Structures, mobilities, electronic and magnetic properties of point defects in silicene.

In the fabrication and processing of silicene monolayers, structural defects are almost inevitable. Using ab initio calculations, we systemically investigated the structures, formation energies, migration behaviors and electronic/magnetic properties of typical point defects in silicene, including the Stone-Wales (SW) defect, single and double vacancies (SVs and DVs), and adatoms. We found that SW can be effectively recovered by thermal annealing. SVs have much higher mobility than DVs and two SVs are very likely to coalesce into one DV to lower the energy. Existence of SW and DVs may induce small gaps in silicene, while the SV defect may transform semimetallic silicene into metallic. Adatoms are unexpectedly stable and can affect the electronic properties of silicene dramatically. Especially, Si adatoms as self-dopants in silicene sheets can induce long-range spin polarization as well as a remarkable band gap, thus achieving an all-silicon magnetic semiconductor. The present theoretical results provide valuable insights into identification of these defects in experiments and understanding their effects on the physical properties of silicene.