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TT: Fachverband Tiefe Temperaturen

TT 72: Graphene II: Adsorption, Intercalation and Doping (joint session O/TT)

TT 72.5: Vortrag

Freitag, 20. März 2020, 11:30–11:45, GER 37

Sidewall epigraphene investigated by STEM — •Markus Gruschwitz, Steffen Schulze, and Christoph Tegenkamp — TU Chemnitz, Chemnitz, Germany

Epitaxial graphene nanoribbons (GNR) grown on SiC facets reveal ballistic transport channels. The structure and growth were studied intensively by STM, LEED and LEEM [1]. Spatially resolved transport measurements and tight-binding calculations suggest that the bonding of the ribbons to the SiC substrate plays an important role [2]. In this study, cross-section STEM on similar structures were performed in order to characterize the interface and bonding between graphene and SiC in more detail.

Indeed, the zig-zag GNRs, grown along the [1100] direction, are delaminated from the SiC facet as seen by high resolution C_S corrected STEM. Mini steps at the top and the bottom of the sidewalls define the edges of the GNRs. Atomically resolved EELS and EDX confirm that the top part of the freestanding GNR merges into a bufferlayer. The SiC facet reveals a silicon deficiency in the three topmost substrate layers. These SiC imperfections were found already for epitaxial graphene on SiC(0001) and result from the sublimation processes [3]. The lower edge merges into SiC and shows a sp³-hybridization. Moreover, differential phase contrast measurements allow the calculation of charge density maps and therefore the visualization of space charge distributions in the substrate. References: [1] Zakharov et al., ACS Appl Nano Mat., 2, 156 (2019) [2] Aprojanz et al., Nat. Comm. 9, 4426, (2018). [3] Gruschwitz et al., PRM 3, 094004 (2019).