Grain Boundaries in Graphene on SiC(0001̅) Substrate
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Abstract
Grain boundaries in epitaxial graphene
on the SiC(0001̅)
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 θ<sub>c</sub> = 19 ± 2°.
Periodic structures are found among the flat large-angle grain boundaries.
In particular, the observed θ = 33 ± 2° 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