First-principles study of elastic, thermal and optical properties of a metal-shrouded two-dimensional semiconductor Tl2O

Abstract

In recent years, two-dimensional (2D) metal-clad materials have been attracted much attention due to their unique properties. 2D-Tl2O is a newly discovered two-dimensional cells material with semiconducting properties, both 1T- Tl2O and 2H- Tl2O. In this work, we study the elastic, thermal and optical properties of single-layer 2D-Tl2O based on first-principles calculations. The elastic properties of 1T-Tl2O and 2H-Tl2O are found to be isotropic and have lower in-plane Young's modulus 28.03 N/m and 33.46 N/m respectively, suggesting the flexible nature. By solving the phonon Boltzmann equation, we note that 1T-Tl2O and 2H-Tl2O are the low thermal conductivity materials, and their lattice thermal conductivities at room temperature are 0.49 W/mK and 1.13 W/mK, respectively. It is found that the thermal conductivity is mainly contributed by the acoustic support, but the influence of optical support can not be ignored. The optical properties are obtained using the DFT + RPA method. Its optical absorption and reflection regions are mainly located in the ultraviolet region and have multiple reflection or absorption peaks. In contrast, 2H-Tl2O has the largest energy loss than 1T-Tl2O. Our results will provide a reference to subsequent theoretical and experimental research.