S. Roth

Bio: S. Roth is an academic researcher from Max Planck Society. The author has contributed to research in topics: Carbon nanotube & Polyacetylene. The author has an hindex of 44, co-authored 281 publications receiving 25195 citations.

Photoinduced Absorption in Poly(p-phenylene vinylene)

Abstract: In this paper we report the results of preliminary investigations of photoinduced absorption in the non-degenerate ground state conjugated polymer poly(p-phenylene vinylene) [PPV]. We present photoinduced spectra for both electronic and vibrational transitions which closely resemble the corresponding spectra observed following charge-transfer doping. The photogenerated charged defects are identified as bipolarons.

Electrical transport through carbon nanotube junction

Abstract: Metal-Semiconductor crossed carbon nanotube junction was prepared by adsorption of carbon nanotubes on Si/SiO2 substrate with predefined electrode contacts. The Schottky barrier was formed in the contact region due to the charge transfer from the metallic tube to semiconducting tube. The charge transport was strongly modified by the formation of barrier, leading to pronounced rectifying behavior. The results were modeled using conventional thermoionic emission theory. The ideality factor in diode is 5.8 eV at room temperature and increases as raising operating temperature.

Local Structure in Halogen-Doped Polyacetylene from X-Ray Absorption Spectroscopy

Abstract: Despite of extensive investigations in the last few years, the structural properties of acceptor-doped polyacetylene are still in the midpoint of current debate /l/. This is due to the fact that the doping process leads to drastic changes of the relatively well-known structure of pristine (CH)x accompanied by a loss of long-range coherence and crystallinity. This limits the application of standard X-ray and neutron diffraction techniques. It has recently been demonstrated for the case of (CHBry)x that X-ray absorption (XA) studies can provide detailed information about the chemical form and local structure of the doped species /2,3/. In this contribution, we report on an extension of these studies to other halogen molecules used as dopants of (CH)x. We demonstrate that both the near-edge structure and the extended fine-structure of the XA spectra (called NEXAFS and EXAFS, respectively) yield a variety of information about the doping process and the orientation of the inserted halogen (poly-)anions with respect to the (CH)x chains. Stretch-oriented (CH)x samples, which represent quasi-one dimensional systems, were used in all investigations. This allows us to exploit the linear polarization of the synchrotron radiation (SR) in performing XA studies which are comparable with optical polarizer/analyser experiments.

Suppression of superconductor quasiparticle tunneling into single-walled carbon nanotubes

Abstract: Electrical transport through single-walled carbon nanotubes with weak electrical coupling to superconducting leads has been studied theoretically and experimentally. A simple model is considered to describe single-particle tunneling into a Luttinger-liquid-like state from electrically weak connected superconducting electrodes. This involves the superconductor's quasiparticle and the Luttinger liquid's excitation density of states. Experimentally, the suppression of quasiparticle tunneling induced current peaks was observed at temperatures below 0.1 K, which we attributed to the Luttinger-liquid-like excitation spectrum of the single-walled carbon nanotube.

The rise of graphene

Abstract: 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 electronic properties of graphene

Abstract: 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.

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

Abstract: 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。

Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Abstract: 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.

Graphene: Status and Prospects

Abstract: 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.