Oxidized Silicon Sulfide: Stability and Electronic Properties of a Novel Two-Dimensional Material

The monolayer form of oxidized silicon sulfide (SiSO) structures are predicted and the stability and electronic properties are investigated by ab initio density functional calculations. The most stable configurations of isolated oxygen impurities for four different two-dimensional (2D) SiS structures are determined and all the calculated binding energies are found larger than those for phosphorene, due to the lower electronegativity of Si atoms. Four 2D stoichiometric SiSO structures corresponding to the most stable oxidation configurations are predicted and 2D \alpha-SiSO is demonstrated to be stable by phonon spectra calculations and ab initio molecular dynamics simulations. Electronic structure calculations indicate that \alpha-SiSO monolayer is semiconducting with a direct band gap, which can be effectively tuned by uniaxial in-layer strain. The value of band gap and thermodynamic stability are found depending sensitively on the degree of oxidation.