Thermal Transport Properties of Na2X (X = O and S) Monolayers

Motivated by the excellent functional thin film devices made from two-dimensional materials, we investigated the thermal transport properties of Na2X (X = O and S) monolayers using first-principle calculations. The thermal conductivity at room temperature was 1.055 W/mK and 1.822 W/mK for the Na2O monolayers and Na2S monolayers, respectively. The high thermal conductivity for the Na2S monolayers is mainly contributed to by in-plane transverse acoustic (TA) phonons. The group velocity for the Na2S monolayers exhibits lower group velocity and a larger phonon relaxation time than the Na2O monolayers. Our results are helpful for functional thin film devices made using Na2X (X = O and S) monolayers.