Ropes Of Single-walled Nanotubes Research Articles

A simple method for creating nanotube field emitters from a surfactant dispersion

A new method has been developed for depositing aligned ropes of single-walled nanotubes (SWNTs) such that a significant number of ropes protrude normally from the surface. The resulting surface has excellent field emission characteristics owing to the high local fields generated at the tips of the protruding nanotubes. Further development of the technique may lead to the construction of a reasonably homogeneous surface bristling with nanotube ropes, which could allow spatially resolved neutral atom detection via field ionization.

Superconductivity in entirely end-bonded multi-walled carbon nanotubes

We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature (Tc) as high as 12K, which is approximately 30 times greater than Tc reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end-bonding, can allow superconductivity due to intershell effects.

Superconductivity in Entirely End-Bonded Multi-Walled Carbon Nanotubes

We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) within Tomonaga-Luttinger liquid (TLL) states at high temperatures can show superconductivity with the transition temperature Tc as high as 12K that is approximately 40-times larger than those in ropes of single-walled nanotubes. We find that emergence of this superconductivity is very sensitive to junction structures of Au electrode/MWNTs. This indicates that MWNTs with optimal numbers of electrically activated shells can allow the superconductivity that overcomes the TLL sates, due to intershell effects.

High- Tc superconductivity in entirely end-bonded multi-walled carbon nanotubes

We report that entirely end-bonded multi-walled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature ( T c) as high as 12 K, which is approximately 30 times greater than T c reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end bonding, can allow superconductivity due to intershell effects.

Effects of Interfacial Friction on the Damping Characteristics of Composites Containing Randomly Oriented Carbon Nanotube Ropes

This article presents a model for describing the damping characteristics of uniaxially stressed polymeric composites filled with randomly oriented single-wall nanotube (SWNT) ropes. A close-packed lattice consisting of seven nanotubes in hexagonal array is used to present the nanoropes. The composite is described as a three-phase system composed of a resin, a resin sheath acting as a shear transfer zone, and SWNT ropes. The concept of ‘stick-slip’ motion caused by frictional contacts is proposed to describe the load transfer behavior between individual nanotubes and between a nanotube rope and a sheath. The results of the analytical study show that both the Young’s modulus and the loss factor of the composite are sensitive to stress magnitude. Also, to show the inter-tube sliding effects due to nanotube aggregation, the Young’s moduli and the loss factors of composites filled with aligned SWNTs, aligned nanoropes, and randomly oriented nanoropes are compared.

Superconductivity in Entirely End-Bonded Multiwalled Carbon Nanotubes

We report that entirely end-bonded multiwalled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature (T(c)) as high as 12 K, which is approximately 30 times greater than T(c) reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end bonding, can allow superconductivity due to intershell effects.

A model dielectric response function for metallic nanotube ropes

We propose a model dielectric function for ropes of single-walled nanotubes distributed in a glassy graphite host medium. We study the significance of the bosonic charge excitations arising in interacting quasi-one-dimensional systems in the screening processes. We also pay special attention to the role of the intertube Coulomb interactions. In order to compare with experiments, weak relaxation processes are also considered in the relaxation-time approximation.

Electronic structure of carbon nanotubes

This paper is a review of the theoretical and experimental studies devoted so far to the electronic structure of pure carbon nanotubes, including single-wall, multiwall, and ropes of single-wall nanotubes. A universal picture of the band structure of single-wall nanotubes is obtained by exploiting a particular helical symmetry. A brief description of the optical properties of the nanotubes is also presented. Potential applications of carbon nanotubes in nanoelectronics are described. To cite this article: Ph. Lambin, C. R. Physique 4 (2003).

A geometrical study of single-walled nanotube ropes by transmission electron microscopy

A geometrical study of single-walled nanotube ropes by transmission electron microscopy

A geometrical study of single-walled nanotube ropes by transmission electron microscopy

Carbon and boron nitride nanotubes have been studied by transmission electron microscopy. Comparison between experiments and simulations showed contrasts in the imaging mode, leading to a delicate evaluation of the diameter of the nanotubes ((dis)appearing fringes due to focus versus chirality of ropes of nanotubes) or to a misinterpretation of their real shape which can appear as non-circular. Focus series are thus necessary to estimate the structural parameters of nanotubes once discrepancies that appear between image simulations and experiments are understood. Electron diffraction was also used to determine both the helicity and the diameter of nanotubes; simulations fit the observations very well. In order to simulate the images of the nanotubes, we have developed a program to calculate the atom coordinates. This program is presented here.

