Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 9: Graphene I: Structure and Growth (joint session O/TT)
TT 9.3: 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 Hoegen1 — 1Universität 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)