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Regensburg 2019 – scientific programme

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O: Fachverband Oberflächenphysik

O 7: Graphene I: Structure and Growth (joint session O/TT)

O 7.3: Talk

Monday, April 1, 2019, 11:15–11:30, H24

Thermodynamically Stable Small-Angle Twisted Domains in Graphene on Iridium (111) — •Karim M. Omambac1, Christian Brand1, Hichem Hattab1, Laurenz Kremeyer1, Giriraj Jnawali1, Alpha T. N’Diaye2, Johann Coraux2, Raoul van Gastel3, Bene Poelsema3, Thomas Michely2, Frank-Jörg Meyer zu Heringdorf1, and Michael Horn-von Hoegen11Universität Duisburg-Essen, Germany — 2Universität zu Köln, Germany — 3University of Twente, The Netherlands

Lattice rotations or twists is one to the characteristics in the catalytic growth of monolayer graphene on a hot metallic surface. In particular, these small-angle twists have not yet been found experimentally but have been predicted partly through density functional theory calculations [1]. In this low energy electron diffraction study we evaluated the distribution of twisted domains of the epitaxially grown graphene on Ir(111) through spot profile analysis of the moiré spots. We find a new class of small-angle twisted domains with clear and distinct twist angles of 1.7, 1.1 and 0.6 at growth temperatures of 1255 K, 1350 K, and 1460 K, respectively. To further analyze, we performed a simple two-dimensional in-plane coincidence site lattice analysis taking only into account the thermal expansion coefficients between the substrate and the epitaxially grown graphene. The results show a very good agreement with the experimental findings suggesting the origin of these small-angle twisted domains is strongly dependent on the variation of the lattice mismatch between graphene and Ir(111) substrate during growth. [1] J. Phys.: Condens. Matter 24, 314214 (2012)

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