Hiroshi Irie

Structure dependence of ferroelectric properties of bismuth layer-structured ferroelectric single crystals

Ferroelectric properties along the a(b) axis and c axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring saturated P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related to the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively, along the a(b) axis. The saturated remanent polarization was larger in the BLSF with a higher Curie temperature. This is attributed to a large atomic displacement accompanied by a high Curie temperature. In contrast, the saturated coercive electric field was smaller in the BLSF with a larger number of m. This phenomenon is assumed to be caused by the decrease in the strain energy of the octahedra from the bismuth layer, which leads to an easy movement of the octahedral cations in the direction of an applied external electric field. Along the c axis, the BLSFs with an odd number of m had the same relatio...

Zeta potential and photocatalytic activity of nitrogen doped TiO2 thin films

Nitrogen doped TiO2 films were fabricated by annealing anatase TiO2 films in gaseous NH3. Nitrogen atoms in these films were substitutionaly introduced into oxygen sites of TiO2 lattice. We have evaluated the zeta potential of these films and have found that it became negative with the amount of nitrogen doping. The photocatalytic decomposition of gaseous 2-propanol was examined under light-limited conditions, and the quantum yield (QY) was estimated while illuminating with ultraviolet (UV) and visible light (VIS). The QY values for the nitrogen doped TiO2 film were 15.4% (UV) and 0.41% (VIS), whereas those for the pure TiO2 film were 18.4% (UV) and 0% (VIS). In addition, the photocatalytic decomposition of ethylamine ions (CH3CH2NH3+) was evaluated in an aqueous solution under UV illumination in a light-rich condition. Consequently, the decomposition rate of the nitrogen doped TiO2 for aqueous ethylamine ions was higher than that of the pure TiO2 because the surface of the nitrogen doped TiO2 film was negatively charged and cationic ethylamine ions were efficiently adsorbed on its surface. The surface structure and the band structure of the nitrogen doped TiO2 are discussed in this paper.

In-plane mobility anisotropy and universality under uni-axial strains in nand p-MOS inversion layers on (100), [110], and (111) Si

An investigation of the inversion layer mobility characteristics on conditions with systematic combinations of three key parameters: surface orientations, in-plane channel directions, and uni-axial strains, was performed. A guiding principle for an optimum combination of above three key parameters in terms of electron and hole mobility enhancement is presented. In addition, it is found experimentally that the definition of the mobility universality should be changed with surface orientations and applied uni-axial strains.

Dielectric and ferroelectric properties of SrBi4Ti4O15 single crystals

SrBi4Ti4O15 single crystals were grown, and their dielectric and ferroelectric properties were investigated along the a(b) axis and c axis, separately. The dielectric permittivity at 1 MHz was 1900 along the a(b) axis at the Curie temperature of 520 °C. This value was ten times higher than that along the c axis. With respect to the ferroelectricity, the saturated remanent polarization was 29 μC/cm2 and the saturated coercive field was 26 kV/cm along the a(b) axis under an electric field of 59 kV/cm, and ferroelectricity was not observed along the c axis.SrBi4Ti4O15 single crystals were grown, and their dielectric and ferroelectric properties were investigated along the a(b) axis and c axis, separately. The dielectric permittivity at 1 MHz was 1900 along the a(b) axis at the Curie temperature of 520 °C. This value was ten times higher than that along the c axis. With respect to the ferroelectricity, the saturated remanent polarization was 29 μC/cm2 and the saturated coercive field was 26 kV/cm along the a(b) axis under an electric field of 59 kV/cm, and ferroelectricity was not observed along the c axis.

Photoinduced Hydrophilic and Electrochemical Properties of Nitrogen-Doped TiO2 Films

A radio frequency sputtering technique was used to fabricate nitrogen-doped titanium dioxide thin films with dopant concentrations of 1.0-2.9 mol %. UV-visible absorption spectra and calculations of the estimated density of states indicated that the changes in the band structure depended on the dopant concentrations. The nitrogen-doped TiO 2 films underwent hydrophilic conversion and approximately 1.9 mol % was the optimal dopant concentration for hydrophilic properties when irradiating with visible light. When irradiating with UV light, the hydrophilic properties increased as the dopant concentration decreased, which reflected the changes in the band structure. Photoelectrical and electrochemical analyses of the nitrogen-doped TiO 2 suggested that it was an n-type semiconductor, and the carrier concentrations increased as the nitrogen concentration increased. Based on these findings, a mechanism for the visible light response, which involves nitrogen incorporation at some of oxygen sites, is proposed.

Visible-light induced hydrophilicity on nitrogen-substituted titanium dioxide films.

Nitrogen-substituted titanium dioxide thin films were found to undergo hydrophilic conversion under irradiation with visible light. The hydrophilicity was enhanced by increasing the degree of nitrogen substitution at oxygen sites. The water contact angle for the thin film with the greatest hydrophilicity, TiO1.9884N0.0116, changed from 20 degrees to 6 degrees following irradiation.

A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO3) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400–530nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO3.

FATAL HEPATIC NECROSIS AFTER SHOCK

A clinicopathological study was undertaken in 15 cases of massive hepatic necrosis after shock. The GOT and GPT level exceeded 1000 units in 10 cases. The 15 cases consisted of 3 diagnosed as fulminant hepatitis clinically and 12 diagnosed as disseminated intravascular coagulation (DIC) or multiple systemic organ failure (MOF) from the unremarkableness of liver dysfunction. It was noteworthy that sepsis and surgery were closely associated with these lesions. The weight of the liver at autopsy ranged from 800 to 2,700 g. Liver necrosis was macroscopically characterized by clear demarcation of the necrotic areas sharply separated from the surrounding liver parenchyma, showing the appearance of so‐called “map‐like necrosis”. Microscopically, the lesions in these subjects showed mainly the pattern of centrilobular necrosis. As observed in the burn shock case (case 12), the shock which provoked in different phases of time seemed to have repeated its attack. These liver necroses were considered to result from severe systemic circulatory disturbance or intrahepatic circulatory disturbance. The possibility is indicated that the generalized or univisceral Shwartzman reaction, and repeated and combined severe shock participated in the pathogenesis. Fibrin thrombi aggrevate tissue perfusion and accelerate anoxia. Heparin therapy seemed effective in these cases if administered at an appropriate time.

Enhanced Ferroelectric Properties of V-Doped BaBi4Ti4O15 Single Crystal

Single crystals of barium bismuth titanate (BaBi4Ti4O15) and BaBi4Ti4O15 partially substituted with V5+ and Ba2+ for Ti4+ and Bi3+ sites, respectively, at 5 at.% (Ba1.2Bi3.8Ti3.8V0.2O15), were grown using slow cooling. The incorporation of vanadium into the B-site of the layered pseudo-perovskite block resulted in a shift of the Curie point to a higher temperature, from 410°C to 425°C, and an increase in dielectric permittivity from 8000 to 9500 along the a(b)-axis direction and from 150 to 160 along the c-axis direction at 1 MHz and at their respective Curie points. The increase in Curie temperature brought about an increase in remanent polarization, and saturated remanent polarization was enhanced from 14.8 µC cm-2 to 15.5 µC cm-2.

Novel Approach to MOS Inversion Layer Mobility Characterization with Advanced Split C-V and Hall Factor Analyses

Parasitic effects and Matthiessens rule have been reinvestigated in the inversion layer mobility analysis. It is shown that an advanced split C-V technique newly developed is very useful for characterizing the intrinsic inversion layer mobility in short channel MOSFETs, even with very large parasitic effects. Furthermore, the validity of Matthiessens rule is experimentally and theoretically investigated through Hall factor analysis