Density functional theory investigation of the electronic structure and thermoelectric properties of layered MoS2, MoSe2 and their mixed-layer compound
“…The effect of layer numbers on the thermoelectric power factor (PF) and ZT product has been predicted theoretically for MoS 2 , MoSe 2 , WS 2 and WSe 2 and the enhancement of ZT product in TMDCs is due to the increased degeneracy of the band edges 9,10 High ZT value close to 1 has been predicted in suspended monolayer and bilayer MoS 2 which is much higher than that of bulk suggests that low dimensionality may be a possible way to enhance the thermoelectric properties [11].By layer mixing or forming heterostructures of different TMDCs thermoelectric performance is enhanced due to increased DOS and reduction of band gap near the Fermi level 12,13 . Theoretical calculation predicted the value of lattice thermal conductivity of monolayer MoS 2 nanoribbon to be 29.2 W/m-K 14 which is higher than previous value of 1.35 W/m-K 15 but matched very well with experimental value of 34.5 W/m-K 16 .…”
Two-dimensional transition metal dichalcogenides show great potential as promising thermoelectric materials due to their lower dimensionality, the unique density of states and
“…The effect of layer numbers on the thermoelectric power factor (PF) and ZT product has been predicted theoretically for MoS 2 , MoSe 2 , WS 2 and WSe 2 and the enhancement of ZT product in TMDCs is due to the increased degeneracy of the band edges 9,10 High ZT value close to 1 has been predicted in suspended monolayer and bilayer MoS 2 which is much higher than that of bulk suggests that low dimensionality may be a possible way to enhance the thermoelectric properties [11].By layer mixing or forming heterostructures of different TMDCs thermoelectric performance is enhanced due to increased DOS and reduction of band gap near the Fermi level 12,13 . Theoretical calculation predicted the value of lattice thermal conductivity of monolayer MoS 2 nanoribbon to be 29.2 W/m-K 14 which is higher than previous value of 1.35 W/m-K 15 but matched very well with experimental value of 34.5 W/m-K 16 .…”
Two-dimensional transition metal dichalcogenides show great potential as promising thermoelectric materials due to their lower dimensionality, the unique density of states and
“…22 It was also suggested that the electrical conductivity and the power factor (PF) of TMDCs can be increased by making hypothetic mixed layer system such as MoS 2 /MoTe 2 or WS 2 /WTe 2 . 23,24 In these studies, they mainly focused on the increase of the electrical conductivity by modifying the band gap using the interlayer interactions. Also, Wickramaratne et al and Huang et al investigated the thermoelectric properties of multilayer TMDCs depending on their thickness by using density functional theory (DFT) calculations 25,26 .…”
We have investigated the valley degeneracy of MoS 2 multilayers and its effect on thermoelectric properties. By modulating the layer thickness and external electric field, the hole valleys at Γ and K points in the highest energy valence band and the electron valleys at K and Σ min points in the lowest energy conduction band are shifted differently. The hole valley degeneracy is observed in MoS 2 monolayer, while that of electron valley is in MoS 2 bilayer and monolayer under the external electric field. By tuning the valley degeneracy, the Seebeck coefficient and electrical conductivity can be separately controlled, and the maximum power factor can be obtained in n-type (p-type) MoS 2 monolayer with (without) the external electric field. We suggest that the transition metal dichalcogenides are good example to investigate the role of valley degeneracy in the thermoelectric and optical properties with the control of interlayer interaction and external electric field strength.
“…It can also be observed from PDoS of HS (Fig. 3 ) that the band gap of HS acquires metallic behavior and hence the Seebeck coefficient of mixed-layer MoS 2 / MoB 2 is smaller than MoS 2 monolayer 61 . Figure 9 Seebeck coefficient (in μ V/K, where μ = 10 −6 ) varying as a function of ( a ) chemical potential μ (in eV) and ( b ) Temperature T(K) of MoS 2 / MoB 2 HS and inset of ( b ) Temperature T(K) of MoS 2 Monolayer.…”
We have performed the density functional theory calculations on heterostructure (HS) of MoS2 and MoB2 monolayers. The aim of this study is to assess the influence of MoB2 on electron transport of adjacent MoS2 layer. In present investigation we predict that the electronic properties of MoS2 monolayer is influenced by 4d-states of Mo in MoB2 monolayer. Whereas, the B atoms of MoB2 and S atoms of MoS2 exhibit overlapping of intermediate atomic orbitals thereby collectively construct the interfacial electronic structure observed to be metallic in nature. From charge density calculations, we have also determine that the charge transfer is taking place at the interface via B-2p and S-3p states. The bonds at the interface are found to be metallic which is also confirmed by adsorption analysis. Thermoelectric performance of this HS is found be in good agreement with available literature. Low Seebeck coefficient and high electrical conductivity further confirms the existence of metallic state of the HS.
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