Investigation of the inter-tube coupling in single-wall nanotube ropes

We present four terminal measurements of resistance as a function of temperature on ropes of single-wall carbon nanotubes. The ropes were intentionally damaged at the surface before the deposition of the metal electrodes. At low temperatures, this damage blocks the transport through the tubes at the surface by localization and the current path changes to lower lying undamaged tubes inside the rope. The pronounced resistance maximum occurring due to this effect is used to extract the inter-tube coupling resistance using a simple resistance network model. The coupling mechanism is argued to be direct tunneling between the tubes.

Optimized contact configuration for the study of transport phenomena in ropes of single-wall carbon nanotubes

The study of the intrinsic transport properties of carbon nanotubes suffers from the difficulties in fabricating noninvasive contacts. Here, we present a scheme for the investigation of transport phenomena in metallic single-wall carbon nanotubes by means of a special four-terminal measurement configuration. To suppress the impact of the contacts on the measured conductance in a tube, we found a combination of top and bottom contacts to the rope of single-wall nanotubes to be most appropriate. Our experimental findings demonstrate that a linear decrease of the sample resistance can be observed under these circumstances without the common increase of resistance for decreasing temperatures.

Measuring the helicity of carbon nanotubes

Most of the properties of a single-wall nanotube depend on its diameter and, to a less extend, on its chiral angle also called the helicity of the structure. These two parameters, diameter and helicity, completely define the pair of Hamada indices ( n, m) that characterize the atomic structure of a nanotube. The most powerful techniques that may give access to both diameter and helicity are STM and electron diffraction. Both techniques are reviewed in this paper. Emphasis is also given to the characterization of ropes of single-wall nanotubes.

Luttinger Liquid Behavior in Multiwall Carbon Nanotubes

The low-energy theory for multiwall carbon nanotubes including the long-ranged Coulomb interactions, internal screening effects, and single-electron hopping between graphite shells is derived and analyzed by bosonization methods. Characteristic Luttinger liquid power laws are found for the tunneling density of states, with exponents approaching their Fermi liquid value only very slowly as the number of conducting shells increases. With minor modifications, the same conclusions apply to transport in ropes of single-wall nanotubes.

Intermolecular Interaction in Carbon Nanotube Ropes

Using Raman spectroscopy we determined the van-der-Waals component of the low-frequency vibration in ropes of single-walled nanotubes at 171 cmy1. While Raman peaks in this frequency range are commonly believed to correspond to the pure radial breathing mode of a single tube, our pressure and temperature-dependent measurements show that van-der-Waals contribution of the peak observed at 514.5 nm excitation is necessary to explain its large pressure coefficient of 9.7 cmy1/GPa. Our results are consistent with the small elastic modulus predicted for nanotube ropes.

Elastic strain of freely suspended single-wall carbon nanotube ropes

We have induced large elastic strains in ropes of single-wall carbon nanotubes, using an atomic force microscope in lateral force mode. Freely suspended ropes were observed to deform as elastic strings with tension proportional to elongation. Ropes were elastically deformed over >10 cycles without showing signs of plastic deformation. The maximum strain observed, 5.8±0.9%, gives a lower bound of 45±7 GPa for the tensile strength (specifically, yield stress) of single-wall nanotube ropes.

Local Electronic Structure in Ordered Aggregates of Carbon Nanotubes: Scanning Tunneling Microscopy/scanning Tunneling Spectroscopy Study

The recent application of tunneling probes in electronic structure studies of carbon nanotubes has proven both powerful and challenging. Using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS), local electronic properties in ordered aggregates of carbon nanotubes (multiwalled nanotubes and ropes of single walled nanotubes) have been probed. In this report, we present evidence for interlayer (concentric tube) interactions in multiwalled tubes and tube-tube interactions in singlewalled nanotube ropes. The spatially resolved, local electronic structure, as determined by the local density of electronic states, is shown to clearly reflect tube-tube interactions in both of these aggregate forms.

Electronic structure of carbon nanotubes with chiral symmetry

The sigma+pi electron densities of states of chiral carbon nanotubes are computed with a tight-binding Hamiltonian. Our calculations show that the electronic structures of carbon nanotubes with chiral symmetry are similar to the zigzag and armchair ones. The implications of these results on the characterization of single-wall nanotube ropes using resonant Raman experiments are discussed.

Carbon nanotubes: The solar approach

Using the same experimental set-up as for the solar production of fullerenes, we can also produce carbon nanotubes by direct vaporization of a mixture of powdered carbon and catalyst (Co, Ni, Y). The structure of the nanotubes is strongly dependent on the experimental conditions (pressure and flow rate of Ar gas) and we can obtain either multi-walled nanotubes or ropes of single-walled nanotubes.