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High-Field Electrical Transport in Single-Wall Carbon Nanotubes  [PDF]
Zhen Yao,Charles L. Kane,Cees Dekker
Physics , 1999, DOI: 10.1103/PhysRevLett.84.2941
Abstract: Using low-resistance electrical contacts, we have measured the intrinsic high-field transport properties of metallic single-wall carbon nanotubes. Individual nanotubes appear to be able to carry currents with a density exceeding 10^9 A/cm^2. As the bias voltage is increased, the conductance drops dramatically due to scattering of electrons. We show that the current-voltage characteristics can be explained by considering optical or zone-boundary phonon emission as the dominant scattering mechanism at high field.
The effect of oxidation on structural and electrical properties of single wall carbon nanotubes  [PDF]
Markovi? Zoran M.,Peru?ko Davor B.,To?i? Dragana D.,Rom?evi? Neboj?a Z.
Hemijska Industrija , 2011, DOI: 10.2298/hemind110221024m
Abstract: Single wall carbon nanotubes (SWCNTs) represent an important group of nanomaterials with attractive electrical, chemical, and mechanical properties. In this work we have investigated the structural, optical and electrical properties of single wall carbon nanotube films deposited on copper substrate and then transferred to polymethyl methacrylate (PMMA). The properties of deposited films were varied by changing different parameters: substrate temperature, deposition time and electric field strength. Atomic force microscopy (AFM) has been used to study the deposition process of SWCNT films on copper substrate. AFM analysis has shown that sodium dodecyl sulfate (SDS) micellas were deposited on copper substrate before carbon nanotubes because of their higher mobility. Raman spectroscopy revealed that SWCNTs deposited at elevated temperatures are oxidized. FTIR results showed that COOH groups and Cu2O were generated during electrophoretic process. The SWCNT films were transferred to PMMA substrate and they achieved a sheet resistance of 360 Ω/sq with 79% transparency at 550 nm wavelength and a strong adhesion to the substrate. The main reasons for higher values of sheet resistances of SWCNT thin films compared to those of other authors are oxidation of carbon nanotubes during electrophoresis and the presence of used surfactans in carbon matrix of deposited films.
Electrical and Thermal Transport in Metallic Single-Wall Carbon Nanotubes on Insulating Substrates  [PDF]
Eric Pop,David Mann,Kenneth Goodson,Hongjie Dai
Physics , 2006, DOI: 10.1063/1.2717855
Abstract: We analyze transport in metallic single-wall carbon nanotubes (SWNTs) on insulating substrates over the bias range up to electrical breakdown in air. To account for Joule self-heating, a temperature-dependent Landauer model for electrical transport is coupled with the heat conduction equation along the nanotube. The electrical breakdown voltage of SWNTs in air is found to scale linearly with their length, approximately as 5 V/um; we use this to deduce a thermal conductance between SWNT and substrate g ~ 0.17 +/- 0.03 W/K/m per tube length, which appears limited by the SWNT-substrate interface rather than the thermal properties of the substrate itself. We examine the phonon scattering mechanisms limiting electron transport, and find the strong temperature dependence of the optical phonon absorption rate to have a remarkable influence on the electrical resistance of micron-length nanotubes. Further analysis reveals that unlike in typical metals, electrons are responsible for less than 15% of the total thermal conductivity of metallic nanotubes around room temperature, and this contribution decreases at high bias or higher temperatures. For interconnect applications of metallic SWNTs, significant self-heating may be avoided if power densities are limited below 5 uW/um, or if the SWNT-surrounding thermal interface is optimized.
