2018 Volume 16 Pages 72-75
Graphene is a two-dimensional sheet of carbon atoms, which consists of two π-electron sublattices. At zigzag-type edges, there is an imbalance between the two sublattices that creates an edge-localized state, which causes a sharp increase of the local density of states (LDOS) at the Dirac point. Simulations of single vacancies on graphene, that also cause localized states, show that the LDOS is suppressed on both sides of the peak energy, where the suppression range depends on the extent of the sublattice imbalance. Here, we studied edges of hexagonal nanopits with monatomic depth prepared by hydrogen-plasma etching of graphite surfaces with scanning tunneling microscopy and spectroscopy at T = 4.7 K and 78 K. In addition to a prominent peak near the Dirac point, we found a clear suppression of the LDOS on both sides of the peak over a ±100 mV range, which has not been observed before. Analogous to single vacancies, such a LDOS can be caused by the high sublattice imbalance, which indicates that the fabricated edges are substantially rich in zigzag structure. An exponential decay of the spectral weight of the edge-state has been observed with a decay length of 1.2 ± 0.3 nm at T = 78 K, which is consistent with previous works. [DOI: 10.1380/ejssnt.2018.72]
