Effect of alloying on lattice thermal conductivity of GaO monolayer: A density functional theory study

Abstract

We have investigated the lattice dynamics and the lattice thermal conductivity $\kappa$ of GaO monolayer by first-principle calculations in relaxation time approximation. Replacing one of the Ga atoms with Al or In atoms, we systematically study the effect of alloying on $\kappa$, which largely depends on the atomic masses of alloying atoms. The phonon dynamic calculations show that GaO, InGaO${}_2$, and AlGaO${}_2$ monolayers could be stable. At 300 K, the values of the calculated $\kappa$ are 16.5, 0.38, and 16.1 Wm⁻¹K⁻¹ for GaO, InGaO${}_2$, and AlGaO${}_2$ monolayers, respectively. The cumulative $\kappa$ as a function of frequency shows that the main contribution of thermal conductivity comes from the lower branches of phonon. The lifetime of the GaO monolayer can reach up to 20 ps, which is 10 times longer than the InGaO${}_2$ monolayer. The mean free path of the GaO monolayer can be up to 1500 Å, while it is only 80 Å for the InGaO${}_2$ monolayer. Our studies of thermal properties on GaO, InGaO${}_2$, and AlGaO${}_2$ monolayers may guide the experimental designs of GaO-based thermoelectric devices.