The Role of Electrical and Thermal Contact Resistance for Joule Breakdown of Single-Wall Carbon Nanotubes  [PDF]
Eric Pop
Physics , 2008, DOI: 10.1088/0957-4484/19/29/295202
Abstract: Several data sets of electrical breakdown in air of single-wall carbon nanotubes (SWNTs) on insulating substrates are collected and analyzed. A universal scaling of the Joule breakdown power with nanotube length is found, which appears independent of the insulating substrates used or their thickness. This suggests the thermal resistances at the interface between SWNT and insulator, and between SWNT and electrodes, govern heat sinking from the nanotube. Analytical models for the breakdown power scaling are presented, providing an intuitive, physical understanding of the breakdown process. The electrical and thermal resistance at the electrode contacts limit the breakdown behavior for sub-micron SWNTs, the breakdown power scales linearly with length for microns-long tubes, and a minimum breakdown power (~ 0.05 uW) is observed for the intermediate (~ 0.5 um) length range.
Beneficial effect of multi-wall carbon nanotubes on the graphitization of polyacrylonitrile (PAN) coating  [PDF]
Mária Darányi,Tamás Csesznok,István Sarusi,ákos Kukovecz
Processing and Application of Ceramics , 2010,
Abstract: Polyacrylonitrile (PAN) solutions were deposited on quartz plates by spin coating to yield 2–3 μm thick PAN films. The films were decomposed at 1000°C in N2 atmosphere into electrically conducting carbonaceous coatings. When the precursor solution contained cobalt (0.2 g Co-acetate per 1 g PAN) and/or multi-wall carbon nanotubes (MWCNTs, 2 mg MWCNT per 1 g PAN) the specific electrical resistance of the product film dropped from the original 492 Ω·cm-1 value down to 46 Ω·cm-1. By excluding all other possibilities we came to the conclusion that the beneficial effect of carbon nanotubes is related to their catalytic action in the final graphitization of condensed nitrogen-containing rings into graphitic nanocrystallites.
Localization, Coulomb interactions and electrical heating in single-wall carbon nanotubes/polymer composites  [PDF]
J. M. Benoit,B. Corraze,O. Chauvet
Physics , 2002, DOI: 10.1103/PhysRevB.65.241405
Abstract: Low field and high field transport properties of carbon nanotubes/polymer composites are investigated for different tube fractions. Above the percolation threshold f_c=0.33%, transport is due to hopping of localized charge carriers with a localization length xi=10-30 nm. Coulomb interactions associated with a soft gap Delta_CG=2.5 meV are present at low temperature close to f_c. We argue that it originates from the Coulomb charging energy effect which is partly screened by adjacent bundles. The high field conductivity is described within an electrical heating scheme. All the results suggest that using composites close to the percolation threshold may be a way to access intrinsic properties of the nanotubes by experiments at a macroscopic scale.
Electrical Spin Injection in Multi-Wall carbon NanoTubes with transparent ferromagnetic contacts  [PDF]
S. Sahoo,T. Kontos,C. Sch?nenberger,C. Sürgers
Physics , 2004, DOI: 10.1063/1.1882761
Abstract: We report on electrical spin injection measurements on MWNTs . We use a ferromagnetic alloy Pd$_{1-x}$Ni$_{x}$ with x $\approx$ 0.7 which allows to obtain devices with resistances as low as 5.6 $k\Omega$ at 300 $K$. The yield of device resistances below 100 $k\Omega$, at 300 $K$, is around 50%. We measure at 2 $K$ a hysteretic magneto-resistance due to the magnetization reversal of the ferromagnetic leads. The relative difference between the resistance in the antiparallel (AP) orientation and the parallel (P) orientation is about 2%.
