It has been a hard work to synthesize metastable or non-equilibrium compounds because they usually can be obtained under high temperatures and high pressures. However, mist CVD technique has potentials to develop new synthesis routes of them. Metastable or non-equilibrium oxides were fabricated under atmosphere or relatively lower temperatures of 500 °C. The key method is a choice of crystal structures of substrates. Crystal structures of thin films fabricated by mist CVD method are strongly influenced by the crystal structure of substrates, because their growth energies are relatively low. Mechanical stress from substrates strongly rock the crystal structures of thin films.
Sublattice reversal has been successfully demonstrated in GaAs-based III-V semiconductors on high-index substrates. A thin layer of Ge was introduced as a group IV material during molecular beam epitaxy of GaAs or AlAs layers on the (113)B- or (113)A-oriented GaAs substrates. The sublattice reversal was realized over the entire wafer area when GaAs/Ga/AlAs system was deposited on the (113)B substrate while it was not realized on the (113)A substrate. On the other hand, the sublattice reversal was completely realized for AlAs/Ga/AlAs system on the (113)A substrate and not on the (113)B substrate. These situations may be explained by self-annihilation of antiphase domains whose boundaries are composed of inclined (111) bond planes. The growth technology of the sublattice reversal epitaxy can be applied to novel kinds of planar-type nonlinear optical devices, which require a polarization-inverted structure in order to satisfy the quasi-phase-matching condition for the second-order nonlinear signal. Here, we will discuss on surface-emitting terahertz devices based on a semiconductor coupled multilayer cavity.
This paper describes morphological, optical, compositional, and structural characteristics of the Hf0.5Zr0.5O2 (HZO) thin films grown on Si and sapphire substrates by a chemical solution deposition method by spin coating using HfCl4 and ZrCl4 for the starting agents. Clear and smooth HZO thin films of about 20 nm thick were obtained after the spin-coating of the chemical solution followed by a drying process at 150°C and a sintering process at 500-800°C. The compositional ratio of Hf : Zr in the HZO thin films was 1 : 1 in good agreement with the molar ratio of HfCl4 and ZrCl4 in the chemical solution. It was revealed that the HZO thin films were crystallized in orthorhombic structure under the sintering in N2, while monoclinic structure became dominant under the sintering in air.
Recently, we have succeeded in developing stable and long-term operation of an extended-gate field effect transistor-type glucose sensor using a silk-fibroin film for the immobilization membrane of glucose oxidase. In this paper, we report the fabrication process and characterization of the fibroin film. High-purity silk fibroin powder was used as the solute material in water. The advantage of this material is high solubility in water, non-toxicity to human body, and capability of stable immobilization of enzyme molecules. The fibroin film was formed on a glass substrate using a spin coating method followed by an insolubilation treatment in 80 wt% ethanol aqueous solution. It was revealed that the bond strength between the film and the substrate was dramatically improved by applying a silane coupling treatment to the substrate. The obtained film showed β-sheet structure and contained dense nanopores on the surface.
Optical transmission properties of two-dimensional photonic crystals of a low refractive index material formed on a metal substrate have been theoretically investigated. The metal-base two-dimensional photonic structure is promising for low-cost fabrication and easy manipulation. We proposed a theoretical model of two-dimensional photonic crystal with the refractive index of n = 1.5 formed on a Ag substrate and calculated the optical transmission spectrum by using the finite difference time domain (FDTD) method. The calculated transmission spectrum shows an obvious photonic band gap even for the photonic crystal contacting to the metal substrate. We introduced a line defect cavity, and it has been clarified that the calculated Q factor increases with the refractive index. These results indicate that metal-base two-dimensional photonic crystal with the low refractive index can be widely applicable for photonic devices.
Laser cooling in rare-earth doped material using anti-Stokes photoluminescence (PL) caused by phonon annihilation realizes novel cooling devices without generating heat and vibration. Yb-doped yttrium aluminum garnet powder crystals, (Y:Yb)AG with the Yb concentration from 2 to 13 mol%, were fabricated by a solid state reaction method. PL of (Y:Yb)AG excited at 659 nm shows the maximum intensity at the Yb concentration of 6 mol% because of concentration quenching of the PL. When we resonantly excite at 1030 nm corresponding to the energy distance between the E5 and E3 levels of the f-f transition of Yb3+, obvious anti-Stoke PL signal has been observed at 968 nm. This result indicates that phonons are absorbed, and, then, an up-converted photon with the energy between the E5 and E1 levels is emitted. The relative cooling efficiency, defined by a product of the ideal cooling efficiency and the integrated PL intensity, becomes maximum at the 1030-nm excitation. The ideal cooling efficiency was estimated to be 1.9% at the Yb concentration of 6 mol% and the 1030-nm excitation at room temperature.
