title: In Situ Atomic Level Dynamics of Heterogeneous Nucleation and Growth of Graphene from Inorganic Nanoparticle Seeds.
abstract: An in situ heating holder inside an aberration-corrected transmission electron microscope (AC-TEM) is used to investigate the real-time atomic level dynamics associated with heterogeneous nucleation and growth of graphene from Au nanoparticle seeds. Heating monolayer graphene to an elevated temperature of 800 °C removes the majority of amorphous carbon adsorbates and leaves a clean surface. The aggregation of Au impurity atoms into nanoparticle clusters that are bound to the surface of monolayer graphene causes nucleation of secondary graphene layers from carbon feedstock present within the microscope chamber. This enables the in situ study of heterogeneous nucleation and growth of graphene at the atomic level. We show that the growth mechanism consists of alternating C cluster attachment and indentation filling to maintain a uniform growth front of lowest energy. Back-folding of the graphene growth front is observed, followed by a process that involves flipping back and attaching to the surrounding region. We show how the highly polycrystalline graphene seed evolves with time into a higher order crystalline structure using a combination of AC-TEM and tight-binding molecular dynamics (TBMD) simulations. This helps understand the detailed lowest-energy step-by-step pathways associated with grain boundaries (GB) migration and crystallization processes. We find the motion of the GB is discontinuous and mediated by both bond rotation and atom evaporation, supported by density functional theory calculations and TBMD. These results provide insights into the formation of crystalline seed domains that are generated during bottom-up graphene synthesis.
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Chuncheng
authors.initials: C
authors.lastname: Gong
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Kuang
authors.initials: K
authors.lastname: He
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Gun-Do
authors.initials: GD
authors.lastname: Lee
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Qu
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Alex W
authors.initials: AW
authors.lastname: Robertson
authors.affiliation: Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, Korea.
authors.forename: Euijoon
authors.initials: E
authors.lastname: Yoon
authors.affiliation: Department of Physics and Graphene Research Institute, Sejong University , Seoul 143-747, Korea.
authors.forename: Suklyun
authors.initials: S
authors.lastname: Hong
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Jamie H
authors.initials: JH
authors.lastname: Warner
keywords: AC-TEM; GB; crystallization; grain growth; graphene; in situ TEM