Promising thermoelectric properties and anisotropic electrical and thermal transport of monolayer SnTe

Motivated by the recent experimental synthesis of atomic-thick SnTe [Liu et al., Science 353(6296), 274 2016] exhibiting a layered orthorhombic phase similar to SnSe, we carried out systematic investigations on its electronic, thermoelectric, and phonon transport properties based on a combination of density functional theory and Boltzmann transport theory. Our results indicate that the monolayer is dynamically stable with a band gap of 1.05 eV. A considerable figure of merit (ZT) is predicted to be 2.9 for n-type doping and 2.2 for p-type doping along the armchair direction at a moderate carrier concentration of 1020 cm−3. The electronic band structure and the Fermi surface with multi-valleys lead to band convergence and anisotropic transport behavior. The synergistic optimization of Seebeck coefficient and electrical conductivity is achieved in anisotropic monolayer SnTe, due to the independence of carrier relaxation time and directional effective mass. A maximum power factor of 37 mW/(mK2) can be achieved for the n-type SnTe monolayer along the armchair direction, almost two times as high as that in the zigzag direction. However, the anisotropy of intrinsic lattice thermal conductivity is relatively low and strong phonon anharmonicity is found due to the coexistence of weak bonding and resonant bonding.

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