An accurate measurement of electron beam induced displacement cross sections for single-layer graphene

We present an accurate measurement and a quantitative analysis of electron-beam induced displacements of carbon atoms in single-layer graphene. We directly measure the atomic displacement ("knock-on") cross section by counting the lost atoms as a function of the electron beam energy and applied dose. Further, we separate knock-on damage (originating from the collision of the beam electrons with the nucleus of the target atom) from other radiation damage mechanisms (e.g. ionization damage or chemical etching) by the comparison of ordinary (12C) and heavy (13C) graphene. Our analysis shows that a static lattice approximation is not sufficient to describe knock-on damage in this material, while a very good agreement between calculated and experimental cross sections is obtained if lattice vibrations are taken into account.Comment: 10 pages including supplementary inf

Defects in bilayer silica and graphene: common trends in diverse hexagonal two-dimensional systems

Peer reviewe

Temperature Relaxation of DC Conductivity of Doped Polypyrrole

score: 0collation: 93-9

Direct transfer of CVD Grown Transparent SWCNT Networks from Growth Substrate to Polymer

Single-wall carbon nanotubes (SWCNTs) are one of the most interesting materials for transparent conductive films. In this work, we show our latest results on growth of transparent nanotube networks on quartz and silicon dioxide, and a new process to make a solid-tosolid direct transfer of these networks on a polycarbonate film to obtain, at room temperature, a conductive transparent material

SWNT probed by multi-frequency EPR and microwave absorption

In addition to g = 2.00 signals seen frequently in EPR spectra of SWNT, signals at g = 2.07 of SWNT prepared by CVD were detected, exhibiting a Pauli susceptibility temperature dependence. This Pauli magnetism in combination with the large g shift is taken as evidence that these signals originate from itinerant electrons of metallic nanotubes. At temperatures below 150 K, a dominant narrow signal develops at g = 2.00. By applying multifrequency EPR up to 319 GHz, its inhomogeneous nature was confirmed. This signal is assigned to defects of the carbon network of the tubes. Comparing room temperature EPR spectra of CVD and arc-grown SWNT, we found a much lower concentration of metallic tubes in arc material. No g = 2.07 signals of itinerant spins could be observed, which might be also caused by the high amount of residing catalyst. A drastic increase in nonresonant microwave absorption is observed below 10 K for both types of samples, if a threshold microwave power level is passed. In the same temperature range a drop in EPR intensity is also detected. These observations are taken as evidence for a transition into a superconducting phase of part of the sample

Conducting and transparent SWNT/polymer composites

Flexible, transparent and conducting poly(methyl methacrylate) (PMMA) composites films were prepared using SOCl2 functionalized SWNTs. Optical absorption spectra measured on composite films confirm that the composite preparation procedure preserves the electronic properties (position of the Fermi level) of the p-doped nanotubes in the polymer matrix. Due to the doping effect of SOCl2 the electrical conductivity of the composites is improved by a factor of 5. The light transmission of the composite films depends on the film thickness and on the nanotube concentration. The optical transmittance of visible light at 500 nm was found to be 92% for 0.1 wt% SWNT loading and 46% for 0.5 wt% SWNT loading. The thickness of the specimens was approximately 20 gm. Conductivity measurement of the thin films performed with the four lead method revealed values 3.5 x 10(-3) S/cm and 4.7 x 10(-1) S/cm, respectively. (c) 2006 WIELEY-VCH Verlag GmbH & Co. KGaA, Weinheim