TY - JOUR

T1 - Cross-plane enhanced thermoelectricity and phonon suppression in graphene/MoS2 van der Waals heterostructures

AU - Sadeghi, Hatef

AU - Sangtarash, Sara

AU - Lambert, Colin J.

N1 - 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

PY - 2016/11/4

Y1 - 2016/11/4

N2 - 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.

AB - 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.

KW - thermoelectric

KW - thermal conductance

KW - molybdenum disulphide MoS2

KW - graphene

KW - figure of merit ZT

U2 - 10.1088/2053-1583/4/1/015012

DO - 10.1088/2053-1583/4/1/015012

M3 - Journal article

VL - 4

JO - 2D Materials

JF - 2D Materials

SN - 2053-1583

IS - 1

M1 - 015012

ER -