Cast Nanostructured Films of Poly(methyl methacrylate-b-butyl acrylate)/Carbon Nanotubes: Influence of Poly(butyl acrylate) Content on Film Evaporation Rate, Morphology, and Electrical Resistance
F. Soriano-Corral,L. F. Ramos-de Valle,F. J. Enríquez-Medrano,P. A. De León-Martínez,M. L. López-Quintanilla,E. N. Cabrera-álvarez
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/352937
Abstract: Nanocomposites of poly(methyl methacrylate-b-butyl acrylate)/multiwalled carbon nanotubes were prepared from different copolymers synthesized by RITP technique using iodine functionalized poly(methyl methacrylate) as macrochain transfer agent to obtain block copolymers with butyl acrylate as comonomer in a sequential copolymerization. Poly(butyl acrylate) contents of 7, 20, and 30 wt% were attained in each copolymer. These copolymers were used to prepare nanostructured films by casting process, using chloroform as solvent, and carboxyl functionalized MWCNT at 0.4, 0.6, 0.8, 1.0, and 1.2 wt%. During the film preparation, the absolute drying rate () was calculated with respect to the poly(butyl acrylate) and MWCNT composition. For copolymers containing 7 and 20 wt% of poly(butyl acrylate) the values slightly decrease with the MWCNT concentration, while for the suspension prepared with the copolymer at 30 wt% of poly(butyl acrylate) the values decrease drastically down to 50% approximately. The MWCNT content at the percolation threshold point was found to be 0.8 wt%, for all nanostructured films. The dispersion of MWCNT within the polymer matrix decreased with increasing the poly(butyl acrylate) composition, but it did not affect the electrical properties, which is assumed to be due to induction of the bridging effect and the MWCNT preference to locate into the poly(methyl methacrylate) phase.
Single wall carbon nanotubes enter cells by endocytosis and not membrane penetration
Peter N Yaron, Brian D Holt, Philip A Short, Mathias L?sche, Mohammad F Islam, Kris Dahl
Journal of Nanobiotechnology , 2011, DOI: 10.1186/1477-3155-9-45
Abstract: SWCNTs localized within fluorescently labeled endosomes, and confocal Raman spectroscopy showed a dramatic reduction in SWCNT uptake into cells at 4°C compared with 37°C. These data suggest energy-dependent endocytosis, as shown previously. We also examined the possibility for non-specific physical penetration of SWCNTs through the plasma membrane. Electrochemical impedance spectroscopy and Langmuir monolayer film balance measurements showed that Pluronic-stabilized SWCNTs associated with membranes but did not possess sufficient insertion energy to penetrate through the membrane. SWCNTs associated with vesicles made from plasma membranes but did not rupture the vesicles.These measurements, combined, demonstrate that Pluronic-stabilized SWCNTs only enter cells via energy-dependent endocytosis, and association of SWCNTs to membrane likely increases uptake.Carbon nanotubes (CNTs) have recently been explored for potential uses in biology and medicine. Their small size, high surface area, inert chemical composition, and unique physical properties have made them extensively investigated for transport of DNA[1], nucleic acids[2], drugs[3], and a variety of other potential therapeutics[4]. Single wall CNTs (SWCNTs) with a 1-2 nm outer diameter have variable length and unique optical and electrical properties[5] desirable for biological applications[6]. Cytotoxicity of SWCNTs depends on SWCNT length, impurities, and dispersion quality (isolated vs. bundles)[7]. SWCNTs dispersed in a biocompatible Pluronic triblock copolymer reorganize sub-cellular structures without inducing cell death[8,9]. To better understand the toxicological effects posed by SWCNTs and to develop SWCNT-related cellular biotechnologies, unambiguous determination of the mechanism of uptake into the cell is essential.Competing hypotheses exist regarding the mechanism by which SWCNTs enter cells: non-specific physical penetration of the cell membrane, endocytosis or both. Numerous studies have imaged CNTs i
Optical microcavity with semiconducting single-wall carbon nanotubes  [PDF]
Etienne Gaufrès,Nicolas Izard,Xavier Le Roux,Sa?d Kazaoui,Delphine Marris-Morini,Eric Cassan,Laurent Vivien
Physics , 2010, DOI: 10.1364/OE.18.005740
Abstract: We report studies of optical Fabry-Perot microcavities based on semiconducting single-wall carbon nanotubes with a quality factor of 160. We experimentally demonstrate a huge photoluminescence signal enhancement by a factor of 30 in comparison with the identical film and by a factor of 180 if compared with a thin film containing non-purified (8,7) nanotubes. Futhermore, the spectral full-width at half-maximum of the photo-induced emission is reduced down to 8 nm with very good directivity at a wavelength of about 1.3 $\mu$m. Such results prove the great potential of carbon nanotubes for photonic applications.
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