Influence of dislocations in multilayer graphene stacks: A phase field crystal study

TL;DR

This study uses a phase field crystal model to analyze how dislocations affect the structure and energy of multilayer graphene stacks, revealing out-of-plane deformations, defect energy trends, and layer interactions.

Contribution

It introduces a PFC model for multilayer graphene that accounts for out-of-plane deformations and predicts defect energy saturation across layers.

Findings

Defect free energy increases with layers and size.

Out-of-plane deformations caused by dislocations influence neighboring layers.

Defect energy saturates after about ten layers.

Abstract

In this work the influence of $5|7$ dislocations in multiplayer graphene stacks (up to six layers) is examined. The study is conducted through a recently developed Phase Field Crystal (PFC) model for multilayer systems incorporating out-of-plane deformations and parameterized to match to density functional theory calculations for graphene bilayers and other systems. The specific configuration considered consists of one monolayer containing four $5|7$ dislocations (i.e., two dislocation dipoles) sandwiched in between perfect graphene layers. The study reveals how the strain field from the dislocations in the defected layer leads to out-of-plane deformations that in turn cause deformations of neighboring layers. Quantitative predictions are made for the defect free energy of the multilayer stacks as compared to a defect-free system, which is shown to increase with the number of layers and system size. Furthermore it is predicted that system defect energy saturates by roughly ten sheets in the stack, indicating the range of defect influence across the multilayer. Variations of stress field distribution and layer height profiles in different layer of the stack are also quantitatively identified.