Karamitaheri, Hossein and Neophytou, Neophytos (2016) On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons. Applied Physics Letters, 109 (6). 063102. doi:10.1063/1.4960528 ISSN 0003-6951.

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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 Wβ. Although in the case of electronic transport, this dependency is very well studied, resulting in W 6 for nanowires and quantum wells and W 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 Wβ 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.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Engineering > Engineering
Journal or Publication Title:	Applied Physics Letters
Publisher:	American Institute of Physics
ISSN:	0003-6951
Official Date:	8 August 2016
Dates:	Date Event 8 August 2016 Published 26 July 2016 Accepted 29 March 2016 Submitted
Volume:	109
Number:	6
Article Number:	063102
DOI:	10.1063/1.4960528
Status:	Peer Reviewed
Publication Status:	Published
Date of first compliant deposit:	30 August 2016
Date of first compliant Open Access:	30 August 2016

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