Graphene nanoribbons grown on the (1-10n) and (-110n) facets of SiC have demonstrated exceptional electronic properties as ballistic transport along their long direction and a band gap in the small direction [1]. In order to understand these electronic properties, we have performed (S)TEM (HAADF, LAADF, ABF, EELS) investigation in combination with STM and ARPES measurements. The (S)TEM have been performed on X-section sample as it can be schematically seen in the figure 1. Using Cs corrected STEM at 60 keV voltage, the structural aspect of the graphene can be maintained for high resolution investigation and EELS spectromicroscopy. In particular we will describe the origin of the metal-semiconductor junction as observed in these graphene [2] and this will be discussed in term of curvature effect, quantum confinement on a complex reconstructed step as presented in figure 2 [3].

[1] Exceptional ballistic transport in epitaxial graphene nanoribbons, J. Baringhaus, M. Ruan, F. Edler, A. Tejeda, M. Sicot, A. Taleb-Ibrahimi, A.-P. Li, Z. Jiang, E.H. Conrad, C. Berger, C. Tegenkamp, and W.A. de Heer, Nature 506, 349 (2014).

[2] A wide band gap metal-semiconductor-metal nanostructure made entirely from graphene, J. Hicks, A. Tejeda, A. A. Taleb-Ibrahimi, M.S. M.S. Nevius, F. F. Wang, K. K. Shepperd, J. J. Palmer, F. Bertran, P. Le Fèvre, J. Kunc, W.A. de Heer, C. Berger, E.H. Conrad, Nature Physics 9, 49 (2013).

[3] Atomic structure of epitaxial graphene sidewall nanoribbons:  flat graphene, miniribbons and confinement gap, Irene Palacio, Arlensiú Celis, Maya N. Nair, Alexandre Gloter, Alberto Zobelli, Muriel Sicot, Daniel Malterre, Meredith S.  Nevius, Walt A. de Heer, Claire Berger, Edward H. Conrad, Amina Taleb-Ibrahimi and Antonio Tejeda, Nano letters 15, 182-189 (2015).

Figures:

Fig1 : General overview of graphene nanoribbons grown on SiC and SiC facets (sidewall ribbons). a) Scheme of the localization of the ribbons on the samples. b) STM image showing the regions with [0001] normal. Plateaus width of 50 nm c) Cross sectional TEM image of the array of ribbons in another sample. Plateaus width of 300 nm.

Fig 2 : Combination of a STEM-ABF image and a STM image on the graphene nano-ribbon grown over SiC. The obtained overall structure of the graphene has be sketched

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EMC Abstracts - https://emc-proceedings.com/abstract/stem-and-eels-investigation-of-graphene-nanoribbons-epitaxially-grown-over-sic/