Drs. Kuang He

Department of Materials, University of Oxford Authors | Kuang He, Alex W. Robertson, Ye Fan, Christopher S. Allen, Yung-Chang Lin, Kazu Suenaga, Angus I. Kirkland and Jamie H. Warner. Email |  jamie.warner@materials.ox.ac.uk

ApplicationTemperature Dependence of the Reconstruction of Zigzag Edges in Graphene
AuthorsKuang He, Alex W. Robertson, Ye Fan, Christopher S. Allen, Yung-Chang Lin, Kazu Suenaga, Angus I. Kirkland and Jamie H. Warner.
JournalACS Nano, 2015
PublicationFull Publication Here – DOI: 10.1021/acsnano.5b01130

Temperature Dependence of the Reconstruction of Zigzag Edges in Graphene

ABSTRACT: We examine the temperature dependence of graphene edge terminations at the atomic scale using an in situ heating holder within an aberration-corrected transmission electron microscope. The relative ratios of armchair, zigzag, and reconstructed zigzag edges from over 350 frames at each temperature are measured. Below 400 C, the edges are dominated by zigzag terminations, but above 600 C, this changes dramatically, with edges dominated by armchair and reconstructed zigzag edges.

We show that at low temperature chemical etching effects dominate and cause deviation to the thermodynamics of the system. At high temperatures (600 and 800 C), adsorbates are evaporated from the surface of graphene and chemical etching effects are significantly reduced, enabling the thermodynamic distribution of edge types to be observed. The growth rate of holes at high temperature is also shown to be slower than at room temperature, indicative of the reduced chemical etching process. These results provide important insights into hthe role of chemical etching effects in the hole formation, edge sputtering, and edge reconstruction in graphene.

Figure above: Edge behavior at room temperature (∼25 C). (ac) Three typical HRTEM images of graphene holes at that temperature. The edges are color-coded to differentiate the types of edge configurations. Red represents armchair; yellow is zigzag, and green is Rec. 57; white indicatesmixed or unidentified edge types. The inset in (a) and (b) shows typical long-ordered zigzag and armchair configurations at this temperature. The statistics for three examples are shown in (d); the percentages of edges occupied by different types of edges are ranked accordingly: black columns represent panel (a), red columns panel (b), and blue columns panel (c). (e,f) Long-ordered zigzag edge from both bulk of graphene and edge of a nanoribbon, respectively. (g) Representative long-ordered armchair edge found at this temperature. The o iginal image ofwhich (eg) are cropped fromthose shown in Figure S1ac of Supporting Information. All scale bars are 1 nm.

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