Annealing process dependence of the photoluminescence in rare-earth-ion-doped chalcogenide glass

We report on the annealing process dependence of the visible photoluminescence (PL) properties of the Pr³⁺-doped Ga₂S₃-GeS₂-La₂S₃ glass, where emission intensities per ion depend not only on the Pr³⁺ concentration but on the annealing process after glass formation. It is demonstrated that enhancement of the photoluminescence to more than four times the intensity can be achieved through improvement on a procedure in the process. Multiple peaks were observed in the PL, and not only the total intensity but also the relative intensity of each peak was changed. Degree of the intensity enhancement was proved to depend on the excited states.     

Interface profile optimization in novel surface passivation scheme for InGaAs nanostructures using Si interface control layer

This paper attempts to control and optimize the interface atomic profiles of a novel surface passivation scheme for InGaAs nanostructures, using a silicon interface control layer (ICL). An in-situ x-ray photoelectron spectroscopy characterization technique was used to establish a process sequence that satisfies the conditions of maintenance of pseudomorphic matching to InGaAs, prevention of direct oxidation of InGaAs, and formation of a good SiO₂/Si interface with minimal suboxide components. It is shown that the above conditions can be satisfied by a new process that is a formation of the thermal SiO₂ at the SiO₂-Si interface by repetition of deposition/oxidation/annealing cycle. A large reduction of interface state density (N_ss) was realized by the optimization of the new process, resulting in a minimum N_ss of 4 × 10¹¹ cm⁻² eV⁻¹. The silicon ICL technique was successfully applied to the passivation of InGaAs wire structures.     

The effect of water and oxyanions on the passivation of iron in mixed dimethylformamide-water solvents

The passive film on iron has been produced anodically in mixed dimethylformamide-water solvents with and without oxyanion, and reduced cathodically in phosphate-borate buffer solution of pH 8.5. The thickness of the passive film was estimated from the chronopotentiogram. The passivation was expedited by the addition of water, molybdate and chromate. These species were directly involved in the passivation process to form the passive film, but the extent of the involvement relied on the nature of oxyanion. The addition of greater quantities of water led to no formation of the passive film. The film growth process was dependent evidently on the stability of the ferric hydroxide and/or (FeL)_ads (L : oxyanion) in the DMF-water media.     

Highly Reactive β-Dicalcium Silicate: V, Influence of Specific Surface Area on Hydration

The hydration of β-C₂S prepared from hillebrandite [Ca₂(SiO₃)(OH)₂] and having specific surface areas of 6.8, 5.5, and 3.1 m²/g was investigated. Different specific areas were obtained by varying the dissociation temperature of hillebrandite. In addition, the hydration of β-C₂S synthesized from high-temperature solid-state reaction was also studied as a comparison. The specific surface area exerts a strong influence on the hydration rate, which increases as the surface area increases. The degree of influence changes with the reaction, becoming greater as hydration progresses. There is initially a linear relationship between specific area and the time required to complete a specific reaction. The specific surface area also affects the reaction mechanism. In the case of specific areas of 5.5 m²/g or less, the reaction changes from a chemical reaction to a diffusion-controlled one, and the degree of reaction comes almost to a halt at 80% to 85%. The Ca/Si ratios of hydrate and the silicate anion structures were also investigated in this study.     

High electronic-optical conversion efficiency in avertical-to-surface transmission electro-photonic device with a verticalcavity

Electronic-optical conversion efficiency of 11.4% in a vertical-to-surface-transmission electrophotonic device with a vertical cavity is reported. Reduction of the electrical resistance by the double mesa structure, efficient confinement of carriers in the active region by the proton implanted structure, and photon recycling by sidewall reflectors lead to this high conversion efficiency. Efficiency over 10% is achieved for the first time in surface-emitting devices     

In situ chamber cleaning using atomic H in catalytic-CVD apparatus for mass production of a-Si:H solar cells

Effects of the chamber cleaning on properties of hydrogenated amorphous Si films prepared by catalytic chemical vapor deposition are shown. It is also revealed that the chamber is easily cleaned by atomic H generated on the heated catalyzer from H₂ gas molecules. In situ chamber cleaning using only H₂ gas is applicable to in-line apparatuses for mass production of solar cells, which brings about the reduction of the production cost.     

Reversible MR findings of hemolytic uremic syndrome with mild encephalopathy

We report the reversible MR findings in a 7-year-old girl with hemolytic uremic syndrome and mild encephalopathy. The splenium of the corpus callosum showed isointense to low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, representing local edema. These findings returned to near normal on MR images obtained 1 week later. The patient recovered without CNS impairment.     

Analysis of dibenzothiophene metabolic pathway in Mycobacterium strain G3

The dibenzothiophene (DBT) metabolic pathway in Mycobacterium strain G3, which is classified as a desulfurizing microorganism with the 4S pathway, was analyzed. 2-Hydroxybiphenyl (HBP), which is an end metabolite in the DBT desulfurization reaction, and 2-methoxybiphenyl (MBP) were found in the reaction mixture, and the methoxylation pathway from HBP to MBP was clarified. Although the substrate in the methoxylation reaction was HBP, there was no relationship between expression of the methoxylation activity and that of the desulfurization activity. Then, 4,6-dimethyl DBT, 4,6-diethyl DBT and benzo[b]naphtho[2,1-d]thiophene were metabolized to their methoxy forms via the desulfurization pathway. We established the methoxylation pathway in Mycobacterium G3.     

Development of micro-beam NRA for hydrogen mapping: Observation of fatigue-fractured surface of glassy alloys

A micro-beam NRA system by means of a resonant nuclear reaction of ¹H(¹⁵N, αγ)¹²C has been developed at the beam line in MALT, University of Tokyo. The beam optics was analyzed in terms of the phase diagram. By carefully suppressing the spherical aberration of the final quadrupole magnetic lens, the ¹⁵N beam at the energy of 6.4 MeV was focused on targets with a size of 17 μm × 30 μm. For the precise positioning of the sample and beam spot, a combination of the mirror and optical microscope was adopted, so that the hydrogen concentration can be measured at a desirable position of the sample. With this new system, the hydrogen concentrations of fatigue-fractured surfaces of glassy alloys were determined from the viewpoint of the hydrogen embrittlement: Zr₅₀Cu₃₇Al₁₀Pd₃ and Zr₅₀Cu₄₀Al₁₀. Depth-resolved two-dimensional (2D) mapping of hydrogen concentration was performed in the area of 3 mm × 3 mm with an in-plane resolution of 150 μm. The maps taken at three different depths revealed that the hydrogen concentration is higher in the fatigue-fractured regions in both samples.