The Critical Role of Substrate in Stabilizing Phosphorene Nanoflake: A Theoretical Exploration

TL;DR

This study uses theoretical simulations to show how substrate interaction strength critically influences the stability of phosphorene nanoflakes, guiding future epitaxial growth methods.

Contribution

It identifies optimal substrate interaction strength (~0.35 eV/P atom) necessary to stabilize phosphorene nanoflakes for epitaxial growth.

Findings

Strong substrate interaction (0.75 eV/P) destabilizes phosphorene.

Weak interaction (0.063 eV/P) fails to stabilize phosphorene.

Moderate interaction (~0.35 eV/P) stabilizes phosphorene nanoflakes.

Abstract

Phosphorene, a new two-dimensional (2D) semiconductor, has received much interest due to its robust direct band gap and high charge mobility. Currently, however, phosphorene can only be produced by mechanical or liquid exfoliation, and it is still a significant challenge to directly epitaxially grow phosphorene, which greatly hinders its mass production and, thus, applications. In epitaxial growth, the stability of nanoscale cluster or flake on a substrate is crucial. Here, we perform ab initio energy optimizations and molecular dynamics simulations to explore the critical role of substrate on the stability of a representative phosphorene flake. Our calculations show that the stability of the phosphorene nanoflake is strongly dependent on the interaction strength between the nanoflake and substrate. Specifically, the strong interaction (0.75 eV/P atom) with Cu(111) substrate breaks up the phosphorene nanoflake, while the weak interaction (0.063 eV/P atom) with h-BN substrate fails to stabilize its 2D structure. Remarkably, we find that a substrate with a moderate interaction (about 0.35 eV/P atom) is able to stabilize the 2D characteristics of the nanoflake on a realistic time scale. Our findings here provide useful guidelines for searching suitable substrates for the directly epitaxial growth of phosphorene.