Predicted XN (X = C, Si, Ge, and Sn) Monolayers with Ultrahigh Carrier Mobility: Potential Photocatalysts for Water Splitting

Using evolutionary search and first-principles methods, we predict new two-dimensional XN (X = C, Si, Ge, Sn) monolayers. They are confirmed to be indirect-gap semiconductors and are stable energetically and dynamically. In particular, the SiN monolayer shows a moderate gap of similar to 2 eV and isotropic mechanical characteristics. The CN monolayer possesses a wide band gap of similar to 6 eV, maximal Young's modulus (similar to 550 N/m), and minimal Poisson's ratio (similar to 0.12). The electron mobility of the SnN monolayer can be as large as similar to 1.55 x 10(4) cm(2)<middle dot>V-1<middle dot>s(-1), exceeding that of previously reported black phosphorene (10(4) cm(2)<middle dot>V-1<middle dot>s(-1)). Besides, the SnN and GeN monolayers also exhibit good light absorptions and excellent catalytic performances in terms of Gibbs free energies. These suggest that the XN (X = C, Si, Ge, or Sn) monolayers have potential applications in nanoelectronic and optoelectronic devices.