Materials with Dirac point are so amazing since the charge carriers are massless and have an effective speed of light. Among the reported two-dimensional silicon allotropes, no one showing such exciting nature was proved experimentally. This fact motivates us to search for other such two-dimensional silicon allotropes. As a result, a new single atomic layer thin silicon allotrope was predicted by employing CALYPSO code in this work. This silicon allotrope is composed of eightmembered rings linked by Si-Si bonds and presents buckling formation. Expectedly, the electronic calculation reveals that there exists Dirac point at Fermi energy level. Furthermore, the ab initio molecular dynamics simulations displays that the original atomic configuration can be remained even at an extremely high temperature of 1000 K. We hope this work can expand the family of single atomic layer thin silicon allotropes with Dirac fermions.

Low-dimensional Si-based semiconductors are unique materials that can both match well with the Si-based electronics and satisfy the demand of miniaturization in modern industry. Owing to the lack of such materials, many researchers put their efforts into this field. In this work, employing a swarm structure search method and density functional theory, we theoretically predict two-dimensional atomically thin mononitrides SiN and GeN, both of which present semiconducting nature. Furthermore study shows that SiN and GeN behave as indirect band gap semiconductors with the gap of 1.75 and 1.20 eV, respectively. The ab initio molecular dynamics calculation tells that both two mononitrides can exist stably even at extremely high temperature of 2000 K. Notably, electron mobilities are evaluated as ∼0.888×10 3 cm 2 V −1 s −1 and ∼0.413×10 3 cm 2 V −1 s −1 for SiN and GeN, respectively. The present work expands the family of low-dimensional Si-based semiconductors.