Tison, YannLagoute, JeromeRepain, VincentChacon, CyrilGirard, YannJoucken, FredericSporken, RobertGargiulo, FernandoYazyev, Oleg V.Rousset, Sylvie2015-02-202015-02-202015-02-20201410.1021/nl502854whttps://infoscience.epfl.ch/handle/20.500.14299/111634WOS:0003457238000551412.3344Grain boundaries in epitaxial graphene on the SiC(000 (1) over bar) substrate are studied using scanning tunneling microscopy and spectroscopy. All investigated small-angle grain boundaries show pronounced out-of-plane buckling induced by the strain fields of constituent dislocations. The ensemble of observations determines the critical misorientation angle of buckling transition theta(c) = 19 +/- 2 degrees. Periodic structures are found among the flat large-angle grain boundaries. In particular, the observed theta = 33 +/- 2 degrees highly ordered grain boundary is assigned to the previously proposed lowest formation energy structural motif composed of a continuous chain of edge-sharing alternating pentagons and heptagons. This periodic grain boundary defect is predicted to exhibit strong valley filtering of charge carriers thus promising the practical realization of all-electric valleytronic devices.Graphenegrain boundariesscanning tunneling microscopyscanning tunneling sepctroscopydensity functional theorytext::journal::journal article::research article