Failure Mechanism of Phosphorene by Nanoindentation

Phosphorene, a new two-dimensional material, has attracted tremendous attention in recent years due to its superior physical and electrical properties. Despite the fact that it may have a strong impact in future flexible electronics, there has been so far little or no atomic-level understanding of the failure process of phosphorene under nanoindentation. Here, we report a systematic study of the deformation and failure mechanism of phosphorene under nanoindentation by using molecular dynamics simulations. Three different regimes of deformation behaviors can be identified. The bump behavior in the first regime is different from that in the graphene and other 2D materials. Our simulations reveal the strong correlation between the normal load and the number of C-P pairs with repulsive force across the contact interface. Furthermore, the failure mechanism does not change with increasing tip size or defect concentration. However, it is found that the failure load decreases by 30% even though the defect concentration is 0.5%. It is rationalized that crack nucleates from the defect located at the contact area and hence the failure load significantly degrades. Our present work provides significant insights into atomic-scale understanding of the mechanical properties and failure mechanisms of phosphorene under nanoindentation.