Spontaneous origami in multi-phase 2D phosphorus

Zhen Zhu, Jie Guan, David Tomanek
Physics and Astronomy Department, Michigan State University, East Lansing, MI, United States
Similar to graphitic carbon, phosphorus monolayers, dubbed phosphorene [1], can be exfoliated from layered black phosphorus. Phosphorene is a p-type semiconductor with a significant band gap. It is stable, flexible, and displays a high carrier mobility [1], suggesting its potential use in 2D electronics. Most interesting, based on ab initio density functional calculations, we found that phosphorus can form four different 2D structural phases that are almost equally stable and may be inter-connected. Connection of two planar phases resembles a sharp origami-style fold, displayed in Fig. 1. This fold occurs naturally in this multi-phase system, whereas in single-phase systems like graphene it requires the presence of defect lines or lines of adsorbed atoms. We also find the possibility of moving this fold by structural transformation from one allotrope to another, with an unusually low activation barrier of <0.5 eV per bond. Since the electronic properties of multi-phase phosphorene may also be tuned by in-layer strain, including a semiconductor-to-metal transition, we postulate that origami-style folded phosphorene should display an unprecedented richness in its electronic behavior.

[1] H. Liu et al. ACS Nano 8 (2014)
[2] Z. Zhu and D. Tomanek, Phys. Rev. Lett. (2014)

Figure 1

Structural coexistence in multi-phase phosphorene, illustrated during the conversion of a black phosphorus monolayer (horizontal, brown) to blue phosphorus (diagonal, blue). The 2D layers are normal to the plane of the display.