Phonon Transport in Single-Layer Transition Metal Dichalcogenides: a First-Principles Study

TL;DR

This study uses first-principles calculations to analyze phonon transport and thermal conductivity in single-layer transition metal dichalcogenides, revealing high thermal conductivities in certain TMDCs and the impact of phonon bandgaps on heat transfer.

Contribution

It provides a systematic first-principles analysis of phonon transport in eight semiconducting TMDCs, comparing approximation methods and identifying key factors affecting thermal conductivity.

Findings

2H-type TMDCs have thermal conductivities above 50 W/mK at room temperature.

Single-layer WS2 exhibits a very high thermal conductivity of 142 W/mK.

Large phonon bandgap in W-S leads to reduced phonon scattering and longer phonon relaxation times.

Abstract

Two-dimensional transition metal dichalcogenides (TMDCs) are finding promising electronic and optical applications due to their unique properties. In this letter, we systematically study the phonon transport and thermal conductivity of eight semiconducting single-layer TMDCs, MX2 (M=Mo, W, Zr and Hf, X=S and Se), by using the first-principles-driven phonon Boltzmann transport equation approach. The validity of the single-mode relaxation time approximation to predict the thermal conductivity of TMDCs is assessed by comparing the results with the iterative solution of the phonon Boltzmann transport equation. We find that the phononic thermal conductivities of 2H-type TMDCs are above 50 W/mK at room temperature while the thermal conductivity values of the 1T-type TMDCs are much lower, when the size of the sample is 1 {\mu}m. A very high thermal conductivity value of 142 W/mK was found in single-layer WS2. The large atomic weight difference between W and S leads to a very large phonon bandgap which in turn forbids the scattering between acoustic and optical phonon modes and thus resulting in very long phonon relaxation time.