Search results for "Ballistic conduction in single-walled carbon nanotubes"
showing 6 items of 6 documents
The diffusion of carbon atoms inside carbon nanotubes
2008
We combine electron irradiation experiments in a transmission electron microscope with kinetic Monte Carlo simulations to determine the mobility of interstitial carbon atoms in single-walled carbon nanotubes. We measure the irradiation dose necessary to cut nanotubes repeatedly with a focused electron beam as a function of the separation between the cuts and at different temperatures. As the cutting speed is related to the migration of displaced carbon atoms trapped inside the tube and to their recombination with vacancies, we obtain information about the mobility of the trapped atoms and estimate their migration barrier to be about 0.25 eV. This is an experimental confirmation of the remar…
Measurements of tunneling conduction to carbon nanotubes and its sensitivity to oxygen gas
2012
We have measured the conductive properties of junctions between carbon nanotubes (CNT) and non-noble metals $M$ ($M$ = Al, Ti, Nb), which are separated by the native oxide (${M}_{\mathit{OX}}$) of the metal. Reproducible and asymmetric current-voltage characteristics were obtained from Ti/Ti${}_{\mathit{OX}}$/CNT and Nb/Nb${}_{\mathit{OX}}$/CNT junctions, while Al/Al${}_{\mathit{OX}}$/CNT exhibited no current until breakdown, which is attributed to the larger bandgap of Al${}_{\mathit{OX}}$. The conduction in the Ti- and Nb-based junctions is not due to direct tunneling since they exhibit strong temperature dependence. The presence of oxygen is shown to drastically, but reversibly, modify t…
Electrical conductance of carbon nanotubes with misaligned ends
2013
During a manufacturing process, when a straight carbon nanotube is placed on a substrate, e.g., production of transistors, its two ends are often misaligned. In this study, we investigate the effects of multiwall carbon nanotubes’ (MWCNTs) outer diameter and chirality on the change in conductance due to misalignment of the two ends. The length of the studied MWCNTs was 120 nm, while the diameters ranged between 4 and 7 nm. A mixed finite element-tight-binding approach was carefully designed to realize reduction in computational time by orders of magnitude in calculating the deformation-induced changes in the electrical transport properties of the nanotubes. Numerical results suggest that ar…
Carbon nanotubes under electron irradiation: Stability of the tubes and their action as pipes for atom transport
2005
The production and migration of carbon interstitials in carbon nanotubes under electron irradiation is studied experimentally and theoretically. It is shown that the threshold for displacing carbon atoms and the defect production rate strongly depend on the diameter of the nanotubes. Multiwalled nanotubes shrink by a loss of atoms and by diffusion of interstitials through the inner hollow in the axial direction. Thus, experimental evidence is given that nanotubes can act as nanoscale pipes for the transport of atoms.
Quantum Transport and Current Distribution at Radio Frequency in Multiwall Carbon Nanotubes
2012
Multiwall carbon nanotubes represent a low-dimensional material that could serve as building blocks for future carbon-based nanoelectronics. The understanding of the electromagnetic performances at radio frequency of these materials for use in nanointerconnects is strictly related to the analysis of their transport properties as function of the working conditions. In this paper, we present an explicit expression of the conducting channels as function of diameter, temperature, doping, and supply voltage for both metallic and semiconducting carbon nanotubes. The proposed formula is based on the Dirac cone approximation of the conducting band energy of graphene nearby the Fermi points, combine…
Dependence of Exciton Mobility on Structure in Single-Walled Carbon Nanotubes
2010
Optically generated excitons in semiconducting single-walled carbon nanotubes (SWCNTs) display substantial diffusional mobility. This property allows excitons to encounter ∼104 carbon atoms during their lifetime and accounts for their efficient deactivation by sparse quenching sites. We report here experimental determinations of the mobilities of optically generated excitons in 10 different (n,m) species of semiconducting SWCNTs. Exciton diffusional ranges were deduced from measurements of stepwise photoluminescence quenching in selected individual SWCNTs coated with sodium deoxycholate surfactant and immobilized in agarose gel. A refined data analysis method deduced mean exciton ranges fro…