Role of disorder on transport in boron-doped multiwalled carbon nanotubes

Abstract

Electrical transport measurements on boron-doped multiwalled carbon nanotubes deposited on top of predefined electrode patterns have been performed. The temperature dependence of the conductance reveals through two-point configuration, the appearance of a zero-bias anomaly which was found to be not compatible with the existence of a Luttinger-liquid-like state in the doped multiwalled carbon nanotubes. The experimental findings indicate that, in order to properly interpret the charge transport properties of multiwalled carbon nanotubes, the doping as well as the energy window in which the experiments are performed are crucial points. DOI: 10.1103/PhysRevB.67.041401 PACS number͑s͒: 73.63.Fg, 72.80.Rj, 73.22.Lp Multiwalled carbon nanotubes ͑MWNTs͒, in contrast to single-walled carbon nanotubes ͑SWNTs͒, consist of a number of stacked-in shells and have a diameter typically of tens of nm's which is one order of magnitude larger than for SWNTs. Despite these differences, MWNTs are often regarded as one-dimensional ͑1D͒ systems, with respect to their electronic properties in the same manner as SWNTs. SWNTs are expected to behave as quasi 1D molecular wires with large mean free paths ͓typically 1 m ͑Ref. 1͔͒, so that ballistic charge transport is observable.2-6 As a direct consequence of the 1D-conducting behavior of carbon nanotubes, strong Coulomb interaction effects are expected that imply a breakdown of the Fermi-liquid theory leading to a Luttingerliquid response characterized by a pronounced power-law suppression of the transport current and density of states. 7The situation for MWNTs is more complex. Earlier experiments 8 found evidence of electron scattering and the transport appeared diffusive rather than ballistic. However, experiments done by dipping a MWNT in a liquid metal 5 show ballistic transport and the ability to carry large electrical currents. These observations suggest that the electrons are well decoupled from the underlying lattice, that is, only a weak electron-phonon interaction is apparent, similar to SWNTs.9 At low temperatures several contradictory observations in the electronic transport properties of MWNTs have been made: magnetotransport data could be successfully interpreted by the Altshuler-Aronov-Spivak effect 10 and in the framework of weak-localization theory, 11 which both point toward a disordered electronic state with 2D character at low temperatures. On the other hand a zero-bias anomaly ͑ZBA͒ in the conductance has been reported. 12 This could be interpreted by the existence of a Luttinger-liquid ͑LL͒-like state which requires a 1D electronic system with repulsive interaction between the electrons.In the present work we report on temperature-dependent electronic transport measurements on boron ͑B͒ -doped MWNTs ͑B-MWNTs͒ with approximately 1% B content which were produced by the arc-discharge method. The use of B-MWNTs aims toward the investigation of the intershellcoupling between neighboring shells, dimensionality of the electron system and the degree of disorder introduced...

Electrical transport in carbon nanotubes: Role of disorder and helical symmetries

“…It might happen that the value of approaches 1/2, such that an effective ''diffusivelike'' regime would develop, having implications on Aharonov-Bohm phenomenon. 9,12 Recent experiments 11 have reported on anomalous scaling of conductance in boron-doped MWNT's. In the light of the present study, an important issue would be to investigate the gate-dependent length scaling of conductance, since a gate voltage will induce some shifting of the position of the Fermi level.…”

“…Although ballistic conduction has been reported in several experiments in SWNT's and MWNT's, 3,5,6 the bias dependence of the conductance in MWNT's highlights the possible role of disorder and/or intershell conduction. [7][8][9][10][11] At large bias, the contribution of several subbands is expected, with an enhanced backscattering for the so-called massive subbands, as compared to the two massless subbands crossing at the CNP. 3 On the other hand, it has been argued theoretically that incommensurability between coupled shells can drive conduction to either diffusive, ballistic, or intermediate transport regime.…”

Intershell resistance in multiwall carbon nanotubes: A Coulomb drag study

“…17,18 Another interesting feature of carbon nanotubes is their one-dimensional nature, which may have profound consequences on the basic physical phenomenology for their description: SWCNT's have been predicted to be Luttinger liquids 19,20 and some experimental evidence exists 21,22 even though other interpretations have been suggested. 23 Whether MWCNT's are Fermi or Luttinger liquids has been investigated extensively experimentally [24][25][26] and theoretically 27 and seems to depend on the situation, but is still subject to debate. Also in ropes the situation is not clear yet.…”

Tunneling spectroscopy of disordered multiwalled carbon nanotubes

“…16 In metallic systems the perturbative treatment is found sufficient, 17 but disordered nanotubes allow one to reach the non-perturbative range experimentally. Measurements on boron-doped multiwalled nanotubes 18 and bulk multiwalled nanotube samples 19 showed deviations from the power law, pointing that this anomaly is relevant in disordered samples. Here we present observations and analysis of this type of behavior in individual disordered multiwalled nanotubes.…”