  During the synthesis of ultra-thin materials with hexagonal lattice structure
Stone-Wales (SW) type of defects are quite likely to be formed and the
existence of such topological defects in the graphene-like structures results
in dramatical changes of their electronic and mechanical properties. Here we
investigate the formation and reactivity of such SW defects in silicene. We
report the energy barrier for the formation of SW defects in freestanding (~2.4
eV) and Ag(111)-supported (~2.8 eV) silicene and found it to be significantly
lower than in graphene (~9.2 eV). Moreover, the buckled nature of silicene
provides a large energy barrier for the healing of the SW defect and therefore
defective silicene is stable even at high temperatures. Silicene with SW
defects is semiconducting with a direct bandgap of 0.02 eV and this value
depends on the concentration of defects. Furthermore, nitrogen substitution in
SW defected silicene shows that the defect lattice sites are the least
preferable substitution locations for the N atoms. Our findings show the easy
formation of SW defects in silicene and also provide a guideline for bandgap
engineering in silicene-based materials through such defects.
