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Title: On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons

Abstract

The thermal conductivity of low-dimensional materials and graphene nanoribbons, in particular, is limited by the strength of line-edge-roughness scattering. One way to characterize the roughness strength is the dependency of the thermal conductivity on the channel's width in the form W{sup β}. Although in the case of electronic transport, this dependency is very well studied, resulting in W{sup 6} for nanowires and quantum wells and W{sup 4} for nanoribbons, in the case of phonon transport it is not yet clear what this dependence is. In this work, using lattice dynamics and Non-Equilibrium Green's Function simulations, we examine the width dependence of the thermal conductivity of ultra-narrow graphene nanoribbons under the influence of line edge-roughness. We show that the exponent β is in fact not a single well-defined number, but it is different for different parts of the phonon spectrum depending on whether phonon transport is ballistic, diffusive, or localized. The exponent β takes values β < 1 for semi-ballistic phonon transport, values β ≫ 1 for sub-diffusive or localized phonons, and β = 1 only in the case where the transport is diffusive. The overall W{sup β} dependence of the thermal conductivity is determined by the width-dependence of the dominant phonon modes (usually themore » acoustic ones). We show that due to the long phonon mean-free-paths, the width-dependence of thermal conductivity becomes a channel length dependent property, because the channel length determines whether transport is ballistic, diffusive, or localized.« less

Authors:
 [1];  [2]
  1. Department of Electrical Engineering, University of Kashan, Kashan 87317-53153 (Iran, Islamic Republic of)
  2. School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom)
Publication Date:
OSTI Identifier:
22594357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COMPUTERIZED SIMULATION; EQUILIBRIUM; GRAPHENE; GREEN FUNCTION; LENGTH; MEAN FREE PATH; NANOWIRES; PHONONS; QUANTUM WELLS; ROUGHNESS; SCATTERING; SPECTRA; THERMAL CONDUCTIVITY; TRANSPORT THEORY; WIDTH

Citation Formats

Karamitaheri, Hossein, and Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk. On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons. United States: N. p., 2016. Web. doi:10.1063/1.4960528.
Karamitaheri, Hossein, & Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk. On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons. United States. doi:10.1063/1.4960528.
Karamitaheri, Hossein, and Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk. Mon . "On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons". United States. doi:10.1063/1.4960528.
@article{osti_22594357,
title = {On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons},
author = {Karamitaheri, Hossein and Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk},
abstractNote = {The thermal conductivity of low-dimensional materials and graphene nanoribbons, in particular, is limited by the strength of line-edge-roughness scattering. One way to characterize the roughness strength is the dependency of the thermal conductivity on the channel's width in the form W{sup β}. Although in the case of electronic transport, this dependency is very well studied, resulting in W{sup 6} for nanowires and quantum wells and W{sup 4} for nanoribbons, in the case of phonon transport it is not yet clear what this dependence is. In this work, using lattice dynamics and Non-Equilibrium Green's Function simulations, we examine the width dependence of the thermal conductivity of ultra-narrow graphene nanoribbons under the influence of line edge-roughness. We show that the exponent β is in fact not a single well-defined number, but it is different for different parts of the phonon spectrum depending on whether phonon transport is ballistic, diffusive, or localized. The exponent β takes values β < 1 for semi-ballistic phonon transport, values β ≫ 1 for sub-diffusive or localized phonons, and β = 1 only in the case where the transport is diffusive. The overall W{sup β} dependence of the thermal conductivity is determined by the width-dependence of the dominant phonon modes (usually the acoustic ones). We show that due to the long phonon mean-free-paths, the width-dependence of thermal conductivity becomes a channel length dependent property, because the channel length determines whether transport is ballistic, diffusive, or localized.},
doi = {10.1063/1.4960528},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = {Mon Aug 08 00:00:00 EDT 2016},
month = {Mon Aug 08 00:00:00 EDT 2016}
}