Ballistic Conduction in Multiwalled Carbon Nanotubes

Abstract

The electrical transport in multiwalled carbon nanotubes is shown to be ballistic at room temperature with mean free paths on the order of tens of microns. The measurements are performed both in air and in the transmission electron microscope by contacting the free end of a nanotube pointing out of a fiber to a liquid metal and measuring the dependence of the nanotube resistance between the contacts. For a specific representative nanotube the resistance per unit length is found to be Rt = 31 +/- 61 omega/micron and the contact resistance with the liquid metal, Rc = 165 +/- 55 omega microns, corresponding to a mean free path l = 200 microns. Current-to-voltage characteristics are in accord with the electronic structure. The nanotubes survive high currents (up to 1 mA, i.e., current density on the order of 10(9) A/cm2). In situ electron microscopy shows that a relatively large fraction of the nanotubes do not conduct (even at high bias), consistent with the existence of semiconducting nanotubes. Discrepancies with other measurements are most likely due to damage caused to the outer layer(s) of the nanotubes during processing. The measured mean free path of clean, undamaged arc-produced multiwalled carbon nanotubes is several orders of magnitude greater than that for metals, making this perhaps the most significant property of carbon nanotubes.

Electrochemistry and Photocurrent Response from Vertically-Aligned Chemically-Functionalized Single-Walled Carbon Nanotube Arrays

“…Due to their high degree of electron delocalization and high aspect ratio, electrons can exhibit ballistic conduction. 10 Carbon nanotubes that have been modified by photosensitive molecules have been studied with increasing frequency due to their application in optoelectronic devices. [11][12][13][14][15][16][17][18] In most cases it is the same Grätzel cell design but with CNTs mixed in with the TiO 2 to modify their electrical properties, such as decreased resistivity within the TiO 2 layer leading to a markedly increased photocurrent ͑J sc ͒ but a slightly decreased fill factor ͑ff͒ and voltage ͑V oc ͒.…”

The Effect of Hydrogen Content on Ballistic Transport Behaviors in the Ni-Nb-Zr-H Glassy Alloys

“…This superior conducting behavior resembles the ballistic transport observed in one-dimensional, nanometer-scale channels, such as quantum wires [6], carbon nanotubes [7,8] and GaAs-AlGaAs [9] at low temperature, in the form of quantum interference associated with coherence. The ballistic electron transport effect is promising for future electron devices and electric power applications such as lower supply voltage and leading to low power consumption.…”

The effect of degree of amorphousness on electronic transport behaviors in the Ni–Nb–Zr–H glassy alloys with subnanometer-sized clusters

“…The chaotic motion in the reflection component S 11 (n) is stagnant around the narrow torus for a superlattice with a cluster size of 0.55 nm and a boundary distance of 0.23 nm, rather than exhibiting global chaos in a strong electric field, showing macroscopic resonant tunneling is prevalent and produces an ensemble of electrons through multi-barriers. Berger et al [30] have reported that the mean free path for ballistic electron transport through multiwalled carbon nanotubes is of the order of tens of microns and several orders of magnitude greater than that for metals at room temperature. Thus we can assume that the increase in degree of amorphousness helps uniformity of cluster morphology, resulting in enhancement of superior ballistic transport.…”