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

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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The electronic properties of graphene

Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16), previously reported mobilities in the 0.5-3 cm(2) V(-1) s(-1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room-temperature single-layer MoS(2) mobility of at least 200 cm(2) V(-1) s(-1), similar to that of graphene nanoribbons, and demonstrate transistors with room-temperature current on/off ratios of 1 × 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.

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Single-layer MoS2 transistors

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

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Graphene and Graphene Oxide: Synthesis, Properties, and Applications

Barkhausen effects in the first order structural phase transition in type-II Weyl semimetal MoTe 2

Few-layer black phosphorus (FLBP), a recently discovered two-dimensional semiconductor, has attracted substantial attention in the scientific and technical communities due to its great potential in electronic and optoelectronic applications. However, reactivity of FLBP flakes with ambient species limits its direct applications. Among various methods to passivate FLBP in ambient environment, nanocomposites mixing FLBP flakes with stable matrix may be one of the most promising approaches for industry applications. Here, we report a simple one-step procedure to mass produce air-stable FLBP/phospholipids nanocomposite in liquid phase. The resultant nanocomposite is found to have ultralow tunneling barrier for charge carriers which can be described by an Efros-Shklovskii variable range hopping mechanism. Devices made from such mass-produced FLBP/phospholipids nanocomposite show highly stable electrical conductivity and opto-electrical response in ambient conditions, indicating its promising applications in both electronic and optoelectronic applications. This method could also be generalized to the mass production of nanocomposites consisting of other air-sensitive two-dimensional materials, such as FeSe, NbSe2, WTe2, etc.

https://iopscience.iop.org/article/10.1088/2053-1583/aaa9a0/pdf

Liquid phase mass production of air-stable black phosphorus/phospholipids nanocomposite with ultralow tunneling barrier

Due to its high sensitivity and sub-micrometer spatial resolution, the microscopic magneto-optical Kerr effect (micro-MOKE) technique has been widely utilized in the study of two-dimensional (2D) magnetic materials and heterostructures. Here, by taking 2D Cr2Ge2Te6 nanoflakes on a silicon wafer substrate as a model system, we present the effect of optical multilayer interference induced “optical artifacts” on the effective micro-MOKE measurements in such a system. It is found that not only the magnitude but also the sign of the micro-MOKE signal could be modulated by the “optical artifacts” with the variation of either the Cr2Ge2Te6 nanoflakes’ thickness or probe light wavelength. The detailed analysis based on the multilayer interference model reveals that there are two kinds of MOKE signals, sign reversal and magnitude modulation behavior, and the interference effect on the MOKE response can be easily predicted from unpolarized optical images. Our findings provide instructional principles on the promotion of micro-MOKE characterization as well as the optical studies in van der Waals magnets.Due to its high sensitivity and sub-micrometer spatial resolution, the microscopic magneto-optical Kerr effect (micro-MOKE) technique has been widely utilized in the study of two-dimensional (2D) magnetic materials and heterostructures. Here, by taking 2D Cr2Ge2Te6 nanoflakes on a silicon wafer substrate as a model system, we present the effect of optical multilayer interference induced “optical artifacts” on the effective micro-MOKE measurements in such a system. It is found that not only the magnitude but also the sign of the micro-MOKE signal could be modulated by the “optical artifacts” with the variation of either the Cr2Ge2Te6 nanoflakes’ thickness or probe light wavelength. The detailed analysis based on the multilayer interference model reveals that there are two kinds of MOKE signals, sign reversal and magnitude modulation behavior, and the interference effect on the MOKE response can be easily predicted from unpolarized optical images. Our findings provide instructional principles on the promoti...

Micro-MOKE with optical interference in the study of 2D Cr2Ge2Te6 nanoflake based magnetic heterostructures

Topological semimetal (TSM) AuTe2Br thin flakes have been studied by Raman spectroscopy and magneto-transport measurement. The angle-resolved polarized Raman spectrum of AuTe2Br (bulk and thin flake) shows strong anisotropy. Together with high resolution transmission electron microscopy (TEM), we establish a non-destructive method to determine the crystallographic orientation of AuTe2Br flakes. At high temperature (T  >  50 K), the magneto-resistance (MR) of AuTe2Br thin flakes shows typical parabolic-like behavior, which can be well fitted by the two-fluid model. However, at low temperature (T  ⩽  30 K), the MR of thin flakes (<17 nm) clearly deviates from the two-fluid model as well as from the Kohler's rule, suggesting a new type of scattering emerging below 30 K. Several possible scattering mechanisms are discussed and the respective corrections to MR are compared with our experimental data. In addition, the conductivity of these metallic crystals is also found to be highly anisotropic, with the hole mobility along the a axis about five times higher than that along the c axis.

https://iopscience.iop.org/article/10.1088/1361-648X/ab5cb4/pdf

Jian-Hao Chen

Papers

Barkhausen effects in the first order structural phase transition in type-II Weyl semimetal MoTe 2

Liquid phase mass production of air-stable black phosphorus/phospholipids nanocomposite with ultralow tunneling barrier

Micro-MOKE with optical interference in the study of 2D Cr2Ge2Te6 nanoflake based magnetic heterostructures

Anisotropic Raman spectrum and transport properties of AuTe2Br flakes.

Liquid phase mass production of air-stable black phosphorus/phospholipids nanocomposite with ultralow tunneling barrier