Two-Dimensional Gold Sulfide Monolayers with Direct Band Gap and Ultrahigh Electron Mobility

It remains a pressing task to search for new two-dimensional (2D) semiconducting materials for future-generation electronic applications. By using density functional theory computations and global structure prediction methods, we demonstrate two new gold sulfide monolayers (2D Au₂S and AuS), both exhibiting excellent electronic properties and high stabilities. All the gold sulfide monolayers are semiconductors with band gaps in the range 1.0-3.6 eV. In particular, the α-Au₂S monolayer is predicted to possess a direct band gap of 1.0 eV and extremely high electron and hole mobilities of 8.45 × 10⁴ and 0.40 × 10⁴ cm² V^-1 S^-1, respectively. The phonon dispersion calculations and ab initio molecular dynamics simulations indicate that the gold sulfide monolayers exhibit robust dynamical and thermal stabilities. Moreover, the α-Au₂S monolayer appears to show strong oxidation resistibility. The novel electronic properties, coupled with structural and chemical stabilities, endow the new gold sulfide monolayers to be highly promising for future applications in nanoelectronics.