Strong phonon anharmonicity and low thermal conductivity of monolayer tin oxides driven by lone-pair electrons

TL;DR

This study uses first-principles calculations to reveal that monolayer tin oxides have low thermal conductivity due to strong phonon anharmonicity driven by lone-pair electrons, with implications for thermoelectric applications.

Contribution

It is the first systematic investigation of thermal conductivity in monolayer SnO and SnO2, highlighting the role of lone-pair electrons in phonon anharmonicity.

Findings

Monolayer SnO has a thermal conductivity of 9.6 W/(mK).

Monolayer SnO2 has a thermal conductivity of 98.8 W/(mK).

Lone-pair Sn-5s electrons are key to low thermal conductivity in SnO.

Abstract

Motivated by the excellent electronic and optoelectronic properties of two-dimensional (2D) tin oxides, we systematically investigated the thermal conductivity of monolayer SnO and SnO2by the first-principles calculations. The room-temperature thermal conductivity of monolayer SnO and SnO2reaches 9.6 W/(mK) and 98.8 W/(mK), respectively. The size effect is much weaker for monolayer SnO than for monolayer SnO2, due to the coexistence of size dependent and independent component in the thermal conductivity of monolayer SnO. The large difference between the thermal conductivity of 2D tin oxides can be attributed to the small phonon group velocity and strong anharmonicity strength of monolayer SnO. Further electronic structure analysis reveals that the existence of lone-pair Sn-5s electrons is the key factor for the small \k{appa} of monolayer SnO. These results provide a guide for the manipulation of thermal transport in the electronic or thermoelectric devices based on 2D tin oxides.