Ultralow lattice thermal conductivity and electronic properties of monolayer 1T phase semimetal SiTe2 and SnTe2

Abstract

2H phase (trigonal prismatic D3h) of layered two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted a lot of interests due to the superior electronic and optoelectronic properties. However, flexible electronic devices and thermoelectric performances based on 2H phase have been potentially limited by the strain sensitive electronic band gap and high lattice thermal conductivity (kappa_L). Here, we predict and calculate two 1T (octahedral Oh) phase monolayer telluride materials SnTe2 and SiTe2 with soft mechanics, ultralow kappa_L and electronic properties. The calculated in-plane Young's modulus of monolayer SnTe2 is softer than most of 1T-MX2 compounds. Furthermore, monolayer SiTe2 and SnTe2 also have relatively flexible electronic properties under large biaxial strain, indicating potential flexible electrode materials. Meanwhile, monolayer SiTe2 and SnTe2 both exhibit ultralow \k{appa}_L (2.27 W/mK of SiTe2 and 1.62 W/mK of SnTe2) at room temperature. Considering both acoustic and polar optical phonon scattering of the electronic relaxation time, the figure of merit (ZT) can achieve 0.46 at 600 K and 0.71 at 900 K for monolayer SiTe2 and SnTe2 respectively.