Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A comparative study

TL;DR

This study systematically analyzes phonon transport anisotropy in 2D IV-VI compounds, revealing diverse behaviors and mechanisms, with implications for thermoelectric and thermal management applications.

Contribution

It provides a comprehensive comparison of phonon transport anisotropy in four 2D IV-VI compounds using first-principles calculations and Boltzmann transport equation.

Findings

GeS shows the strongest anisotropy in thermal conductivity.

SnS and SnSe exhibit near isotropic phonon transport.

Nanostructuring can effectively modulate thermal conductivity and anisotropy.

Abstract

New classes two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport property is one of the fundamental physical parameters. In this paper, we systematically investigated the phonon transport properties of 2D orthorhombic group IV-VI compounds of $GeS$, $GeSe$, $SnS$ and $SnSe$ by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite the similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, Young's modulus and lattice thermal conductivity ($\kappa$), etc. Especially, the $\kappa$ along the zigzag and armchair directions of monolayer $GeS$ shows the strongest anisotropy while monolayer $SnS$ and $SnSe$ shows an almost isotropy in phonon transport. The origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in detail. With limited size, the $\kappa$ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications in nanoscale thermoelectrics and thermal management. Our study offers fundamental understanding of the anisotropic phonon transport properties of 2D materials, and would be of significance for further study, modulation and aplications in emerging technologies.