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

Electrical Transport in Graphene: Carrier Scattering by Impurities and Phonons

For two decades, two-dimensional carbon species, including graphene, have been the core of research in pursuing next-generation logic applications beyond the silicon technology. Yet the opening of a gap in a controllable range of doping, whilst keeping high conductance outside of this gapped state, has remained a grand challenge in them thus far. Here we show that, by bringing Bernal-stacked bilayer graphene in contact with an anti-ferromagnetic insulator CrOCl, a strong insulating behavior is observed in a wide range of positive total electron doping $n_\mathrm{tot}$ and effective displacement field $D_\mathrm{eff}$ at low temperatures. Transport measurements further prove that such an insulating phase can be well described by the picture of an inter-layer excitonic state in bilayer graphene owing to electron-hole interactions. The consequential over 1 $\mathrm{G\Omega}$ excitonic insulator can be readily killed by tuning $D_\mathrm{eff}$ and/or $n_\mathrm{tot}$, and the system recovers to a high mobility graphene with a sheet resistance of less than 100 $\mathrm{\Omega}$. It thus yields transistors with "ON-OFF" ratios reaching 10$^{7}$, and a CMOS-like graphene logic inverter is demonstrated. Our findings of the robust insulating phase in bilayer graphene may be a leap forward to fertilize the future carbon computing.

Realization of graphene logics in an exciton-enhanced insulating phase

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In situ monitoring of resistivity and carrier concentration during molecular beam epitaxy of topological insulator Bi$_2$Se$_3$

We have fabricated a superconducting single electron transistor (sSET) on a GaAs/AlGaAs substrate containing a two-dimensional electron gas (2DEG) about 100 nm below the surface. The island separating the two junctions, each of resistance 18 kΩ, and the leads connected to the sSET are capacitively coupled to the 2DEG. Depleting the 2DEG by means of a voltage applied to a back gate enables us to decrease the dissipation experienced by the sSET in situ. The measured minimum zero-bias conductance, G o min , of the sSET follows the approximate power law dependences G o min ∝ T α g β , where T is the temperature and g ≡ R K /4R g ; here R K = h/e 2 and R g is the resistance per square of the 2DEG. We find α ≈ — 1 and β ≈ 0.2 — 0.4, depending on the temperature. These results are in qualitative agreement with the theory of Wilhelm et al. However, the fact that β, in particular, has a temperature dependence suggests that one cannot separate the temperature and dissipation dependences with the functional form Tαg β .

The Superconducting Single Electron Transistor: in situ Variation of the Dissipation

1 Department of Chemistry, University of California Berkeley, Berkeley, CA USA 2 Department of Physics, University of California Berkeley, Berkeley, CA USA 3 Materials Science Division, Lawrence Berkeley National Lab, Berkeley CA USA 4 National Center for Electron Microscopy, Berkeley, CA USA 5 Department of Materials Science, Pennsylvania State University, State College, PA USA 6 Department of Physics, Peking University, Beijing, China

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Jian-Hao Chen

Papers

Electrical Transport in Graphene: Carrier Scattering by Impurities and Phonons

Realization of graphene logics in an exciton-enhanced insulating phase

In situ monitoring of resistivity and carrier concentration during molecular beam epitaxy of topological insulator Bi$_2$Se$_3$

The Superconducting Single Electron Transistor: in situ Variation of the Dissipation

In Situ High Temperature Atomic Resolution Transmission Electron Microscopy of 2D Nanomaterials