Journal
ACS NANO
Volume 5, Issue 5, Pages 3779-3787Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn200114p
Keywords
thermal transport; electronic transport; thermoelectric; graphene; carbon
Categories
Funding
- NSF [DMR 0844082]
- ARO
- ONR
- DOE
- German Research Foundation (DFG) [SPP-1386, CU 44/11-1]
- cluster of excellence of the Free State of Saxony ECEMP-European Center for Emerging Materials and Processes Dresden
- European Social Funds (ESF) in Saxony (research group InnovaSens)
- South Korean Ministry of Education, Science, and Technology [R31-2008-000-10100-0]
- Center for Information Services and High Performance Computing (ZIH) at the TU-Dresden
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The influence of the structural detail and defects on the thermal and electronic transport properties of graphene nanoribbons (GNRs) is explored by molecular dynamics and non-equilibrium Green's function methods. A variety of randomly oriented and distributed defects, single and double vacancies, Stone Wales defects, as well as two types of edge form (armchair and zigzag) and different edge roughnesses are studied for model systems similar in sizes to experiments (>100 nm long and >15 nm wide). We observe substantial reduction in thermal conductivity due to all forms of defects, whereas electrical conductance reveals a peculiar defect-type-dependent response. We find that a 0.1% single vacancy concentration and a 0.23% double vacancy or Stone Wales concentration lead to a drastic reduction in thermal conductivity of GNRs, namely, an 80% reduction from the pristine one of the same width. Edge roughness with an rms value of 7.28 angstrom leads to a similar reduction in thermal conductivity. Randomly distributed bulk vacancies are also found to strongly suppress the ballistic nature of electrons and reduce the conductance by 2 orders of magnitude. However, we have identified that defects close to the edges and relatively small values of edge roughness preserve the quasi-ballistic nature of electronic transport. This presents a route of Independently controlling electrical and thermal transport by Judicious engineering of the defect distribution; we discuss the implications of this for thermoelectric performance.
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