Kinetically Determined Shapes of Grain Boundaries in Graphene.

Abstract

A large-scale chemical synthesis of graphene produces a polycrystalline material with grain boundaries (GBs) that disturb the lattice structure and drastically affect material properties. An uncontrollable formation of GB can be detrimental, yet precise GB engineering can impart added functionalities onto graphene-and its noncarbon two-dimensional "cousins." While the importance of growth kinetics in shaping single-crystalline graphene islands has lately been appreciated, kinetics' role in determining a GB structure remains unaddressed. Here we report on the analysis of the GB formation as captured by kinetic Monte Carlo simulations in contrast with global minimum guided GB structures considered previously. We identified a key parameter-edge misorientation angle-that describes the initial geometry of merging grains and unambiguously defines the resulting GB structure, while a commonly used lattice tilt angle corresponds to several qualitatively different GB structures. A provided systematic analysis of GB structures formed from a full range of edge misorientation angles reveals conditions that result in straight and periodic GBs as well as conditions responsible for meandering and disordered GBs. Additionally, we address the special case of translational GBs, where lattices of merging grains are aligned but shifted compared to each other. Collected data can be used for deliberate GB structural engineering, for example, by a three-dimensional patterning of the substrate surface to introduce disclinations creating a graphene lattice tilt.