We developed a heterodyne interferometry system cancelling the noise caused by floor vibration and mechanical vibration using accelerometers. The interferometry is one of the powerful tools to precisely measure the flatness of a polished semiconductor wafer. Generally, the noise caused by vibration affects the displacement measured by the interferometers, and it is difficult to completely avoid the noise even if we use a vibration isolation table or perform motor tuning of the driving parts. The noise cancelling has been conducted by compensating the distance between a pair of interferometers using the signals obtained by accelerometers mounted on near the interferometers. Here, we propose and demonstrate a noise cancelling method. Utilizing the system, we successfully reduced the influence of floor vibration and mechanical vibration, and the precision of the measurement of the wafer flatness has been improved 38% by the technique in this experiment.
The Hashin-Hansen’s equation introduced from the low of mixture is established for estimating the static modulus of elasticity of the cement concrete as a two-phase composite material. In previous study, the authors proposed an estimating formula of the static modulus of elasticity of porous concretes based on the Hashin-Hansen’s equation with a correction coefficient of voids. However, the proposed formula was introduced by using the estimated value of the static modulus of elasticity of the coarse aggregate. This paper defines the compressive properties of the porous concretes using coarse aggregates with the known value of the static modulus of elasticity, and then the applicability of the estimating formula of the static modulus of elasticity of porous concretes and the equation for the correction coefficient of voids are discussed. The porous concretes using cement mortars as a binder and coarse aggregates of crushed hard sandstone and limestone are prepared with the water-cement ratios of 22.5, 25.0 and 30.0%, and the percentage of target voids of 10, 15, 20, 25 and 30%. The porous concrete specimens are cured under 24h-20°C-90%(RH)-moist+ 24h-70°C-hot water+1h-20°C-water and subjected to the total voids test and compression test for measuring the static modulus of elasticity. The cement mortar specimens are prepared by same procedures and measured for the static modulus of elasticity. The test results show that the correlation between the estimated and measured values of the static modulus of elasticity of the porous concretes are recognized. In conclusion, the applicability of the previously proposed formula for estimating the static modulus of elasticity of porous concretes is recognized. And the equation of the correction coefficient of voids is newly proposed.
Recently, aging of infrastructures constructed in large amount during high economic growth period is becoming one of social problem. Because water is necessary for almost of all deteriorations of concrete structures, organic coating materials are often used for preventing water. It is well known that organic coating materials are deteriorated by ultra-violet ray with time, and accelerated weathering test is carried out for evaluating weatherability of coating materials. However, details of deterioration mechanism of organic coating materials are still unclear and relationship between weathering test and deterioration by sunlight is not made clear. Therefore, quantitative evaluation method of deterioration of organic coating materials has not been established so far. Then in this study, Raman spectroscopy is focused on as an available method in fields, it was tried to develop deterioration index of organic coating materials with Raman spectroscopy. As results, it was made clear that fluorescence increases with propagation of UV deterioration because carbonyl turn into carboxyl due to deterioration. And deterioration of organic coating materials can be evaluated by using photobleaching of fluorescence peak in Raman spectrum.
Surface coating is one of the repair methods for chloride-induced corrosion in reinforced concrete. In maintenance procedures for the surface coating so far, qualitative evaluation base on experience is adopted and obtained knowledge are accumulated to judge necessity of re-repair for deteriorated surface coating. That is, quantitative evaluation is not yet fully established for influence of performance degradation and/or defect of surface treatment on life of a concrete structure. In this study, pinhole and delamination are focused as deterioration phenomena of surface coating. As a first step to the quantitative evaluation, 3-dimentional ingress of chloride ion into surface-coated mortar specimens with modeled deterioration phenomena were investigated. As a result, if areas of deterioration phenomena are large enough, chloride ion ingress can be predicted using FE analysis based on Fick's diffusion law, which enables establishing effective re-repair strategy.
DC potential drop method enables to determine surface crack configurations. A batch processing program for the determination of surface crack configuration by DC potential drop method has been developed. The production of the mesh element has been considerably improved by the introduction of a three dimensional boundary fitted coordinates transformation technique. The curved grid can be automatically changed to correspond to the actual crack shape. The program is available for the plate like material and the pipes with the surface crack. The results of application to the simulated surface crack showed good agreement between the analyzed crack configuration and the actual one with an accuracy of about 0.1mm.