  Defects are inevitably present in materials and always can affect their
properties. Here, first-principles calculations are performed to systematically
study the stability, structural and electronic properties of ten kinds of point
defects in semiconducting phosphorene, including the Stone-Wales (SW-1 and
SW-2) defect, single (SV59 and SV5566) and double vacancy (DV585-1, DV585-2,
DV555777-1, DV555777-2, DV555777-3 and DV4104) defects. We find that these
defects are all much easily created in phosphorene with higher areal density
compared with graphene and silicene. They are easy distinguish each other and
correlate with their defective atomic structures with simulated scanning
tunneling microscopy images at positive bias. The SW, DV585-1, DV555777 and
DV4104 defects have little effect on phosphorene's electronic properties and
defective phosphorene monolayers still show semiconducting with similar band
gap values to perfect phosphorene. The SV59 and DV585-2 defects can introduce
unoccupied localized states into phosphorene's fundamental band gap.
Specifically, the SV59 and 5566 defects can induce hole doping in phosphorene,
and only the stable SV59 defect can result in local magnetic moments in
phosphorene different from all other defects.
