Electronic and thermoelectric properties of few-layer transition metal dichalcogenides

Darshana Wickramaratne; Ferdows Zahid; Roger K Lake

doi:10.1063/1.4869142

Electronic and thermoelectric properties of few-layer transition metal dichalcogenides

J Chem Phys. 2014 Mar 28;140(12):124710. doi: 10.1063/1.4869142.

Authors

Darshana Wickramaratne¹, Ferdows Zahid², Roger K Lake¹

Affiliations

¹ Department of Electrical Engineering, University of California, Riverside, California 92521-0204, USA.
² Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.

PMID: 24697473
DOI: 10.1063/1.4869142

Abstract

The electronic and thermoelectric properties of one to four monolayers of MoS2, MoSe2, WS2, and WSe2 are calculated. For few layer thicknesses, the near degeneracies of the conduction band K and Σ valleys and the valence band Γ and K valleys enhance the n-type and p-type thermoelectric performance. The interlayer hybridization and energy level splitting determine how the number of modes within kBT of a valley minimum changes with layer thickness. In all cases, the maximum ZT coincides with the greatest near-degeneracy within kBT of the band edge that results in the sharpest turn-on of the density of modes. The thickness at which this maximum occurs is, in general, not a monolayer. The transition from few layers to bulk is discussed. Effective masses, energy gaps, power-factors, and ZT values are tabulated for all materials and layer thicknesses.