Absence of edge states near the 120 corners of zigzag graphene nanoribbons

Abstract

Based on first-principles total-energy calculations, we studied the energetics and electronic structure of zigzag graphene nanoribbons with nanometer-scale corners. We found that the formation energy of a short zigzag edge with a 120 corner is substantially smaller than that of a straight zigzag edge with an infinite length. We also found that zigzag graphene ribbons with 120 corners are semiconductors for which the band-gap decreases with increasing length between adjacent corners. The edge state is absent for zigzag graphene ribbons with short corner-corner distances, while the edge state emerges for zigzag ribbons that have a corner-corner distance greater than 1.5 nm. The remarkable stability of the 120 corner of the short zigzag edges is in good agreement with the experimental observation of such corners of graphene edges. © 2013 American Physical Society.