Cross-plane enhanced thermoelectricity and phonon suppression in graphene/MoS2 van der Waals heterostructures

Sadeghi, Hatef and Sangtarash, Sara and Lambert, Colin J. (2016) Cross-plane enhanced thermoelectricity and phonon suppression in graphene/MoS2 van der Waals heterostructures. 2D Materials, 4 (1). ISSN 2053-1583

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Abstract

The thermoelectric figures of merit of pristine two-dimensional materials are predicted to be significantly less than unity, making them uncompetitive as thermoelectric materials. Here we elucidate a new strategy that overcomes this limitation by creating multi-layer nanoribbons of two different materials and allowing thermal and electrical currents to flow perpendicular to their planes. To demonstrate this enhancement of thermoelectric efficiency ZT, we analyse the thermoelectric performance of monolayer molybdenum disulphide (MoS2) sandwiched between two graphene monolayers and demonstrate that the cross-plane (CP) ZT is significantly enhanced compared with the pristine parent materials. For the parent monolayer of MoS2, we find that ZT can be as high as approximately 0.3, whereas monolayer graphene has a negligibly small ZT. In contrast for the graphene/MoS2/graphene heterostructure, we find that the CP ZT can be as large as 2.8. One contribution to this enhancement is a reduction of the thermal conductance of the van der Waals heterostructure compared with the parent materials, caused by a combination of boundary scattering at the MoS2/graphene interface which suppresses the phonons transmission and the lower Debye frequency of monolayer MoS2, which filters phonons from the monolayer graphene. A second contribution is an increase in the electrical conductance and Seebeck coefficient associated with molybdenum atoms at the edges of the nanoribbons.

Item Type: Journal Article
Journal or Publication Title: 2D Materials
Additional Information: This is an author-created, un-copyedited version of an article accepted for publication/published in 2D Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.1088/2053-1583/4/1/015012
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/2200/2210
Subjects:
Departments: Faculty of Science and Technology > Physics
ID Code: 82620
Deposited By: ep_importer_pure
Deposited On: 04 Nov 2016 09:24
Refereed?: Yes
Published?: Published
Last Modified: 21 Oct 2019 00:53
URI: https://eprints.lancs.ac.uk/id/eprint/82620

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