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While epitaxial growth secures a source of high-quality graphene for large-scale applications, it also provides ample possibilities to study and tune the properties of graphene in terms of its structure, electronic bands or electron correlations. In particular, the choice of the substrate and growing conditions can be considered as a tool to form more complex structures based on epitaxial graphene. In this talk I will first present low energy electron microscopy characterization of graphene on Ir(111) and discuss the "intrinsic" stress-relaxation features, wrinkles, which are a result of graphene growth process on many substrates. It will be shown how the specific substrate interaction leads to a macroscopic quasi-hexagonal network of wrinkles. Also, the frustration within the network is identified as a governing force for the formation of complex wrinkle profiles with multiple lobes. Furthermore, the use of vicinal substrates for the growth of epitaxial graphene will be explored as a route for the uniaxial engineering of graphene. Based on scanning tunneling microscopy and angle-resolved photoemission spectroscopy experimental results as well as van der Waals-density functional theory calculations, we propose a general mechanism for the observed vicinal substrate restructuring induced by graphene. Moreover, by comparing graphene grown on flat and vicinal Ir substrates, we observe locally variable doping, the Dirac cone anisotropy, and a pronounced localization of states at step edges. In particular, the anisotropy is associated to a nanoscale potential modulation induced by the uniaxial pattern, and the pronounced states to an enhanced chemical binding and charge transfer. We will also show by atomic force microscopy and Raman spectroscopy that upon the transfer of such epitaxial graphene to a flat substrate, the uniaxial strain imposed by the growth process on a vicinal substrate is macroscopically preserved.

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Marko Kralj, Institute of Physics - Zagreb
Seminar Room of the Institute of Physics II
Contact: Carsten Busse