Large phosphorene in-plane contraction induced by interlayer interactions in graphene-phosphorene heterostructures

TL;DR

This study reveals significant in-plane contraction of phosphorene in graphene-phosphorene heterostructures due to interlayer interactions, affecting electronic properties and indicating strong substrate effects in 2D material interfaces.

Contribution

It introduces a novel DFT approach to analyze incommensurate heterostructures and uncovers substrate-induced contraction effects in phosphorene.

Findings

Phosphorene contracts by ~4% in the armchair direction within heterostructures.

Electronic properties shift from direct to indirect optical transitions due to contraction.

Aligned crystalline directions are energetically favored in heterostructure stacking.

Abstract

Intralayer deformation in van der Waals (vdW) heterostructures is generally assumed to be negligible due to the weak nature of the interactions between the layers, especially when the interfaces are found incoherent. In the present work, graphene-phosphorene vdW-heterostructures are investigated with the Density Functional Theory (DFT). The challenge of treating nearly incommensurate (very large) supercell in DFT is bypassed by considering different energetic quantities in the grand canonical ensemble, alternative to the formation energy, in order to take into account the mismatch elastic contribution of the different layers. In the investigated heterostructures, it is found that phosphorene contracts by ~4% in the armchair direction when compared to its free-standing form. This large contraction leads to important changes in term of electronic properties, with the direct electronic optical transition of phosphorene becoming indirect in specific vdW-heterostructures. More generally, such a contraction indicates strong substrate effects in supported or encapsulated phosphorene -neglected hitherto- and paves the way to substrate-controlled stress- tronic in such 2D crystal. In addition, the stability of these vdW-heterostructures are investigated as a function of the rotation angle between the layers and as a function of the stacking composition. The alignment of the specific crystalline directions of graphene and phosphorene is found energetically favored. In parallel, several several models based on DFT-estimated quantities are presented; they allow notably a better understanding of the global mutual accommodation of 2D materials in their corresponding interfaces, that is predicted to be non-negligible even in the case of incommensurate interfaces.