다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

We introduce the 2D counterpart of layered black phosphorus, which we call phosphorene, as an unexplored p-type semiconducting material. Same as graphene and MoS2, single-layer phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct, and appreciable band gap. Our ab initio calculations indicate that the band gap is direct, depends on the number of layers and the in-layer strain, and is significantly larger than the bulk value of 0.31–0.36 eV. The observed photoluminescence peak of single-layer phosphorene in the visible optical range confirms that the band gap is larger than that of the bulk system. Our transport studies indicate a hole mobility that reflects the structural anisotropy of phosphorene and complements n-type MoS2. At room temperature, our few-layer phosphorene field-effect transistors with 1.0 μm channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm2/V·s, and an...

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Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility

There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.

Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives

Preceding the current interest in layered materials for electronic applications, research in the 1960's found that black phosphorus combines high carrier mobility with a fundamental band gap. We introduce its counterpart, dubbed few-layer phosphorene, as a new 2D p-type material. Same as graphene and MoS2, phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct and appreciable band-gap that depends on the number of layers. Our transport studies indicate a carrier mobility that reflects its structural anisotropy and is superior to MoS2. At room temperature, our phosphorene field-effect transistors with 1.0 um channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm2/Vs, and an on/off ratio up to 1E4. We demonstrate the possibility of phosphorene integration by constructing the first 2D CMOS inverter of phosphorene PMOS and MoS2 NMOS transistors.

Phosphorene: A New 2D Material with High Carrier Mobility

Magnetism and ferroelectricity are essential to many forms of current technology, and the quest for multiferroic materials, where these two phenomena are intimately coupled, is of great technological and fundamental importance. Ferroelectricity and magnetism tend to be mutually exclusive and interact weakly with each other when they coexist. The exciting new development is the discovery that even a weak magnetoelectric interaction can lead to spectacular cross-coupling effects when it induces electric polarization in a magnetically ordered state. Such magnetic ferroelectricity, showing an unprecedented sensitivity to ap plied magnetic fields, occurs in 'frustrated magnets' with competing interactions between spins and complex magnetic orders. We summarize key experimental findings and the current theoretical understanding of these phenomena, which have great potential for tuneable multifunctional devices.

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Multiferroics: a magnetic twist for ferroelectricity

Diffusion bonding was used to join silicon carbide (SiC) to SiC substrates using three kinds of interlayers: physical-vapor-deposited (PVD) Ti coatings (10 and 20 μm) on the substrate, Ti foils (10 and 20 μm), and a Mo–B foil (25 μm). Two types of substrates were used: chemical-vapor-deposited SiC and SiC fiber bonded ceramic (SA-TyrannohexTM), the latter having a microstructure consisting of SiC fibers and a carbon layer. The microstructures of the phases formed during diffusion bonding were investigated using transmission electron microscopy (TEM) and selected-area diffraction analysis. TEM samples were prepared using a focused ion beam, which allowed samples to be taken from the reacted area. The effect of the interlayer material and the direction of the SiC fibers in the substrate with respect to the interlayer was evaluated. Scanning electron microscopy and TEM revealed good diffusion bonds in all samples; however, some samples exhibited small amounts of microcracking. The diffusion bonded CVD SiC sample using the 10-μm-thick PVD-Ti interlayer formed more of the stable phase and less of the intermediate phases than the sample using the Ti foil. This behavior was caused by the presence of columnar Ti grains in the interlayer, which may have enhanced the migration of Si and C atoms in the interlayer. In the SA-Tyrannohex samples using the Ti-foil interlayer, the chemical reaction proceeded more rapidly when the fibers were parallel to the interlayer than when they were perpendicular. This behavior was likely caused by the hexagonal carbon layer always facing the Ti interlayer in the sample with perpendicular fibers; this peculiar microstructure reduced the mobility of Si and C migrating into the interlayer. The SA-Tyrannohex sample using the Mo–B foil as the interlayer had excellent diffusion bonds with no microcracks or voids. In this system, Mo5Si3C, Mo2C, and Mo5Si3 formed. While phases have anisotropic coefficient of thermal expansion (CTE), the CTE mismatch between those phases and the substrate was apparently smaller than the mismatch in the samples using Ti interlayers.

Transmission Electron Microscopy of Interfaces in Diffusion-Bonded Silicon Carbide Ceramics

We examined structural changes related to the charge ordering (CO) in the temperature window between 100K and room temperature (RT) in YFe2O4 − δ by transmission electron microscopy. Characteristic diffuse scattering elongated along the [1] direction through the (1/3 1/3 0)-type reciprocal positions was found at RT, which is related to nano-sized domains due to the CO. In addition, we found the presence of the superlattice structures characterized by the (1/4 1/4 0)-type modulation vector at 150K and by the (0 1/2 0)-type modulation vector at 200 K. The changes in the superlattice structures as a function of the temperature should be strongly related to the dielectric anomalies in YFe2O4 − δ.

Dielectric Anomaly and Structural Phase Transitions in YFe2O4 − δ

Ferroelectric domains in hexagonal YMnO3

We investigated the microstructures and local structures of perovskite PbCrO3, which shows a metal-to-insulator transition and a 9.8% volume collapse, by electron diffraction, high-resolution transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). It is revealed that the charge glass state is characterized by the unique coexistence of the crystalline state with a cubic symmetry on average and the noncrystalline state. HAADF-STEM observation at atomic resolution revealed that Pb ions were displaced from the ideal A site position of the cubic perovskite structure, which gives rise to characteristic diffuse scatterings around the fundamental Bragg reflections. These structural inhomogeneities are crucial to the understanding of the unique physical properties in the charge glass state of PbCrO3.

https://iopscience.iop.org/article/10.7567/JJAP.57.050301/pdf

Unusual inhomogeneous microstructures in charge glass state of PbCrO3

1. CEMS, RIKEN (The Institute of Physical and Chemical Research), Hatoyama, Saitama, Japan 2. Department of Materials Science, Osaka Prefecture University, Sakai, Osaka, Japan 3. Graduate School of Science & Technology, Meijo University, Nagoya, Aichi, Japan 4. Research & Development Group, Hitachi, Ltd., Hatoyama, Saitama, Japan 5. Department of Applied Quantum Physics, Kyushu University, Fukuoka, Fukuoka, Japan 6. IMRAM, Tohoku University, Sendai, Miyagi, Japan

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Shigeo Mori

Papers

Transmission Electron Microscopy of Interfaces in Diffusion-Bonded Silicon Carbide Ceramics

Dielectric Anomaly and Structural Phase Transitions in YFe2O4 − δ

Ferroelectric domains in hexagonal YMnO3

Unusual inhomogeneous microstructures in charge glass state of PbCrO3

Double-Slit Electron Interference Experiment with Zero Propagation Distance Using Electron Biprism