Spatially resolving and energy splitting of edge state in zigzag edged triangle graphene quantum dots on Cu(111) surface

The electronic structure of graphene nanoribbons (GNRs) and graphene quantum dots (GQDs) has been predicted to depend sensitively on the crystallographic orientation of their edges. However, direct observation of edge state for triangle graphene quantum dots (TGQDs) has not been verified experimentally. Here we explore, using the scanning tunneling spectroscopy (STS), the zigzag edged electronic property of varisized TGQDs. Predominantly zigzag-edged TGQDs exhibit edge-localized states with the energy splittings of about 0.2-0.3 V when its lateral dimension is less than 7 nm. The measured energy splittings agree with theoretical calculations, and show that these edge states originate from a hybridization effect of the substrate, and not from a magnetic splitting of the edge state.