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Growth of graphene on a stepped iridium surface: morphology, domains and electronic fingerprints

A promising route for modification of graphene properties is the growth of graphene on a substrate with a periodic arrangement of steps. We have used scanning tunneling microscopy and spectroscopy (STM/STS) and low energy electron diffraction (LEED) to study the growth of graphene on such periodically stepped Ir(332) surface. We have found that graphene continuously extends over iridium terraces and steps. Moreover, new distinctive mesoscopic features of the underlying surface are formed involving large, flat terraces accompanied by groups of narrower steps [1]. These morphologically different regions are also distinctive by their spectroscopic features found in STS. The distribution of the newly formed terraces as well as the contribution of various graphene orientations is sensitive to the preparation temperature. Below 800°C we find that the terrace width distribution is closer to the intrinsic distribution of clean Ir(332) than for higher temperatures. Additionally, graphene grown at low temperatures has a prominent contribution of a domain rotated by 30° with respect to the substrate. We find that the microscopic shape of steps after graphene formation strongly depends on the orientation of graphene. [1] I. Šrut, et al., submitted

graphene; vicinal surfaces; electronic structure; morphology

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