ZnMgTe(Cladding)/ZnTe(Core)/ZnMgTe(Cladding) thin film waveguide had been grown by molecular beam epitaxy (MBE) and presented a great potential to be a high performance Electro-optical (EO) modulator. For a low propagation loss ZnMgTe/ZnTe waveguide, thick cladding layer with high Mg composition (Mg %) is needed. However, the in-plane lattice mismatch of the fabricated device with high Mg % and thick cladding layer was large. It might cause the cladding/core interface roughness and asperities due to the misfit dislocation, and degrade the device performance. Because EO property of waveguide device is primarily influence by the structure thickness, the device efficiency improvement in this study was only considered to reduce the defects asperities that would cause propagation loss without decreasing the Mg % or the total thickness of the cladding layers. Therefore, we introduced a low Mg % layer between the cladding and the core layer to circumvent the effect of large lattice mismatch. The in-plane lattice mismatch of the devices was monitored using reciprocal space mapping, and surface morphologies were also observed using atom force microscope. The two-step index ZnMgTe/ZnTe waveguide had shown to have lower degree of relaxation compared to that of single-step index waveguide device with close Mg % and cladding layer thickness. Therefore, the crystal degradation of the two-step-index waveguide caused by lattice mismatch was successfully suppressed by introduction extra low Mg % layers. The morphologies of the two kinds of waveguide structures have similar surface asperities, which indicated the extra inserted layers did not produce additional large scale asperities at the interfaces that would increase the propagation loss.

We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations (Ishiyama et al. 2015; Oogi et al. 2015). We assume that a major merger of galaxies triggers quasar activity. We find that the quasar bias does not depend significantly on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. The quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

Conventional phosphor materials are doped ternary or quaternary compounds; hence it would be difficult to prepare nanoparticles of those materials by build up methods. Ba2ZnS3:Mn (BZS), SrGa2S4:Eu, and BaAl2S4:Eu nanoparticles were prepared by a break down method, namely the ball-milling method. Transmission electron microscopy (TEM) and TEM- energy-dispersive X-ray spectroscopy (EDX) measurements showed several-nanometer-size stoichiometric and dispersed nanoparticles were achieved. ZnO-coating was performed and the uniform coating layers were formed on the phosphor nanoparticles. The ZnO-coated nanoparticles exhibited an improved stability in Photoluminescence. Red color phosphor material, namely BZS, was ball-milled and sprayed on the glass substrate. Mn doped BZS absorbs ultra violet light and emits red light peaking at around 640nm. When the single crystal Si solar cell was placed under the transparent nanoparticle layer, short wavelength light was absorbed and converted to long wavelength light.

We study the initial value problem for the drift-diffusion model arising in semiconductor device simulation and plasma physics. We show that the corresponding stationary problem in the whole space ℝn admits a unique stationary solution in a general situation. Moreover, it is proved that when n ≥ 3, a unique solution to the initial value problem exists globally in time and converges to the corresponding stationary solution as time tends to infinity, provided that the amplitude of the stationary solution and the initial perturbation are suitably small. Also, we show the sharp decay estimate for the perturbation. The stability proof is based on the time weighted Lp energy method.

SrS:Ce nanoparticles were prepared using a reverse micelle method and coated by ZnO. The mono-dispersed nanoparticles whose size was as small as 3nm were observed by transmission electron microscope (TEM) and dynamic light scattering (DLS) method. Optical properties of the core-shell SrS:Ce/ZnO nanoparticle was studied. UV-visible absorption and photoluminescence (PL) properties were measured and compared with those of SrS:Ce and SrS nanoparticles. Bright blue photoluminescence (around 440 nm) was observed from SrS:Ce at a room temperature when nanoparticles were excited using a Hg lamp. The PL peak intensity enhancement was observed after forming the ZnO shell. The optical absorption profile of nanoparticles was associated with the band edge feature of SrS. The coating of the SrS:Ce surface by ZnO has affected the electronic structure of SrS:Ce nanoparticles.

The fabrication of ZnO coated ZnS:Mn2+ nanoparticles were achieved using simple methods. ZnS:Mn2+ nanoparticles were prepared by a mechanical milling method. Coating of ZnO was then performed using a simple chemical method. Structural properties were evaluated by the X-ray powder diffraction (XRD) and the transmission electron microscope (TEM). Optical properties of the ZnO coated ZnS:Mn2+ nanoparticle were characterized by exciting the particle included solvent using an UV-LED (400 nm). Bright orange color fluorescence was observed, and the fluorescence intensity of ZnO coated ZnS:Mn2+ nanoparticles was enhanced as compared to uncoated ZnS:Mn2+ nanoparticles. The capping of the core surface has probably terminated surface defects of ZnS:Mn2+ nanoparticles, and resulted in the improved fluorescence intensity.

Nitrogen and helium mixed gas plasma was used to grow p-ZnSe. Using the mixed gas, the acceptor concentration could be controlled from 6x1016 to 7x1017 cm−3 while films doped using the nitrogen plasma exhibited the acceptor concentration of 3x1017 cm−3. Doping characteristics such as the acceptor concentration and the PL properties depend on the gas mixing ratio and the rf power. Plasma spectroscopy was used to characterize the variety of the species in the plasma. Although the variety of the nitrogen related peaks in the spectrum were not significantly affected by the gas mixing, several peaks (for example 745nm and 825nm) showed intensity variation that was similar to the acceptor concentration variation with respect to the N2 and He gas mixing ratio.

The strain rate dependence of anisotropic compression behavior in porous iron with cylindrical pores oriented in one direction was investigated. Through high strain rate (˜103 s−1) compression tests along the orientation direction of pores using the split Hopkinson pressure bar method, it was shown that the stress–strain curve exhibits a unique plateau-stress region where deformation proceeds with almost no stress increase. The appearance of the plateau-stress region is related to the buckling deformation of the iron matrix and provides superior energy absorption. However, for the middle (˜10−1 s−1) and low strain rates (˜10−4 s−1), compression along the same direction produces no such plateau region. In fact, in contrast to compression in the parallel direction, compression perpendicular to the orientation direction of pores produces no plateau-stress regions in any of the three strain rates.

Methicillin-resistant Staphylococcus aureus (MRSA) has been causing a large number of serious hospital infections in some of the major hospitals in Japan. Among the precautions to prevent MRSA infection in hospitals, antisepsis or disinfection is one of the most universal. The in vitro activities of commonly used antiseptics and disinfectants against several strains of MRSA isolated in the University of Tokyo Hospital were evaluated.