Oxygen Defects in Phosphorene

Surface reactions with oxygen are a fundamental cause of the degradation of phosphorene. Using first-principles calculations, we show that for each oxygen atom adsorbed onto phosphorene there is an energy release of about 2 eV. Although the most stable oxygen adsorbed forms are electrically inactive and lead only to minor distortions of the lattice, there are low energy metastable forms which introduce deep donor and/or acceptor levels in the gap. We also propose a mechanism for phosphorene oxidation involving reactive dangling oxygen atoms and we suggest that dangling oxygen atoms increase the hydrophilicity of phosphorene.

Figure 1

Dangling oxygen: (a) projections of the structure; (b) electronic band structure (left) and DOS (right). The top of the valence band is set to zero. The band structure of pristine phosphorene is provided in the Supplemental Material [19].

Figure 2

Interstitial oxygen: (a) projections of the structure; (b) electronic band structure (left) and DOS (right). The top of the valence band is set to zero.

Figure 3

Horizontal oxygen bridge: (a) projections of the structure; (b) electronic band structure (left) and DOS (right). The top of the valence band is set to zero.

Figure 4

Possible configurations for two chemisorbed dangling oxygens.

Figure 5

Schematic configuration-coordinate diagram for possible mechanisms for phosphorene oxidation. The solid (dotted) lines indicate the PESs calculated with fixed (variable) total magnetization. Singlet (black) and triplet (red) PESs as a function of the ${\mathrm{O}}_2$-phosphorene distance are shown in the inset.