▎ 摘 要
Narrow graphene nanoribbons (GNRs) exhibit electronic and optical properties that are not present in extended graphene. Most importantly, they possess band gaps in the order of a few electron volts, which has been subject to numerous studies. Here we report on the experimental observation of exctionic states in the band gap of N = 7 armchair GNRs (7-GNR) on Au(111) and Au(788) using energy- and angle-resolved two -photon photoemission spectroscopy. Thereby, an exciton binding energy in the 7-GNR on Au(111) of 160 60 meV has been determined. On the stepped Au(788) surface, the exciton binding energy is in the same range.