First-principles study of defects in blue phosphorene

Using first-principles density functional theory calculations, we investigate the energetics and electronic properties of Stone Wales and vacancy defects in blue phosphorene. Among these defects, the Stone Wales defect has the lowest formation energy of 1.49 eV. Single and double vacancy defects have much larger formation energies (2.35 similar to 2.90 eV). All the defects induce mid-gap bands that are relatively flat, which indicates the localized nature of the defect states. Our spin-polarized calculations further show that a single vacancy defect exhibits local magnetic moments (1.0 mu(B)), which can be attributed to the existence of an unpaired electron. Besides, we propose new types of defects with irregular buckling configurations. These new defects have even lower formation energies (1.01 and 1.30 eV). The present work may serve as an important guidance for designing and defect engineering of blue phosphorene-based devices.