Periodic
Grain Boundaries Formed by Thermal Reconstruction
of Polycrystalline Graphene Film
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Abstract
Grain boundaries
consisting of dislocation cores arranged in a
periodic manner have well-defined structures and peculiar properties
and can be potentially applied as conducting circuits, plasmon reflectors
and phase retarders. Pentagon-heptagon (5–7) pairs or pentagon-octagon-pentagon
(5–8–5) carbon rings are known to exist in graphene
grain boundaries. However, there are few systematic experimental studies
on the formation, structure and distribution of periodic grain boundaries
in graphene. Herein, scanning tunneling microscopy (STM) was applied
to study periodic grain boundaries in monolayer graphene grown on
a weakly interacting Cu(111) crystal. The periodic grain boundaries
are formed after the thermal reconstruction of aperiodic boundaries,
their structures agree well with the prediction of the coincident-site-lattice
(CSL) theory. Periodic grain boundaries in quasi-freestanding graphene
give sharp local density of states (LDOS) peaks in the tunneling spectra
as opposed to the broad peaks of the aperiodic boundaries. This suggests
that grain boundaries with high structural quality can introduce well-defined
electronic states in graphene and modify its electronic properties