Surface passivation technology for III-V semiconductor nanoelectronics

The present status and key issues of surface passivation technology for III-V surfaces are discussed in view of applications to emerging novel III-V nanoelectronics. First, necessities of passivation and currently available surface passivation technologies for GaAs, InGaAs and AlGaAs are reviewed. Then, the principle of the Si interface control layer (ICL)-based passivation scheme by the authors’ group is introduced and its basic characterization is presented. Ths Si ICL is a molecular beam epitaxy (MBE)-grown ultrathin Si layer inserted between III-V semiconductor and passivation dielectric. Finally, applications of the Si ICL method to passivation of GaAs nanowires and GaAs nanowire transistors and to realization of pinning-free high-k dielectric/GaAs MOS gate stacks are presented.     

Iterative-method performance evaluation for multiple vectors associated with a large-scale sparse matrix

ABSTRACT

Ensemble computing, which is an instance of capacity computing, is an effective computing scenario for exascale parallel supercomputers. In ensemble computing, there are multiple linear systems associated with a common coefficient matrix. We improve the performance of iterative solvers for multiple vectors by solving them at the same time, that is, by solving for the product of the matrices. We implemented several iterative methods and compared their performance. The maximum performance on Sparc VIIIfx was 7.6 times higher than that of a naïve implementation. Finally, to deal with the different convergence processes of linear systems, we introduced a control method to eliminate the calculation of already converged vectors.     

Optical and magnetic studies on the phosphorescent state of phthalazine in polar and non-polar hosts

The ground state potential energy curve for the beryllium dimer is calculated using non-degenerate many-body perturbation theory and the multi-configuration self-consistent-field/configuration interaction method. Quasi-degeneracy in this system makes it useful in exploring the limitation of the applicability of the non-degenerate formulation of diagrammatic many-body perturbation theory. Both methods are applied within the algebraic approximation defined by a contracted gaussian basis set of triple zeta quality. It is shown that non-degenerate perturbation theory can lead to a potential energy curve which is in close agreement with the configuration interaction curve when taken to third order in the energy and [2/1] Padé approximants constructed.     

A mycelium with polyelectrolyte complex-bunched hyphae: several important factors affecting on the fermentation performance at a very high cell density

We have reported in the previous paper (Colloids Surf. B (2006) in press) a marked increase in the rate of gluconic acid production at a very high cell concentration (40 g/l) of filamentous fungus (Aspergillus niger IFO 31012) which was immobilized with polyelectrolyte complex consisting of potassium poly(vinyl alcohol) sulfate and trimethylammonium glycol chitosan iodide [6-O-(2-hydroxyethyl)-2-(trimethylammonio)-chitosan iodide]. The present study was carried out to look at what factors play a crucial role in this enhancement. We measured viscosity of broth, mass-transfer coefficient (k(L)a) for oxygen and diffusion coefficient of glucose (substrate). It has become apparent that there is only a difference in the diffusion coefficient of glucose between the free and immobilized cells. Therefore, we believe that the diffusion limitation by substrates as a problem in submerged mycelial processes is improved by immobilization based on polyelectrolyte complexes.     

High-conversion-efficiency organic dye-sensitized solar cells with a novel indoline dye

An indoline dye (D205), the synthesis method of which is disclosed in this report, gave high-efficiency organic dye-sensitized solar cells (9.52%) using an anti-aggregation reagent (chenodeoxycholic acid).     

Photoresponsive dithienylethene-urea-based organogels with "reversed" behavior

Dithienylperhydrocyclopentene-bisurea-based low molecular weight gelators are described that function as photoresponsive organogels that show a remarkable gel-to-liquid transition upon irradiation. The two series of derivatives, with and without alkyl spacers between the urea hydrogen bonding groups and the photochromic unit, show different gelation behavior. Upon UV irradiation of the gels, a gel liquified at only 1.4% conversion of the photochromic unit. Transmission electron microscopy (TEM) shows that the gel fibres consist of thin ribbons. Semi-empirical (PM3) calculations indicate that the hydrogen bonding between the open-ring isomer (o) molecules is weak, and that formation of the closed-ring isomer (c) destabilises the hydrogen bonding further. The results indicate that a small amount of the closed-ring isomer will disrupt the intermolecular hydrogen-bonding, leading to disintegration of the gel fibre ribbons and hence reversible liquification.     

A novel blue dye for near-IR 'dye-sensitised' solar cell applications

A squaraine dye incorporating two carboxylic acid attaching groups has been synthesised and used successfully in both liquid and solid-state solar cells, with solar energy to electricity conversion efficiencies (eta) under AM 1.5 G irradiation (100 mW cm(-2)) of 3.7 and 1.5% and short-circuit current densities (J(sc)s) of 8.6 and 4.2 mA cm(-2), with open-circuit voltages (V(oc)) of 591 and 681 mV and fill factors (FF) of 73 and 53%, respectively.     

White and Taylor Type Guest Host Displays Without Scattering Effects Using the Tilted Boundary Conditions

White and Taylor type guest host displays using the tilted boundary condition have been reported. The parallel or the perpendicular boundary condition is usually used for these displays and both conditions cause scattering phemomena after the electric field removal. The present paper reports the relaxation processes of samples with the tilted boundary after the field removal. Using the tilted boundary, two types of nonscattering conditions depending on the thickness of the liquid crystal layer (d), the natural pitch (Po) and the boundary condition (φ) exist. Both types of conditions are discussed in detail.