sensitive solid-state imager has been made by connecting an avalanche multiplier film to a MOS readout circuit through microbump electrodes. Optimization of the vapor-deposition conditions for the indium bump material made it possible for microbumps 5 /spl mu/m in diameter and 5 /spl mu/m in height to be formed into a 2/3-in matrix array of 380 000 pixels. A prototype imager was constructed with a 0.5-/spl mu/m thick avalanche photoconductive film. Clear avalanche multiplication of about ten times was observed at an applied voltage of 75 V. The imager had a good resolution and no recognizable afterimages.

Tuning the interaction between propagating and localized surface plasmons for surface enhanced Raman scattering in water for biomedical and environmental applications

With a view to biomedical and environmental applications, we investigate the plasmonic properties of a rectangular gold nanodisk array in water to boost surface enhanced Raman scattering (SERS) effects. To control the resonance wavelengths of the surface plasmon polariton and the localized surface plasmon, their dependence on the array period and diameter in water is studied in detail using a finite difference time domain method. A good agreement is obtained between calculated resonant wavelengths and those of gold nanodisk arrays fabricated using electron beam lithography. For the optimized structure, a SERS enhancement factor of 7.8u2009×u2009107 is achieved in water experimentally.

Development of a novel image intensifier of an amplified metal-oxide semiconductor imager overlaid with electron-bombarded amorphous silicon

We developed a novel image intensifier (II) of an amplified metal-oxide-semiconductor (MOS) imager (AMI) overlaid with electron-bombarded (EB) amorphous silicon (a-Si). The electron bombardment gain (EB gain) was 1500 at an accelerating voltage of 10 kV. Since the multiplication process was free from a phosphorescent screen and a coupling fiber plate as in the conventional II, the resolution was high and the picture quality was good and free from granularity noises, white spots, lag and sticking. As for fatigue of X-ray irradiation, the contrasts of a vertical stripe (Smear) are not detectable and damaged areas in AMI are weak whereas both of those in charge-coupled devices (CCDs) are strong.

Robustness of surface-enhanced Raman scattering substrate with a mercaptosilane adhesive layer for in vivo sensing applications

A highly robust surface-enhanced Raman scattering (SERS) substrate for in vivo sensing applications is reported. In vivo sensing demands structurally robust substrates with good optical performance. SERS substrates containing gold nanostructures on SiO2 supports often suffer from a low adhesion strength of gold on SiO2. The proposed SERS substrate contains a mercaptosilane adhesive layer, which provides a high robustness without deteriorating the plasmon performance, in contrast to traditional titanium adhesive layers. The mercaptosilane-modified SERS substrate is sufficiently robust for in vivo sensing, as evidenced by its implantation in the animal skin for 2 months.

Studies On Ionization Coefficients of Targets in an Amorphous Selenium APD for Pick-up Tubes by New Type Least Squares

The ionization coefficients of electrons and holes (i.e. α and β) have been determined only by the voltage and current characteristics of targets of a-Se APD in the operation state of pick-up tubes. These determinations were based on selfconsistently solving 12 simultaneous transcendent Webbs equations by using random numbers and linear approximations. The values obtained for β and α(1/cm) varied from β=7.36×106 exp (-8.24×106/E) and α=8.09×102 exp (-0.04×106/E), to β=24.6×106 exp (-9.80×106/E) and α=3.60×102 exp (-0.11×106/E) (unit of E; V/cm). The excess noise factor (K) for a gain equaling 10 varied from 2 to 3. The differences in the obtained values were attributed to differences in sample histories.