title: Rapid identification of stacking orientation in isotopically labeled chemical-vapor grown bilayer graphene by Raman spectroscopy.
abstract: The growth of large-area bilayer graphene has been of technological importance for graphene electronics. The successful application of graphene bilayers critically relies on the precise control of the stacking orientation, which determines both electronic and vibrational properties of the bilayer system. Toward this goal, an effective characterization method is critically needed to allow researchers to easily distinguish the bilayer stacking orientation (i.e., AB stacked or turbostratic). In this work, we developed such a method to provide facile identification of the stacking orientation by isotope labeling. Raman spectroscopy of these isotopically labeled bilayer samples shows a clear signature associated with AB stacking between layers, enabling rapid differentiation between turbostratic and AB-stacked bilayer regions. Using this method, we were able to characterize the stacking orientation in bilayer graphene grown through Low Pressure Chemical Vapor Deposition (LPCVD) with enclosed Cu foils, achieving almost 70% AB-stacked bilayer graphene. Furthermore, by combining surface sensitive fluorination with such hybrid (12)C/(13)C bilayer samples, we are able to identify that the second layer grows underneath the first-grown layer, which is similar to a recently reported observation.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Fang
authors.forename: Allen L
authors.initials: AL
authors.lastname: Hsu
authors.forename: Roman
authors.initials: R
authors.lastname: Caudillo
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.forename: A Glen
authors.initials: AG
authors.lastname: Birdwell
authors.forename: Eugene
authors.initials: E
authors.lastname: Zakar
authors.forename: Martin
authors.initials: M
authors.lastname: Kalbac
authors.forename: Madan
authors.initials: M
authors.lastname: Dubey
authors.forename: Tomás
authors.initials: T
authors.lastname: Palacios
authors.forename: Millie S
authors.initials: MS
authors.lastname: Dresselhaus
authors.forename: Paulo T
authors.initials: PT
authors.lastname: Araujo
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
mesh_terms: D005740:Gases / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D007553:Isotope Labeling; D049329:Nanostructures / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D005740:Gases; D006108:Graphite