Ground state structure and physical properties of silicon monoxide sheet

Abstract Two-dimensional (2D) silicon oxides have received considerable attention in recent years because of their excellent compatibility with the well-developed Si-based semiconductor technology. Though the ground state structure of 2D silicon dioxide (SiO2) was identified many years ago, the corresponding study of 2D silicon monoxide (SiO) has not yet been reported. Herein, using global structure search method combined with density functional theory and Boltzmann transport theory, we find the ground state structure of 2D SiO, named Orth-SiO, and systematically study its physical properties. Orth-SiO is found to be thermally, dynamically and mechanically stable, and possesses a direct band gap of 1.52 eV, which is much smaller as compared to that of α-2D silica (7.31 eV). Moreover, it exhibits significant anisotropies in mechanical properties and optical adsorption due to its exceptional atomic configuration. The lattice thermal conductivity of Orth-SiO is 80.45 and 33.79 W/mK along the x and y directions at room temperature, respectively, much higher than that of many Si-based materials due to its weak anharmonicity. In addition, the carrier mobility is 8.5×103 cm2·V-1·s-1, much greater than that of many other oxides. These results add new features to silicon oxides family.