Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The rise of graphene

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

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

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Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.

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Graphene: Status and Prospects

In the present work, we use Raman spectroscopy as sensitive tool for the characterization of graphene samples. We observed diverse shifts in the position of the Raman mode close to 2650 cm -1 in various as-prepared graphene flakes. In order to elucidate the reason for this variation, we checked different substrates (Si/SiO 2 and Si/Al 2 O 3 ) and the effect of the annealing of graphene in argon. We find that most of as-prepared graphene flakes were non-intentional doped by holes, i.e. by physisorbed water and/or oxygen.

Investigation of the shift of Raman modes of graphene flakes

The potential application of carbon nanotubes ~CNT’s ! as molecular wires in submicron devices has initiated a variety of conductance experiments. Phenomena like Coulomb blockade 1,2 and signatures of Luttinger liquids 3 in singlewalled carbon nanotubes ~SWCNT’s!, as well as Aharanov‐ Bohm oscillations, 4 quantized conductance and quasiballistic transport at room temperature ~RT! in multiwalled carbon nanotubes ~MWCNT’s! were reported. 5 Except for the observations of Coulomb blockade, a low contact resistance between leads and the CNT is required in such experiments. In the present study, electron-beam lithography ~EBL! was used to contact SWCNT’s with electrodes on top, similar to Ref. 3. Electrode arrays consisting of three equidistant stripes were prepared from AuPd ~40 wt %/60 wt %!. The electrical transport investigations at room temperature presented here focus on samples with SWCNT bundles, which are connected by three low-Ohmic contacts, in contrast to recent measurements with only two contacts. 3,6 For sample preparation, 7 arc-discharge SWCNT raw material was dispersed by ultrasonic treatment in aqueous surfactant solution, and purified by centrifugation. As substrate, an As doped Si wafer with a thermally grown SiO2 layer was used. Before adsorption of the SWCNT’s, the substrate was treated with a 0.1 wt % aqueous solution of 3-~aminopropyl!triethoxysilane for 2 min. In order to perform EBL ~EBL 100 system, LEICA! on top of the SWCNT’s, a two-layer resist system was used. 2 After EBL, AuPd ~thickness ’17 nm! or Au ~thickness ’24 nm! was thermally evaporated on the substrate at a base pressure of p’10 27 mbar using a rate of 1 A/s.

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S. Roth

Papers

Investigation of the shift of Raman modes of graphene flakes

Phase breaking in three-terminal contacted single-walled carbon nanotube bundles

Picosecond spectroscopy and hyperlinear photoluminescence in poly(para-phenylene)-type ladder polymers

Spatial variations in the electronic structure of pure and B-doped nanotubes

The orientational phase transition in C60 films followed by infrared spectroscopy