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